KEY CONCEPTS
15.1 Morgan showed that Mendelian inheritance has its physical
basis in the behavior of chromosomes: Scientific inquiry
15.2 Sex-linked genes exhibit unique patterns of inheritance
15.3 Linked genes tend to be inherited together because they are located near each other on the same chromosome
15.4 Alterations of chromosome number or structure cause
some genetic disorders
15.5 Some inheritance patterns are exceptions to standard
Mendelian inheritance
Chromosomal Basis of Inheritance
Be familiar with patterns of inheritance for autosomal and sex linked genes
Understand the concept of “Linked Genes”
Understand how traits affected by incomplete dominance and codominance differ from autosomal dominant and autosomal recessive traits
Understand how nondisjunction of chromosomes can lead to disorders.
Linked genes: are those that reside on the same chromosome and tend to be inherited together
Humans have 23 pairs of chromosomes
Autosomal genes reside on the autosomal chromosomes (pairs 1-22)
Sex-linked genes are found on the sex chromosomes
(pair 23, usually on the X)
Autosomal genes are usually represented by a pair of alleles
The phenotype of the gene reflects the dominant or recessive relationship of the alleles.
Most autosomal genetic diseases are autosomal recessive meaning the individual need to be homozygous recessive to exhibit the condition
(example: cystic fibrosis) Production of abnormmaly thick mucus. Leading to the blockage of panreatic duct, intestines and respiratory infection.
Huntington’s disease is an autosomal dominant disorder meaning that is a single Huntingtons allele is inherited, the individual will have the disease.
Some alleles do not show a dominance hierarchy
Incomplete dominance: the phenotype of a heterozygous genotype is intermediate in appearance
Codominance: each allele in the genotype for a particular gene will be expressed in the phenotype
Males and females differ in their sex chromosome combination
(females XX; males XY)
Because the X contains genes and the Y “does not”, inheritance patterns of sex-linked genes vary between the sexes
recessive traits more prevalent in males
Genetic disorders can also occur due to errors in the number of inherited chromosomes
This condition arises through a problem that occurs during meiosis
Although female mammals, including humans, inherit two X chromosomes, one X chromosome in each cell becomes almost completely inactivated during embryonic development.
Barr body
Nondisjunction:
Leads to aneuploidy:
Aneuploidy: is the condition of having less than or more than the normal diploid number of chromosomes, and is the most frequently observed type of cytogenetic abnormality.
Mendelian inheritance has its physical basis in the behavior of chromosomes during sexual life cycles.
Morgan traced a gene to a specific chromosome.
Sex-linked genes have unique patterns of inheritance.
Alterations of chromosome numbers or structure cause some genetic disorders.
Linked genes tend to be inherited together because they are located on the same chromosome.
Independent assortment of chromosomes and crossing over produce genetic variation (recombinants)
Geneticists can use recombination data to map a chromosomes genetic loci.
Chromosomal basis for sex is dependent upon the organism.
Chromosomal Basis of Inheritance
Be familiar with patterns of inheritance for autosomal and sex linked genes
Understand the concept of “Linked Genes”
Understand how traits affected by incomplete dominance and codominance differ from autosomal dominant and autosomal recessive traits
Understand how nondisjunction of chromosomes can lead to disorders.
Linked genes: are those that reside on the same chromosome and tend to be inherited together
Humans have 23 pairs of chromosomes
Autosomal genes reside on the autosomal chromosomes (pairs 1-22)
Sex-linked genes are found on the sex chromosomes
(pair 23, usually on the X)
Autosomal genes are usually represented by a pair of alleles
The phenotype of the gene reflects the dominant or recessive relationship of the alleles.
Most autosomal genetic diseases are autosomal recessive meaning the individual need to be homozygous recessive to exhibit the condition
(example: cystic fibrosis) Production of abnormmaly thick mucus. Leading to the blockage of panreatic duct, intestines and respiratory infection.
Huntington’s disease is an autosomal dominant disorder meaning that is a single Huntingtons allele is inherited, the individual will have the disease.
