Question

Part 2: Mendelian Genetics - Post-Lab Questions: Generation Data Produced by Monohybrid Crosses

1. How much genotypic variation do you find in the randomly picked parents of your crosses?

2. How much in the offspring?

3. Pool all of the offspring from your five replicates.How much phenotypic variation do you find?

4. Is the ratio of observed phenotypes the same as the ratio of predicted phenotypes? Why or why not?

Answer 1

Ans-1 As in monohybrid cross, the parents are usually pure breed and homozygous, i am considering random parent of the cross.

Type TT × tt- parents

Tt Tt Tt Tt- gametes

Genotypically , the parents are very different. One parent is Homozygous dominant for the gene while one is homozygous recessive .T means tallness gene and t means dwarfness

Ans-2 genotypic variation in offsprings-

All the offsprings will be genotypically heterozygous. Means they contain one dominant gene and one recessive but dominant gene will show its effect and the offsprings remain dominant.

Ans-3 replication of offsprings

Tt× Tt

TT Tt Tt tt- gametes

Again phenotypically , there are only two traits, one is tall plant and other is dwarf plant . More individuals after the cross are tall as compared to dwarf phenotype.

Ans- 4

Normally the phenotypic ratio is 3:1. Means 3 individuals/plants are dominant while one is recessive. The cross we have considered here is same as normal monohybrid cross. So the ratio of observed phenotypes is similar but as there are 5 individuals so this may vary. I mean it could happen that any two individuals have same characteristics apart from the four offsprings shown in ans-3.

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