Uploaded byveneethmathew
PPT, PDF16,578 views

Ch 15: The Chromosomal Basis of Inheritance

1) The document summarizes a lecture on the chromosomal basis of inheritance, beginning with an overview of how genes are located on chromosomes. 2) It then discusses Mendelian inheritance having a physical basis in chromosome behavior during meiosis and fertilization. Thomas Morgan's experiments with fruit flies provided evidence linking genes to chromosomes. 3) The lecture also covers sex-linked inheritance patterns and how linked genes on the same chromosome tend to be inherited together.

Embed presentation

Downloaded 480 times
LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick The Chromosomal Basis of Inheritance Chapter 15
Overview: Locating Genes Along Chromosomes • Mendel’s “hereditary factors” were genes • Today we can show that genes are located on chromosomes • The location of a particular gene can be seen by tagging isolated chromosomes with a fluorescent dye that highlights the gene © 2011 Pearson Education, Inc.
Figure 15.1
Concept 15.1: Mendelian inheritance has its physical basis in the behavior of chromosomes • Mitosis and meiosis were first described in the late 1800s • The chromosome theory of inheritance states: – Mendelian genes have specific loci (positions) on chromosomes – Chromosomes undergo segregation and independent assortment • The behavior of chromosomes during meiosis can account for Mendel’s laws of segregation and independent assortment © 2011 Pearson Education, Inc.
Figure 15.2 P Generation F1 Generation Yellow-round seeds (YYRR) Green-wrinkled seeds (yyrr) × Meiosis Fertilization Gametes Y Y R R YR y y r y r All F1 plants produce yellow-round seeds (YyRr). Meiosis Metaphase I Anaphase I Metaphase II R R R R R R R R R R R R r r r r r r r r r r r r Y Y Y Y Y Y Y Y Y Y Y Y y y y y y y y y y y y y Gametes LAW OF SEGREGATION The two alleles for each gene separate during gamete formation. LAW OF INDEPENDENT ASSORTMENT Alleles of genes on nonhomologous chromosomes assort independently during gamete formation. 1 2 2 1 1 /4 1 /4 1 /4 1 /4YR yr Yr yR F2 Generation 3 3Fertilization recombines the R and r alleles at random. Fertilization results in the 9:3:3:1 phenotypic ratio in the F2 generation. An F1 × F1 cross-fertilization 9 : 3 : 3 : 1 r
Figure 15.2a P Generation Yellow-round seeds (YYRR) Green-wrinkled seeds (yyrr) × Meiosis Fertilization Gametes Y Y R R YR y y r y r r
Figure 15.2b F1 Generation All F1 plants produce yellow-round seeds (YyRr). Meiosis Metaphase I Anaphase I Metaphase II R R R R R R R R R R R R r r r r r r r r r r r r Y Y Y Y Y Y Y Y Y Y Y Y y y y y y y y y y y y y Gametes LAW OF SEGREGATION The two alleles for each gene separate during gamete formation. LAW OF INDEPENDENT ASSORTMENT Alleles of genes on nonhomologous chromosomes assort independently during gamete formation. 1 2 2 1 1 /4 1 /4 1 /4 1 /4YR yr Yr yR
Figure 15.2c F2 Generation 3Fertilization recombines the R and r alleles at random. Fertilization results in the 9:3:3:1 phenotypic ratio in the F2 generation. An F1 × F1 cross-fertilization 9 : 3 : 3 : 1 LAW OF SEGREGATION LAW OF INDEPENDENT ASSORTMENT 3
Morgan’s Experimental Evidence: Scientific Inquiry • The first solid evidence associating a specific gene with a specific chromosome came from Thomas Hunt Morgan, an embryologist • Morgan’s experiments with fruit flies provided convincing evidence that chromosomes are the location of Mendel’s heritable factors © 2011 Pearson Education, Inc.
Morgan’s Choice of Experimental Organism • Several characteristics make fruit flies a convenient organism for genetic studies – They produce many offspring – A generation can be bred every two weeks – They have only four pairs of chromosomes © 2011 Pearson Education, Inc.
• Morgan noted wild type, or normal, phenotypes that were common in the fly populations • Traits alternative to the wild type are called mutant phenotypes © 2011 Pearson Education, Inc.
Figure 15.3
Figure 15.3a
Figure 15.3b
Correlating Behavior of a Gene’s Alleles with Behavior of a Chromosome Pair • In one experiment, Morgan mated male flies with white eyes (mutant) with female flies with red eyes (wild type) – The F1 generation all had red eyes – The F2 generation showed the 3:1 red:white eye ratio, but only males had white eyes • Morgan determined that the white-eyed mutant allele must be located on the X chromosome • Morgan’s finding supported the chromosome theory of inheritance © 2011 Pearson Education, Inc.
Figure 15.4 All offspring had red eyes. P Generation F1 Generation F2 Generation F2 Generation F1 Generation P Generation Eggs Eggs Sperm Sperm X X X Y w+ w+ w+ w+ w+ w+ w+ w+ w+ w+ w+ w w w w w w RESULTS EXPERIMENT CONCLUSION
Figure 15.4a All offspring had red eyes. P Generation F1 Generation F2 Generation RESULTS EXPERIMENT
Figure 15.4b F2 Generation P Generation Eggs Eggs Sperm Sperm X w+ CONCLUSION X X Y w+ w+ w+ w+ w+ w+ w+ w+ w+ w+ w w w w w w F1 Generation
Concept 15.2: Sex-linked genes exhibit unique patterns of inheritance • In humans and some other animals, there is a chromosomal basis of sex determination © 2011 Pearson Education, Inc.
The Chromosomal Basis of Sex • In humans and other mammals, there are two varieties of sex chromosomes: a larger X chromosome and a smaller Y chromosome • Only the ends of the Y chromosome have regions that are homologous with corresponding regions of the X chromosome • The SRY gene on the Y chromosome codes for a protein that directs the development of male anatomical features © 2011 Pearson Education, Inc.
Figure 15.5 X Y
• Females are XX, and males are XY • Each ovum contains an X chromosome, while a sperm may contain either an X or a Y chromosome • Other animals have different methods of sex determination © 2011 Pearson Education, Inc.
Figure 15.6 Parents or Sperm or Egg Zygotes (offspring) 44 + XY 44 + XX 22 + X 22 + Y 22 + X 44 + XX 44 + XY 22 + XX 22 + X 76 + ZW 76 + ZZ 32 (Diploid) 16 (Haploid) (a) The X-Y system (b) The X-0 system (c) The Z-W system (d) The haplo-diploid system
Figure 15.6a Parents or Sperm or Egg Zygotes (offspring) 44 + XY 44 + XX 22 + X 22 + Y 22 + X 44 + XX 44 + XY 22 + XX 22 + X (a) The X-Y system (b) The X-0 system
Figure 15.6b 76 + ZW 76 + ZZ 32 (Diploid) 16 (Haploid) (c) The Z-W system (d) The haplo-diploid system
• A gene that is located on either sex chromosome is called a sex-linked gene • Genes on the Y chromosome are called Y-linked genes; there are few of these • Genes on the X chromosome are called X-linked genes © 2011 Pearson Education, Inc.
Inheritance of X-Linked Genes • X chromosomes have genes for many characters unrelated to sex, whereas the Y chromosome mainly encodes genes related to sex determination © 2011 Pearson Education, Inc.
• X-linked genes follow specific patterns of inheritance • For a recessive X-linked trait to be expressed – A female needs two copies of the allele (homozygous) – A male needs only one copy of the allele (hemizygous) • X-linked recessive disorders are much more common in males than in females © 2011 Pearson Education, Inc.
Figure 15.7 Eggs Eggs Eggs Sperm Sperm Sperm (a) (b) (c) XN XN Xn Y XN Xn XN Y XN Xn Xn Y Xn Y XN Y YXn Xn Xn XN XN XN XNXN Xn XN Y XN Y XN Y XN Y Xn Y Xn YXN Xn XN Xn XN Xn XN XN Xn Xn
• Some disorders caused by recessive alleles on the X chromosome in humans – Color blindness (mostly X-linked) – Duchenne muscular dystrophy – Hemophilia © 2011 Pearson Education, Inc.
X Inactivation in Female Mammals • In mammalian females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development • The inactive X condenses into a Barr body • If a female is heterozygous for a particular gene located on the X chromosome, she will be a mosaic for that character © 2011 Pearson Education, Inc.
Figure 15.8 Early embryo: X chromosomes Allele for orange fur Allele for black fur Two cell populations in adult cat: Cell division and X chromosome inactivation Active X Inactive X Active X Black fur Orange fur
Figure 15.8a
• Each chromosome has hundreds or thousands of genes (except the Y chromosome) • Genes located on the same chromosome that tend to be inherited together are called linked genes Concept 15.3: Linked genes tend to be inherited together because they are located near each other on the same chromosome © 2011 Pearson Education, Inc.
How Linkage Affects Inheritance • Morgan did other experiments with fruit flies to see how linkage affects inheritance of two characters • Morgan crossed flies that differed in traits of body color and wing size © 2011 Pearson Education, Inc.
Figure 15.9-1 P Generation (homozygous) Wild type (gray body, normal wings) b+ b+ vg+ vg+ b b vg vg Double mutant (black body, vestigial wings) EXPERIMENT
Figure 15.9-2 P Generation (homozygous) Wild type (gray body, normal wings) F1 dihybrid (wild type) TESTCROSS b+ b+ vg+ vg+ b+ b vg+ vg b b vg vg b b vg vg Double mutant (black body, vestigial wings) Double mutant EXPERIMENT
Figure 15.9-3 P Generation (homozygous) Wild type (gray body, normal wings) F1 dihybrid (wild type) Testcross offspring TESTCROSS b+ b+ vg+ vg+ b+ b vg+ vg b b vg vg b b vg vg Double mutant (black body, vestigial wings) Double mutant Eggs Sperm EXPERIMENT Wild type (gray-normal) Black- vestigial Gray- vestigial Black- normal b+ vg+ bvg b+ vg b vg+ b+ b vg+ vg bb vg vg b+ bvgvg bb vg+ vg bvg
Figure 15.9-4 P Generation (homozygous) Wild type (gray body, normal wings) F1 dihybrid (wild type) Testcross offspring TESTCROSS b+ b+ vg+ vg+ b+ b vg+ vg b b vg vg b b vg vg Double mutant (black body, vestigial wings) Double mutant Eggs Sperm EXPERIMENT RESULTS PREDICTED RATIOS Wild type (gray-normal) Black- vestigial Gray- vestigial Black- normal b+ vg+ bvg b+ vg b vg+ b+ b vg+ vg bb vg vg b+ bvgvg bb vg+ vg 965 944 206 185 1 1 1 1 1 0 1 0 If genes are located on different chromosomes: If genes are located on the same chromosome and parental alleles are always inherited together: : : : : : : : : : bvg
• Morgan found that body color and wing size are usually inherited together in specific combinations (parental phenotypes) • He noted that these genes do not assort independently, and reasoned that they were on the same chromosome © 2011 Pearson Education, Inc.
Figure 15.UN01 Most offspring F1 dihybrid female and homozygous recessive male in testcross or b+ vg+ b vg b+ vg+ b vg b vg b vg b vg b vg
• However, nonparental phenotypes were also produced • Understanding this result involves exploring genetic recombination, the production of offspring with combinations of traits differing from either parent © 2011 Pearson Education, Inc.
Genetic Recombination and Linkage • The genetic findings of Mendel and Morgan relate to the chromosomal basis of recombination © 2011 Pearson Education, Inc.
Recombination of Unlinked Genes: Independent Assortment of Chromosomes • Mendel observed that combinations of traits in some offspring differ from either parent • Offspring with a phenotype matching one of the parental phenotypes are called parental types • Offspring with nonparental phenotypes (new combinations of traits) are called recombinant types, or recombinants • A 50% frequency of recombination is observed for any two genes on different chromosomes © 2011 Pearson Education, Inc.
Figure 15.UN02 Gametes from green- wrinkled homozygous recessive parent (yyrr) Gametes from yellow-round dihybrid parent (YyRr) Recombinant offspring Parental- type offspring YR yr Yr yR yr YyRr yyrr Yyrr yyRr
