Mendel/genetic crosses

Question 1

What happens in a first generation cross in relation to mendel’s 3rd law?

Answer 1

There is a true breeding parent, all results show the same results,e.g. R, R vs r, r results in Rr in all.

Question 2

What happens in a second generation cross?

Answer 2

Phenotypic ratio 3:1
Genotypic ratio 1:2:1

R, r vs R, r results in RR, Rr, R,r and rr.

Question 3

What is the name of the cross for parents in a biological diagram

Answer 3

Punnet square(generald punnet)

Question 4

Explain the 3rd law with a punnet square explanation

Answer 4

If one of the genotypes has a dominant allele and there a single dominant gene, then this is enough to allow for a normal outcome in offspring for dominant phenotype.

ie. R=Smooth
r= wrinkly
so it is smooth.

Question 5

Long explanation of third law…dominant, recessive?

Answer 5

DOMINANT alleles tend to be functional alleles (or even gain-of-function)
RECESSIVE alleles tend to be loss-of-function alleles (a “broken copy” of a gene)