Consider the following tetrahybrid cross in pea plants: TtRrwAa x ItRcYvaa Assum
ID: 183208 • Letter: C
Question
Consider the following tetrahybrid cross in pea plants: TtRrwAa x ItRcYvaa Assume that T = tall (dominant), t = dwarf (recessive), R = round (dominant), r wrinkled (recessive), Y = yellow (dominant), y = green (recessive), A = axial (dominant), and a terminal (recessive). Assume that the alleles of all four genes assort independently. a. What proportion of the offspring will be tall, round, green, and terminal b. What proportion of the offspring plant has the ttRrYvAa genotype? c. What proportion of the offspring will be heterozygous for all four genes? d. What proportion of the offspring will be dwarf, wrinkled, yellow, and axial?Explanation / Answer
Q) consider the following tetrahybrid cross in pea plant Tt Rr yy Aa crossed with Tt Rr Yy aa , here T is tall dominant , t -dwarf recessive, R -round , dominant, r - wrinkled recessive , Y -Yellow dominant, y -Green , recessive, A-Axial , dominant, a - terminal recessive.
1 ) What proportion of offspring will be tall round green and terminal .
Tall Round Green Terminal - Tt Rr yy aa, TT RR yy aa
Answer : -
A tetrahybrid cross, consists of four characters , so probability of homozygotes would be (XX, xx)= 1/4 ,
and the probability of heterozygotes would be (Xx) = 2/4 or 1/2.
in question 1 the proportion of offspring having Tall Round Green and Terminal character would be
TT RR yy aa = 1/4 * 1/4*1/4* 1/4 = 1/256.
and for Tt Rr yy aa = 1/2 * 1/2 * 1/4 * 1/4 = 1/64.
Explanation :- in question 1 we get two combination of charatcers in case 1 - all are homozygotes , so we get 1/256 due to the multiplication rule of probability, in case -2 -half of the caracters are homozygotes and half are heterozygotes so when the rule of multiplication is applied result obtained is 1/64.
Q2 ) What proportion of offspring plant has tt Rr Yy Aa genotype - Dwarf round yellow Axial
Answer :-
tt Rr Yy Aa = 1/4 * 1/2 * 1/2 * 1/2 = 1/32
Explanation :- Here one trait - Dwarfness (tt) is homozygous and all other traits ( Round Yellow Axial) are heterozygous so the proportion would be multiplication of single homozygous and three heterozygous traits.
Q3 ) What proportion of offspring will be heterozygous for all four genes?
Answer :- The offsprings having heterozygous characters for all four genes would be Tt Rr Yy Aa
Tt Rr Yy Aa = 1/2 * 1/2 * 1/2 * 1/2 = 1/16
Explanation :- By using the heterozygote probability (1/2) and using multiplication rule of probability the result is 1/16.
Q4) What proportion of the offspring will be Dwarf Wrinkled Yellow Axial ?
Answer :- Here we get two types of offsprings they are tt rr YY AA and tt rr Yy Aa.
in case -1 Proportion of tt rr YY AA = 1/4 * 1/4 * 1/4 * 1/4 = 1/256 and in case -2 proportion of tt rr Yy Aa would be = 1/4 * 1/4 * 1/2 * 1/2 = 1/64.
Explanation :-
Dwarf Wrinkled Yellow Axial = tt rr YY AA , tt rr Yy Aa there are two combinations .
for tt rr YY AA combination as it is all homozygous the proportion would be by using multiplication rule of probability- 1/4 * 1/4 * 1/4 * 1/4 = 1/256.
For tt rr Yy Aa combination proportion would be as here two homozygotes and two heterozygotes are there = 1/4 * 1/4 * 1/2 * 1/2 = 1/64 .