Some alleles do not show a dominance hierarchy
Incomplete dominance: the phenotype of a heterozygous genotype is intermediate in appearance
Codominance: each allele in the genotype for a particular gene will be expressed in the phenotype
Males and females differ in their sex chromosome combination
(females XX; males XY)
Because the X contains genes and the Y “does not”, inheritance patterns of sex-linked genes vary between the sexes
recessive traits more prevalent in males
Genetic disorders can also occur due to errors in the number of inherited chromosomes
This condition arises through a problem that occurs during meiosis
Although female mammals, including humans, inherit two X chromosomes, one X chromosome in each cell becomes almost completely inactivated during embryonic development.
Barr body
Nondisjunction:
Leads to aneuploidy:
Aneuploidy: is the condition of having less than or more than the normal diploid number of chromosomes, and is the most frequently observed type of cytogenetic abnormality.
Mendelian inheritance has its physical basis in the behavior of chromosomes during sexual life cycles.
Morgan traced a gene to a specific chromosome.
Sex-linked genes have unique patterns of inheritance.
Alterations of chromosome numbers or structure cause some genetic disorders.
Linked genes tend to be inherited together because they are located on the same chromosome.
Independent assortment of chromosomes and crossing over produce genetic variation (recombinants)
Geneticists can use recombination data to map a chromosomes genetic loci.
Chromosomal basis for sex is dependent upon the organism.
Allelic and Non-allelic interactions : Complete dominance; Incomplete dominance-in Four O'clock plant, Mirabilis jalapa and Snapdragon, Antirrhinum majus ; Co-dominance- MN blood group, AB blood group, Roan coat colour in shorthorn breed of cattle; Inheritance of Comb pattern in Poultry; Epistasis -Dominant - Fruit colour in Summer squash, Recessive - Coat colour in mice; Complementary gene interaction -Purple flower colour in Sweet pea (Lathyrus odoratus)
Codominance is the situation when the effect of both genes are observed. This presentation describes how codominant traits work to determine human blood types and flower coloring .
MENDELE'S EXPERIMNENT AND TERMINOLOGY, BY MR. DINABANDHU BARAD, MSC TUTOR, DEPARTMENT OF PEDIATRIC, SUM NURSING COLLEGE, SIKSHA 'O' ANUSANDHAN DEEMED TO BE UNIVERSITY
KEY CONCEPTS
10.1 Photosynthesis converts light energy to the chemical energy of food
10.2 The light reactions convert solar energy to the chemical energy of ATP and NADPH
10.3 The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar
10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates
KEY CONCEPTS
6.1 Biologists use microscopes and the tools of biochemistry to
study cells
6.2 Eukaryotic cells have internal membranes that
compartmentalize their functions
6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes
6.4 The endomembrane system regulates protein traffic and
performs metabolic functions in the cell
6.5 Mitochondria and chloroplasts change energy from one form to another
6.6 The cytoskeleton is a network of fibers that organizes structures and activities in the cell
6.7 Extracellular components and connections between cells help coordinate cellular activities
Allelic and Non-allelic interactions : Complete dominance; Incomplete dominance-in Four O'clock plant, Mirabilis jalapa and Snapdragon, Antirrhinum majus ; Co-dominance- MN blood group, AB blood group, Roan coat colour in shorthorn breed of cattle; Inheritance of Comb pattern in Poultry; Epistasis -Dominant - Fruit colour in Summer squash, Recessive - Coat colour in mice; Complementary gene interaction -Purple flower colour in Sweet pea (Lathyrus odoratus)
Codominance is the situation when the effect of both genes are observed. This presentation describes how codominant traits work to determine human blood types and flower coloring .