Recombination of Linked Genes: Crossing Over • Morgan discovered that genes can be linked, but the linkage was incomplete, because some recombinant phenotypes were observed • He proposed that some process must occasionally break the physical connection between genes on the same chromosome • That mechanism was the crossing over of homologous chromosomes © 2011 Pearson Education, Inc. Animation: Crossing Over
Figure 15.10 Testcross parents Replication of chromosomes Gray body, normal wings (F1 dihybrid) Black body, vestigial wings (double mutant) Replication of chromosomes Meiosis I Meiosis II Meiosis I and II Recombinant chromosomes Eggs b+ vg+ b vg b+ vg+ b+ vg+ b+ vg+ b+ vg b vg+ b vg b vg b vg b vg b vg b vg b vg b vg b vg b+ vg+ b+ vgb vg b vg+ Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Sperm Parental-type offspring Recombinant offspring Recombination frequency 391 recombinants 2,300 total offspring × 100 = 17%= b+ vg+ b vg+b+ vgb vg b vg b vg b vg b vg b vg
Figure 15.10a Testcross parents Replication of chromosomes Gray body, normal wings (F1 dihybrid) Black body, vestigial wings (double mutant) Replication of chromosomes Meiosis I Meiosis II Meiosis I and II Recombinant chromosomes Eggs b+ vg+ b vg b+ vg+ b+ vg+ b+ vg+ b+ vg b vg+ b vg b vg b vg b vg b vg b vg b vg b vg b vg b+ vg+ b+ vgb vg b vg+ Sperm b vg
Figure 15.10b Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Sperm Parental-type offspring Recombinant offspring Recombination frequency 391 recombinants 2,300 total offspring × 100 = 17%= b+ vg+ b vg+ b+ vgb vg b vg b vg b vg b vg b vg Eggs Recombinant chromosomes b+ vg+ b vg b+ vg b vg+
New Combinations of Alleles: Variation for Normal Selection • Recombinant chromosomes bring alleles together in new combinations in gametes • Random fertilization increases even further the number of variant combinations that can be produced • This abundance of genetic variation is the raw material upon which natural selection works © 2011 Pearson Education, Inc.
Mapping the Distance Between Genes Using Recombination Data: Scientific Inquiry • Alfred Sturtevant, one of Morgan’s students, constructed a genetic map, an ordered list of the genetic loci along a particular chromosome • Sturtevant predicted that the farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency © 2011 Pearson Education, Inc.
• A linkage map is a genetic map of a chromosome based on recombination frequencies • Distances between genes can be expressed as map units; one map unit, or centimorgan, represents a 1% recombination frequency • Map units indicate relative distance and order, not precise locations of genes © 2011 Pearson Education, Inc.
Figure 15.11 Chromosome Recombination frequencies 9% 9.5% 17% b cn vg RESULTS
• Genes that are far apart on the same chromosome can have a recombination frequency near 50% • Such genes are physically linked, but genetically unlinked, and behave as if found on different chromosomes © 2011 Pearson Education, Inc.
• Sturtevant used recombination frequencies to make linkage maps of fruit fly genes • Using methods like chromosomal banding, geneticists can develop cytogenetic maps of chromosomes • Cytogenetic maps indicate the positions of genes with respect to chromosomal features © 2011 Pearson Education, Inc.
Figure 15.12 Mutant phenotypes Short aristae Black body Cinnabar eyes Vestigial wings Brown eyes Long aristae (appendages on head) Gray body Red eyes Normal wings Red eyes Wild-type phenotypes 104.567.057.548.50
Concept 15.4: Alterations of chromosome number or structure cause some genetic disorders • Large-scale chromosomal alterations in humans and other mammals often lead to spontaneous abortions (miscarriages) or cause a variety of developmental disorders • Plants tolerate such genetic changes better than animals do © 2011 Pearson Education, Inc.
Abnormal Chromosome Number • In nondisjunction, pairs of homologous chromosomes do not separate normally during meiosis • As a result, one gamete receives two of the same type of chromosome, and another gamete receives no copy © 2011 Pearson Education, Inc.
Meiosis I Nondisjunction Figure 15.13-1
Meiosis I Meiosis II Nondisjunction Non- disjunction Figure 15.13-2
Meiosis I Meiosis II Nondisjunction Non- disjunction Gametes Number of chromosomes Nondisjunction of homo- logous chromosomes in meiosis I (a) Nondisjunction of sister chromatids in meiosis II (b) n + 1 n − 1n + 1 n − 1 n − 1n + 1 n n Figure 15.13-3
• Aneuploidy results from the fertilization of gametes in which nondisjunction occurred • Offspring with this condition have an abnormal number of a particular chromosome © 2011 Pearson Education, Inc.
• A monosomic zygote has only one copy of a particular chromosome • A trisomic zygote has three copies of a particular chromosome © 2011 Pearson Education, Inc.
• Polyploidy is a condition in which an organism has more than two complete sets of chromosomes – Triploidy (3n) is three sets of chromosomes – Tetraploidy (4n) is four sets of chromosomes • Polyploidy is common in plants, but not animals • Polyploids are more normal in appearance than aneuploids © 2011 Pearson Education, Inc.
Alterations of Chromosome Structure • Breakage of a chromosome can lead to four types of changes in chromosome structure – Deletion removes a chromosomal segment – Duplication repeats a segment – Inversion reverses orientation of a segment within a chromosome – Translocation moves a segment from one chromosome to another © 2011 Pearson Education, Inc.
Figure 15.14 (a) Deletion (b) Duplication (c) Inversion (d) Translocation A deletion removes a chromosomal segment. A duplication repeats a segment. An inversion reverses a segment within a chromosome. A translocation moves a segment from one chromosome to a nonhomologous chromosome. A B C D E F G H A B C E F G H A B C D E F G H A B C D E F G HB C A B C D E F G H A D C B E F G H A B C D E F G H M N O P Q R GM N O C HFED A B P Q R
Figure 15.14a (a) Deletion (b) Duplication A deletion removes a chromosomal segment. A duplication repeats a segment. BA C D E F G H A B C D E F G H A B C D E F G HB C A B C E F G H
Figure 15.14b (c) Inversion (d) Translocation An inversion reverses a segment within a chromosome. A translocation moves a segment from one chromosome to a nonhomologous chromosome. A B C D E F G H A D C B E F G H A B C D E F G H M N O P Q R GM N O C HFED A B P Q R
Human Disorders Due to Chromosomal Alterations • Alterations of chromosome number and structure are associated with some serious disorders • Some types of aneuploidy appear to upset the genetic balance less than others, resulting in individuals surviving to birth and beyond • These surviving individuals have a set of symptoms, or syndrome, characteristic of the type of aneuploidy © 2011 Pearson Education, Inc.
Down Syndrome (Trisomy 21) • Down syndrome is an aneuploid condition that results from three copies of chromosome 21 • It affects about one out of every 700 children born in the United States • The frequency of Down syndrome increases with the age of the mother, a correlation that has not been explained © 2011 Pearson Education, Inc.
Figure 15.15
Figure 15.15a
Figure 15.15b
Aneuploidy of Sex Chromosomes • Nondisjunction of sex chromosomes produces a variety of aneuploid conditions • Klinefelter syndrome is the result of an extra chromosome in a male, producing XXY individuals • Monosomy X, called Turner syndrome, produces X0 females, who are sterile; it is the only known viable monosomy in humans © 2011 Pearson Education, Inc.
Disorders Caused by Structurally Altered Chromosomes • The syndrome cri du chat (“cry of the cat”), results from a specific deletion in chromosome 5 • A child born with this syndrome is mentally retarded and has a catlike cry; individuals usually die in infancy or early childhood • Certain cancers, including chronic myelogenous leukemia (CML), are caused by translocations of chromosomes © 2011 Pearson Education, Inc.
Figure 15.16 Normal chromosome 9 Normal chromosome 22 Reciprocal translocation Translocated chromosome 9 Translocated chromosome 22 (Philadelphia chromosome)
Concept 15.5: Some inheritance patterns are exceptions to standard Mendelian inheritance • There are two normal exceptions to Mendelian genetics • One exception involves genes located in the nucleus, and the other exception involves genes located outside the nucleus • In both cases, the sex of the parent contributing an allele is a factor in the pattern of inheritance © 2011 Pearson Education, Inc.
Genomic Imprinting • For a few mammalian traits, the phenotype depends on which parent passed along the alleles for those traits • Such variation in phenotype is called genomic imprinting • Genomic imprinting involves the silencing of certain genes that are “stamped” with an imprint during gamete production © 2011 Pearson Education, Inc.
Figure 15.17 (a) Homozygote Paternal chromosome Maternal chromosome Normal Igf2 allele is expressed. Normal Igf2 allele is not expressed. Normal-sized mouse (wild type) Mutant Igf2 allele inherited from mother Mutant Igf2 allele inherited from father Normal-sized mouse (wild type) Dwarf mouse (mutant) Normal Igf2 allele is expressed. Mutant Igf2 allele is expressed. Mutant Igf2 allele is not expressed. Normal Igf2 allele is not expressed. (b) Heterozygotes
Figure 15.17a (a) Homozygote Paternal chromosome Maternal chromosome Normal Igf2 allele is expressed. Normal Igf2 allele is not expressed. Normal-sized mouse (wild type)
Figure 15.17b Mutant Igf2 allele inherited from mother Mutant Igf2 allele inherited from father Normal-sized mouse (wild type) Dwarf mouse (mutant) Normal Igf2 allele is expressed. Mutant Igf2 allele is expressed. Mutant Igf2 allele is not expressed. Normal Igf2 allele is not expressed. (b) Heterozygotes
• It appears that imprinting is the result of the methylation (addition of —CH3) of cysteine nucleotides • Genomic imprinting is thought to affect only a small fraction of mammalian genes • Most imprinted genes are critical for embryonic development © 2011 Pearson Education, Inc.
Inheritance of Organelle Genes • Extranuclear genes (or cytoplasmic genes) are found in organelles in the cytoplasm • Mitochondria, chloroplasts, and other plant plastids carry small circular DNA molecules • Extranuclear genes are inherited maternally because the zygote’s cytoplasm comes from the egg • The first evidence of extranuclear genes came from studies on the inheritance of yellow or white patches on leaves of an otherwise green plant © 2011 Pearson Education, Inc.
Figure 15.18
• Some defects in mitochondrial genes prevent cells from making enough ATP and result in diseases that affect the muscular and nervous systems – For example, mitochondrial myopathy and Leber’s hereditary optic neuropathy © 2011 Pearson Education, Inc.
Figure 15.UN03 P generation gametes Sperm Egg This F1 cell has 2n = 6 chromo- somes and is heterozygous for all six genes shown (AaBbCcDdEeFf). Red = maternal; blue = paternal. Each chromosome has hundreds or thousands of genes. Four (A, B, C, F) are shown on this one. The alleles of unlinked genes are either on separate chromosomes (such as d and e) or so far apart on the same chromosome (c and f) that they assort independently. Genes on the same chromo- some whose alleles are so close together that they do not assort independently (such as a, b, and c) are said to be genetically linked. D C B A F E d c b a f e D C B A F e d E f c ba
Figure 15.UN04
Figure 15.UN05
Figure 15.UN06

