Biology Punnet Squares? ! Help!

The easiest way to do these types of questions is to understand the terms.

Genotype- the genetic makeup of an organism (AA, Aa, aa)
Phenotype- The physical appearance of trait ( Black hair, blue eyes etc. )
Allele- A version of a gene.
Dominance-when one allele masks the effect of another. In genetics, dominant alleles are denoted by a Capital letter and recessive alleles a lower case.
Homozygous- Having two copies of the same allele.

Example, If A is dominant to a than AA is homozygous dominant and aa is homozygous recessive.

Heterozygous- having two different copies of an allele for one gene (Aa)
Codominace- When both alleles contribute equally to the phenotype.
Incomplete dominance- A heterozygote whose phenotype is a blend of the two homozygotes.

Example, A red flower (AA) is mated with a white flower (aa) to produce a pink flower (Aa).

Sex-linked traits are normally found on the X chromosome. It is important to remember that females are XX and males are XY.

Carrier- carries the allele for the trait but does not express the phenotype.

With that being said I will help you with a couple of these questions and hopefully you will do the rest. I honestly don't think this is a test review.


1.
____A_____A
a___Aa____Aa
a___Aa____Aa

There is no genotypic or phenotypic ratio because you only have one outcome. That is to say that !00% of the offspring will have the genotype Aa and will all have attached earlobes ( A is dominant to a).


5.

_____R______R'
R'___RR'_____R'R'
R'___RR'_____R'R'

Genotypic ratio: 2RR': 2R'R' or 1:1
Phenotypic ratio: 2 Pink(RR') : 2 white (R'R')


9. Blood types are codominant.