Mastering Biology 3 - Mendelian Genetics

1/4

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first child will be an albino?

0 homozygous black (BB): 1 heterozygote (black) (Bb): 1 homozygous orange (bb) The heterozygous black-eyed MendAlien has the genotype Bb. The orange-eyed MendAlien has the genotype bb. The result of this cross is two Bb offspring and two bb offspring. This 2:2 ratio reduces to 1:1.

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the genotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

1 black : 1 orange The heterozygous black-eyed MendAlien has the genotype Bb. The orange-eyed MendAlien has the genotype bb. The result of this cross is two Bb offspring and two bb offspring. This means that two of the offspring have black eyes and two of the offspring have orange eyes. This 2:2 ratio then reduces to 1:1.

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

3 round-seed producing plants:1 wrinkled-seed producing plants.

In Mendel's experiment with round- and wrinkled-seed plants, the F1 plants, which produced only round seeds, were grown up andmatured and were allowed to self-fertilize. What was the ratio of round to wrinkled seeds in the F2 generation?

0

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?

Genotype: 1/2 Rr: 1/2 rr; Phenotype: 1/2 Round: 1/2 Wrinkled

In peas, the allele for round seeds (R) is dominant to the allele for wrinkled seeds (r). What would be the genotype and phenotype ratios of offspring from a cross between Rr and rr individuals?

50 percent

In tigers, a recessive allele causes a white tiger (absence of fur pigmentation). If one phenotypically normal tiger that is heterozygous is mated to another that is phenotypically white, what percentage of their offspring is expected to be white?

traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1 generation

Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that ________.

Dominant

Mendel mated plants that produced only round seeds and to those that produced only wrinkled seeds. In the next generation, all the pea plants produced only round seeds. Which term describes how the round-seed allele is inherited?

phenotype

Mendel studied the inheritance of several types of pea-plant traits, including seed color. Seed color is an observable trait of the plant, and is termed a ___________________ .

phenotype

Mendel studies seven different traits in the garden pea. What genetic term is used to describe an observable trait, such as those studied by Mendel?

No. It clearly shows that the null hypothesis is correct. Although the results do not support the stated hypothesis, they provide conclusive evidence of which hypothesis (null versus experimental) is correct.

Should the experiment shown in Figure 14.3 be considered a failure? Why or why not?

Mendel's law of segregation Mendel's law of segregation is based on gametes getting only one copy of each allele of each gene.

That each gamete contains a single allele of the eye color gene is an illustration of _____.

are all Rr This cross indicates that the wild type head top allele is dominant to the flat head top allele, so all offspring are indeed Rr.

The result of the following cross indicates that genotypically the offspring _____.

RR Because wild type head top is dominant to flat head top and because all of the F1 generation are wild type head top, the genotype of the female parent must be homozygous dominant.

The result of the following cross indicates that the genotype of the female parent is

rr Because wild type head top is dominant to flat head top, the only genotype that produces the flat head top phenotype is homozygous recessive.

The result of the following cross indicates that the genotype of the male parent is _____.

recessive to The result of this cross indicates that both parents are heterozygous for eye color.

The result of the following cross indicates the orange eyes are _____ black eyes.

The two major hypotheses of the time were blending inheritance and inheritance of acquired characteristics.

The work of Gregor Mendel provided an answer to two prevailing hypotheses popular at the time. What were these two hypotheses?

This Punnett square shows three different alleles for blood type. *True* This Punnett square represents a cross between I Ai and I AI B parents. *True* This Punnett square shows that if the parents had four offspring, each offspring would have a different genotype. *False* There is not enough information in the model to be sure whether the female gametes are shown on the left or top of the Punnett square. *True* This Punnett square shows that the gametes are haploid and the offspring are diploid. *True* This Punnett square shows that the parents will have four offspring. *False*

This Punnett square focuses on the inheritance of human blood types. Interpret the model. This Punnett square shows three different alleles for blood type. *T/F* This Punnett square represents a cross between I Ai and I AI B parents. *T/F* This Punnett square shows that if the parents had four offspring, each offspring would have a different genotype. *T/F* There is not enough information in the model to be sure whether the female gametes are shown on the left or top of the Punnett square. *T/F* This Punnett square shows that the gametes are haploid and the offspring are diploid. *T/F* This Punnett square shows that the parents will have four offspring. *T/F*

D.

Three of these student models predict the same frequencies of offspring genotypes. Which one is different?

A and C

Three students have drawn a Punnett square to figure out the likelihood that a healthy mother with no family history of sickle cell anemia and a healthy father carrying the recessive allele (a) for sickle cell anemia will have a child with sickle cell anemia. Which students have shown the correct genotypes in their models?

the parents were both heterozygous for the particular trait

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This ratio suggests that _____.

1, 2, and 3

Use the figure and the following description to answer the question(s) below. 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?

½ homozygous dominant and ½ heterozygous

What are the frequencies of each offspring genotype in a cross between Rr female and a RR male?

1:1

When Mendel crossed yellow-seeded and green-seeded pea plants, all the offspring were yellow seeded. When he took these F1 yellow-seeded plants and crossed them to green-seeded plants, what genotypic ratio was expected?

50 percent

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

A and E

Which of these Punnett squares shows a cross that predicts round seeds (RR or Rr) in half of the offspring?

A? x aa A testcross is used to determine whether an individual expressing the dominant phenotype is homozygous dominant or heterozygous.

Which of these is a testcross? A? x A? A? x Aa A? x AA aa x aa A? x aa

One allele was dominant.

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?