Ch. 4

Question 1

An individual with two identical alleles for a gene is ___ for that gene

Answer 1

homozygous

Question 2

An individual with two different alleles is

Answer 2

heterozygous

Question 3

The __ describes the outward expression of an allele combination.

Answer 3

phenotype

Question 4

A ___ phenotype is a variant of a gene’s expression that arises when the gene undergoes a change.

Answer 4

mutant

Question 5

One trait that masks another is __ trait.

Answer 5

dominant

Question 6

The most common expression of a particular allele combination is called the ___ phenotype.

Answer 6

wild type

Question 7

Monogenic

Answer 7

mutations in single genes

Question 8

Modes of inheritance

Answer 8

patterns in which single-gene traits and disorders occur in families

Question 9

Autosomal dominant

Answer 9

affects both sexes w/ equal frequency and appears in every generation
ex. Huntington disease

affected individuals may be heterozygous

Question 10

Autosomal recessive

Answer 10

affects both sexes and can skip generations through carriers
ex. cystic fibrosis

affected individuals are always homozygous

Question 11

Hemizygous

Answer 11

having a single copy of gene instead of customary 2 copies

all genes on single X chromosome in males are hemizygous

Question 12

X-Linked Traits

Answer 12

females have 2 X chromosomes (can be heterozygous or homozygous for x-linked traits)

males have 1 X chromosome, hemizygous for all x-linked straight

Question 13

Disorders w/ X-Linked Recessive Inheritance Patterns

Answer 13

• more common than X-Linked dominant traits
• hemizygous males & homozygous recessive females are affected
• males carrying one X-linked recessive allele express the recessive phenotype
• more common in males, rare traits exclusive to males
• affected males pass affected allele to all daughters but none to sons
  ex. color blindness

Question 14

Paternal Inheritance

Answer 14

genes from the Y chromosome are passed directly from father to son

Y-linked genes are all expressed (hemizygous for males)

Question 15

If a father has a Y chromosome-linked disease, what is the chance of his son getting this disease? How about his daughter?

Answer 15

Son: 100% Daughter: 0%

Question 16

If a father has a X-linked dominant disease, what is the chance of his son getting this disease? How about his daughter? (assuming the mother is a healthy female?)

Answer 16

Son: 0% Daughter 100%

Question 17

If a father has a X-linked recessive disease, what is the chance of his son getting this disease? How about his daughter? (assuming the mother is a healthy female)

Answer 17

Son: 0% Daughter: 0% disease but 100% carrier

Question 18

If a trait is autosomal dominant, then an individual who expresses the trait may have parents who do not express the trait.

Answer 18

False; they have at least one parent with the trait (unless they had a de novo mutation)

Question 19

An autosomal dominant trait may be transmitted from father to son.

Answer 19

True; Autosomal dominant traits can be transmitted regardless of the sex of the parents and children.

Question 20

Individuals who express autosomal recessive traits are always homozygous.

Answer 20

True; Affected individuals with an autosomal recessive trait have a homozygous recessive genotype.

Question 21

Autosomal recessive traits never skip a generation

Answer 21

False; can skip a generation

Question 22

Individuals who express autosomal dominant traits are always homozygous.

Answer 22

False; can be heterozygous or homozygous

Question 23

Similar to the inheritance of single-gene diseases, infectious disease inheritance can be easily calculated.

Answer 23

False

Question 24

Single-gene diseases can be much more common in some populations than in others

Answer 24

True

Question 25

If an individual has the allele(s) for a single-gene disease, they will definitely become ill with the disease

Answer 25

False

Question 26

Some genetic diseases may be treated by providing a missing enzyme or protein

Answer 26

True

Question 27

Single-gene traits and diseases are called Mendelian.

Answer 27

True

Question 28

Based on Mendel’s laws of independent assortment and segregation, what are the possible gametes for a cell with the genotype CCBb?

Answer 28

CB and Cb