Solved Problems Module 2 Part 3 - Atamian Lab

Solved Problems

Module 2

Part 3

1- Because snapdragons posses the pigment anthocyanin, they have reddish-purple petals. Two pure anthocyanin-less lines of snapdragons were developed one in California and one in Holland. They looked identical in having no red pigment at all, manifested as white (albino) flowers. However, when petals from the two lines were ground up together in buffer in the same test tube, the solution, which appeared colorless at first, gradually turned red.

What control experiments should an investigator conduct before proceeding with further analysis?
What could account for the production of the red color in the test tube?
According to your explanation for part b, what would be the genotypes of the two lines?
If the two white lines were crossed, what would you predict the phenotypes of the F2 to be?
What do we call this type of inheritance?

2- Consider production of flower color in the Japanese morning glory. Dominant alleles of either of two separate genes (A- bb or aa B-) produce purple petals.

A- B- produce blue petals and aa bb produce scarlet petals. Deduce the genotypes of the parents and progeny in the following crosses:

Cross	Parents	Progeny
1	blue x scarlet	¼ blue, ½ purple, ¼ scarlet
2	purple x purple	¼ blue, ½ purple, ¼ scarlet
3	blue x blue	¾ blue, ¼ purple
4	blue x purple	3/8 blue, 4/8 purple, 1/8 scarlet
5	purple x scarlet	½ purple, ½ scarlet

3- Consider the following F1 individuals in different species and the F2 ratios produced by selfing:

Cross	F1	F2 phenotypic ratio
1	Cream	12/16 cream, 3/16 black, 1/16 gray
2	Orange	9/16 orange, 7/16 yellow
3	Black	13/16 black, 3/16 white
4	Solid red	9/16 solid red, 3/16 mottled red, 4/16 small red dots

If each F1 was testcrossed, what phenotypic ratios would result in the progeny of the testcross?

4- The normal color of snapdragons is red. Some pure lines showing variations of flower color have been found. When these pure lines were crossed, they have the following results:

Cross	Parents	F1	F2
1	orange x yellow	orange	3 orange:1 yellow
2	red x orange	red	3 red: 1 orange
3	red x yellow	red	3 red: 1 yellow
4	red x white	red	3 red: 1 white
5	yellow x white	red	9 red: 3 yellow: 4 white
6	orange x white	red	9 red: 3 orange: 4 white
7	red x white	red	9 red: 3 yellow: 4 white

Explain the inheritance of these colors
Write the genotypes of the parents, F1, and F2.

5- When homozygous yellow rats are crossed homozygous black rats, the F1 is all gray. Mating the F1 among themselves produced an F2 consisting of 10 yellow, 28 Gray, 2 cream-colored and 8 black.

how are these colors inherited?
using appropriate genetic symbols show the genotypes for each color.
how many of the 48 F2 rats were expected to be cream-colored?
how many of the 48 F2 rats were expected to be homozygous?

6- Four comb shapes in poultry are known to be governed by 2 gene loci. The genotype R-P- produces Walnut comb, characteristic of the Malay breed; R-pp producers Rose comb, characteristic of the Wyandotte breed; rrP- producers pea comb, characteristic of the Brahma breed; rrpp produces single comb, characteristic of the Leghorn breed.

if pure Wyandottes crossed with pure brahmas, what phenotypic ratios are expected in the F1 and F2?
A Malay hen was crossed to a Leghorn cock and produced a dozen eggs, 3 of which grew into birds with rose combs and 9 with walnut combs. What is the probable genotype of the hen?
Determine the proportion of comb types that would be expected in offspring from each of the following crosses:
i. Rrpp x RrPP
ii. rrPp x RrPp
iii. rrPP x RRPp
iv. RrPp x rrpp
v. RrPp x RRpp

7- White fruit color in summer squash is governed by a dominant gene (H) and colored fruit by its recessive allele (h). Yellow fruit is governed by an independently assorting hypostatic gene (G) and green by its recessive allele (g). When dihybrid plants are crossed, The Offspring appear in the ratio 12 White: 3 yellow: 1 green. What fruit color ratios are expected from the crosses

Hhgg x HhGG
HhGg x green
Hhgg x hhGg
HhGg x Hhgg
If two plants are crossed producing half yellow and half green progeny, what are the genotypes and phenotypes of the parents?