MENDELE'S EXPERIMNENT AND TERMINOLOGY, BY MR. DINABANDHU BARAD, MSC TUTOR, DEPARTMENT OF PEDIATRIC, SUM NURSING COLLEGE, SIKSHA 'O' ANUSANDHAN DEEMED TO BE UNIVERSITY
KEY CONCEPTS
10.1 Photosynthesis converts light energy to the chemical energy of food
10.2 The light reactions convert solar energy to the chemical energy of ATP and NADPH
10.3 The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar
10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates
KEY CONCEPTS
6.1 Biologists use microscopes and the tools of biochemistry to
study cells
6.2 Eukaryotic cells have internal membranes that
compartmentalize their functions
6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes
6.4 The endomembrane system regulates protein traffic and
performs metabolic functions in the cell
6.5 Mitochondria and chloroplasts change energy from one form to another
6.6 The cytoskeleton is a network of fibers that organizes structures and activities in the cell
6.7 Extracellular components and connections between cells help coordinate cellular activities
KEY CONCEPTS
4.1 Organic chemistry is the study of carbon compounds
4.2 Carbon atoms can form diverse molecules by bonding to four other atoms
4.3 A few chemical groups are key to molecular function
Chapter 50: Sensory and Motor MechansimsAngel Vega
KEY CONCEPTS
50.1 Sensory receptors transduce stimulus energy and transmit signals to the central nervous system
50.2 The mechanoreceptors responsible for hearing and
equilibrium detect moving fluid or settling particles
50.3 The diverse visual receptors of animals depend on light-
absorbing pigments
50.4 The senses of taste and smell rely on similar sets of sensory receptors
50.5 The physical interaction of protein filaments is required for muscle function
50.6 Skeletal systems transform muscle contraction into
locomotion
KEY CONCEPTS
9.1 Catabolic pathways yield energy by oxidizing organic
fuels
9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
9.3 After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules
9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
9.5 Fermentation and anaerobic respiration enable cells to
produce ATP without the use of oxygen
9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways
KEY CONCEPTS
14.1 Mendel used the scientific approach to identify two laws of inheritance
14.2 Probability laws govern Mendelian inheritance
14.3 Inheritance patterns are often more complex than predicted by simple Mendelian genetics
14.4 Many human traits follow Mendelian patterns of
inheritance
KEY CONCEPTS
11.1 External signals are converted to responses within the cell
11.2 Reception: A signaling molecule binds to a receptor protein, causing it to change shape
11.3 Transduction: Cascades of molecular interactions relay
signals from receptors to target molecules in the cell
11.4 Response: Cell signaling leads to regulation of transcription or cytoplasmic activities
11.5 Apoptosis integrates multiple cell-signaling pathways
KEY CONCEPTS
43.1 In innate immunity, recognition and response rely on traits
common to groups of pathogens
43.2 In adaptive immunity, receptors provide pathogen-specific
recognition
43.3 Adaptive immunity defends against infection of body fluids and body cells
43.4 Disruptions in immune system function can elicit or exacerbate disease
KEY CONCEPTS
13.1 Offspring acquire genes from parents by inheriting
chromosomes
13.2 Fertilization and meiosis alternate in sexual life cycles
13.3 Meiosis reduces the number of chromosome sets from diploid to haploid
13.4 Genetic variation produced in sexual life cycles contributes to evolution
KEY CONCEPTS
12.1 Most cell division results in genetically identical daughter cells
12.2 The mitotic phase alternates with interphase in the cell cycle
12.3 The eukaryotic cell cycle is regulated by a molecular
control system
KEY CONCEPTS
48.1 Neuron structure and organization reflect function in information transfer
48.2 Ion pumps and ion channels establish the resting potential of a neuron
48.3 Action potentials are the signals conducted by axons
48.4 Neurons communicate with other cells at synapses
KEY CONCEPTS
45.1 Hormones and other signaling molecules bind to target
receptors, triggering specific response pathways
45.2 Feedback regulation and coordination with the nervous system are common in endocrine signaling
45.3 Endocrine glands respond to diverse stimuli in regulating homeostasis, development,
and behavior
Bio chapter 2: A Chemical Connection to BiologyAngel Vega
KEY CONCEPTS
2.1 Matter consists of chemical elements in pure form and
in combinations called compounds
2.2 An element’s properties depend on the structure of its atoms
