Extensions Of Mendel’s Law Part 2

Question 1

In large populations , more than one wild-type allele ma y occur—a p henomenon known as

Answer 1

Genetic polymorphism

Question 2

prevalent alleles in a natural population as

Answer 2

wild-t yp e alleles

Question 3

random mutations occur in population and alter preexistig alleles.

Answer 3

Mutant alleles

Question 4

Because random mutations are more likel y to disrupt gene function,____ are often defective in their abilit ability to express a functional p rotein. Such _____ tend to be rare in natural populations. They are typically, but not alwa y s, inherited in a recessive fashion

Answer 4

mutant alleles

Question 5

Phenylketonuria

Answer 5

Phenylalanine hydroxylase

Question 6

Albinism

Answer 6

Tyrosinase

Question 7

Tay-Sachs disease

Answer 7

Hexosaminidase A

Question 8

Sandhoff disease

Answer 8

Hexosaminidase B

Question 9

Cystic fibrosis

Answer 9

Chloride transporter

Question 10

Lesch-Nyhan syndrome

Answer 10

Hypoxanthine-guanine phosphoribosyl transferase

Question 11

One of three mechanisms accounts for most dominant mutant alleles:

Answer 11

a gain-of-function mutation

a dominant-negative mutation

haploinsufficiency .

Question 12

chan g e the g ene or the p rotein encoded by a gene so that it gains a new or abnormal function

Answer 12

Gain-of-function mutations

Question 13

For exam p le, a mutant g ene ma y be overex p ressed, thereb y p roducin g too much of the encoded p rotein.

Answer 13

Gain-of-function mutations

Question 14

change protein such that the mutant protein acts antagonistically to the normal protein. In a heterozygote, the mutant p rotein counteracts the effects of the normal protein, thereby altering the phenotype.

Answer 14

Dominant-negative mutations

Question 15

, the dominant mutant allele is a lossof-function allele.

Answer 15

Haploinsufficiency

Question 16

is used to describe p atterns of inheritance in which a heteroz yg ote ( with one functional allele and one inactive allele ) exhibits an abnormal or disease phenotype

Answer 16

Haploinsufficiency

Answer 17

Haploinsufficiency

Question 18

Another term used to describe the outcome of a trait is the degree to which the trait is expressed, or its______. In the case or polydactyly, the number or extra digits can vary. ror exam-ple, one mnaiviauar may nave an extra toe on only one root, wnereds a second individual may have extra digits on both the hands and feet.

Answer 18

expressivity

Question 19

the range of phenotvpes is often due to two factors.

The______ may affect the outcome of the phenotype
One or more _____may also affect the phenotype.

Answer 19

environment

modifier genes

Question 20

are those that are prevalent in a natural popu-lation.

Answer 20

Wild-type alleles

Question 21

When a gene exists in two or more wild-type alleles, this
is

Answer 21

Genetic polymorphism

Question 22

are often due to mutations that result in a reduction or loss of function of the encoded protein

Answer 22

Recessive alleles

Question 23

Dominant mutant alleles are most commonly caused by

Answer 23

gain-or-function mutations, dominant-negative mutations, or haploinsufficiency

Question 24

occurs when an allele that is expected to be expressed is not expressed

Answer 24

Incomplete penetrance

Question 25

are those that are prevalent in a natural popu-lation. When a gene exists in two or more wild-type alleles, this is genetic

Answer 25

Wild-type alleles

Question 26

A dramatic example of the relationship between environment and phenotype can be seen in the human genetic disease known as______ This autosomal recessive disease is caused by a defect in a gene that encodes the enzyme phenylalanine hydroxylase.

Answer 26

phenylketonuria (PKU)

Question 27

refers to the effects of environmental variation on a phenotype. Specifi-cally, it is the phenotypic range seen in individuals with a particular genotype.

Answer 27

norm of reaction

Question 28

Occurs When Two Alleles Produce an Intermediate Phenotype

Answer 28

Incomplete Dominance

Question 29

Occurs When Heterozygotes Have Greater Reproductive Success

Answer 29

Overdominance

Question 30

Such heterozygotes may be more likely to survive and reproduce. For example, a heterozygote may be larger, more disease-resistant, or better able to withstand harsh environmental conditions.

Answer 30

Overdominance

Question 31

Alleles of the ABO Blood Group Can Be

Answer 31

Dominant, Recessive, or Codominant

Question 32

. The i allele is recessive to both /^ and /". A person who is homozygous ii has type___ blood and produces a relatively short oligosaccharide, which is called H antigen.

Answer 32

O

Question 33

two alleles are both expressed in the heterozygous individual is called____. In this case, the /^ and /" alleles are codominant to each other.

Answer 33

codominance

Question 34

The term _____refers to the phenomenon in which an allele is dominant in one sex but recessive in the opposite sex. Therefore, sex _____ is a phenomenon of heterozygotes.

Answer 34

sex-influenced inheritance

Question 35

The genes that govern ____traits are auto-somal, not on the X or Y chromosome.

Answer 35

sex-influenced

Question 36

Some Traits Are Limited to One Sex

Answer 36

Sex-limited inheritance

Question 37

Sex-limited traits are responsible for______, in which members of the opposite sex have different morphological features. This phenomenon is common among many animal species and is often striking among various species of birds in which the male has more ornate plumage than the female.

Answer 37

sexual dimorphism

Question 38

• For___ traits such as scurs in cattle, heterozygous males and females have different phenotypes

Answer 38

sex-influenced

Question 39

• are expressed in only one sex, thereby resulting in sexual dimorphism

Answer 39

Sex-limited traits

Question 40

When the alleles of one gene mask the phenotypic effects of the alleles of another gene at a different locus, the phenomenon is called_____.

Answer 40

epistasis