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peachimpala542Lv1

28 Sep 2019

n swine, erect ears are thought to be controlled by a dominant gene (E_), while drooping ears are the result of the homozygous recessive ee. The presence of a white belt running upward from the front legs over the withers (NB) is dominant to no belt (nb). If purebred Hampshires, homozygous for white belt and erect ears, are mated with purebred Durocs, homozygous for no belt and drooping ears:

a. What are the genotype and phenotype in the F1 generation?

b. If the F1 offspring are intermated, what will the genotypic and phenotypic ratios in the F2 generation be?

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Nestor RutherfordLv2

28 Sep 2019

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1. a). The position of the flower on the stem of the garden pea is governed by a pair of alleles. Flowers growing in the axis (upper angle between petiole and stem) are produces by the action of a dominant allele 'T', those growing only at the tip of the stem by its recessive allele 't'. Colored flowers are produced by a dominant gene 'C', and white flowers by its recessive allele 'c'. A dihybrid plant with colored flowers in the leaf axis is crossed to a pure strain of the same phenotype. What genotypic and phenotypic ratios are expected in the F1 progeny?

b). In summer squash, white fruit color is governed by a dominant allele (W) and yellow fruit color by the recessive (w). A dominant allele at another locus (S) produces disc-shaped fruit and its recessive allele (s) yields sphere-shaped fruit. If a homozygous white disc variety of genotype 'WWSS' is crossed with a homozygous yellow sphere variety (wwss), the F1 are all white disc dihybrids of genotype 'WwSs'. If the F1 is allowed to mate at random, what would be the phenotypic ratio expected in the F2 generation?

Hi, Can you please explain clearly. Thank you.

burgundyhedgehog579

Problem A. You cross two homozygous parents: RRYY (round yellow) and rryy (wrinkled green) to produce an F1 generation. Round seeds are dominant, yellow seeds are dominant. You cross two F1s to produce the F2 generation. In the F2 generation, you find an individual with round yellow seeds. You do a testcross to find out the genotype of this âmysteryâ dominant/dominant phenotype. In the offspring of the cross, you find 1?2 have round yellow seeds and 1?2 have wrinkled yellow seeds.

1. Based on these data what was the genotype of the mystery F2?

Problem B. You carry out a dihybrid cross between a red-flowered rose with long pollen grains (A1A1 LL) and a white-flowered rose with round pollen (A2A2 l l). The flower color gene (A) shows incomplete dominance, and long pollen is completely dominant to round pollen. The genes for these traits are on different chromosomes so assort independently

2. What would be the phenotypes of the F1 generation?

3. What fraction of the F2 generation is expected to have red flowers and long pollen? (As always when traits are independent, what rule can you apply to save time?)

Problem D. In the example of epistasis presented in class, the agouti allele in mice (A) codes for striped hairs and is dominant to the allele for all black hairs (a). A loss-of-function allele for the pigment gene (b) produces no pigment and is recessive to the normal, dominant allele (B). The recessive allele at b masks the effect of the A gene. A dihybrid cross of AABB and aabb is carried out.

5. Name all of the genotypes in the F2 generation that can produce an albino (no pigment) phenotype.

Problem E. A cross is made between homozygous fruit flies that differ for eye color (the st gene) and

body color (the e gene). The F1 double heterozygote is shown below using chromosome notation.

st+ e

--------------------------------------

st e+

st = the recessive allele for scarlet eyes; st+ = the dominant wildtype allele for red eyes e = the recessive allele for ebony body; e+ is the dominant wildtype allele for gray body

6. Are the chromosomes shown in the genotype above in cis or trans configuration?

7. Based on this notation, what were the genotypes and phenotypes of the two parents of the F1? (Think carefully here...)

8. With what phenotype would you cross this F1 to measure recombination frequency?

cyansnail823

Diagram a cross between a true breeding pea plant that produces yellow seeds (G/G) with one that produces green seeds (g/g). Carry the cross out to the F2 generation. Answer the following questions:

What was the F1 genotype and phenotype?

What kinds of gametes could the F1 individuals produce?

What were the F2 genotypes and phenotypes, and in what ratios would you expect each to occur?

Diagram a cross between a true breeding pea plant that produces round seeds and purple flowers, with one that produces wrinkled seeds and white flowers. (Round and purple are the dominant traits.) Carry the cross out to the F2 generation. Answer the following questions:

What are the P1 genotypes?

What is the F1 genotype and phenotype?

What kinds of gametes will the F1 individuals produce?

What are the F2 genotypes and phenotypes?

What genotypic and phenotypic ratios are expected in the F2 progeny?

Diagram a cross between a true breeding pea plant that produces yellow seeds (G/G) and purple flowers (W/W) with one that produces green seeds (g/g) and white flowers (w/w). Carry the cross out to the F2 generation. Answer the following questions:

What was the F1 genotype and phenotype?

What kinds of gametes could the F1 individuals produce?

What were the F2 genotypes and phenotypes, and in what ratios would you expect each to occur?

Diagram a test cross of the F1 individuals from the question above, with the homozygous recessive parent strain. What genotypes and phenotypes would you expect in the testcross progeny, and in what ratios?

If you had a fruitfly with phenotype A, what test would you make to determine if it was Aa or AA? Explain the different outcomes expected if the fly in question is AA or Aa.

If individuals of genotype AaBbCc are intercrossed:

How many different genotypes can occur in their progeny? How many different phenotypes can occur in the progeny?