2.3 The formation and function of molecules depend on chemical bonding between atoms
2.4 Chemical reactions make and break chemical bonds
Chapter 16: Molecular Basis of InheritanceAngel Vega
KEY CONCEPTS
16.1 DNA is the genetic material
16.2 Many proteins work together in
DNA replication and repair
16.3 A chromosome consists of a DNA molecule packed together with proteins
KEY CONCEPTS
18.1 Bacteria often respond to environmental change by
regulating transcription
18.2 Eukaryotic gene expression is regulated at many stages
18.3 Noncoding RNAs play multiple roles in controlling gene
expression
18.4 A program of differential gene expression leads to the different cell types in a multicellular organism
18.5 Cancer results from genetic changes that affect cell cycle control
KEY CONCEPTS
5.1 Macromolecules are polymers, built from monomers
5.2 Carbohydrates serve as fuel and building material
5.3 Lipids are a diverse group of hydrophobic molecules
5.4 Proteins include a diversity of structures, resulting in a wide range of functions
5.5 Nucleic acids store, transmit, and help express hereditary
information
5.6 Genomics and proteomics have transformed biological inquiry and applications
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
2. Mendelian inheritance has its physical
basis in the behavior of chromosomes
• Several researchers proposed in the early 1900s
that genes are located on chromosomes
• The behavior of chromosomes during meiosis
was said to account for Mendel’s laws of
segregation and independent assortment
• The location of a particular gene can be seen by
tagging isolated chromosomes with a
fluorescent dye that highlights the gene
4. • The chromosome theory of inheritance states that:
– Mendelian genes have specific loci (positions) on
chromosomes
– It is the chromosomes that undergo segregation and
independent assortment
• Biologists began to see parallels between the behavior
of Mendel’s proposed hereditary factors and
chromosomes
• Around 1902, Sutton and Boveri and others
independently noted the parallels and the
chromosome theory of inheritance began
to form
5. Figure 15.2
P Generation
F1 Generation
Yellow-round
seeds
(YYRR)
Gametes
Meiosis
Fertilization
Green-wrinkled
seeds (yyrr)
Meiosis
Metaphase
I
Anaphase I
Metaphase
II
All F1 plants produce
yellow-round seeds (YyRr).
LAW OF
SEGREGATION
The two alleles for each
gene separate.
LAW OF INDEPENDENT
ASSORTMENT Alleles of
genes on nonhomologous
chromosomes assort
independently.
Y
Y
Y
Y
R R
R R
R R
R
y
y
y
y y
Y
r
r
r
rr
r r
Y Y
Y Y
YY
y y
y y
y y
RR
R R
r r
r r
rr rr
Y Y Y Y
R R R R
YR yr Yr yR1
4
1
4
1
4
1
4
F2 Generation
Fertilization
recombines the
R and r alleles at random.
An F1 × F1 cross-fertilization Fertilization results
in the 9:3:3:1
phenotypic ratio in
the F2 generation.
9 : 3 : 3 : 1
1
2 2
1
3
3
y
y y y
6. Morgan’s Experimental Evidence: Scientific Inquiry
• The first solid evidence associating a specific
gene with a 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
• Morgan noted wild type, or normal, phenotypes
that were common in the fly populations
• Traits alternative to the wild type are called
mutant phenotypes
12. Figure 15.7
(a)
(b) (c)
Sperm
Sperm Sperm
Eggs
Eggs Eggs
XN
XN Xn
Y
XN
Xn
XN
Xn
XN
Y
XN
Y
XN
Y
Xn
Y
XN
Y
Xn
Y
XN
Y Xn
Y
XN
XN
XN
Xn
XN
Xn
XN
Xn
XN
Xn
Xn
Xn
XN
XN
XN
XN
Xn
XN
Xn
Xn
Xn
Y
YY
X-linked genes
produce different
phenotypic ratios in
males and females
13. • Some disorders caused by recessive alleles on
the X chromosome in humans:
– Color blindness
– Duchenne muscular dystrophy
– Hemophilia
14. 1. In cats, a sex-linked gene affects coat color. The O allele produces an
enzyme that converts eumelanin, a black or brown pigment, into
phaeomelanin, an orange pigment. The o allele is recessive to O and
produces a defective enzyme, one that does not convert eumelanin into
phaeomelanin. Which of the following statements is/are accurate?
a. The phenotype of o-Y males is black/brown because the
nonfunctional
allele o does not convert eumelanin into phaeomelanin.
b. The phenotype of OO and Oo males is orange because the
functional allele O converts eumelanin into phaeomelanin.
c. The phenotype of Oo males is mixed orange and black/brown
because the functional allele O converts eumelanin into
phaeomelanin in some cell groups (orange) and because in other
cell groups the nonfunctional allele o does not convert eumelanin
into phaeomelanin.
d. The phenotype of O-Y males is orange because the nonfunctional
allele O does not convert eumelanin into phaeomelanin, while the
phenotype of o-Y males is black/brown because the functional allele
o converts eumelanin into phaeomelanin.
