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### Course: Class 10 Biology (India)>Unit 4

Lesson 2: Heredity & Mendel's experiment

# Independent assortment (dihybrid cross)

Let's explore the law of independent assortment. Created by Mahesh Shenoy.

## Want to join the conversation?

• Could there be a possibility for a trihybrid cross, tetra hybrid cross, or poly hybrid cross?
And for the second question, does a sperm contains a variation of all particular genes or are some variations of gene reserved for some sperms?
• Yes, in nature its generally poly hybrid cross are more prevalent. One example being skin colour.
As for the second question, it depends upon linkage or how far the genes are from each other in the DNA that determines what are the different variation.
There is no reservation of variation for genes for some sperms, it is all a game of probability.
• so if we are given a particular conditions how we will be able to recognize the recessive and a dominant character
• Simple, if we get the F1 progeny of the organism the characters which is shown is the dominant allele and the characters which aren't shown are recessive.
For example: Suppose we take a pure bred tall plant and cross it with a pure bred short plant all the progeny (offsprings) we get will be tall.
This is because tall trait is masking the short trait resulting in tallness of the plant
this shows that tallness is dominant and shortness is recessive.
• what is the genotype ratio for the same example given above in the video?
(1 vote)
• for f1 generation the ratio would be 1 (TtYy)
and for f2 generation it would be 1:2:1:2:4:2:1:2:1
• Is the answer to the third question given at the end the same as that of a dihybrid cross between homozygous dominant and recessive plants? If not, please explain the answer.
(1 vote)
• How does the sperm have traits from the mother like shown at ? Doesn’t the characters in the sperm all come from the father? Same for the eggs...?