Download Genetics Study Guide

Genetics Study Guide
Name ________________________
In horses, the coat color black is dominant (B) over chestnut (b). The trotting gait is dominant
(T) over the pacing gait (t). If a homozygous black pacer is mated to a homozygous chestnut,
heterozygous trotter, what will be the ratios for genotype and phenotype of the F1 generation?
Make sure to discover the genotypes of both parents before you begin making the punnett square. Also
remember to use the FOIL technique to figure out what goes on the outside of the square.
Codominance and Incomplete Dominance
In central Kentucky there is a creature know as a wildcat. It comes in three colors, blue, white,
and light-blue. This trait is controlled by a single locus gene with incomplete dominance. A
homozygous (BB) individual is blue, a homozygous (bb) individual is white, and a
heterozygous (Bb) individual is light-blue. What would be the genotypes and phenotypes of the
offspring if a baby-blue wildcat were crossed with a white one?
Sex-Linked Traits
Coat color in cats is a codominant trait and is also located on the X chromosome. Cats can be
black, yellow or calico. A calico cat has black and yellow splotches. In order to be calico the cat
must have an allele for the black color and an allele for the yellow color. Use a punnett square to
show why there are no male calico cats. Remember to attach the alleles to the X chromosome (X-).
A female calico cat is crossed with a male black cat. What are the phenotypes of the offspring
and in what proportion.
Multiple Alleles
In humans there are four different blood types: A, B, AB, and O. The alleles for A (IA) and B (IB)
are codominant and the allele for O (i) is recessive. The genotype for a person with blood type A
could either be IAIA or IAi. Suppose a father of blood type A and a mother of type B has a child of
type O. What blood types are possible in their children?
If a man with A type blood marries a woman of O type blood and they have five children, all of
blood type A. What is the most probable genotype of the man?
What is the genotype of the woman? _________
Pedigree Charts
Draw a pedigree chart for the family described below and use the chart to determine the
genotype or possible genotypes of each member of the family. Be sure to define your variables.
Remember that males are represented by squares and females are circles. Shade in all
individuals who possess the trait that is being looked at.
In humans, having freckles is dominant over not having them. Both Mr. And Mrs. Chambers
have freckles. Of their three children, Robin and Daniel have freckles but Alex does not. Robin
marries Stephen, who does not have freckles. They have two children, Kevin and Beth, who do
not have freckles. Daniel marries Diane who also has freckles. They have one son, Phillip, who
also has freckles. Alex marries Mary, who has freckles. They have one daughter, Norma, who
does not have freckles.
***Also for pedigrees, make sure you can tell if a the inherited trait is dominant or recessive.***
Key Terms to be familiar with: heredity, traits, characteristic, pedigree, diploid, haploid, gene,
allele, homozygous, heterozygous, phenotype, genotype, Mendel’s Laws, monohybrid,
dihybrid, non-Mendelian genetics (codominance, incomplete dominance, sex linkage, multiple
alleles), Karyotypes, Monosomy, Trisomy, Nondisjunction