In: Biology
Organisms with the genotypes AABbCcDd and AaBbCcDd are crossed. What are the expected proportions of the following progeny?
a. A_B_C_D_
b. AabbCcDd
c. a phenotype identical to either parent
d. A_B_ccdd
Hi
These kind of question can be answered using probability.
When the parents AABbCcDd and AaBbCcDd are crossed, we can get many
different type of progeny. Simplest way to determine the type of
progeny is to consider each group of alleles at a time. Note that
AA or Aa show same phenotype, as A is dominant over a. ( similar
rule applies to rest of the genes as well).
Let us consider AA x Aa; The gametes formed are (A) from first
parent and (A, a) from second parent. When these two gamets mate,
we can get AA and Aa genotypes. So probability to get AA or Aa
combination is 1. probabilty to get Aa only = 1/2
SImilarly, for Bb x Bb, the progeny possible are: BB, Bb, Bb and
bb. So chance to get BB or Bb = 3/4. chance to get bb only or BB
only = 1/4.; chance to get Bb only = 1/2
Similarly, for Cc x Cc, chance to get CC or Cc = 3/4
Similarly, for Dd x Dd , chance to get DD or Dd = 3/4.
a. So in total probability to get A-B-C-D- combination = 1x 3/4 x 3/4 x 3/4 = 27/64 progenies.
b. Chance to get AabbCcDd:
Aa = 1/2.
bb= 1/4
Cc= 1/2
Dd = 1/2
total probability = 1/2 x 1/4 x 1/2 x 1/2 = 1/32 progenies.
c. Phenotypically identical to parents.
It will be same as a.
d. A-B-ccdd
= 1 x 3/4 x 1/4 x 1/4
= 3/64