genetics hw

Achondroplasia is a common form of dwarfism caused by autosomal dominant mutation in the fibroblast growth factor receptor 3 (Fgfr3) gene. If a person with achondroplasia (Aa) married and had children with a person of normal height, what is the probability that both their first child and second child would have achondroplasia?

1/4

Human diseases like cystic fibrosis show similar patterns of inheritance as that of Mendel's garden peas. For instance, cystic fibrosis is a recessively inherited trait that is the most common lethal genetic disease among Caucasians. Individuals with cystic fibrosis produce a mutated Cl- channel protein that results in abnormal ion and water transport across epithelia such as that lining the lung, often making it difficult to breath. Individuals who are heterozygous for the cystic fibrosis gene are carriers but do not exhibit the disease. The wild type or normal gene is designated Cf, and the cystic fibrosis gene is designated cf. Drag the individual crosses to their appropriate phenotypic outcome

100% normal CfcfXCfcf cfcf X cfcf cfcf X cfcf cfcfXcfcf 25% cystic fibrosis, 75% normal CfcfXCfcf 100% cystic fibrosis cfcfXcfcf

Suppose a male with genotype AA and a female with genotype aa mate and produce offspring. Fill in the Punnett square below to illustrate the possible genotypes of the offspring for the A gene. (Put alleles inherited from the mother on the top of the Punnett square and alleles inherited from the father along the left side of the Punnett square. Labels may be used more than once or not at all.)

4 Aa

If you cross RrYy and RRyy pea plants, what fraction of the offspring will have yellow peas? R = round, r = wrinkled, Y = yellow, y = green

50%

If you cross two heterozygous (Yy) pea plants, what proportion of the offspring will be heterozygous?

50%

If you cross two heterozygous Yy pea plants, what proportion of the offspring will be the dominant color yellow?

75%

Let P = purple flowers and p = white, and T = tall plants and t = dwarf. What combinations of gametes could be produced by a heterozygote for both the traits?

PT, Pt, pT, pt

In garden peas the allele for tall plants (T) is dominant over the allele for dwarf plants (t). A true breeding tall plant (TT) is bred with a true breeding dwarf plant (tt) to produce heterozygous tall plants. These F1 heterozygotes then self fertilize to yield F2 offspring. Complete the Punnett square for this monohybrid cross with the appropriate genotype of the F1 gametes and the F2 genotype/phenotype combination

TT Tall Tt Tt tt-dwarf

In Drosophila, white eyes is caused by a recessive allele (r) located on the X chromosome. The dominant allele (R) produces red eyes. Suppose a white-eyed female mates with a red-eyed male. Knowing this, complete the sentences with the correct terms.

The genotype of the male is best represented as RY. The genotype of the female is best represented as rr. Among the male F₁ offspring, the predicted proportion with white eyes is 100%. Among the female F₁ offspring, the predicted proportion with white eyes is 0%. Among all F₂ offspring, the predicted proportion with white eyes is 50%

In humans, the allele for dimples (D) is dominant to the allele for no dimples (d). At another gene locus, the allele for broad eyebrows (B) is dominant to the allele for slender eyebrows (b). These two allele pairs assort independently. A man who is heterozygous for both traits marries a woman who has no dimples and who is heterozygous at the gene locus controlling eyebrow width. Complete the sentences about this dihybrid cross with the correct terms.

The genotype of the man is DdBb. The genotype of the woman is ddBb. The genotype of the gametes produced by the man is 25% DB, 25% Db, 25% dB, 25% db. The genotype of the gametes produced by the woman is 50% dB and 50% db. The probability that their first child will have dimples is 1/2. The probability that their first child will have dimples and slender eyebrows is 1/8.

In pea plants there is a dominant allele (A) for green pods and a recessive allele (a) for yellow pods. Suppose a heterozygous plant is crossed with a plant that has yellow pods. Complete the sentences about this monohybrid cross with the correct terms.

The phenotype of the heterozygous plant is green pods. The genotype of the heterozygous plant is Aa. The genotype of the plant with yellow pods is aa. The genotype of the gametes produced by the heterozygous plant is 50% A and 50% a. The genotype of the gametes produced by the plant with yellow pods is 100% a. The expected frequency of F₁ plants with yellow pods is 50%. The expected frequency of F₁ plants with the genotype AA is 0%.

Alternate forms of the same gene are called

alleles

An allele that exerts its effects whenever it is present is

dominant.

In a heterozygous individual the allele being expressed is

dominant.

A diploid organism that has two identical alleles for the same trait is called _______ for that particular trait.

homozygous

All gametes contain

one set of chromosomes

Let P = purple flowers and p = white, and T = tall plants and t = dwarf. What would be the appearance of a plant with the genotype PpTt?

purple flowers, tall

An allele for a particular trait that is only expressed when present in two copies is called a(n)

recessive allele

A particular species of plants can have yellow or green seeds. This trait is determined by one gene. The yellow-seeded plants might be homozygous or heterozygous. We could find out which by crossing these plants with

true breeding green-seeded plants.

The probability of obtaining a dominant phenotype from self-fertilization of a heterozygous individual is

¾.