Bio 115 Quiz 4

The probability that two parents will have 3 girls and 1 boy in their family is

1/16

What is the ratio of phenotypes in the offspring produced by the cross Aa x Aa? Assume complete dominance for the trait.

75% dominant: 25% recessive

All of the following combinations are possible in the gametes of an organism that is AaBb Except A. aa B. ab C. AB D. aB E. Ab

A. aa

Blood typing is often used as evidence in paternity cases in court. In one case, the mother had blood type B and the child had blood type O. Which of the following blood types could the father NOT have?

AB

The vast majority of people afflicted with recessive disorders are born to parents who were

not affected at all by the disease

Sickle cell anemia is a disease whose phenotype includes not only one anemia, but damage too many different organs. All phenotypes, however, can be traced to a single gene. This is an example of

pleiotropy

Human skin color is the result of

polygenic inheritance

When alleles move into different gametes, this demonstrates

segregation

A particular genetic cross in which the individual in question is crossed with an individual known to be homozygous for a recessive trait is referred to as a

test cross

How many different types of gametes can be generated by an individual with genotype AaBB?

2

The phenotypic ratio resulting from a dihybrid cross showing independent assortment is expected to be

9:3:3:1

When Mendel used true-breeding white flowers and true-breeding purple flowers as the parental generation, what were the results? (Purple flower is dominant over white.)

All of the offspring had purple flowers

In humans, brown eye color (B) is dominant to blue eyes (b). Two parents with brown eyes have a large family of 24 children. 18 of the children have brown eyes, and 6 of them have blue eyes. This indicates that the parents' genotypes are

Bb and Bb

What type of allele produces its effects in only homozygous individuals?

Recessive

If a round pea has a wrinkled parent, the round pea is

Rr

Alleles of genes are found at __________ chromosomes

The same locus on homologous

A Mendelian test cross is used to determine whether

an individual is homozygous or heterozygous

For most sexually reproducing organisms, Mendel's laws

cannot strictly account for most patterns of inheritance

An _____ gene masks the expression of a different, non allelic gene

epistatic

For traits that show incomplete dominance, the phenotype of a heterozygote is

intermediate between the homozygous dominant and homozygous recessive phenotypes

Human eye color is the result of

polygenic inheritance

In garden peas, the allele for tall plants is dominant over the allele for short plants. A true-breeding tall plant is crossed with a short plant, and one of their offspring is test crossed. Out of 20 offspring resulting from the test cross, about _______ should be tall.

10

In a test cross, what percentage of the offspring will have the same genotype as the tested parent of the parent is homozygous?

100%

Assuming that the probability of having a female child is 50% and the probability of having a male child is also 50%, what is the probability that a couple's first-born child will be female and that their second-born child will be male?

25%

In pea plants, tall plants are dominant over short, and green pods are dominant over yellow. If you were to cross true-breeding tall, green-podded plants with true-breeding short, yellow-podded plants, and then were to cross the F1 individuals among themselves, what proportion of the F2 offspring would you expect to be tall and yellow-podded?

3/16

If you cross pea plants that are heterozygous for purple flowers and yellow seeds (PpYy), and you examine 800 offspring for flower and seed color, about how many do you expect to have white flowers and green seeds?

50

If an individual who is homozygous for type B blood marries a heterozygous type A individual, what is the chance that their first child will have type AB blood?

50%

In crossing a homozygous recessive with a heterozygote, what is the chance of getting a homozygous recessive phenotype in the F1 generation?

50%

In the individual with genotype AaBB, what percent of gametes will contain the A allele?

50%

Classical albinism results from a recessive allele. Which of the following is the expected offspring from a normally pigmented male with an albino father and an albino wife?

50% normal; 50% albino

In a dihybrid cross, if heterozygotes are crossed, what fraction of the offspring are expected to have both the dominant phenotypes?

9/16

Two individuals with medium-brown skin have five children. Two of the children have dark skin, one has white skin, and two have medium-brown skin. Which of the following types of inheritance best explains this phenomenon? A. Linked genes B. Polygenic inheritance C. Incomplete dominance D. Codominance E. Sex-linked inheritance

B. Polygenic inheritance

In Labrador retrievers, black coat color is dominant to chocolate coat color. Labradors also are prone to a serious eye ailment, called progressive retinal atrophy (PRA), which is recessive to normal vision. If two black labradors with normal vision are mated, and one puppy in a litter of seven entirely black puppies has PRA, what are the likely genotypes of the parents?

