Mendelian Genetics Lab Questions

Mendel's monohybrid cross of tall parents with the genotype Tt resulted in a tall to short ratio of

3:1

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

50%

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.)

a a A Aa Aa A Aa Aa

Autosomes

are chromosomes that are the same for both sexes.

An allele that exerts its effects whenever it is present is

dominant.

A portion of DNA that encodes a specific protein is called a(n)

gene.

When Mendel crossed two purple-flowered pea plants with each other, he obtained a phenotypic ratio of 3:1 (purple-flowered pea plants to white-flowered pea plants). His results are consistent with which of the following sets of parents?

heterozygous purple pea plant and heterozygous purple pea plant

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.

Traits that are carried on the X chromosome are said to be

x-linked.

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

¾

Place the stages of the fruit fly life cycle in the correct order.

1. Fertilized Egg2. First Instar Larvae3. Second Instar Larvae4. Third Instar Larvae5. Pupa6. Adult

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

100%

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: CfCf x CfCf, CfCf x Cfcf, CfCf x cfcf 25% cystic fibrosis, 75% normal: Cfcf x Cfcf 100% cystic fibrosis: cfcf x cfcf

If a female was a carrier for sex-linked color blindness, what percentage of her male children would also be color blind?

50%

In the experiment determining the parental genotype of fruit flies from a monohybrid cross, if the number of long wing offspring was equal to the number of short wing offspring, what would the parental genotype have been?

Ll X ll

When predicting the phenotypic ratio of a crossing between two heterozygous fruit flies, the ratio was shown to be 9:3:3:1. What would the parental fruit fly's genotype have been if the resulting offspring had a 1:1:1:1 ratio instead?

Llbb X llBb

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 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 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%.

In a heterozygous individual the allele being expressed is

dominant.

If an individual is heterozygous for a particular trait

each parent contributed a different allele for that trait.

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

homozygous

If the two alleles for a particular gene are identical the gene pair is

homozygous.

When predicting the phenotypic ratio of a crossing between two heterozygous corn plants (PpSs), the ratio was shown to be 9:3:3:1. What would the phenotypic ratio be if we crossed two homozygous corn plants, with one homozygous dominant for both color and texture (PPSS) and the other homozygous recessive for both traits (ppss)?

1:0:0:0

In the study of genetics the offspring of the P generation is referred to as the

F1 generation.