More Related Content

PPT
14 mendel and the gene idea
bykindarspirit
 
PPT
Ch 14: Mendel and the Gene Idea
byveneethmathew
 
PPT
16 the molecular basis of inheritance
bykindarspirit
 
PPT
Ch 16: The Molecular Basis of Inheritance
byveneethmathew
 
PPT
21 lecture genome_and_evolution
byveneethmathew
 
PPT
23 lecture evolution_populations
byveneethmathew
 
PPT
Ch 17: From Gene to Protein
byveneethmathew
 
PPT
22 lecture descent_with_modification
byveneethmathew
 
14 mendel and the gene idea
bykindarspirit
 
Ch 14: Mendel and the Gene Idea
byveneethmathew
 
16 the molecular basis of inheritance
bykindarspirit
 
Ch 16: The Molecular Basis of Inheritance
byveneethmathew
 
21 lecture genome_and_evolution
byveneethmathew
 
23 lecture evolution_populations
byveneethmathew
 
Ch 17: From Gene to Protein
byveneethmathew
 
22 lecture descent_with_modification
byveneethmathew
 

What's hot

PPT
Ch 12: Cell Cycle
byveneethmathew
 
PPT
13 meiosis and sexual life cycles
bykindarspirit
 
PPT
Ch 11: Cell Communication
byveneethmathew
 
PPT
25 lecture history_of_life
byveneethmathew
 
PPT
27 lecture bacteria
byveneethmathew
 
PPT
Ch 13: Meiosis and Sexual Life Cycles
byveneethmathew
 
PPT
18 Regulation of Gene Expression
bykindarspirit
 
PPT
21 genomes and their evolution
bykindarspirit
 
PPT
20 lecture biotech
byveneethmathew
 
PPT
12 the cell cycle
bykindarspirit
 
PPT
22 descent with modification a darwinian view
bykindarspirit
 
PPT
Ch 7: Membrane Structure and Function
byveneethmathew
 
PPT
24 lecture origin_of_species
byveneethmathew
 
PPT
23 the evolution of populations
bykindarspirit
 
PPT
26 lecture phylogeny
byveneethmathew
 
PPT
19 - Viruses
bykindarspirit
 
PPT
17 - From Gene to Protein
bykindarspirit
 
PPT
Ch 10: Photosynthesis
byveneethmathew
 
PPT
04 carbon and the molecular diversity of life
bykindarspirit
 
PPT
Ch 8: Introduction to Metabolism
byveneethmathew
 
Ch 12: Cell Cycle
byveneethmathew
 
13 meiosis and sexual life cycles
bykindarspirit
 
Ch 11: Cell Communication
byveneethmathew
 
25 lecture history_of_life
byveneethmathew
 
27 lecture bacteria
byveneethmathew
 
Ch 13: Meiosis and Sexual Life Cycles
byveneethmathew
 
18 Regulation of Gene Expression
bykindarspirit
 
21 genomes and their evolution
bykindarspirit
 
20 lecture biotech
byveneethmathew
 
12 the cell cycle
bykindarspirit
 
22 descent with modification a darwinian view
bykindarspirit
 
Ch 7: Membrane Structure and Function
byveneethmathew
 
24 lecture origin_of_species
byveneethmathew
 
23 the evolution of populations
bykindarspirit
 
26 lecture phylogeny
byveneethmathew
 
19 - Viruses
bykindarspirit
 
17 - From Gene to Protein
bykindarspirit
 
Ch 10: Photosynthesis
byveneethmathew
 
04 carbon and the molecular diversity of life
bykindarspirit
 
Ch 8: Introduction to Metabolism
byveneethmathew
 

Viewers also liked

PPT
Cap 12 - Ciclo Celular
byCae Upr Cayey
 
PPT
Biology in Focus - Chapter 12
bympattani
 
PPTX
Dihybrid Crosses, Gene Linkage and Recombination
byStephen Taylor
 
PPT
09 lecture presentation
bylvalera
 
PPT
Chapter 13 Biology 201
bystephaniehudon
 
PPT
2014 plant-meiosis
byAndrew Hutabarat
 
PPTX
Linkage and recombination of gene
byPromila Sheoran
 
PPTX
Genetics chapter 5 part 1
byvanessawhitehawk
 
PDF
Recombination and gene linkage
bypaprescott
 
PPTX
Basics of linkage and recombination
byAyush Jain
 
PPT
15 the chromosomal basis of inheritance
bykindarspirit
 
PPTX
Genetic linkage and crossing over
byDr. Samira Fattah
 
PPTX
Genetics chapter 5 part 2(1)
byvanessawhitehawk
 
PPT
Meiosis and sexual life cycle
byEman Abdallah
 
Cap 12 - Ciclo Celular
byCae Upr Cayey
 
Biology in Focus - Chapter 12
bympattani
 
Dihybrid Crosses, Gene Linkage and Recombination
byStephen Taylor
 
09 lecture presentation
bylvalera
 
Chapter 13 Biology 201
bystephaniehudon
 
2014 plant-meiosis
byAndrew Hutabarat
 
Linkage and recombination of gene
byPromila Sheoran
 
Genetics chapter 5 part 1
byvanessawhitehawk
 
Recombination and gene linkage
bypaprescott
 
Basics of linkage and recombination
byAyush Jain
 
15 the chromosomal basis of inheritance
bykindarspirit
 
Genetic linkage and crossing over
byDr. Samira Fattah
 
Genetics chapter 5 part 2(1)
byvanessawhitehawk
 
Meiosis and sexual life cycle
byEman Abdallah
 

Similar to Ch 15: The Chromosomal Basis of Inheritance

PPTX
Chapter 15 chromosomes
byHeather Fogell
 
PPTX
15 Lecture BIOL 1030-30 Gillette College
bydeskam2
 
PPT
15 chromosomalinheritance text
by1slid
 
PPT
Chapter 15(2)
byktanaka2
 
PPT
CHROMOSOMES CHROMOSOMES CHROMOSOMES CHROMOSOMES.ppt
byNicholaEka
 
PPT
1.AGR 251-Plant Genetics-Chromosomal Basis of inheritence.ppt
byalexander19e71
 
PPT
AP_Bio_Ch_12_15_.ppt
bySaydakramAminjonov
 
PPT
The Chromosomal Basis Of Inheritance
byCrystal Wood
 
PPTX
Genetics-and-Heredity-Intro-
bysherylbadayos
 
PDF
ptani 1iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii...
byVanshTalwar4
 
