Download Probability and Punnett Squares – notes

Probability and Punnett Squares – notes
Topic
Probability
Details
• A concept that can be used to ____________the results of a particular event
– Examples
• Chance of a specific team winning a sporting event
• Chance of a coin landing on heads in a coin toss
– Predict what is ______________ to occur, not necessarily what will
actually occur
•
Punnett
Square
___________________________ – A chart that shows how parents’ alleles
might combine in an offspring
– a tool that can help you understand the ______________ of heredity
– Geneticists use Punnett Squares to show all the
_____________________ outcomes of a genetic cross and to
determine the probability of a particular outcome
What is the probability of…..
• The offspring having a yellow seed
color?
________ or ________
–
Using a
Punnett
Square
The offspring having a green seed
color?
_______
or ________
In rabbits, black fur color is dominant to white. What is the probability of
producing a white rabbit if two heterozygous rabbits mate? ____________%
Step 1: Figure out the genotype of the parents.
•
Black is dominant to white.
– B - ______________
– b - ______________
•
Step 2: Set up a Punnett Square.
Step 3: Fill in the Punnett Square.
Step 4: Count the results.
• Genotypes
– _____ homozygous dominant
– _____ heterozygotes
– _____ homozygous recessive
•
Phenotypes
– _____ black fur
– _____ white fur
Parents are heterozygous.
– _________ - dad
– _________- mom
Ratios
•
Probability can also be represented in _______________
– A ratio ___________________ or shows the relationship between a
part to the whole
• Example the probability that a coin will land on heads in a
single coin toss is 1 in 2 or 50%
– As a ratio, the probability would be written as 1:2 and would be read
as, “One to two.”
– In _________________ we use rations to represent probability
•
Practice
Genotypes
– 1 homozygous
dominant
– 2 heterozygotes
– 1 homozygous recessive
– Genotypic Ratio =
____:____: ____
•
Phenotypes
– 3 black fur
– 1 white fur
– Phenotypic Ratio =
____: _____
In pine trees, long needles are dominant over short needles. Cross a homozygous
dominant plant with a plant that is heterozygous. What is the probability that the
parents will produce offspring that have short needles? Give the genotypic and
phenotypic ratios.
Probability of short needles: ________
Genotypic Ratio: _________________
Phenotypic Ratio: ________________
2. In cats, a striped coat is dominant over a solid coat. Cross a cat with a solid coat
with a cat that is heterozygous for a striped coat. What is the probability that the
parents will produce offspring with a solid coat? Give the genotypic and
phenotypic ratios.
Probability of solid coat: ________
Genotypic Ratio: _________________
Phenotypic Ratio: ________________
3. In humans, dark hair is dominant over light hair. Cross a man that is
homozygous recessive with a woman that is homozygous dominant. What is the
probability that the parents will produce offspring with light hair? Give the
genotypic and phenotypic ratios.
Probability of light hair: ________
Genotypic Ratio: _________________
Phenotypic Ratio: ________________