MOL 542

Question 1

For a homozygous recessive trait, what are the odds an unaffected individual is a carrier?
(1)

Answer 1

2/3

Question 2

What are the six patterns of inheritance?

1

Answer 2

1. X-linked recessive
2. X-linked dominant
3. Autosomal dominant
4. Autosomal recessive
5. Mitochondrial
6. Y-linked

Question 3

Can you rule out X-linkage? Can you rule out autosomal?

1

Answer 3

Yes, no

Question 4

The chances of inheriting a novel Huntington’s Disease allele is 1 in 10^4. What are the odds of inheriting two? If you know someone with an HF allele, what are the odds that they are homozygous?
(1)

Answer 4

10^8

10^4

Question 5

How do you determine if a mutation causes a dominant or recessive phenotype?
(2)

Answer 5

Look at heterozygotes

Question 6

Mendel’s Laws?

2

Answer 6

1. Law of segregation: parental genes are randomly segregated so each sex cell contains one gene.
2. Law of independent assortment: genes for different traits are sorted separately
3. Law of dominance: organisms with alternate forms of a gene will express the dominant form

Question 7

How can you determine if a wild type allele is haplosufficient?
(2)

Answer 7

Make a null allele/wild type hybrid.

If resulting phenotype is wild-type it is haplosufficient. Otherwise it is haploinsufficient.

Question 8

If the wild type allele is ___, LOF alleles are ___ and if the wild type allele is ___, LOF alleles are ___.
(2)

Answer 8

If the wild type allele is haplosufficient, LOF alleles are recessive and if the wild type allele is haploinsufficient, LOF alleles are dominant.

Question 9

When is a mutant allele a GOF allele?

2

Answer 9

In the presence of a haplosufficient wild type allele, a GOF acts in a dominant fashion that produces a phenotype different from the null allele.

Question 10

What is a DN allele?

2

Answer 10

Dominant negative alleles produce a dominant phenotype in the presence of a haplosufficient wild type allele. The phenotype produced mimics the null phenotype.

Question 11

Are alleles dominant or recessive?

2

Answer 11

No, traits are.

Question 12

What does the term pleiotropic mean?

2

Answer 12

Allele leads to two or more phenotypes.

Question 13

AaBbCcDdEe x aabbccddee
What fraction will be Aa? Why?
(2)

Answer 13

1/2. The law of independent assortment (2nd law) says you can consider A by itself. The law of equal segregations says half will get A and half will get a (1st law).

Question 14

Seperation of chromosomes in Mitosis vs. Meiosis

2

Answer 14

Mitosis: Sister chromatids split
Meiosis: Homologous chromosomes split

Question 15

What is the relationship between the terms polygenic and continuous variation?
(2)

Answer 15

Polygenic traits are governed by multiple genes.
This allows for….
Continuous variation which describes traits whose phenotypes occur on a continuum, rather than having a limited number of possible phenotypes.

Question 16

Dominance vs Epistasis:

2

Answer 16

Dominance: phenotype due to interaction between alleles of a single gene (phenotype of one allele masks/prevents another allele).
Epistasis: phenotype due to interaction between alleles of different genes (phenotype of one locus masks/prevents another locus).

Question 17

What are the hallmarks of recessive and dominant inheritance?
(1)

Answer 17

Trait skips a generation/trait found in every generation

Question 18

What are the hallmarks of X-linked recessive and dominant traits?
(1)

Answer 18

Affected mothers pass always pass the trait to all sons

Affected fathers always pass trait to all daughters

Question 19

Hallmark of Y-linked genes

1

Answer 19

Passes from fathers to all sons and none of the daughters.

Question 20

Hallmark of mitochondrial-linked genes

1

Answer 20

Passed from mothers to all offspring, but never transmitted from father to offspring.