Download Probability and Heredity

Probability and Heredity
Probability
• Probability- in the number that describes how
likely it is that an even will occur.
• The laws of probability predict what is likely to
occur, not necessarily what will occur.
• If I flip a coin there is a 50% chance it will land
on heads or tails.
Probability and Genetics
• How is probability related to genetics?
After mendel’s experiment he realized that
the probability of crossing a tall plant was 3 in
4. The probability of crossing a short plant was
1 in 4.
 Mendel was the first scientist to recognize
this.
Punnett Squares
• Punnett Square- is a chart that shows all the
possible combinations of alleles that can
result from a genetic cross.
Setting it up
• Draw the box.
• Write the male parent’s
alleles along the top of the square and the female
parents along the left side.
M---top-
R
r
F—side R
r
Punnett Square
• Bring down the traits
R
R
r
RR
Rr
Rr
rr
r
In a genetic cross, the allele that each parent
will pass onto its offspring is based on
probability.
RR=1 in 4, Rr= 2 in 4, rr= 1 in4
Punnet Square
• Remember that the Dominant allele will
masks the recessive allele.
Phenotype and Genotype
• Phenotype- is an organisms physical
appearance or visible traits.
• Genotype -is its genetic make up or allele
combinations.
• Homozygous- has two identical alleles for a
trait.
• Heterozygous- has two different alleles for a
trait.
Codominance
• In Mendel’s experiments he always had a
dominant allele while the other allele was
recessive.
• This is not always the case.
• In Codominance, the alleles are neither
dominant nor recessive.
• Because of this, both alleles are expressed in
the offspring.