Describe Mendel’s dihybrid cross. Draw the Punnett square to show possible off springs. Write the phenotypic ratio of F2 generation.
Answers
Answer:
Explanation:
Dihybrid cross is a cross between two different lines/genes that differ in two observed traits. According to Mendel's statement, between the alleles of both these loci there is a relationship of completely dominant - recessive traits. In the example pictured to the right, RRYY/rryy parents result in F1 offspring that arn the name "Dihybrid cross", the "di" indicates that there are two traits involved (e.g. R and Y), the "hybrid" means that each trait has two different alleles (e.g. R and r, or Y and y), and "cross" means that there are two individuals (usually a mother and father) who are combining or "crossing" their genetic informatione heterozygous for both R and Y (RrYy)
The Dihybrid cross is easy to visualize using a Punnett square of dimensions 16:
RY Ry rY ry
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
the 9 represents the proportion of individuals displaying both dominant traits:
RRYY + 2 x RRYy + 2 x RrYY + 4 x RrYy
the first 3 represents the individuals displaying the first dominant trait and the second recessive trait:
RRyy + 2 x Rryy
the second 3 represents those displaying the first recessive trait and second dominant trait:
rrYY + 2 x rrYy
the 1 represents the homozygous, displaying both recessive traits:
rryy
The Dihybrid ratio=9:3:3:1
The genotypic ratios are: RRYY 1: RRYy 2: RRyy 1: RrYY 2: RrYy 4: Rryy 2: rrYY 1: rrYy 2: rryy 1.