3 2 dihybrid
TRANSCRIPT
Launch Mr. McCaffrey is colorblind, as is his father.
His mother is color normal, but we don’t know whether she is a carrier or not. A. What is McCaffrey’s genotype B. What is the genotype of McCaffrey’s father? C. Complete a cross/punnett square to figure out
his mother’s genotype D. Explain whether or not the fact that his father
has the disease is important
Identify the disease below:
Inheritance of Genes:
What does it mean to be a carrier? A person who is a carrier is heterozygous
(Aa). They carry the gene for the disease (a);
BUT they do not have the disease because they are protected by the dominant gene (A).
We use Punnett Squares to determine what the probability of being a carrier
We call this -> a monohybrid cross
AA Aa
Aa aa
A
a
A
aFather
Mother
Dihybrid Crosses Dihybrid crosses let you look at two traits at
the same time. Sixteen boxes instead of four
Mendel’s Law of Segregation According to Mendel’s law, each gamete
will only have one version (allele) of each chromosome
Essentially all gametes are haploid instead of diploid and each gamete has one version of each chromosome from 1-23
Mendel’s Law of Independent Assortment
According to Mendel’s law, which allele goes into each gamete, is random for each chromosome.
Distributive Properties We use distribution to determine the gamete
possibilities:
AaBb
Possible gametes: AB, Ab, aB, ab
What are the possible gametes for
DdFF?
Dihybrid Crosses The ratio we use for a dihybrid involves 4 different
possibilities
Dominant for both traits (A_B_) Dominant for the first trait, but not the second
(A_bb) Dominant for the second trait but not the first
(aaB_) Recessive for both traits (aabb)
AARR AARr AaRR AaRr
AARr AArr AaRr Aarr
AaRR AaRr aaRR aaRr
AaRr Aarr aaRr aarr
AR araRAr
ar
aR
Ar
ARDominant for
both traits
Dominant for one, recessive for the second
Dominant for the second, recessive for
the first
Recessive for both traits