Genetics Chapter 4

A mutant allele can exert its dominance over a wild-type allele by which of the following changes?

-Dominant-negative mutations -Haploinsufficiency -Gain-of function mutations

Pleiotropy can be caused by:

-Expression of one gene at different stages of development. -Expression of one gene in different cell types. -Expression of one gene that affects cell function in more than one way.

What are the chances that a man with type O blood and a woman with type AB blood could have a child with type O blood?

0%

Consider the following four sets of parents: Set I: AB type father and AB type mother Set II: AB type father and O type mother Set III: B type father and A type mother Set IV: AB type father and B type mother How many sets could possibly produce a baby with type blood O?

1

In beetle, two independently assorting genes, P and C, control the thorax pattern and color, respectively. Thorax pattern can be square (PP), circular (Pp) or absent (pp). Thorax color can be red (CC), pink (Cc) or white (cc). Two dihybrid beetles are crossed. What proportion of the offspring is expected to have a thorax with pink squares?

1/8

The genes R, E and D are independently assorting and control production of red pigment as follows (recessive alleles are not functional) Precursor->White->Yellow->Red RREEDD and rreedd individuals are crossed, and their offspring are testcrossed. What proportion of the F2 progeny is expected to be red?

1/8

Consider a human autosomal gene with four alleles. The number of different genotypes that are possible is

10

In the "sheperd's purse" weed, Capsella bursa-pastoris, fruit shape is governed by two independently assorting genes, A and B. Double recessive (aabb) fruits are narrow-shaped (ovoid). The presence of at least one dominant allele at either locus results in a heart-shaped (triangular) fruit. What is the expected phenotypic ratio in the offspring of an AaBb x aabb cross?

12 heart-shaped:4 narrow-shaped

In humans, how many different genotypes are possible for an X-linked gene with four alleles?

14

Duplicate gene action produces a phenotypic ratio of

15:1

In mallard ducks, plumage color is controlled by a gene with three alleles: MR for restricted pattern, M for mallard and m for dusky. The dominance hierarchy is MR > M > m. What is the genotypic ratio expected in the offspring of the mating MRM x Mm.

1:1:1:1

Instead of the Mendelian ratio of 3:1, the ratio of phenotypes for offspring from a cross between two individuals who are heterozygous for sickle cell disease is ___:___:___

1:2:1

A woman finds out that both of her parents have Huntington disease. What is the probability that she will develop the disease? Assume the Huntington allele is completely penetrant.

2/3

Mickey and Minnie are carriers of albinism, an autosomal recessive trait. Their son Donald is phenotypically normal. What is the probability that he is a carrier?

2/3

Refer to the sets of parents in question 2. How many sets could possibly produce a baby with type blood AB?

3

Bob has blood type A+, and Barb has blood type B+. Their first child has blood type O-. The probability (in fractions) that their next two children consist of a boy with blood type A+ and then a girl with blood type O- is

3/1024 or 0.0029

A woman who has blood genotype IBIO marries a man with blood genotype IAIO. Both are heterozygous for the H-substance. What is the probability that they will have a child with blood type AB?

3/16

Refer to the pathway of question 19. If RrEEDd and RrEEDd individuals are crossed, what proportion of the progeny is expected to be yellow?

3/16

Genes A, B, and C are independently assorting and control production of a black pigment. The dominant alleles A, B and C code for functional enzymes whereas the recessive alleles a, b, and c code for nonfunctional enzymes. An individual of genotype AABBCC is crossed with one of genotype aabbcc, and the resulting F1 individuals are cross-fertilized. For the following pathway state what proportion of the F2 progeny is colorless? Colorless->Colorless->Colorless->Black

37/64

An autosomal gene in humans has four alleles with the dominance hierarchy A1 > A2 > A3 = A4. How many different phenotypes are possible in the population?

5

Refer to the mating in question 11. What proportion of the offspring is expected to have a thorax with a colored pattern?

9/16

Reciprocal Cross

A second cross in which the sexes and phenotypes are reversed.

In a particular animal, coat color is under the control of two independently assorting genes, A and B. Animals can be gray (A-B-), cinnamon (A-bb), black (aaB-) or brown (aaabb). Which of the following crosses will yield offspring in a ratio of 3/4 gray : 1/4 cinnamon?

AABb x aaBb

In blood transfusions, the "universal recipient" is type _____, whereas the "universal donor" is type _____.

AB; O

Sickle cell trait is common in individuals of ________ descent because of the prevalence of _________ in that continent.

African; malaria

Huntington disease is a lethal condition for which symptoms begin to appear in middle age. The age at which a person begins to show disease symptoms is called the _____ of _____.

Age; Onset

For Mendel's pea plants, the tall phenotype is determined by a dominant allele and the dwarf phenotype is determined by a recessive allele. In the first or F1 generation, what is the outcome of a cross between true-breeding tell and true-breeding dwarf plants?