Both parents are heterozygous carriers of PRA, but we can't determine what their coat-color genotype is

Which one of the following is an example of incomplete dominance in humans? A. Sickle-cell disease B. Skin color C. Hypercholesterolemia D. ABO blood groups E. None of the choices are correct

C. Hypercholesterolemia

Which of the following statements is false? A. Matings between individuals with recessive phenotypes usually do not produce offspring with dominant phenotypes B. Individuals with the same phenotype might have different genotypes C. Matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes D. Individuals with the same genotype might have different phenotypes E. All of the above choices are correct

C. Matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes

Which of the following is essentially the converse of pleiotropy? A. Blending inheritance B. Incomplete dominance C. Polygenic inheritance D. Codominance E. Multiple alleles

C. Polygenetic inheritance

A pea plant with red flowers is test crossed and one half of the resulting progeny have red flowers, while the other half have white flowers. You know that the genotype of the test crossed parent was A. rr B. RR C. Rr D. either RR or Rr E. Cannot tell unless the genotypes of both parents are known

C. Rr

Which of the following is false? A. The offspring of two different varieties are called hybrids B. The parental plants of a cross are the P generation C. Hybridization is also called a cross D. The hybrid offspring of a cross are the P1 generation E. The hybrid offspring of an F1 cross are the F2 generations

D. the hybrid offspring of a cross are the P1 generation

What is the genotype of a dominant individual if some of its offspring show the recessive phenotype?

Dd

Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes?

Dd and Dd

Which of the following best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders?

Most individuals carrying a lethal disease allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce

If all of Mendel's monohybrid crosses had involved incomplete dominance, would that have given him the same results as blending inheritance? (Assume a snap dragon flower color example)

No, half of the offspring would be red or white

What is the basis for incomplete dominance?

One allele produces some functioning protein; the other allele is nonfunctional

A monohybrid cross is

a breeding experiment in which the parental varieties differ in only one trait

What is a testcross?

a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest

Martians normally have three eyes (E), but the rare "humanoid" mutation (e) causes monsters with two eyes to be born. Eye color in Martians is inherited similarly to humans, with brown eyes (B) being dominant to blue (b). Assuming these two genes are carried on separate chromosomes, what must the genotypes of two normal, brown-eyed parents be if they have a blue-eyed, humanoid son?

both EeBb

Codominance occurs when

both of the alleles in a heterozygote are expressed phenotypically in an individual

A person with AB blood illustrates the principle of

codominance

Sickle-cell disease represents

codominance and pleiotropy

The inheritance of traits in humans is best studied by

construction and evaluating family pedigrees

Mendel's Law of Independent Assortment states that

each pair of alleles segregates independently of the other pairs of alleles during gamete formation

According to the Law of Segregation, in an organism with the genotype Aa

half the gametes will have A and the other half will have a

If the allele for inflated pea pods (I) is dominant to the allele for constricted pods (i), then the cross Ii x ii is expected to produce

half with inflated and half with constricted pods

A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring.

heterozygous for the trait and able

The results of a test cross reveal that all the offspring resemble the parent being tested. This parent must be

homozygous

In snapdragons, red x white = pink. This pattern of inheritance is explained by

incomplete dominance

Mendel's Law of Segregation states that

members of a pair of alleles move away from each other during gamete formation.

Imagine that we mate two black Labrador dogs with normal vision and find that three of the puppies are like the parents, but one puppy is chocolate with normal vision and another is black with PRA (progressive retinal atrophy, a serious disease of vision). We can conclude that

the alleles for color and vision segregate independently during gamete formation

Yellow-seeded pea plants may be homozygous or heterozygous. To find out which, we can cross the plants with

trie-breeding green-seeded plants

Varieties of plants in which self-fertilization produces offspring that are identical to the parents are referred to as

true-breeding

Individuals that are heterozygous for a particular trait have

two different alleles of the gene

A recessive gene is one

whose effect is masked by a dominant allele