Cell Bio EXAM 4

Use the figure and the following description to answer the question. In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes marked 1-4 correspond to plants with dark leaves?

1, 2, 3

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What proportion of the offspring of the cross BbTt × BBtt will have black fur and long tails?

1/2

Huntington's disease is a lethal disease caused by an autosomal (meaning not sex-linked) dominant allele. If a father has Huntington's (his genotype is Hh) and the mother is normal, what is the probability that an offspring of this couple will inherit this lethal disease?

1/2

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

1/2 chance the gametes will have A and 1/2 chance a. all the gametes will have gene a.

Widow's peak (W) is dominant to continuous hairline(w), and presence of freckles (F) is dominant to no freckles (f). A homozygous dominant man marries a homozygous recessive woman, and their son marries a homozygous recessive woman, what is the probability for their grandchild to have widow's peak and no freckles?

1/4

The pattern of inheritance can be predicted from data if one is given the parent or offspring genotypes or phenotypes. Two organisms, with genotypes BbDD and BBDd, are mated. Assuming independent assortment of the B/b and D/d genes, determine the genotypic ratios in offspring that would occur.

1/4 BBDD, 1/4 BbDD, 1/4 BBDd, 1/4 BbDd

In a cross AaBbCc × AaBbCc, what is the probability of producing an organism with the genotype AAbbCC?

1/64

The allele for normal pigmentation (P) is completely dominated to the allele for lack of pigmentation (albino)(p). In cattle, red coat color (R) dominates black coat color (r). For an organism to exhibit either color, it must have at least one allele for normal pigment (P) production. An albino bull is crossed with a red cow. An albino bull that is heterozygous for a red coat is crossed with a red cow that is heterozygous for both normal pigment production and for red coloring. What is the probability to get black cattle?

1/8

A plant heterozygous for both traits is test crossed to a plant with wrinkled green seeds with the following results: Green, wrinkled 440 green, round 51 yellow wrinkle 49 yellow, round 460 What is the recombination frequency? What is the distance of the two loci in centiMorgan (cM)? Show your work in detail.

10 %, 10 cM, [(460+49)/1000)x100)= 10

Cinnabar eyes is a X-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type (red-eyed) male, what percentage of the F1 males will have cinnabar eyes?

100%

Two unlinked genes are found in an animal, one for a round head shape (H), and the other for long tail length (T). Its genotype is HhTT. How many possible genotypes can be found in the gametes?

2

A dominant allele P causes the production of purple pigment in corn; pp individuals are white. A dominant allele C is also required for color production; cc individuals are white. What proportion of offspring will be purple from a ppCc × PpCc cross?

3/8

In rabbits, long ears (L) are dominant to short (l) and a black coat (Cb) is incompletely dominant to the white coat (Cw) so that heterozygotes for coat color are gray. These two genes are on separate chromosomes and assort independently. In this cross, what is the probability of obtaining a gray offspring with long ears? (CbCwLI x CwCwLI)

3/8

Crossing a homozygous recessive with a heterozygous, what is the chance of getting a homozygous recessive phenotype in the F1 generation?

50%

An recessive allele is one...

A and B, whose effect is masked by a dominant allele in heterozygous condition. that produces an effect only when in the homozygous condition.

Use the following map of four genes on a chromosome to answer the question. Between which two genes would you expect the highest frequency of recombination?

A and G

In snapdragons, tall (T) is dominant to dwarf (t) and a flower color is incompletely dominant with colors expressed as red (CRCR), pink (CRCW), or white flower (CWCW). A homozygous tall, pink-flowered plant is crossed with a dwarf, pinked-flowered plant. What are all the possible phenotypes in the offspring? What is the expected phenotypic ratio? Explain your result in detail.

All of the possible phenotypes in the offspring will be tall because the homozygous tall plant is dominant over the recessive trait. When it comes to the incomplete dominance, half will be tall and pink, a fourth will be tall and red, and the last fourth will be tall and white. (Out of the 16 different outcomes). The phenotypic ratio is 1:2:1 in this outcome.

n fruit flies, white-eyed is an X-linked recessive trait (Xr). Red-eyed (XR) is dominant over white-eyed. Heterozygous female flies are crossed with red-eyed male flies. Predict the phenotypes of the offspring and the phenotypic ratio. Include the sex of the offspring. (For example: red-eyed male, white-eyed female, etc.) Explain your result in detail.

Answer: The possible phenotypes are having a homozygous red-eyed female, a heterozygous red-eyed female, a red-eyed male, and finally a white-eyed male. So only 1 of them resulted in a white-eyed offspring. This would make the phenotypic ratio be 1/4 for white-eyes.