All of the offspring will be tall.

Lethal alleles

Alleles that have the potential to cause death.

What percentage of the functional protein product of a gene should be found in a cell that is heterozygous for that gene?

At least 50%

A person with blood type B can give blood to people with blood types

B and AB only

Muscle cells in people with Duchenne muscular dystrophy show weakening of the cytoskeleton due to a deficiency of the protein _____.

Dystrophin

Incomplete penetrance

Failure to express a dominant phenotype even though the individual carries the dominant allele for the trait

Which of the following sets of children could NOT be the biological children of a man with blood type B, M and a woman with blood type A, MN?

a child with blood type A, N and a child with blood type B, N

Simple Mendelian Inheritance

Follows a strict dominant/recessive relationship.

A population that contains more than one wild-type allele demonstrates

Genetic polymorphism

Hemophilia is inherited with an X-linked recessive allele. Which term describes the genotype for a male who has a blood-clotting disorder?

Hemizygous

Hemophilia is an X-linked recessive trait. In order for a female child to have hemophilia:

Her father must have hemophilia and her mother may have hemophilia or be a carrier.

Codominance

Heterozygote expresses both alleles simultaneously

Incomplete dominance

Heterozygote has intermediate phenotype

Genes located only on the Y chromosome are called _____ genes.

Holandric

Which genotype would the effects of codominance be observed in the individual's phenotype?

I^AI^B

NEITHER are true

In codominance, the phenotype of a heterozygous offspring is intermediate between that of the parents In incomplete dominance, the phenotype of a heterozygous offspring is a mixture of those of the parents.

Which pattern is shown by a heterozygous individual that has a phenotype that is intermediate between the phenotypes of the dominant and recessive homozygotes?

Incomplete dominance

Some individuals who inherited this allele had clear vision throughout their lives while others became completely blind by thirteen years of age. The likely explanation for this difference is:

Incomplete penetrance.

Even though it leads to sickle cell disease in homozygous individuals, the allele Hb^S is retained in some populations because it confers resistance to _____ for heterozygotes.

Malaria

In Suffolk sheep, a single locus with two alleles controls the presence or absence of horns, with horned (H) being dominant to hornless (h). In males the genotypes HH or Hh have horns, and hh is hornless; in females the genotype HH has horns, and Hh or hh are hornless. Two hornless sheep are mated and produce a male lamb with horns. What are the genotypes of the hornless parents?

Male hh and female Hh

What phenomenon os observed in a population when three or more alleles can be found for a single gene?

Multiple alleles

Genes A, B, and C are independently assorting and control production of a black pigment. The dominant alleles A, B and C code for functional enzymes whereas the recessive alleles a, b, and c code for nonfunctional enzymes. An individual of genotype AABBCC is crossed with one of genotype aabbcc, and the resulting F1 individuals are cross-fertilized. For the following pathway state what proportion of the F2 progeny is colorless? Colorless->Colorless->Black

None of these choices

What is the name for the situation where heterozygotes have greater reproductive success that either of the to homozygotes?

Overdominance

While causing sickle-cell anemia in homozygous individuals, the product of the Hb^S allele provides resistance to malaria in individuals with the Hb^A Hb^S genotype. This advantage to heterozygotes demonstrates:

Overdominance

Suppose that one allele for an enzyme codes for a form that is active from 25-30 C and another allele for this enzyme codes for a form that is active from 28-35 C. Heterozygous individuals show enzyme activity from 25-35 C, an advantage which demonstrates:

Overdominance.

Codominance

Pattern in which both alleles are expressed in the heterozygote without blending

Incomplete dominance

Pattern producing an intermediate phenotype in the heterozygote

The pattern where one gene affects many traits is called _______.

Pleiotropy

Which type of allele is likely to be responsible for an inherited human disease when the symptoms are due to a decrease in the production of a specific protein?

Recessive mutant allele

Males and females can inherit the same alleles, but the influence of hormones in the pathway to gender development leads to expression of these alleles in only one gender for _____-_____ inheritance.

Sex Limited

Chromosomes that differ in size and composition between males and females are called:

Sex chromosomes

For ______ inheritance, a given allele is dominant in one sexy and recessive in the opposite sex.

Sex-influenced

In humans, a gene found in the X chromosome but not the Y chromosome is called a(n)

Sex-linked gene.

Tail and neck plumage in domestic fowl is an example of ______-______ inheritance that is under the control of a(n) ______ gene.

Sex; Limited; Autosomal

A phenomenon involving animals of the same species but of opposite sexes that have different physical features is called ______ ______.

Sexual dimorphism

The gene on the mammalian Y chromosome that is essential for the development of male characteristics is called ___.