PPT
2014 sex-linkage
byAndrew Hutabarat
 
PPTX
Lecture 6.pptx
byYacheeShah
 
PPT
603062_chuong 3_Chromosomal inheritance.ppt
byleminh59264
 
PPTX
chromosomal basis of inheritance
byakramsana
 
PPT
Chapter 15: Chromosomal Basis of Inheritance
byAngel Vega
 
PDF
B4FA 2012 Nigeria: Principles of Genetics - Charles Amadi
byb4fa
 
PPT
2014-sex-linkage.ppt
byMAHAZELTEOLOGO3
 
PPT
Chromosomal theory of heredity. Genetics of a sex
byEneutron
 
PPTX
Genetics chapter 3 part 2
byvanessawhitehawk
 
PDF
Power Point Genetika dan Hereditas kelas 9.pdf
byikahasanah6
 
Chapter 15 chromosomes
byHeather Fogell
 
15 Lecture BIOL 1030-30 Gillette College
bydeskam2
 
15 chromosomalinheritance text
by1slid
 
Chapter 15(2)
byktanaka2
 
CHROMOSOMES CHROMOSOMES CHROMOSOMES CHROMOSOMES.ppt
byNicholaEka
 
1.AGR 251-Plant Genetics-Chromosomal Basis of inheritence.ppt
byalexander19e71
 
AP_Bio_Ch_12_15_.ppt
bySaydakramAminjonov
 
The Chromosomal Basis Of Inheritance
byCrystal Wood
 
Genetics-and-Heredity-Intro-
bysherylbadayos
 
ptani 1iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii...
byVanshTalwar4
 
2014 sex-linkage
byAndrew Hutabarat
 
Lecture 6.pptx
byYacheeShah
 
603062_chuong 3_Chromosomal inheritance.ppt
byleminh59264
 
chromosomal basis of inheritance
byakramsana
 
Chapter 15: Chromosomal Basis of Inheritance
byAngel Vega
 
B4FA 2012 Nigeria: Principles of Genetics - Charles Amadi
byb4fa
 
2014-sex-linkage.ppt
byMAHAZELTEOLOGO3
 
Chromosomal theory of heredity. Genetics of a sex
byEneutron
 
Genetics chapter 3 part 2
byvanessawhitehawk
 
Power Point Genetika dan Hereditas kelas 9.pdf
byikahasanah6
 

More from veneethmathew

PPT
19 lecture viruses
byveneethmathew
 
PPT
Ch 6: A Tour of the Cell
byveneethmathew
 
PPT
Ch 5: The Structure and Function of Large Biological Molecules
byveneethmathew
 
