Question

In: Biology

. You cross true breeding blue and red morning glories and get all blue offspring. a)...

. You cross true breeding blue and red morning glories and get all blue offspring.

a) Based on this information alone:

i) How many loci are involved in the expression of this trait? How many alleles? What are the dominant and recessive interactions between the alleles at the locus/loci?

ii)what are the possible genotypes of the parents and F1s?

iii) Based on your hypothesized genotypes from ii, what do you expect the outcome of a cross between the F1's to be? (i.e. what phenotypes in what ratios?

b) You then cross the F1 individuals and you obtain the following results

Blue - 200

purple - 126

red - 24

i) Are these results statistically consistent with your hypothesis above? (prove it)

ii) If not, what is an alternative hypothesis that might explain these results?

Are these results the result of one locus or 2?

Test your new hypothesis using chi-squared test. Discuss the meaning of your results. (Note: If your hypothesis proves wrong, that is OK!!! But you have to be able to discuss why you think it's wrong.)

Solutions

Expert Solution

1. One locus with two alleles. Blue (B) is dominant over red (b).

2. BB (blue) × bb (red) = Bb (blue)

3. Bb × Bb

Gametes	B	b
B	BB blue	Bb blue
b	Bb blue	bb red

Blue = 3/4

Red = 1/4

4. # total progenies = 200 + 126 + 24 = 350

Null hypothesis = blue is completely dominant over red.

Phenotype	# observed	# expected	(O-E)^2/E
Blue	200	262.5	14.88
Purple	126	0	0
Red	24	87.5	46.02

Degrees of freedom = 4 - 1 = 3

Calculated chi square = 14.88 + 0 + 46.02 = 60.9

p value < 0.05

Null hypothesis rejected

Blue colour is not completely dominant over red colour.

Alternate hypothesis - Blue colour is not completely dominant over red colour. In the second generation we are able to see purple coloured progenies which is an intermediate between blue and red. It may mean that blue colour is in completely dominant over red colour resulting in intermediate phenotype of heterozygotes.

Please give a good rating.

gladiator answered 1 year ago

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