Question

n the shrub Ixococ meloites, red flower color is incompletely dominant to white flower color. If a true-breeding plant with red flowers is crossed to a true breeding plant with white flowers, what would be the phenotype of the F1 plants? a. The plants will all have red flowers. b. The plants will all have white flowers. c. The some of the flowers on an F1 plant will be red and other flowers on the same plant will be white. d. All of the flowers will be pink (whitish red). e. All of the flowers will be green.

2. From the data in the above cross, you want to construct a genetic map, to position genes A, B, C and D on a chromosome. Therefore you also obtain additional genetic information from the cross in the previous question. You find 14% of the offspring show recombination between genes A and C; 16% show recombination between genes A and D; 17% show recombination between genes B and D; and 2% show recombination between genes C and D. Based on this information and the data from the previous question, what is the order of the four genes A, B, C and D on the chromosome?

	a.	A-B-C-D.
	b.	A-C-B-D.
	c.	B-A-C-D.
	d.	B-C-A-D.
	e.	B-D-A-C.

3. If the F1 generation plants from question 19 above are crossed to themselves (selfed), what percentage of the F2 plants will have red flowers?

	a.	0%.
	b.	25%.
	c.	50%.
	d.	75%.
	e.	100%.
4. If you perform a genetic cross and you find that 1% of the offspring show recombination between genes A and B; but 15% of the offspring show recombination between genes B and C. Which of the statements below is true: a. Gene C controls the expression of gene B. b. Gene C controls the expression of gene A. c. Gene A is epistatic to gene B. d. Genes A and B are likely physically closer together on the same chromosome than genes B and C. e. Genes B and C are likely physically closer together on the same chromosome than genes A and B.

5.if a heterozygous female (a carrier of color blindness, but not color blind herself) has children with a normal man, what percentage of the female progeny (children) will be color blind?

	a.	0%.
	b.	25%.
	c.	50%.
	d.	75%.
	e.	100%.

6. if a heterozygous female (a carrier of color blindness) has children with a normal man, what percentage of the male progeny will be color blind?

	a.	0%.
	b.	25%.
	c.	50%.
	d.	75%.
	e.	100%.

7. if a heterozygous female (a carrier of color blindness) has children with a normal man, what percentage of the female progeny will be carriers of the color blindness allele?

	a.	0%.
	b.	25%.
	c.	50%.
	d.	75%.
	e.	100%.

Answer 1

1)  red flower color is incompletely dominant to white flower color.

let the alleles be R-red, W-white

the genotype of the true-breeding plant with red flower is RR and the genotype of the true-breeding plant with white flower WW

RR * WW

RW

incomplete dominance means heterozygotes produced intermediate phenotype compared to homozygotes.

so the phenotype of F1 progeny are pink. d) All of the flowers will be pink (whitish red)

2) recombination frequency in percentage is the distance between genes in map units.

distance between A and C= 14 cM, the distance between A and D= 16 cM, the distance between B and D= 17 cM, the distance between C and D= 2 cM

here distance between A and D= distance between A to C + distance between C to D

= 14+ 2

= 16 cM

so the order of genes is A-C-D

only one option has this sequence so the answer is c) B-A-C-D

3) RW * RW

	R	W
R	RR ( red)	RW ( pink)
W	RW ( pink)	WW ( white)

percentage of red-flowered plants in the F2= ( number of red-flowered plants/total number of plants)100

= (1/4)100

= 25%

so the answer is b) 25%

4) if the recombination frequency is less than 50% the genes are linked on a chromosome.

recombination frequency in percentage is the distance between genes in map units.

if recombination frequency between genes is low then the genes are linked more closely to each other, so the answer is

d) Genes A and B are likely physically closer together on the same chromosome than genes B and C.