0
By:
Muhammad Iqbal Khan
SS Biology
Email ID: mikhan1313@yahoo.com
Changes made by Anna Tzemach
Thanks for Anna Tzemach
2
Genetic Information
• Gene – basic unit of genetic
information. Genes determine the
inherited characters.
• Genome – the...
3
Chromosome Logical Structure
• Locus – location of a gene/marker
on the chromosome.
• Allele – one variant form of a
gen...
4
Human Genome
Most human cells
contain 46 chromosomes:
• 2 sex chromosomes (X,Y):
XY – in males.
XX – in females.
• 22 pa...
5
Genotypes Phenotypes
• At each locus (except for sex chromosomes)
there are 2 genes. These constitute the
individual’s g...
6
Genotypes Phenotypes (example)
• Eb
- dominant allele.
• Ew
- recessive allele.
genotypes
phenotypes
7
Dominant vs. Recessive
• A dominant allele is
expressed even if it is
paired with a recessive
allele.
•A recessive allel...
8
One Locus Inheritance
heterozygote homozygote
21A | A a | a
A | a 3 4 a | a
A | a 5 6 a | a
Male
Female
9
Two members of a gene pair segregate from each other into
the gametes, so half the gametes carry one member of the
pair ...
10
Calculating Probabilities
• We want to predict
patterns of inheritance
of traits and diseases in
pedigrees.
• E.g., we ...
11
X-linked Inheritance
Different results obtained
from reciprocal crosses
between red-eyed and
white-eyed Drosophila.
Exp...
12
Mendel’s 2nd
Law
• Different gene pairs assort independently
in gamete formation.
Gene pairs on SEPARATE CHROMOSOMES
as...
13
Medical Genetics
When studying rare disorders, 6 general
patterns of inheritance are observed:
• Autosomal recessive
• ...
14
Medical Genetics (cont.(
Autosomal recessive
• The disease appears
in male and female
children of
unaffected parents.
•...
15
Medical Genetics (cont.(
Autosomal dominant
• Affected males and
females appear in each
generation of the
pedigree.
• A...
16
Medical Genetics (cont.(
X-linked recessive
• Many more males than
females show the disorder.
• All the daughters of an...
17
Medical Genetics (cont.(
X-linked dominant
• Affected males pass the
disorder to all daughters
but to none of their son...
18
Medical Genetics (cont.(
Codominant inheritance
• Two different versions
(alleles) of a gene can be
expressed, and each...
19
Medical Genetics (cont.(
Mitochondrial inheritance
• This type of inheritance
applies to genes in
mitochondrial DNA
• M...
20
Question #1
1 2
• Write the genotypes in every possible place.
• If individuals 1 and 2 marry, what is the probability ...
21
Question #2
• PKU is a human hereditary disease resulting from
inability of the body to process the chemical
phenylalan...
22
Question #2-Solution Highlights
P/p P/p P/p P/p
p/p p/pP-/ P-/
P – the normal allele
p – the mutant allele
23
Question #3
1 2 3 4 5 6 7 8 9 10
a. What is the most likely mode of inheritance ?
b. What would be the outcomes of the ...
24
a. Observations:
– After the disease is introduced into the family in generation
#2, it appears in every generation  d...
25
Notes
• Cystic fibrosis – disease affecting the mucus lining of
the lungs, leading to breathing problems and other
diff...
26
Notes
• Hemophilia-illness that impair the body's ability
to control bleeding.
• Fragile X syndrome - is a genetic cond...
27
Notes -cont
• DNA - a pair of molecules joined by hydrogen bonds: it is
organized as two complementary strands, head-to...
28
Notes -cont
• Mitosis is the process by which a cell separates
its duplicated genome into two identical halves
• Meiosi...
