Ch 20 Practice

Question 1

A diagram that uses sperms genotypes on one side and egg genotypes on the other side to predict the genotypes of offspring is called a ______ ______.

Answer 1

Punnett square

Question 2

If a male exhibits a sex-linked trait, the allele for the trait came from the mother and resides on the ______.

Answer 2

X chromosome

Question 3

Phenotype

Answer 3

The physical appearance of a trait (e.g., blue eyes)

Question 4

Genotype

Answer 4

The specific combination of alleles an individual is born with

Question 5

Alternate forms of a gene are called ______.

Answer 5

Allele

Question 6

______ alleles require two copies to be present in order to exert their effect.

Answer 6

Recessive

Question 7

An organism with a ______ genotype carries two identical alleles for a given gene.

Answer 7

Homozygous

Question 8

For each gene, an individual inherits ______ allele(s) with ______ being contained in the sperm and ______ being contained in the egg.

Answer 8

2, 1, 1

Question 9

If neither parent is affected by an autosomal dominant disorder, what percentage of their children will be affected?

Answer 9

0; Both parents possess the recessive traits.

Question 10

What are the characteristics of polygenic phenotype?

Answer 10

• Alleles have additive effects on phenotype
• Phenotype variation appears continuous
• The phenotype can be influenced by the environment

Question 11

How many copies of a damaged allele must be present for a recessive genetic disease to be expressed?

Answer 11

2

Question 12

The specific genes or combination of alleles for a trait is called an individual’s ______.

Answer 12

Genotype

Question 13

A person who is heterozygous for an autosomal recessive disorder and shows the dominant phenotype is called a(n) ______.

Answer 13

Carrier

Question 14

All combinations of alleles are possible in the gametes because the ______ align independently during meiosis.

Answer 14

Chromosomes

Question 15

How many traits are being considered in a dihybrid cross?

Answer 15

2

Question 16

The position of a gene on a chromosome is called its ______.

Answer 16

Locus

Question 17

______ occurs when one gene affects multiple, seemingly unrelated traits.

Answer 17

Pleiotropy

Question 18

An individual with one recessive allele and one ______ allele has a heterozygous genotype.

Answer 18

Dominant

Question 19

An individual hat inherits two copies of the same form of a gene from his or her two parents has a ______ genotype.

Answer 19

Homozygous

Question 20

A genetic system in which alleles are equally expressed in a heterozygote is called ______.

Answer 20

Codominance

Question 21

Sickle-cell disease is an example of which type of condition?

Answer 21

Autosomal recessive disorder

Question 22

A genetic system in which a heterozygous individual displays a phenotype intermediate between that of an individual homozygotic for either allele is called ______ ______.

Answer 22

Incomplete dominance

Question 23

In simple one-trait crosses, one gene affects one trait. In ______ inheritance, multiple genes govern a trait, and in ______, one gene affects many traits.

Answer 23

Polygenic, pleiotropy

Question 24

The ______ allele of a gene is represented with an uppercase letter.

Answer 24

Dominant

Question 25

An Ff x Ff cross is an example of:

Answer 25

A monohybrid cross