Chapter 8, Lesson 2

Probability and Heredity

Chapter 8, Lesson 2

​Pages 302-307

How is Probability Related to Inheritance?

Probability - number that describes how likely it is that an event will occur

The laws of probability predict what is likely to occur, not what will occur

Probability and Genetics

Mendel discovered that probability applies to genetics too

• the probability of a hybrid cross producing the dominant trait is 3 out of 4

Mendel was the first scientist to recognize that genetics could be predicted using probability

Phenotypes and Genotypes

Phenotype - an organisms physical appearance or visible traits

Genotype - an organisms genetic makeup or alleles

Naming Genotypes

Geneticists use other terms to describe genotypes

Homozygous - organism that has two identical alleles for a trait (PP, pp, TT, tt) --> PUREBRED

Heterozygous - organism that has two different alleles for a trait (Pp, Tt) --> HYBRID

Multiple Choice

What is probability?

• A number that predicts an outcome.

• A number that describes how likely it is an event will occur.

• A number that is exactly what will happen.

• A prediction of future events.

Multiple Choice

What is the Phenotype of this flower?

• It has a white phenotype.

• It has a green phenotype.

• Phenotype... what's that?

• It has a purple phenotype.

Multiple Select

What are the possible Genotypes of this flower? (there are two--remember purple color is dominant!)

• PP

• pp

• Zxy

• Pp

Multiple Choice

What is the possible genotype for this flower? (Remember white flowers are a recessive trait.)

• PP

• Pp

• XYSE

• pp

Multiple Select

Which of the following alleles are heterozygous?

• Ww

• Qq

• Rr

• ff

Multiple Select

Which of the following alleles are Homozygous Dominant?

• DD

• dd

• AA

• aa

Multiple Select

Which of the following alleles are Homozygous Recessive?

• rr

• RR

• dd

• DD

Punnett Squares

Punnett Square - chart that shows all the possible ways alleles can combine in a genetic cross

In a genetic cross, the combination of alleles that parents can pass to an offspring is based on probability
Punnett squares can be used to explain why Mendel saw the results he did

Multiple Choice

What is this graphic tool called?

• A guessing space.

• An "R" square.

• A Punnett Square

• A Prediction box

Multiple Choice

Finish the empty box on this Punnett square.

Multiple Choice

What is the scientific way to name this?

• Homozygous Dominant

• Homozygous Recessive

• Heterozygous

Multiple Choice

Looking at his Punnett Square, what is the probability that the offspring will have a yellow seed pod?

• 1/2 or 50%

• 1/4 or 25%

• 0% chance

• 100%

Multiple Choice

Looking at this Punnett Square what is the probability of having a brown haired offspring?

• 25%

• 50%

• 100%

• 75%

Multiple Choice

Looking at this Punnett Square, what is the probability of having a heterozygous offspring?

• 25%

• 10%

• 50%

• 75%