A true breeding red bull is crossed with a true breeding white cow. All the offspring are roan cattle (meaning their fur show both red and white colors). Which extension of Mendelian laws does this example demonstrate?

Codominance

The allele for normal pigmentation (P) is completely dominated to the allele for lack of pigmentation (albino)(p). In cattle, red coat color (R) dominates black coat color (r). For an organism to exhibit either color, it must have at least one allele for normal pigment (P) production. An albino bull is crossed with a red cow. What extension of Mendelian law does this demonstrate?

Epistasis

Three babies were mixed up in a hospital. After consideration of the data below, which of the following represent the correct baby and parent combinations?

I-2, II-3, III-1

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, how will this affect the gametes at the completion of meiosis?

One-quarter of the gametes descended from cell X will be n + 1, one-quarter will be n - 1, and half will be n.

The allele for normal pigmentation (P) is completely dominated to the allele for lack of pigmentation (albino)(p). In cattle, red coat color (R) dominates black coat color (r). For an organism to exhibit either color, it must have at least one allele for normal pigment (P) production. An albino bull is crossed with a red cow. If half of the offspring from the cross are albino, what is possibly the genotype for the red cow?

RrPp

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

The gene involved is located on the X chromosome.

Which of the following statements about independent assortment or segregation is correct?

The law of independent assortment describes the behavior of two or more genes relative to one another.

How would one explain the results of a dihybrid testcross (for example AaBb × aabb) in which more parental-type offspring than recombinant-type offspring are produced? That is, the phenotypic ratio of the offspring is not 1:1:1:1.

The two genes are on the same chromosome.

Which of the following phrases correctly defines what one map unit is?

a 1% frequency of recombination between two genes

A Barr Body is___.

an inactive X chromosome in female cells

Since colorblindness is a X-linked recessive trait,

fathers of all colorblind daughters must be colorblind.

A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their sons would be color blind and of normal height?

half

German scientist Carl Correns found that the inheritance of variegated color on the leaves of certain plants was determined only by the maternal parent. What phenomenon explains this pattern of inheritance?

inheritance of plastid genes

Based on the information in the last question, if a roan bull is crossed with a white cow, what is the probability for the F1 cattle to be red?

none

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is the inheritance of this trait sex-linked or autosomal?

recessive ; sex-linked

If you mutate one gene that accounts for the feather shape in chicken, and you observe that the offspring show abnormal body temperature, lay lower number of eggs and eat more food, what extension of Mendelian law are you observing?

Pleiotropy

When you cross true-breeding tall and short tobacco plants you get an F1 that is intermediate in heights. When this F1 is self crossed, it yields an F2 with a bell-shape curve distribution of various heights. Which extension of Mendel is demonstrated?

Polygeniic inheritance

A 9:3:3:1 phenotypic ratio is expected from which of the following?

a dihybrid cross for two unlinked genes

The SRY gene is best described as ________.

a gene present on the Y chromosome that triggers male development

n the cross AaBbCcDd X AabbCcDD, what is the probability of getting aabbCCdd in the offspring?

0

In Guinea pigs, black hair (B) is dominant over white (b), rough coat texture (R) is dominant over smooth (r), and short hair (S) is dominant over long hair (s). These three genes are on separate chromosomes and assort independently. A homozygous black, heterozygous rough, heterozygous short-haired male guinea pig is crossed with and a white, smooth, long-haired female guinea pig. (1) What is the genotype of the male (2) What is the genotype of the female? (3) What is the probability of producing a black, smooth, long-haired offspring? (4) What is the probability of producing a white, smooth, short-haired offspring? (5) What is the probability of producing a black, rough, long-haired offspring?

1) BBRrSs 2) bbrrss 3) 1/4 4) 0 5) 1/4

In Labrador retrievers, the dominant gene B determines black coat color and bb produces chocolate brown. A separate gene E shows recessive epistasis over both the B and b alleles resulting in a golden coat (_ _ee). These two genes are on different chromosomes. Neither gene is sex-linked. A breeder wants to know the genotypes of her three dogs, so she breeds them and makes note of the offspring of several litters. Based on these results, you can infer the genotypes of her three dogs. Note: neither of these genes is sex-linked—this is an example of epistasis! This can be solved by writing down what is known about the genotypes and then using logic to "fill in the blanks" for the dogs' genotypes. Golden female (dog 1) x chocolate male (dog 2) Black female (dog 3) x chocolate male (dog 2) offspring: 4 golden, 2 black, 2 chocolate offspring: 2 golden, 3 black, 3 chocolate Answer the following: Genotype of golden female (dog 1) _________ Genotype of chocolate male (dog 2) ____________ Genotype of black female (dog 3) _________

1) Bbee 2) bbEE 3) BBEE

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this type of chromosomal alteration called?

translocation