Sry

Himalayan coloring in rabbits is due to a dominant allele that codes for a tyrosinase enzyme which participates in the production of the dark pigment melanin. In cold temperatures, dark coloring is only found in the ears, nose and feet of the animal. White coloration develops on the body areas where blood flow keeps the animal warm. The tyrosinase enzyme is most likely a:

Temperature sensitive enzyme

Which two fundamental laws of inheritance did Mendel discover?

The Law of Segregation and the Law of independent assortment

A trait that a son can only inherit from his mother must be due to an allele found on:

The X chromosome

Cuttings from a single yarrow plant were grown at different altitudes in the Sierra Nevada Mountain range. These plant pieces had 38 cm, 40 cm and 30 cm of growth at low, medium and high elevations respectively. This range of phenotypes is called:

The norm of reaction.

Haploinsufficiency

The dominant mutant allele loses its function so that a heterozygous individual shows an abnormal phenotype or disease phenotype.

Dominant-negative mutation

The product of the dominant mutant allele interacts with the product of the normal allele causing an altered phenotype.

Gain-of-Function mutation

The product of the dominant mutant allele is expressed in cells where it is not normally active, leading to a change in phenotype.

Individuals with an Hb^sHb^s genotype suffer from sickle cell anemia because:`

They produce hemoglobin S, a variant that causes their red blood cells to form a crescent shape when oxygen concentration is low.

Sex-influenced

Trait is inherited by both sexes but with different dominant/recessive patterns

Sex-limited

Trait only occurs in one of the two sexes

X-linked

Traits for which males inherit only one allele while females inherit two alleles.

Which pattern is shown by genes with pseudoautosomal inheritance?

Two copies are inherited; one from the father and one from the mother.

A person with type A blood can safely donate blood to people with:

Type A and type AB blood

Cystic fibrosis results from a deficiency of a chloride-ion channel protein usually found in the membranes of cells lining the airway passages. Carriers produce sufficient amounts of the channel protein to avoid disease symptoms. The allele that prevents the disease in carriers is a _____ allele and the one that causes the disease is a _____ allele.

Wild-type; Mutant

A temperature-sensitive allele that causes that death of an organism only with exposure to a specific range of temperature is:

a conditional lethal allele

Huntington chorea is a disease caused by

a dominant lethal allele

A pattern bald woman is married to a pattern bald man. They are expecting a girl. What is the probability that she will develop pattern baldness?

cannot determine from the given information

Brittle Bone Disease is caused by a mutation in a gene that codes for collagen fibers. The product of the mutant allele binds to normal collagen and disrupts proper fiber formation. The mutation can be described as a:

dominant-negative mutation.

The ability to prevent the symptoms of phenylketonuria by restricting the diets of patients who inherit the disease is an example of _____ effects on a phenotype.

environmental

A gene that codes for a product that is necessary for the survival of an organism is called a(n)_____ ______.

essential gene

The pattern observed when individuals with the same genotype show slight differences in the resulting phenotype is called variable ______.

expressivity

The type of mutation that leads to increased expression of an altered protein in a cell which does not normally express the protein is called a _____-_____-_____ mutation.

gain-of-function

The Antennapedia mutation causes fruit flies to develop legs in the places on their heads where antenna would normally be found. Expression of the Antennapedia gene product in a location where it is not usually active due to a

gain-of-function mutation for a dominant mutant allele.

If a heterozygous individual shows a disease phenotype despite having one functional allele, the inheritance pattern is called ______.

haploinsufficiency

The growth of scores, small horn-like growths on the faces of cattle, is inherited with the sex-influenced alleles Sc and sc. The trait is dominant in males and recessive in females. If an animal is heterozygous for these alleles, It will:

have scars if it is male but have no scurs if it is female.

Genes located only on the Y chromosome are called ______ genes.

holandric

When a preexisting allele is changed to a new version that no longer codes for a functional protein, the new allele is called a ______ allele.

mutant

A man with type O blood has

neither A nor B antigens on the surface of his red blood cells.

The phenotypic range for individuals with a specific genotype is called the ____ of _____.

norm of reaction

The situation where a heterozygote has a characteristic that makes is more likely than either homozygous individual to reproduce in a given environment is called ______.

over dominance

The phenomenon in which a single gene affects a number of seemingly unrelated characters is

pleiotropy

Genes found in homologous regions of the X and Y chromosomes demonstrate ______ inheritance.

pseudoautosomal

The inheritance pattern for a gene that is located on a sex chromosome but appears to be inherited like an autosomal gene is ______ inheritance.

pseudoautosomal

For X-linked genes, ______ crosses give different outcomes.

reciprocal

An allele that causes death in some, but not all individuals in a population is a(n)

semilethal allele

Colorblindness is due to an X-linked recessive allele. To be colorblind, females must inherit _____ copy(ies) of this allele and males must inherit _____ copy(ies).

two; one

The most commonly-occurring allele in a population is called the _____ - ______ allele.

wild type