15. 1. In cats, a sex-linked gene affects coat color. The O allele produces an
enzyme that converts eumelanin, a black or brown pigment, into
phaeomelanin, an orange pigment. The o allele is recessive to O and
produces a defective enzyme, one that does not convert eumelanin into
phaeomelanin. Which of the following statements is/are accurate?
a. The phenotype of o-Y males is black/brown because the
nonfunctional
allele o does not convert eumelanin into phaeomelanin.
b. The phenotype of OO and Oo males is orange because the
functional allele O converts eumelanin into phaeomelanin.
c. The phenotype of Oo males is mixed orange and black/brown
because the functional allele O converts eumelanin into
phaeomelanin in some cell groups (orange) and because in other
cell groups the nonfunctional allele o does not convert eumelanin
into phaeomelanin.
d. The phenotype of O-Y males is orange because the nonfunctional
allele O does not convert eumelanin into phaeomelanin, while the
phenotype of o-Y males is black/brown because the functional allele
o converts eumelanin into phaeomelanin.
16. X inactivation in Female Mammals
• Dosage compensation from having an additional
X-chromosome occurs in the female in mammals
by inactivating > 90 % of the genes on one X
• In mammalian females, one of the two X
chromosomes in each cell is randomly
inactivated during embryonic development
(called Barr body)
• If a female is heterozygous for a particular gene
located on the X chromosome, she will be a
mosaic for that character
17. Figure 15.8
X chromosomes
Allele for
orange fur
Allele for
black fur
Cell division and
X chromosome
inactivation
Early embryo:
Two cell
populations
in adult cat:
Active X
Inactive
X
Black fur Orange fur
Active X
18. 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
• Aneuploidy results from the fertilization of
gametes in which non-disjunction occurred
• Offspring with this condition have an abnormal
number of a particular chromosome
19. Figure 15.13-3
Meiosis I
Meiosis II
Nondisjunction
Non-
disjunction
Gametes
Number of chromosomes
(a) Nondisjunction of homo-
logous chromosomes in
meiosis I
(b) Nondisjunction of sister
chromatids in meiosis II
n + 1 n + 1 n + 1 n nn − 1 n − 1 n − 1
20. • A trisomic zygote has three copies of a particular
chromosome
• A monosomic zygote has only one copy of a
particular chromosome
• Polyploidy is a condition in which an organism has
more than two complete sets of chromosomes
22. 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 a segment within a chromosome
– Translocation moves a segment from one non-
homologous chromosome to another
23. Figure 15.14
(a) Deletion (c) Inversion
(b) Duplication (d) Translocation
A deletion removes a
chromosomal segment.
An inversion reverses a
segment within a chromosome.
A duplication repeats
a segment. 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 B C D E F G H
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
M N O C D E F G H A B P Q R
24. 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
25. 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
27. 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
28.
29. Disorders Caused by Structurally Altered
Chromosomes
• One 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
32. 2. Triploid species are usually sterile (unable to
reproduce), whereas tetraploids are often fertile. Which of
the following is likely a good explanation of these facts?
(Hint: Synapsis.)
a. In mitosis, some chromosomes in triploids have no
partner at synapsis, but chromosomes in tetraploids
do have partners.
b. In meiosis, some chromosomes in triploids have no
partner at synapsis, but chromosomes in tetraploids
do have partners.
c. In mitosis, some chromosomes in tetraploids have no
partner at synapsis, but chromosomes in triploids do
have partners.
d. In meiosis, some chromosomes in tetraploids have no
partner at synapsis, but chromosomes in triploids do
have partners.
33. 2. Triploid species are usually sterile (unable to
reproduce), whereas tetraploids are often fertile. Which of
the following is likely a good explanation of these facts?