PPT
Ch 4: Carbon and Diversity
byveneethmathew
 
PPT
Ch 3: Water and Life
byveneethmathew
 
PPT
Ch 2: The Chemical Context of Life
byveneethmathew
 
PPT
Ch 1: Themes in the Study of Life
byveneethmathew
 
19 lecture viruses
byveneethmathew
 
Ch 6: A Tour of the Cell
byveneethmathew
 
Ch 5: The Structure and Function of Large Biological Molecules
byveneethmathew
 
Ch 4: Carbon and Diversity
byveneethmathew
 
Ch 3: Water and Life
byveneethmathew
 
Ch 2: The Chemical Context of Life
byveneethmathew
 
Ch 1: Themes in the Study of Life
byveneethmathew
 

Ch 15: The Chromosomal Basis of Inheritance

  • 1.
    LECTURE PRESENTATIONS For CAMPBELLBIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick The Chromosomal Basis of Inheritance Chapter 15
  • 2.
    Overview: Locating GenesAlong Chromosomes • Mendel’s “hereditary factors” were genes • Today we can show that genes are located on chromosomes • The location of a particular gene can be seen by tagging isolated chromosomes with a fluorescent dye that highlights the gene © 2011 Pearson Education, Inc.
  • 3.
  • 4.
    Concept 15.1: Mendelianinheritance has its physical basis in the behavior of chromosomes • Mitosis and meiosis were first described in the late 1800s • The chromosome theory of inheritance states: – Mendelian genes have specific loci (positions) on chromosomes – Chromosomes undergo segregation and independent assortment • The behavior of chromosomes during meiosis can account for Mendel’s laws of segregation and independent assortment © 2011 Pearson Education, Inc.
  • 5.
    Figure 15.2 P Generation F1Generation Yellow-round seeds (YYRR) Green-wrinkled seeds (yyrr) × Meiosis Fertilization Gametes Y Y R R YR y y r y r All F1 plants produce yellow-round seeds (YyRr). Meiosis Metaphase I Anaphase I Metaphase II R R R R R R R R R R R R r r r r r r r r r r r r Y Y Y Y Y Y Y Y Y Y Y Y y y y y y y y y y y y y Gametes LAW OF SEGREGATION The two alleles for each gene separate during gamete formation. LAW OF INDEPENDENT ASSORTMENT Alleles of genes on nonhomologous chromosomes assort independently during gamete formation. 1 2 2 1 1 /4 1 /4 1 /4 1 /4YR yr Yr yR F2 Generation 3 3Fertilization recombines the R and r alleles at random. Fertilization results in the 9:3:3:1 phenotypic ratio in the F2 generation. An F1 × F1 cross-fertilization 9 : 3 : 3 : 1 r
  • 6.
    Figure 15.2a P GenerationYellow-round seeds (YYRR) Green-wrinkled seeds (yyrr) × Meiosis Fertilization Gametes Y Y R R YR y y r y r r
  • 7.
    Figure 15.2b F1 Generation AllF1 plants produce yellow-round seeds (YyRr). Meiosis Metaphase I Anaphase I Metaphase II R R R R R R R R R R R R r r r r r r r r r r r r Y Y Y Y Y Y Y Y Y Y Y Y y y y y y y y y y y y y Gametes LAW OF SEGREGATION The two alleles for each gene separate during gamete formation. LAW OF INDEPENDENT ASSORTMENT Alleles of genes on nonhomologous chromosomes assort independently during gamete formation. 1 2 2 1 1 /4 1 /4 1 /4 1 /4YR yr Yr yR
  • 8.
    Figure 15.2c F2 Generation 3Fertilization recombinesthe R and r alleles at random. Fertilization results in the 9:3:3:1 phenotypic ratio in the F2 generation. An F1 × F1 cross-fertilization 9 : 3 : 3 : 1 LAW OF SEGREGATION LAW OF INDEPENDENT ASSORTMENT 3
  • 9.
    Morgan’s Experimental Evidence: ScientificInquiry • The first solid evidence associating a specific gene with a specific chromosome came from Thomas Hunt Morgan, an embryologist • Morgan’s experiments with fruit flies provided convincing evidence that chromosomes are the location of Mendel’s heritable factors © 2011 Pearson Education, Inc.
  • 10.
    Morgan’s Choice ofExperimental Organism • Several characteristics make fruit flies a convenient organism for genetic studies – They produce many offspring – A generation can be bred every two weeks – They have only four pairs of chromosomes © 2011 Pearson Education, Inc.
  • 11.
    • Morgan notedwild type, or normal, phenotypes that were common in the fly populations • Traits alternative to the wild type are called mutant phenotypes © 2011 Pearson Education, Inc.
  • 12.
  • 13.
  • 14.
  • 15.
    Correlating Behavior ofa Gene’s Alleles with Behavior of a Chromosome Pair • In one experiment, Morgan mated male flies with white eyes (mutant) with female flies with red eyes (wild type) – The F1 generation all had red eyes – The F2 generation showed the 3:1 red:white eye ratio, but only males had white eyes • Morgan determined that the white-eyed mutant allele must be located on the X chromosome • Morgan’s finding supported the chromosome theory of inheritance © 2011 Pearson Education, Inc.
  • 16.
    Figure 15.4 All offspring hadred eyes. P Generation F1 Generation F2 Generation F2 Generation F1 Generation P Generation Eggs Eggs Sperm Sperm X X X Y w+ w+ w+ w+ w+ w+ w+ w+ w+ w+ w+ w w w w w w RESULTS EXPERIMENT CONCLUSION
  • 17.
    Figure 15.4a All offspring hadred eyes. P Generation F1 Generation F2 Generation RESULTS EXPERIMENT
  • 18.
  • 19.
    Concept 15.2: Sex-linkedgenes exhibit unique patterns of inheritance • In humans and some other animals, there is a chromosomal basis of sex determination © 2011 Pearson Education, Inc.
  • 20.
    The Chromosomal Basisof Sex • In humans and other mammals, there are two varieties of sex chromosomes: a larger X chromosome and a smaller Y chromosome • Only the ends of the Y chromosome have regions that are homologous with corresponding regions of the X chromosome • The SRY gene on the Y chromosome codes for a protein that directs the development of male anatomical features © 2011 Pearson Education, Inc.
  • 21.
  • 22.
    • Females areXX, and males are XY • Each ovum contains an X chromosome, while a sperm may contain either an X or a Y chromosome • Other animals have different methods of sex determination © 2011 Pearson Education, Inc.
  • 23.
    Figure 15.6 Parents or Sperm or Egg Zygotes (offspring) 44+ XY 44 + XX 22 + X 22 + Y 22 + X 44 + XX 44 + XY 22 + XX 22 + X 76 + ZW 76 + ZZ 32 (Diploid) 16 (Haploid) (a) The X-Y system (b) The X-0 system (c) The Z-W system (d) The haplo-diploid system
  • 24.
    Figure 15.6a Parents or Sperm or Egg Zygotes (offspring) 44+ XY 44 + XX 22 + X 22 + Y 22 + X 44 + XX 44 + XY 22 + XX 22 + X (a) The X-Y system (b) The X-0 system
  • 25.
    Figure 15.6b 76 + ZW 76+ ZZ 32 (Diploid) 16 (Haploid) (c) The Z-W system (d) The haplo-diploid system
  • 26.
    • A genethat is located on either sex chromosome is called a sex-linked gene • Genes on the Y chromosome are called Y-linked genes; there are few of these • Genes on the X chromosome are called X-linked genes © 2011 Pearson Education, Inc.
  • 27.
    Inheritance of X-LinkedGenes • X chromosomes have genes for many characters unrelated to sex, whereas the Y chromosome mainly encodes genes related to sex determination © 2011 Pearson Education, Inc.
  • 28.
    • X-linked genesfollow specific patterns of inheritance • For a recessive X-linked trait to be expressed – A female needs two copies of the allele (homozygous) – A male needs only one copy of the allele (hemizygous) • X-linked recessive disorders are much more common in males than in females © 2011 Pearson Education, Inc.
  • 29.
    Figure 15.7 Eggs EggsEggs Sperm Sperm Sperm (a) (b) (c) XN XN Xn Y XN Xn XN Y XN Xn Xn Y Xn Y XN Y YXn Xn Xn XN XN XN XNXN Xn XN Y XN Y XN Y XN Y Xn Y Xn YXN Xn XN Xn XN Xn XN XN Xn Xn
  • 30.
    • Some disorderscaused by recessive alleles on the X chromosome in humans – Color blindness (mostly X-linked) – Duchenne muscular dystrophy – Hemophilia © 2011 Pearson Education, Inc.
  • 31.
    X Inactivation inFemale Mammals • In mammalian females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development • The inactive X condenses into a Barr body • If a female is heterozygous for a particular gene located on the X chromosome, she will be a mosaic for that character © 2011 Pearson Education, Inc.
