In pea plants, the allele for yellow seeds (Y) is dominant over the one for green seeds (y) and the allele for round seeds (R) is dominant over the one for wrinkled seeds (r). A homozygous yellow, round seed is crossed with a homozygous green, wrinkled seed. The offspring of this cross are then crossed. What is the probability that an offspring of the second generation will be green and wrinkled? (Express your answer as the simplest fraction.) _________

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Beverley SmithLv2

2 Sep 2018

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2. Cross a homozygous tall yellow seeded plant with a homozygous short green seeded plant. This is called the P1 cross, and it will produce offspring called the F1 generation. Tallness is dominant to shortness, so use a capital T to represent the tallness allele and lower case t to represent the shortness allele. Yellow seeds are dominant to green sees, so use a capital Y to represent the yellow seed allele and a lower case y to represent the green seed allele.

a) What is the genotype of the tall plant?

b) What gametes can the tall plant make?

c) What is the genotype of the short plant?

d) What gametes can the short plant make?

e) Create a punnett square explaining this

f) What is the genotypic ratio of the F1 plants?

g) What is the phenotypic ration of the F1 plants?

tanwalrus385

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

You recently discovered a new variety of sweetpea plants in the area surrounding Chernobyl that cannot be crossedwith the sweet pea plants used in Mendel's experiments. Youidentify several pure breeding strains with characteristics thatare similar to those described by Mendel. You found that round (R)was dominant over wrinkled (r) for pea shape and yellow (Y) wasdominant over green (y) for pea colour in monohybridcrosses.

(a) show the expected outcome of a dihybridcross starting with pure breeding plants with round yellow peas andpure-breeding wrinkled green peas. Include all phenotypes and thecorresponding genotypes for parental, F1 and F2 generations. Alsoinclude the expected phenotypic ratios for the F2 generation.Surprisingly, when you performed this cross, you notice someinteresting differences from Mendel's experiments. Although all F1progeny had round yellow peas, the F1 self cross resulted in farfewer round green and wrinkled yellow peas than expected. Beingvery clever, you hypothesize that these loci may be linked in thisvariety of pea and you performed a testcross between F1 plants anddouble homozygous plants with wrinkled green peas. You obtained thefollowing progeny: 445 Round yellow, 48 round green, 52 wrinkledyellow and 455 wrinkled green. (b) Identify the parental andrecombinant classes from the test cross (2 marks). (c) Estimate therecombination frequency using these data, and show your work. (d)Indicate the distance between loci in map units, and show yourwork. (e) Using the recombination frequency you calculated in (c),predict the phenotypic ratio in the F2 generation in the dihybridcross in (a)