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Basic genetics

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  • References : Kenneth Lange “Mathematical and Statistical Methods for Genetic Analysis” Jurg Ott “Analysis of Human Genetic Linkage” http://www.accessexcellence.com/AB/GG/ http://www.nhgri.nih.gov/DIR/VIP/Glossary/index.html http://www.tokyo-med.ac.jp/genet/index-e.htm
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  • Transcript of "Basic genetics"

    1. 1. By: Muhammad Iqbal Khan SS Biology Email ID: mikhan1313@yahoo.com Changes made by Anna Tzemach Thanks for Anna Tzemach
    2. 2. 2 Genetic Information • Gene – basic unit of genetic information. Genes determine the inherited characters. • Genome – the collection of genetic information. • Chromosomes – storage units of genes. • DNADNA - is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms
    3. 3. 3 Chromosome Logical Structure • Locus – location of a gene/marker on the chromosome. • Allele – one variant form of a gene/marker at a particular locus. Locus1 Possible Alleles: A1,A2 Locus2 Possible Alleles: B1,B2,B3
    4. 4. 4 Human Genome Most human cells contain 46 chromosomes: • 2 sex chromosomes (X,Y): XY – in males. XX – in females. • 22 pairs of chromosomes named autosomes.
    5. 5. 5 Genotypes Phenotypes • At each locus (except for sex chromosomes) there are 2 genes. These constitute the individual’s genotype at the locus. • The expression of a genotype is termed a phenotype. For example, hair color, weight, or the presence or absence of a disease.
    6. 6. 6 Genotypes Phenotypes (example) • Eb - dominant allele. • Ew - recessive allele. genotypes phenotypes
    7. 7. 7 Dominant vs. Recessive • A dominant allele is expressed even if it is paired with a recessive allele. •A recessive allele is only visible when paired with another recessive allele.
    8. 8. 8 One Locus Inheritance heterozygote homozygote 21A | A a | a A | a 3 4 a | a A | a 5 6 a | a Male Female
    9. 9. 9 Two members of a gene pair segregate from each other into the gametes, so half the gametes carry one member of the pair and the other half carry the other member of the pair. Two members of a gene pair segregate from each other into the gametes, so half the gametes carry one member of the pair and the other half carry the other member of the pair. Mendel’s 1st Law Y / y y / y ½y/y ½Y/y ½y ½Y all yGamete production Gamete production
    10. 10. 10 Calculating Probabilities • We want to predict patterns of inheritance of traits and diseases in pedigrees. • E.g., we want to know the likelihood that a dog chosen at random from the study population will have blue eyes.
    11. 11. 11 X-linked Inheritance Different results obtained from reciprocal crosses between red-eyed and white-eyed Drosophila. Explanation: The gene responsible for eye-color is X-linked. Females have 2X-chromosomes, while males have 1 X-chromosome and 1 Y-chromosome.
    12. 12. 12 Mendel’s 2nd Law • Different gene pairs assort independently in gamete formation. Gene pairs on SEPARATE CHROMOSOMES assort independently at meiosis. Gene pairs on SEPARATE CHROMOSOMES assort independently at meiosis. This “law” is true only in some cases.
    13. 13. 13 Medical Genetics When studying rare disorders, 6 general patterns of inheritance are observed: • Autosomal recessive • Autosomal dominant • X-linked recessive • X-linked dominant • Codominant • Mitochondrial
    14. 14. 14 Medical Genetics (cont.( Autosomal recessive • The disease appears in male and female children of unaffected parents. • e.g., cystic fibrosis
    15. 15. 15 Medical Genetics (cont.( Autosomal dominant • Affected males and females appear in each generation of the pedigree. • Affected mothers and fathers transmit the phenotype to both sons and daughters. • e.g., Huntington disease.