  • 32.
    Figure 15.8 Early embryo: Xchromosomes Allele for orange fur Allele for black fur Two cell populations in adult cat: Cell division and X chromosome inactivation Active X Inactive X Active X Black fur Orange fur
  • 33.
  • 34.
    • Each chromosomehas hundreds or thousands of genes (except the Y chromosome) • Genes located on the same chromosome that tend to be inherited together are called linked genes Concept 15.3: Linked genes tend to be inherited together because they are located near each other on the same chromosome © 2011 Pearson Education, Inc.
  • 35.
    How Linkage AffectsInheritance • Morgan did other experiments with fruit flies to see how linkage affects inheritance of two characters • Morgan crossed flies that differed in traits of body color and wing size © 2011 Pearson Education, Inc.
  • 36.
    Figure 15.9-1 P Generation(homozygous) Wild type (gray body, normal wings) b+ b+ vg+ vg+ b b vg vg Double mutant (black body, vestigial wings) EXPERIMENT
  • 37.
    Figure 15.9-2 P Generation(homozygous) Wild type (gray body, normal wings) F1 dihybrid (wild type) TESTCROSS b+ b+ vg+ vg+ b+ b vg+ vg b b vg vg b b vg vg Double mutant (black body, vestigial wings) Double mutant EXPERIMENT
  • 38.
    Figure 15.9-3 P Generation(homozygous) Wild type (gray body, normal wings) F1 dihybrid (wild type) Testcross offspring TESTCROSS b+ b+ vg+ vg+ b+ b vg+ vg b b vg vg b b vg vg Double mutant (black body, vestigial wings) Double mutant Eggs Sperm EXPERIMENT Wild type (gray-normal) Black- vestigial Gray- vestigial Black- normal b+ vg+ bvg b+ vg b vg+ b+ b vg+ vg bb vg vg b+ bvgvg bb vg+ vg bvg
  • 39.
    Figure 15.9-4 P Generation(homozygous) Wild type (gray body, normal wings) F1 dihybrid (wild type) Testcross offspring TESTCROSS b+ b+ vg+ vg+ b+ b vg+ vg b b vg vg b b vg vg Double mutant (black body, vestigial wings) Double mutant Eggs Sperm EXPERIMENT RESULTS PREDICTED RATIOS Wild type (gray-normal) Black- vestigial Gray- vestigial Black- normal b+ vg+ bvg b+ vg b vg+ b+ b vg+ vg bb vg vg b+ bvgvg bb vg+ vg 965 944 206 185 1 1 1 1 1 0 1 0 If genes are located on different chromosomes: If genes are located on the same chromosome and parental alleles are always inherited together: : : : : : : : : : bvg
  • 40.
    • Morgan foundthat body color and wing size are usually inherited together in specific combinations (parental phenotypes) • He noted that these genes do not assort independently, and reasoned that they were on the same chromosome © 2011 Pearson Education, Inc.
  • 41.
    Figure 15.UN01 Most offspring F1dihybrid female and homozygous recessive male in testcross or b+ vg+ b vg b+ vg+ b vg b vg b vg b vg b vg
  • 42.
    • However, nonparentalphenotypes were also produced • Understanding this result involves exploring genetic recombination, the production of offspring with combinations of traits differing from either parent © 2011 Pearson Education, Inc.
  • 43.
    Genetic Recombination andLinkage • The genetic findings of Mendel and Morgan relate to the chromosomal basis of recombination © 2011 Pearson Education, Inc.
  • 44.
    Recombination of UnlinkedGenes: Independent Assortment of Chromosomes • Mendel observed that combinations of traits in some offspring differ from either parent • Offspring with a phenotype matching one of the parental phenotypes are called parental types • Offspring with nonparental phenotypes (new combinations of traits) are called recombinant types, or recombinants • A 50% frequency of recombination is observed for any two genes on different chromosomes © 2011 Pearson Education, Inc.
  • 45.
    Figure 15.UN02 Gametes fromgreen- wrinkled homozygous recessive parent (yyrr) Gametes from yellow-round dihybrid parent (YyRr) Recombinant offspring Parental- type offspring YR yr Yr yR yr YyRr yyrr Yyrr yyRr
  • 46.
    Recombination of LinkedGenes: Crossing Over • Morgan discovered that genes can be linked, but the linkage was incomplete, because some recombinant phenotypes were observed • He proposed that some process must occasionally break the physical connection between genes on the same chromosome • That mechanism was the crossing over of homologous chromosomes © 2011 Pearson Education, Inc. Animation: Crossing Over
  • 47.
    Figure 15.10 Testcross parents Replication ofchromosomes Gray body, normal wings (F1 dihybrid) Black body, vestigial wings (double mutant) Replication of chromosomes Meiosis I Meiosis II Meiosis I and II Recombinant chromosomes Eggs b+ vg+ b vg b+ vg+ b+ vg+ b+ vg+ b+ vg b vg+ b vg b vg b vg b vg b vg b vg b vg b vg b vg b+ vg+ b+ vgb vg b vg+ Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Sperm Parental-type offspring Recombinant offspring Recombination frequency 391 recombinants 2,300 total offspring × 100 = 17%= b+ vg+ b vg+b+ vgb vg b vg b vg b vg b vg b vg
  • 48.
    Figure 15.10a Testcross parents Replication of chromosomes Graybody, normal wings (F1 dihybrid) Black body, vestigial wings (double mutant) Replication of chromosomes Meiosis I Meiosis II Meiosis I and II Recombinant chromosomes Eggs b+ vg+ b vg b+ vg+ b+ vg+ b+ vg+ b+ vg b vg+ b vg b vg b vg b vg b vg b vg b vg b vg b vg b+ vg+ b+ vgb vg b vg+ Sperm b vg
  • 49.
    Figure 15.10b Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal Sperm Parental-typeoffspring Recombinant offspring Recombination frequency 391 recombinants 2,300 total offspring × 100 = 17%= b+ vg+ b vg+ b+ vgb vg b vg b vg b vg b vg b vg Eggs Recombinant chromosomes b+ vg+ b vg b+ vg b vg+
  • 50.
    New Combinations ofAlleles: Variation for Normal Selection • Recombinant chromosomes bring alleles together in new combinations in gametes • Random fertilization increases even further the number of variant combinations that can be produced • This abundance of genetic variation is the raw material upon which natural selection works © 2011 Pearson Education, Inc.
  • 51.
    Mapping the DistanceBetween Genes Using Recombination Data: Scientific Inquiry • Alfred Sturtevant, one of Morgan’s students, constructed a genetic map, an ordered list of the genetic loci along a particular chromosome • Sturtevant predicted that the farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency © 2011 Pearson Education, Inc.
  • 52.
    • A linkagemap is a genetic map of a chromosome based on recombination frequencies • Distances between genes can be expressed as map units; one map unit, or centimorgan, represents a 1% recombination frequency • Map units indicate relative distance and order, not precise locations of genes © 2011 Pearson Education, Inc.
  • 53.
  • 54.
    • Genes thatare far apart on the same chromosome can have a recombination frequency near 50% • Such genes are physically linked, but genetically unlinked, and behave as if found on different chromosomes © 2011 Pearson Education, Inc.
  • 55.
    • Sturtevant usedrecombination frequencies to make linkage maps of fruit fly genes • Using methods like chromosomal banding, geneticists can develop cytogenetic maps of chromosomes • Cytogenetic maps indicate the positions of genes with respect to chromosomal features © 2011 Pearson Education, Inc.
  • 56.
    Figure 15.12 Mutant phenotypes Short aristae Black body Cinnabar eyes Vestigial wings Brown eyes Longaristae (appendages on head) Gray body Red eyes Normal wings Red eyes Wild-type phenotypes 104.567.057.548.50
  • 57.
    Concept 15.4: Alterationsof chromosome number or structure cause some genetic disorders • Large-scale chromosomal alterations in humans and other mammals often lead to spontaneous abortions (miscarriages) or cause a variety of developmental disorders • Plants tolerate such genetic changes better than animals do © 2011 Pearson Education, Inc.
