biology.need help please?

Question

1) In two families,tongue rolling
R is dominant
A non-roller marries a female who is shomozygous dominant roller.

b) Use a genetic diagram(cross diagram) to show the possible
genotypes and phenotype of the offspring.

Answer 1

1. The non-roller must have the genotype (rr) since tongue rolling allele (R) is dominant.

2. Homozygous= same allele (homo=same, hetero=different) dominant = (R)
Thus, female is (RR)

3. Punnet square is used to to show genetic crosses, ie possible offspring geno- and pheno-types.

RR x rr = 100% heterozygous (Rr) = genotype
100% tongue rollers = phenotype (since (R) is dominant)

Check out this great site for Punnet square calculations:

http://www.changbioscience.com/genetics/punnett.html

Answer 2

RRxrr = 4Rr's

All genotypes will be Rr

All phenoytypes will be tonguerollers