Unit 2: Genetics

Question 1

What is incomplete dominance?

Answer 1

The heterozygous phenotype is a blend of both alleles resulting in a third new phenotype

Question 2

What is codominance?

Answer 2

The alleles share traits within the offspring without blending.

Question 3

What is the expected phenotypic ratio of the offspring between double heterozygous individuals?

Answer 3

9:3:3:1

Question 4

What is a dihybrid cross phenotypic ratio?

Answer 4

9:3:3:1

Question 5

If a fly is heterozygous for 2 genes, how many unique gametes will they make?

Answer 5

2^n where n = number of heterozygous pairs

Question 6

What is the probability of an AABBCC offspring from AaBbCc x AaBbCc?

Answer 6

1/64

Question 7

What is the phenotype of a fly that is homozygous dominant for body color and heterozygous for wing size?

Answer 7

Wild type body and wings

Question 8

What is a ‘wild type’?

Answer 8

The most common allele in a population.

Question 9

If a gene has a homozygous dominant lethal genotype, what is the genotype ratio of the offspring?

Answer 9

2:1 (excluding AA, which does not survive)

Question 10

What is genetic linkage mapping?

Answer 10

How frequently genes are inherited together.

Question 11

How do you calculate distance between genes?

Answer 11

1. Find recombinant offspring by calculating possible offspring.

Question 12

How do you determine the phenotype ratio from a Punnett square?

Answer 12

Count offspring with same phenotypes, compare with total.

Question 13

What is Mendel’s Law of Segregation?

Answer 13

Alleles separate during gamete formation and unite randomly at fertilization.

Question 14

What is Mendel’s Law of Independent Assortment?

Answer 14

Each pair of alleles segregates independently during gamete formation.

Question 15

What is the probability of offspring being aa from Aa x Aa?

Answer 15

1/4

Question 16

What is the probability of heterozygous Bb from Bb x Bb?

Answer 16

50%

Question 17

How do you calculate the probability of aabbcc from AaBbCc x AaBbCc?

Answer 17

1/64

Question 18

How do you calculate the probability of AABbcc from AaBbCc x AaBbCc?

Answer 18

1/32

Question 19

What type of dominance shows a blended trait?

Answer 19

Incomplete dominance

Question 20

What type of dominance shows both alleles fully expressed?

Answer 20

Codominance

Question 21

What are the genotypes for human blood types?

Answer 21

IA, IB, i

Question 22

What blood type alleles are codominant?

Answer 22

IA and IB

Question 23

What blood type alleles are dominant over i?

Answer 23

IA and IB

Question 24

What is the genotype of someone with type O blood?

Answer 24

ii

Question 25

What is the genotype of someone with AB blood?

Answer 25

IAIB

Question 26

What is the ratio of genotypes from a monohybrid cross (Aa x Aa)?

Answer 26

1:2:1

Question 27

What is the ratio of phenotypes from a monohybrid cross (Aa x Aa)?

Answer 27

1:2:1

Question 28

What is a polygenic trait?

Answer 28

A trait controlled by many genes, like height or skin color.

Question 29

What is a carrier?

Answer 29

An individual who is heterozygous for a recessive disorder.

Question 30

What is a sex-linked trait?

Answer 30

A trait associated with genes found on sex chromosomes.

Question 31

Who is more likely to express an X-linked recessive trait?

Answer 31

Males (because they have only one X chromosome)

Question 32

What is an autosomal recessive disorder?

Answer 32

A disorder expressed only if both alleles are recessive.

Question 33

What is an example of an autosomal recessive disorder?

Answer 33

Cystic fibrosis, Tay-Sachs, albinism.

Question 34

What is an autosomal dominant disorder?

Answer 34

A disorder expressed with just one dominant allele.

Question 35

What is an example of an autosomal dominant disorder?

Answer 35

Huntington's disease, polydactyly.

Question 36

How does environment affect phenotype?

Answer 36

Environmental factors can influence gene expression (e.g., soil pH and flower color).

Question 37

What is the genotype of a male with an X-linked recessive trait?

Answer 37

XʳY

Question 38

What is the genotype of a female carrier of an X-linked recessive trait?

Answer 38

XʳX

Question 39

What is a Punnett square?

Answer 39

A diagram used to predict genotypes of offspring.

Question 40

How many gametes are possible from RrYy?

Answer 40

RY, Ry, rY, ry

Question 41

How do you find recombinant frequency?

Answer 41

Recombinants ÷ Total offspring

Question 42

What does 1% recombination equal?

Answer 42

1 centimorgan (cM) — a unit of map distance