  • 58.
    Abnormal Chromosome Number •In nondisjunction, pairs of homologous chromosomes do not separate normally during meiosis • As a result, one gamete receives two of the same type of chromosome, and another gamete receives no copy © 2011 Pearson Education, Inc.
  • 59.
  • 60.
  • 61.
    Meiosis I Meiosis II Nondisjunction Non- disjunction Gametes Numberof chromosomes Nondisjunction of homo- logous chromosomes in meiosis I (a) Nondisjunction of sister chromatids in meiosis II (b) n + 1 n − 1n + 1 n − 1 n − 1n + 1 n n Figure 15.13-3
  • 62.
    • Aneuploidy resultsfrom the fertilization of gametes in which nondisjunction occurred • Offspring with this condition have an abnormal number of a particular chromosome © 2011 Pearson Education, Inc.
  • 63.
    • A monosomiczygote has only one copy of a particular chromosome • A trisomic zygote has three copies of a particular chromosome © 2011 Pearson Education, Inc.
  • 64.
    • Polyploidy isa condition in which an organism has more than two complete sets of chromosomes – Triploidy (3n) is three sets of chromosomes – Tetraploidy (4n) is four sets of chromosomes • Polyploidy is common in plants, but not animals • Polyploids are more normal in appearance than aneuploids © 2011 Pearson Education, Inc.
  • 65.
    Alterations of ChromosomeStructure • Breakage of a chromosome can lead to four types of changes in chromosome structure – Deletion removes a chromosomal segment – Duplication repeats a segment – Inversion reverses orientation of a segment within a chromosome – Translocation moves a segment from one chromosome to another © 2011 Pearson Education, Inc.
  • 66.
    Figure 15.14 (a) Deletion (b)Duplication (c) Inversion (d) Translocation A deletion removes a chromosomal segment. A duplication repeats a segment. An inversion reverses a segment within a chromosome. A translocation moves a segment from one chromosome to a nonhomologous chromosome. A B C D E F G H A B C E F G H A B C D E F G H A B C D E F G HB C A B C D E F G H A D C B E F G H A B C D E F G H M N O P Q R GM N O C HFED A B P Q R
  • 67.
    Figure 15.14a (a) Deletion (b)Duplication A deletion removes a chromosomal segment. A duplication repeats a segment. BA C D E F G H A B C D E F G H A B C D E F G HB C A B C E F G H
  • 68.
    Figure 15.14b (c) Inversion (d)Translocation An inversion reverses a segment within a chromosome. A translocation moves a segment from one chromosome to a nonhomologous chromosome. A B C D E F G H A D C B E F G H A B C D E F G H M N O P Q R GM N O C HFED A B P Q R
  • 69.
    Human Disorders Dueto Chromosomal Alterations • Alterations of chromosome number and structure are associated with some serious disorders • Some types of aneuploidy appear to upset the genetic balance less than others, resulting in individuals surviving to birth and beyond • These surviving individuals have a set of symptoms, or syndrome, characteristic of the type of aneuploidy © 2011 Pearson Education, Inc.
  • 70.
    Down Syndrome (Trisomy21) • Down syndrome is an aneuploid condition that results from three copies of chromosome 21 • It affects about one out of every 700 children born in the United States • The frequency of Down syndrome increases with the age of the mother, a correlation that has not been explained © 2011 Pearson Education, Inc.
  • 71.
  • 72.
  • 73.
  • 74.
    Aneuploidy of SexChromosomes • Nondisjunction of sex chromosomes produces a variety of aneuploid conditions • Klinefelter syndrome is the result of an extra chromosome in a male, producing XXY individuals • Monosomy X, called Turner syndrome, produces X0 females, who are sterile; it is the only known viable monosomy in humans © 2011 Pearson Education, Inc.
  • 75.
    Disorders Caused byStructurally Altered Chromosomes • The syndrome cri du chat (“cry of the cat”), results from a specific deletion in chromosome 5 • A child born with this syndrome is mentally retarded and has a catlike cry; individuals usually die in infancy or early childhood • Certain cancers, including chronic myelogenous leukemia (CML), are caused by translocations of chromosomes © 2011 Pearson Education, Inc.
  • 76.
    Figure 15.16 Normal chromosome9 Normal chromosome 22 Reciprocal translocation Translocated chromosome 9 Translocated chromosome 22 (Philadelphia chromosome)
  • 77.
    Concept 15.5: Someinheritance patterns are exceptions to standard Mendelian inheritance • There are two normal exceptions to Mendelian genetics • One exception involves genes located in the nucleus, and the other exception involves genes located outside the nucleus • In both cases, the sex of the parent contributing an allele is a factor in the pattern of inheritance © 2011 Pearson Education, Inc.
  • 78.
    Genomic Imprinting • Fora few mammalian traits, the phenotype depends on which parent passed along the alleles for those traits • Such variation in phenotype is called genomic imprinting • Genomic imprinting involves the silencing of certain genes that are “stamped” with an imprint during gamete production © 2011 Pearson Education, Inc.
  • 79.
    Figure 15.17 (a) Homozygote Paternal chromosome Maternal chromosome NormalIgf2 allele is expressed. Normal Igf2 allele is not expressed. Normal-sized mouse (wild type) Mutant Igf2 allele inherited from mother Mutant Igf2 allele inherited from father Normal-sized mouse (wild type) Dwarf mouse (mutant) Normal Igf2 allele is expressed. Mutant Igf2 allele is expressed. Mutant Igf2 allele is not expressed. Normal Igf2 allele is not expressed. (b) Heterozygotes
  • 80.
    Figure 15.17a (a) Homozygote Paternal chromosome Maternal chromosome NormalIgf2 allele is expressed. Normal Igf2 allele is not expressed. Normal-sized mouse (wild type)
  • 81.
    Figure 15.17b Mutant Igf2allele inherited from mother Mutant Igf2 allele inherited from father Normal-sized mouse (wild type) Dwarf mouse (mutant) Normal Igf2 allele is expressed. Mutant Igf2 allele is expressed. Mutant Igf2 allele is not expressed. Normal Igf2 allele is not expressed. (b) Heterozygotes
  • 82.
    • It appearsthat imprinting is the result of the methylation (addition of —CH3) of cysteine nucleotides • Genomic imprinting is thought to affect only a small fraction of mammalian genes • Most imprinted genes are critical for embryonic development © 2011 Pearson Education, Inc.
  • 83.
    Inheritance of OrganelleGenes • Extranuclear genes (or cytoplasmic genes) are found in organelles in the cytoplasm • Mitochondria, chloroplasts, and other plant plastids carry small circular DNA molecules • Extranuclear genes are inherited maternally because the zygote’s cytoplasm comes from the egg • The first evidence of extranuclear genes came from studies on the inheritance of yellow or white patches on leaves of an otherwise green plant © 2011 Pearson Education, Inc.
  • 84.
  • 85.
    • Some defectsin mitochondrial genes prevent cells from making enough ATP and result in diseases that affect the muscular and nervous systems – For example, mitochondrial myopathy and Leber’s hereditary optic neuropathy © 2011 Pearson Education, Inc.
  • 86.
    Figure 15.UN03 P generation gametes SpermEgg This F1 cell has 2n = 6 chromo- somes and is heterozygous for all six genes shown (AaBbCcDdEeFf). Red = maternal; blue = paternal. Each chromosome has hundreds or thousands of genes. Four (A, B, C, F) are shown on this one. The alleles of unlinked genes are either on separate chromosomes (such as d and e) or so far apart on the same chromosome (c and f) that they assort independently. Genes on the same chromo- some whose alleles are so close together that they do not assort independently (such as a, b, and c) are said to be genetically linked. D C B A F E d c b a f e D C B A F e d E f c ba
  • 87.
  • 88.
  • 89.