    16. 16. 16 Medical Genetics (cont.( X-linked recessive • Many more males than females show the disorder. • All the daughters of an affected male are “carriers”. • None of the sons of an affected male show the disorder or are carriers. • e.g., hemophilia
    17. 17. 17 Medical Genetics (cont.( X-linked dominant • Affected males pass the disorder to all daughters but to none of their sons. • Affected heterozygous females married to unaffected males pass the condition to half their sons and daughters • e.g. fragile X syndrome
    18. 18. 18 Medical Genetics (cont.( Codominant inheritance • Two different versions (alleles) of a gene can be expressed, and each version makes a slightly different protein • Both alleles influence the genetic trait or determine the characteristics of the genetic condition. • E.g. ABO locus
    19. 19. 19 Medical Genetics (cont.( Mitochondrial inheritance • This type of inheritance applies to genes in mitochondrial DNA • Mitochondrial disorders can appear in every generation of a family and can affect both males and females, but fathers do not pass mitochondrial traits to their children. • E.g. Leber's hereditary optic neuropathy (LHON)
    20. 20. 20 Question #1 1 2 • Write the genotypes in every possible place. • If individuals 1 and 2 marry, what is the probability that their first child will be sick?
    21. 21. 21 Question #2 • PKU is a human hereditary disease resulting from inability of the body to process the chemical phenylalanine (contained in protein that we eat). • It is caused by a recessive allele with simple Mendelian inheritance. • Some couple wants to have children. The man has a sister with PKU and the woman has a brother with PKU. There are no other known cases in their families. • What is the probability that their first child will have PKU ?
    22. 22. 22 Question #2-Solution Highlights P/p P/p P/p P/p p/p p/pP-/ P-/ P – the normal allele p – the mutant allele
    23. 23. 23 Question #3 1 2 3 4 5 6 7 8 9 10 a. What is the most likely mode of inheritance ? b. What would be the outcomes of the cousin marriages 1 x 9, 1 x 4, 2 x 3, and 2 x 8 ? • The disease is rare.
    24. 24. 24 a. Observations: – After the disease is introduced into the family in generation #2, it appears in every generation  dominant! – Fathers do not transmit the phenotype to their sons  X-linked! a. The outcomes: – 1 x 9: 1 must be A/a 9 must be A/Y – 1 x 4: 1 must be A/a 4 must be a/Y – 2 x 3: 2 must be a/Y 3 must be A/a – 2 x 8: 2 must be a/Y 8 must be a/a Same All normal Question #3-Solution Highlights
    25. 25. 25 Notes • Cystic fibrosis – disease affecting the mucus lining of the lungs, leading to breathing problems and other difficulties • Huntington disease - or Huntington's chorea is an inherited disorder characterized by abnormal body movements called chorea, and loss of memory. There also is evidence that doctors as far back as the Middle Ages knew of this devastating disease. The incidence is 5 to 8 per 100,000. It takes its name from the New York physician George Huntington who first described it precisely in 1872.
    26. 26. 26 Notes • Hemophilia-illness that impair the body's ability to control bleeding. • Fragile X syndrome - is a genetic condition that causes a range of developmental problems including learning disabilities and mental retardation. Usually males are more severely affected by this disorder than females. In addition to learning difficulties, affected males tend to be restless, fidgety, and inattentive. Affected males also have characteristic physical features that become more apparent with age.
    27. 27. 27 Notes -cont • DNA - a pair of molecules joined by hydrogen bonds: it is organized as two complementary strands, head-to-toe, with the hydrogen bonds between them. Each strand of DNA is a chain of chemical "building blocks", called nucleotides, of which there are four types:adenide (abbreviated A), cytozyne (C), guanine (G) and thymine (T). • Mitochondria, which are structures in each cell that convert molecules into energy, each contain a small amount of DNA. • A chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. During either process, the word "chromosome" indicates a pair of two exactly identical ("sister") chromatids joined at the central point of each chromatid, called the centromere.
    28. 28. 28 Notes -cont • Mitosis is the process by which a cell separates its duplicated genome into two identical halves • Meiosis is the process that transforms one diploid into four haploid cells. • Reciprocal cross a cross, with the phenotype of each sex reversed as compared with the original cross, to test the role of parental sex on inheritance pattern. A pair of crosses of the type genotype A(female) X genotype B(male) and genotype B(female) X genotype A(male).
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