Chapter 21

Question 1

Dominant alleles

Answer 1

Mask the expression of recessive alleles

Question 2

Recessive alleles

Answer 2

An allele that is only expressed in the absence of a dominant allele

Question 3

Genotype

Answer 3

The genes of an individual

Question 4

Phenotype

Answer 4

The physical appearance of a trait

Question 5

Monohybrid cross

Answer 5

A one-trait cross

Use a punnet square to predict phenotypes

Question 6

Dihybrid cross

Answer 6

A two trait cross

Phenotypic rate:
Dominant Dominant: 9
Dominant Recessive: 3
Recessive Recessive: 3
Recessive Dominant: 1

Question 7

Pedigree

Answer 7

Charts that can be used to predict the pattern of inheritance, and therefore predict the likelihood of inheriting a disorder.

Females are denoted as circles

Males are denoted as squares

Question 8

Chromosomes:
Autosomes
Sex chromosomes

Answer 8

Autosomes are chromosomes 1-22

Sex chromosome is chromosome 23

Males have XY sex chromosomes

Females have XX sex chromosomes

Sperm determine gender

Question 9

X and Y linked genes

Answer 9

X-linked genes are genes found on the X chromosomes

X-linked disorders are more common in men than in women because men only have one X chromosome

Y-linked genes are genes that are found on the Y chromosome

Question 10

Polygenic inheritance

Answer 10

A trait that is inherited that requires the inheritance of several genes

Example: Eye color

Question 11

Multifactorial inheritance

Answer 11

Part-genes, part-environment

Example: Height, skin color, the bunny rabbit

Question 12

Pleiotropy

Answer 12

When a single mutant gene affects two or more distinct and seemingly unrelated traits

Example: Diabetes and Marfan’s syndrome

Question 13

Incomplete dominance

Answer 13

When the heterozygote is intermediate between the two homozygotes

Example: Wavy hair (Curly+Straight)

Question 14

Codominance

Answer 14

When alleles are equally expressed in a heterozygote

Example: AB blood type (Dominant A + Dominant B)

Question 15

Multiple allelism