If the F1 plants with red flowers were crossed to each other

If the F1 plants with red flowers were crossed to each other, what progeny would be produced and in what proportions? On occasion, genetically identical humans are produced by a natural cloning process. The result is identical, or monozygotic, twins. These individuals have all 23 pairs of chromosomes identical to those of their twin. Fraternal twins are produced when two eggs are ovulated and fertilized simultaneously, but independently. What is the likelihood that two fraternal twins will be genetically identical? On average, what proportion of their alleles do siblings have in common with each other? On average, what is the probability that any particular X-linked allele carried by a man is also carried by his brother? On average, what proportion of their alleles do children have in common with a parent? You work as a genetics consultant for a local attorney. She is currently working on five cases of disputed paternity. Tests have produced the following information on blood types:

Solution

2A. Fraternal twins are formed from the fertilization of two different ovules by two different sperms and are hence also known as \'dizygotic\'. This implies that there is hardly any likelihood of being any more identical than two siblings, which is 50 percent. However, they can be formed either due to the presence of hyperovulation gene in the mother, which makes the mother release more than one egg at a time, or by multiple fathers within a span of few days. In the first case, the likehood of being identical is 50 percent or more, whereas in the second case, it\'s only the mother\'s gene which is similar in the twins.

2B. Each sibling gets half an allele from each parent, so 50% is all they get from the parents. So one extreme can be each sibling getting the alleles from parents and which the other didn\'t get, while the other extreme can be each sibling getting exactly the same allele. Hence the probability ranges from 0 (no similarity) to 1 (exactly same). So on a average, the proportion of alleles they share is (0+1)/2 = 0.5.

2C. For a man and his brother, the X linked genes can only come from their mother since they will recieve Y gene from their father. Hence, the likelihood is 50%. However, to get the same X-linked genes from mother, the likelihood reduces to 25% (Please refer to the table below).

X1-M, X-F (25%)

(Daughter)

X2-M, X-F (25%)

(Daughter)

X1-M, Y-F (25%)

(Son)

X2-M, Y-F (25%)

(Son)

2D. Since each child receives only half allele from each parent, on an average the have only 50% common with a parent.

		Mother	Mother
		X1-M	X2-M
Father	X-F	X1-M, X-F (25%) (Daughter)	X2-M, X-F (25%) (Daughter)
Father	Y-F	X1-M, Y-F (25%) (Son)	X2-M, Y-F (25%) (Son)