A Model used to show the possible ways genes can combine during fertilization.

Helps you keep track of traits.

Punnett Squares

What is a trait?

Trait: a genetically determined characteristic or conditionExamples: dominant and recessive traits

.

Dominant and recessive alleles

are represented by letters.

Punnett Squares

A capital letter (T) is used for dominant alleles.

T

Punnett Squares

A lowercase letter (t) is used for recessive alleles.

Punnett Squares

Monohybrid Cross

Monohybrid cross is a genetic cross made to examine the distribution of ONE specific set of alleles in the resulting offspring.

~We will be using a 2X2 box

If you wanted to know the type of offspring a cross between two parents would produce, you can use a punnett square.

Tt x Tt

TT,Tt for tall

Tt for short

Punnett Squares

The letters representing the alleles from one parent are placed along the top of the square.

T t

Punnett Squares

The letters representing the two alleles from the second

Parent are placed along the side of the square.

T

t

Punnett Squares

T t x T t

T t

T

t

Punnett Squares

Punnett Squares

Squares are filled by writing the letter at the top beside the letter on the side.

TT Tt

Tt t t

T t

T

t

Punnett Squares

The letters in each of the squares represents the Genotypes of the offspring that the parents could produce.

TT Tt

Tt t t

T t

T

t

TT

Tt

Tt

t t

Genotype is the genetic makeup of an organism

Phenotype is the physical appearance of an organism due to the genotpe

Punnett Squares

Genotype Phenotype

TT tall

Tt tall

Tt tall

t t short

Punnett Sqaures

Punnett Squares

Probability: the ratio that a particular event could occur.

out of 4 offspring3 would be tall

1 would be short

Punnett Squares:

•Help you keep track of traits.

•Predict genotype and phenotype.

•Calculate probability.