8- Mating between black rats of identical genotype produced offspring as follows: 14 cream colored, 47 black, and 19 albino.

What epistatic ratio is approximated by these offspring?
What type of epistasis is operative?
What are the genotypes of the parents and the offspring?

9- The Black langshan breed of chickens has feathered shanks. When langshans are crossed to the Buff Rock breed with unfeathered shanks, all the F1 have feathered shanks. Out of 360 F2 progeny, 24 were found to have non-feathered shanks and 336 had feathered shanks.

What is the mode of interaction in this trait?
What proportion of the F2 would be expected to be heterozygous at one Locus and homozygous at the other?

9- The Black langshan breed of chickens has feathered shanks. When langshans are crossed to the Buff Rock breed with unfeathered shanks, all the F1 have feathered shanks. Out of 360 F2 progeny, 24 were found to have non-feathered shanks and 336 had feathered shanks.

What is the mode of interaction in this trait?
What proportion of the F2 would be expected to be heterozygous at one Locus and homozygous at the other?

10- On chromosome 3 of corn there is a dominant gene A1 which together with the dominant gene A2 on chromosome 9 produces colored aleurone. All other genetic combinations produce colorless aleurone. Two pure colorless strains are crossed to produce an all colored F1.

What were the genotypes of the parental strains and the F1?
What phenotypic proportions are expected among the F2?

11- A plant of the genus Capsella, produces a seed capsule the shape of which is controlled by two independently assorting genes. When dihybrid plants were interpollinated, 6% of the progeny were found to have ovoid shaped seed capsules. The other 94% of the progeny had triangular shaped seed capsules.

What two factor epistatic ratio is approximated by the progeny?
What type of interaction is operative?

12- A variety of opium poppy having lacerate leaves was closed with a variety that has normal lives. All the F1 had lacerate leaves. Two F1 plants were interbreed to produce F2. Of the F2, 249 had lacerate leaves and 16 have normal leaves. Give genotypes for all the plants in the parental, F1 and F2 generations. Explain how lacerate leaves are determined in the Opium poppy.

13- E. W. Lindstrom crossed two corn plants with green seedlings and obtained the following progeny 3,583 green seedlings, 853 white seedlings, and 260 yellow seedlings.

Give the genotypes for the green white and yellow progeny
explain how color is determined in the seedlings.
Is there an epistasis among the genes that determine color in corn seedlings? If so, which gene is epistatic, and which gene is hypostatic?

14- A dog breeder liked yellow and brown Labrador Retrievers. In an attempt to produce yellow and brown puppies, she bought a yellow Labrador male and a brown Labrador female and mated them. Unfortunately, all the puppies produced in this cross were black. When she crossed the two black F1 dogs the results were followed: 215 black, 105 yellow, and 75 Brown.

Explain this result
How might the breeder go about producing yellow and brown Labradors?

15- When a yellow female Labrador Retriever was mated with a brown male, half of the puppies were brown and half were yellow. The same female when mated with a different brown male, produced only brown offspring. Explain these results.

16- The summer of squash plant that produces disc-shaped fruit is crossed with a plant that produces long fruit. All the F1 have disc-shaped fruit. When the F1 are intercrossed, F2 progeny are produced in the following ratio: 9/16 disc-shaped fruit, 6/16 spherical fruit, 1/16 long fruit. Give the genotypes of the F2 progeny.

17- Some sweet pea plants have purple flowers and other plants have white flowers. A homozygous variety of pea that has purple flowers is crossed with homozygous variety that has white flowers. All the F1 have purple flowers. When this F1 is self-fertilized the F2 appears in a ratio of 9/16 purple to 7/16 White.

Give genotypes for purple and white flowers in these crosses.