Punnett SquaresIntroduction

What is it used for?

Used to predict the possible outcomes that may result from the mating process between two individuals

What is it used for?

Using the Create-A-Kid activity

Example:

Using the Create-A-Kid activity◦ What did the letters you flipped for represent?

Example:

Using the Create-A-Kid activity◦ What was different about the way genes were

inherited in the activity done in class versus real life inheritance?

◦ Hint**- Do you know which alleles you will receive from your parents?

Example:

How many alleles do your parents have for each trait?

Inheritance

How many alleles do your parents have for each trait?◦ TWO (or more)!!

◦ SO, how do you know which one you will get?

Inheritance

How many alleles do your parents have for each trait?◦ TWO (or more)!!

◦ SO, how do you know which one you will get?

◦ YOU DON’T!! You can only predict POSSIBLE outcomes

Inheritance

WHY??

Law of Segregation Law of Independent Assortment

Mendel’s Laws

States that every individual possesses a pair of alleles for every trait and that each parent passes a RANDOM copy of only ONE of these to its offspring

Allele pairs SEPERATE during gamete formation

RANDOMLY unite at fertilization One (RANDOM) allele from each parent

Law of Segregation

States that separate genes for separate traits are passed independently of one another from parents to offspring

Meaning- Traits are independent of another◦ Just because you get brown eyes does NOT mean

you will get brown hair

Law of Independent Assortment

Example: Earlobe shape

Attached= Dominant (E)◦ Possible genotypes?

Hanging free= homozygous Recessive (e)

How do you set a punnett square up?

Example: Earlobes Attached= Dominant (E) Hanging free= homozygous Recessive (e)

1. What is the mothers genotype?

How do you set a punnett square up?

Example: Earlobes Attached= Dominant (E) Hanging free= homozygous Recessive (e)

1. What is the mothers genotype? 2. What is the fathers genotype?

How do you set a punnett square up?

Example: Earlobes Attached= Dominant (E) Hanging free= homozygous Recessive (e)

1. What is the mothers genotype? 2. What is the fathers genotype? 3. Write combination in squares

How do you set a punnett square up?

If the mother has attached ear lobes and the father has earlobes that hang free, what kind of earlobes will their child have?

Poll◦ Text 376-06

Predict!!!

Punnett Square Set Up•Each cell within the square is representative of one possible genotypic outcome for any offspring

In purple people eaters, one-horn is dominant (P) and no horns is recessive (p). Draw a Punnet Square showing the cross of a purple people eater that is heterozygous for horns with a purple people eater that does not have horns. Summarize the genotypes & phenotypes of the possible offspring.

White boards

Practice Problem

In garden peas, round seed coats (R) is dominant over wrinkled seed coats (r).  What will the results be of a cross between a homozygous dominant male and a recessive female. 

White boards

Practice Problem

One cat carries heterozygous, long-haired traits (Ss), and its mate carries homozygous short-haired traits (ss). Use a Punnett square to determine the probability of one of their offspring having long hair.

What is the probability of one of their offspring having long hair?

Practice Problem

Write your own genetics problem that can be solved using a Punnett square. When finished, raise your hand to show me and we will switch with another student.

Write your own!!