Editor's Notes

  • #4 Figure 15.1 Where are Mendel’s hereditary factors located in the cell?
  • #6 Figure 15.2 The chromosomal basis of Mendel’s laws.
  • #7 Figure 15.2 The chromosomal basis of Mendel’s laws.
  • #8 Figure 15.2 The chromosomal basis of Mendel’s laws.
  • #9 Figure 15.2 The chromosomal basis of Mendel’s laws.
  • #13 Figure 15.3 Morgan’s first mutant.
  • #14 Figure 15.3 Morgan’s first mutant.
  • #15 Figure 15.3 Morgan’s first mutant.
  • #17 Figure 15.4 Inquiry: In a cross between a wild-type female fruit fly and a mutant white-eyed male, what color eyes will the F1 and F2 offspring have?
  • #18 Figure 15.4 Inquiry: In a cross between a wild-type female fruit fly and a mutant white-eyed male, what color eyes will the F1 and F2 offspring have?
  • #19 Figure 15.4 Inquiry: In a cross between a wild-type female fruit fly and a mutant white-eyed male, what color eyes will the F1 and F2 offspring have?
  • #22 Figure 15.5 Human sex chromosomes.
  • #24 Figure 15.6 Some chromosomal systems of sex determination.
  • #25 Figure 15.6 Some chromosomal systems of sex determination.
  • #26 Figure 15.6 Some chromosomal systems of sex determination.
  • #30 Figure 15.7 The transmission of X-linked recessive traits.
  • #33 Figure 15.8 X inactivation and the tortoiseshell cat.
  • #34 Figure 15.8 X inactivation and the tortoiseshell cat.
  • #37 Figure 15.9 Inquiry: How does linkage between two genes affect inheritance of characters?
  • #38 Figure 15.9 Inquiry: How does linkage between two genes affect inheritance of characters?
  • #39 Figure 15.9 Inquiry: How does linkage between two genes affect inheritance of characters?
  • #40 Figure 15.9 Inquiry: How does linkage between two genes affect inheritance of characters?
  • #42 Figure 15.UN01 In-text figure, p. 294
  • #46 Figure 15.UN02 In-text figure, p. 294
  • #48 Figure 15.10 Chromosomal basis for recombination of linked genes.
  • #49 Figure 15.10 Chromosomal basis for recombination of linked genes.
  • #50 Figure 15.10 Chromosomal basis for recombination of linked genes.
  • #54 Figure 15.11 Research Method: Constructing a Linkage Map
  • #57 Figure 15.12 A partial genetic (linkage) map of a Drosophila chromosome.
  • #60 Figure 15.13 Meiotic nondisjunction.
  • #61 Figure 15.13 Meiotic nondisjunction.
  • #62 Figure 15.13 Meiotic nondisjunction.
  • #67 Figure 15.14 Alterations of chromosome structure.
  • #68 Figure 15.14 Alterations of chromosome structure.
  • #69 Figure 15.14 Alterations of chromosome structure.
  • #72 Figure 15.15 Down syndrome.
  • #73 Figure 15.15 Down syndrome.
  • #74 Figure 15.15 Down syndrome.
  • #77 Figure 15.16 Translocation associated with chronic myelogenous leukemia (CML).
  • #80 Figure 15.17 Genomic imprinting of the mouse Igf2 gene.
  • #81 Figure 15.17 Genomic imprinting of the mouse Igf2 gene.
  • #82 Figure 15.17 Genomic imprinting of the mouse Igf2 gene.
  • #85 Figure 15.18 Variegated leaves from English holly (Ilex aquifolium).
  • #87 Figure 15.UN03 In-text figure, p. 294
  • #88 Figure 15.UN04 In-text figure, p. 294
  • #89 Figure 15.UN05 In-text figure, p. 294
  • #90 Figure 15.UN06 In-text figure, p. 294