(Hint: Synapsis.)
a. In mitosis, some chromosomes in triploids have no
partner at synapsis, but chromosomes in tetraploids
do have partners.
b. In meiosis, some chromosomes in triploids have no
partner at synapsis, but chromosomes in tetraploids
do have partners.
c. In mitosis, some chromosomes in tetraploids have no
partner at synapsis, but chromosomes in triploids do
have partners.
d. In meiosis, some chromosomes in tetraploids have no
partner at synapsis, but chromosomes in triploids do
have partners.
34. 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
35. 3. Which of the following is a type of
chromosomal alteration that differ from all
of the others?
a. aneuploidy
b. polyploidy
c. triploidy
d. tetraploidy
e. octaploidy
36. 3. Which of the following is a type of
chromosomal alteration that differ from all
of the others?
a. aneuploidy
b. polyploidy
c. triploidy
d. tetraploidy
e. octaploidy
37. Figure 15.UN02
Gametes from yellow-round
dihybrid parent (YyRr)
Gametes from
testcross
homozygous
recessive
parent (yyrr)
Parental-
type
offspring
Recombinant
offspring
yyRrYyRr Yyrryyrr
YR yr Yr yR
yr
Ratio of 1:1:1:1
For independent
assortment
38. • Each chromosome has hundreds or thousands
of genes
• Genes located on the same chromosome that
tend to be inherited together are called linked
genes
• 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
39. Figure 15.9
Experiment
Results
P Generation
(homozygous)
Wild type (gray
body, normal wings)
Double mutant
(black body, vestigial wings)
F1 dihybrid testcross
Wild-type F1 dihybrid
(gray body, normal wings)
Homozygous
recessive (black
body, vestigial wings)
Testcross
offspring Eggs
Sperm
Wild type
(gray-normal)
Black-
vestigial
Gray-
vestigial
Black-
normal
b+
vg+
b vg b+
vg b vg+
b vg
b+
b vg+
vg b b vg vg b+
b vg vg b b vg+
vg
b+
b+
vg+
vg+
b+
b vg+
vg
b b vg vg
b b vg vg
PREDICTED RATIOS
Genes on different
chromosomes:
Genes on the same
chromosome:
1 : 1 : 1 : 1
1 : 1 : 0 : 0
965 : 944 : 206 : 185
40. • From the results, Morgan reasoned that body color
and wing size are usually inherited together in
specific combinations (parental phenotypes)
because the genes are on the same chromosome
• However, nonparental phenotypes were also
produced (non-parental = recombinant)
• Understanding this result involves exploring genetic
recombination, production of offspring with
combinations of traits differing from either parent
41. 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
42. Recombination of Linked Genes:
Crossing Over
• Morgan discovered that genes can be linked,
but the linkage was incomplete, as evident from
recombinant phenotypes
• Morgan proposed that some process must
sometimes break the physical connection
between genes on the same chromosome
• That mechanism was the crossing over of
homologous chromosomes
43. Figure 15.10 P generation
(homozygous)
Wild type (gray body,
normal wings)
b+
vg+
Double mutant (black body,
vestigial wings)
Wild-type F1
dihybrid (gray body,
normal wings)
F1 dihybrid
testcross
Homozygous recessive
(black body,
vestigial wings)
Replication of
chromosomes
Meiosis I
Meiosis I and II
Meiosis II
Replication of
chromosomes
Recombinant
chromosomes
Eggs
Testcross
offspring
Parental-type
offspring
Recombinant
offspring
Recombination
frequency
391 recombinants
2,300 total offspring
× 100 = 17%=
Sperm
965
Wild type
(gray-normal)
944
Black-
vestigial
206
Gray-
vestigial
185
Black-
normal
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 vg
b vg
b+
vg
b+
vg
b vg+
b vg+
b vg
b vgb vgb vgb vg
b vgb+
vg+
b+
vg b vg+
44. Linkage Mapping: 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
45. • 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
47. • 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
48. Figure 15.12
Mutant phenotypes
Wild-type phenotypes
Short
aristae
Maroon
eyes
Black
body
Cinnabar
eyes
Vestigial
wings
Down-
curved
wings
Brown
eyes
Long
aristae
(appendages
on head)
Red
eyes
Gray
body
Red
eyes
Normal
wings
Normal
wings
Red
eyes
0 16.5 48.5 57.5 67.0 75.5 104.5
49. Some inheritance patterns are
exceptions to the standard
chromosome theory
• 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
50. 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
51. Figure 15.17
Normal Igf2 allele
is expressed.
