Q: Huntington's disease is an autosomal dominant trait. If an affected individual (heterozygous) has three children with a normal partner, what is the probability that exactly two of the children will have the disorder?

$3 \times (0.5)^2 \times (0.5)^1 = 0.375$

Question 1

In a genetic cross between F1 plants heterozygous for a given allele, a 3:1 phenotypic ratio in the F2 generation is observed. What type of cross is this?

Accepted Answer

monohybrid cross

Question 2

A diploid cell undergoes meiosis. How many different types of gametes can it produce if it is heterozygous at three independent loci?

Accepted Answer

$2^3 = 8$

Question 3

Commercial potatoes are tetraploid. If a potato plant undergoes meiosis, how many copies of the genome will each gamete have?

Accepted Answer

Two

Question 4

Bananas are triploid and rarely produce seeds. If a banana plant is triploid for all chromosomes, what will happen if it undergoes meiosis?

Accepted Answer

Most meiotic products will be aneuploid and not viable

Question 5

Humans have a gene, T, that controls tongue rolling. If both parents are heterozygous (Tt), but their child cannot roll their tongue, what can be said about the inheritance?

Accepted Answer

Tongue rolling is dominant

Question 6

Individuals who inherit a defective copy of the BRCA1 gene are at high risk for developing breast or ovarian cancer. However, not all carriers develop cancer. This is an example of:

Accepted Answer

incomplete penetrance

Question 7

Men who have the mutated BRCA1 allele have a smaller, but still elevated cancer risk compared to women. This is an example of:

Accepted Answer

sex-limited inheritance

Question 8

A female fly heterozygous for short bristles (s/s+) and ebony body (e/e+) is testcrossed to a male homozygous for the recessive alleles. The following progeny are observed: long bristles, ebony color: 537; short bristles, normal color: 542; long bristles, normal color: 46; short bristles, ebony color: 75. Are these two genes linked?

Accepted Answer

Yes, they are linked

Question 9

What is the recombination frequency (in %) between the bristle and body color genes in the previous fly cross? (Use the formula $	ext{RF} = \frac{	ext{recombinants}}{	ext{total}} 	imes 100$)

Accepted Answer

$10.1\%$

Question 10

A tomato plant with genotype D/d, J/j, T/t is crossed with a plant of genotype d/d, j/j, t/t. Assuming the genes are not linked, what is the probability of having an offspring of phenotype D J T?

Accepted Answer

$0.125$

Question 11

Huntington's disease is an autosomal dominant trait. If an affected individual (heterozygous) has three children with a normal partner, what is the probability that exactly two of the children will have the disorder?

Accepted Answer

$3 	imes (0.5)^2 	imes (0.5)^1 = 0.375$

Question 12

The mutation leading to Huntington's disease is an example of which type of unusual mutation?

Accepted Answer

trinucleotide repeat expansion

Question 13

Which two conditions are inherited as X-linked recessive in humans?

Accepted Answer

Hemophilia factor X and Red-green color blindness

Question 14

In a population of 10,000 Hopi, 25 are phenotypic albinos. Using Hardy-Weinberg equilibrium, what is the frequency ($q$) of the albino allele? (Assume $q^2 = \frac{25}{10000}$)

Accepted Answer

$0.05$

Question 15

How many of the 10,000 Hopi would be carriers (heterozygous) for the albino allele? (Use $2pq$ and $p = 1 - q$)

Accepted Answer

950

Question 16

The relationship between relative fitness ($w$) and selection ($s$) is as follows:

Accepted Answer

$s = 1 - w$

Question 17

Genetic drift is the random fluctuation of allele frequencies over time independent of natural selection. What mathematical concept governs the extent of genetic drift?

Accepted Answer

Binomial theorem

Question 18

A well-known disease allele in humans where heterozygotes have a large fitness advantage is:

Accepted Answer

Sickle cell disease

Question 19

In eukaryotes, the units for map distances on the genetic map are in ________, while the units for physical map distances are in ________.

Accepted Answer

centiMorgan; basepair

Question 20

In a small population, changes in allele frequency can occur just by chance. This effect is called:

Accepted Answer

Genetic drift

Comprehensive Genetics Study Guide: Mendelian, Linkage, Pedigree, and Population Genetics

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