Genetics Part II

Question 1

___ - location/position of gene on chromosome

Answer 1

locus

Question 2

____ - different base pair sequences for a particular gene (versions for the same gene)

Answer 2

allele

Question 3

____ - 2+ common alleles within a population

Answer 3

Polymorphic allele

Question 4

____ - maternal & paternal allele are the same

Answer 4

homozygous

Question 5

____ - maternal & paternal allele are different

Answer 5

heterozygous

Question 6

What are the 4 components to formal/Mendelian genetics?

Answer 6

1. Single gene
2. Law of Segregation (RY together in one cell and ry in the other)
3. Law of Independent Assortment (rY together in one cell, Ry in the other)
4. Law of Dominance

Question 7

What is the difference between genotype and phenotype?

Answer 7

Genotype - DNA sequence(s) for a given locus
Phenotype - Gene + environment
- Observable characteristics: appearance, development, behavior, biochemical/physiological

Question 8

_____ - % of individuals with genotype that exhibit the expected phenotype

Answer 8

penetrance

Question 9

____ - extent of phenotype variation

Answer 9

Expressivity

Question 10

How many copies of an allele do you need for dominant phenotype expression?

Answer 10

1

Question 11

How many copies of an allele do you need for recessive phenotype expression?

Answer 11

2

Question 12

What is codominance? Give an example.

Answer 12

both alleles expressed (I.e., ABO blood groups - 1 A allele and 1 B allele = both A & B expressed (AB blood type))

Question 13

____ - phenotypically normal individual who has a disease causing recessive allele in their genome

Answer 13

carrier

Question 14

Who will be affected from autosomal dominant transmission?

Answer 14

Heterozygous affected (Dd) => 50% children affected

Question 15

What is the difference between autosomal dominant and autosomal recessive transmission? How are they similar?

Answer 15

Autosomal dominant - no skipping generations; heterozygous affected parent (Dd) = 50% children affected
Autosomal recessive - can skip generations (2 carrier parents (Dd) = 25% children affected); consanguinity (descending from same ancestor)
Number of affected females = number of affected males (generally)

Question 16

What does “autosomal dominant” mean?

Answer 16

individuals with at least 1 dominant allele are affected

Question 17

What does “autosomal recessive” mean”?

Answer 17

individuals with recessive allele are affected

Question 18

Who is affected from autosomal recessive transmission?

Answer 18

homozygous affected (dd) - 25% of children affected (dd) from 2 carrier parents (Dd)

Question 19

Who are the carriers for autosomal recessive transmission?

Answer 19

heterozygous carriers (Dd)

Question 20

____ - 2+ genotypes in one individual

Answer 20

Genetic mosaicism

Question 21

____ - the fusion of more than one fertilized zygote in the early stages of embryonic development

Answer 21

Chimerism

Question 22

What kind of cells are involved with genetic mosaicism?

Answer 22

germline (sperm and egg)

Question 23

____ - gene that affects sex determination

Answer 23

SRY

Question 24

Which sex chromosome is SRY a gene of?

Answer 24

Y chromosome

Question 25

What sex will an individual be if SRY is on the X chromosome? Is this a type of syndrome? If so, which one?

Answer 25

Male; Klinefelter (47, XX+Y)

Question 26

What sex will an individual be if SRY is on the Y chromosome? Is this a type of syndrome? If so, which one?

Answer 26

Male; normal

Question 27

What sex will an individual be if no SRY is found on the Y chromosome? Is this a type of syndrome? If so, which one?

Answer 27

Female; Turner syndrome (XY?)

Question 28

What sex will an individual be if no SRY is found on the X chromosome? Is this a type of disorder? If so, which one/

Answer 28

Female; normal

Question 29

What are Barr bodies?

Answer 29

inactive X-chromosome in a cell with more than one X chromosome

Question 30

In X-linked recessive transmission, number of males affected ___ than number of females affected

Answer 30

>

Question 31

Who is affected in X-linked recessive transmission?

Answer 31

male with recessive allele (XhY)

Question 32

If an affected father and a normal homozygous dominant mother have children, which ones will be affected or made carrriers?

Answer 32

100% carrier females; 0% affected males (because X is coming from the mother and not the affected father)

Question 33

If an x-recessive affected father and a normal homozygous dominant mother have children, which ones will be affected or made carriers?

Answer 33

100% carrier females; 0% affected males (because X chromosome is coming from the mother and not the affected father)

Question 34

If a carrier mother and a non-affected x-recessive father have children, which ones will be affected or made carriers?

Answer 34

50% carrier female; 50% affected males

Question 35

What are 2 sex-influenced traits?

Answer 35

1. Male pattern baldness
2. Breast cancer

Question 36

What are the 2 sex-limited traits?

Answer 36

1. uterus, ovaries
2. prostate, testicles

Question 37

List and define the 3 principles of multifactorial inheritance.

Answer 37

1. Polygenic traits - effects of multiple genes cause the variations in traits (more difficult to predict phenotype)
2. Multifactorial traits - genetic, environmental, and lifestyle factors cause variations in traits
3. Quantitative traits - are measured on a continuous numeric scale (follow a normal bell curve for distribution)

Question 38

What causes an increase in polygenic recurrence risk?

Answer 38

1. If more than one family member is affected
2. If the expression of the disease in the proband (the first individual identified with the disease) is more severe
3. If the proband is of the less commonly affected sex

Question 39

Why would recurrence risk for a disease decrease?

Answer 39

decreases rapidly in remotely related individuals

Question 40

identical twins

Answer 40

monozygotic

Question 41

fraternal twins

Answer 41

dizygotic

Question 42

_____ - if one twin has a characteristic, the probability that an individual pair of individuals will both have the characteristic

Answer 42

Concordance