Normal Igf2 allele
is expressed.
Normal Igf2 allele
is not expressed.
Normal Igf2 allele
is not expressed.
Mutant Igf2 allele
is not expressed.
Mutant Igf2 allele
is expressed.
Mutant Igf2 allele
inherited from mother
Mutant Igf2 allele
inherited from father
Normal-sized mouse
(wild type)
Normal-sized mouse (wild type) Dwarf mouse (mutant)
Paternal
chromosome
Maternal
chromosome
(a) Homozygote
(b) Heterozygotes
52. • 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
53. Inheritance of Organelle Genes
• Extranuclear genes are genes found in organelles in
the cytoplasm
• The inheritance of traits controlled by extranuclear
genes depends on the maternal parent 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
Figure 15.1 Where are Mendel’s hereditary factors located in the cell?
Figure 15.2 The chromosomal basis of Mendel’s laws
Figure 15.3 Morgan’s first mutant
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?
Figure 15.7 The transmission of X-linked recessive traits
Answer: A
This focuses on the color of males and the action of the enzyme that converts eumelanin (brown/black pigment) to phaeomelanin (orange pigment). Male genotypes will be either O-Y or o-Y, with phenotypes of either orange or black/brown, respectively. In O-Y males, the eumelanin is converted to phaeomelanin, and in o-Y males, the eumelanin is unchanged. To answer this question, a student must know that males have only one copy of the gene and must understand that a functional allele produces an enzyme that catalyzes the chemical reaction.
Answer: A
This focuses on the color of males and the action of the enzyme that converts eumelanin (brown/black pigment) to phaeomelanin (orange pigment). Male genotypes will be either O-Y or o-Y, with phenotypes of either orange or black/brown, respectively. In O-Y males, the eumelanin is converted to phaeomelanin, and in o-Y males, the eumelanin is unchanged. To answer this question, a student must know that males have only one copy of the gene and must understand that a functional allele produces an enzyme that catalyzes the chemical reaction.
Figure 15.8 X inactivation and the tortoiseshell cat
Figure 15.13-3 Meiotic nondisjunction (step 3)
Figure 15.14 Alterations of chromosome structure
Figure 15.15 Down syndrome
Figure 15.16 Translocation associated with chronic myelogenous leukemia (CML)
Answer: B
The point of this question is to make students think about mitosis and meiosis in relation to polyploids. To answer this question, students should draw chromosomes of a triploid and a tetraploid as they go through mitosis and meiosis. Answers A and C are incorrect because chromosomes do not synapse during mitosis. Answer D is incorrect because tetraploids do have partners at synapsis but triploids do not. Answer B is correct—one-third of the chromosomes do not have a partner.
Answer: B
The point of this question is to make students think about mitosis and meiosis in relation to polyploids. To answer this question, students should draw chromosomes of a triploid and a tetraploid as they go through mitosis and meiosis. Answers A and C are incorrect because chromosomes do not synapse during mitosis. Answer D is incorrect because tetraploids do have partners at synapsis but triploids do not. Answer B is correct—one-third of the chromosomes do not have a partner.
Answer: A
Answer: A
Figure 15.UN02 In-text figure, Punnett square, p. 300
Figure 15.9 Inquiry: How does linkage between two genes affect inheritance of characters?
Figure 15.UN01 In-text figure, testcross, p. 300
Figure 15.10 Chromosomal basis for recombination of linked genes
Figure 15.11 Research method: constructing a linkage map
Figure 15.12 A partial genetic (linkage) map of a Drosophila chromosome
Figure 15.17 Genomic imprinting of the mouse Igf2 gene
Figure 15.18 A painted nettle coleus plant
Figure 15.UN03b Skills exercise: using the chi-square test (part 2)