Punnett Squares Predicting Traits

Genetics How to make and read a punnett square

What is a trait? A

notable feature or quality

 Hair

color, eye color, height, skin color

What is an allele?  The

different forms or type of a gene

 Gene

is eye color

 Allele

is color of eyes – brown, blue, hazel

Types of alleles  Dominant  The

one that wins or shows  Shown by using a capitol letter  Recessive  Over

powered by a dominant  Shown by using a lowercase letter

Predicting traits  The

traits a person will inherit can be predicted by using a punnett square  A Punnett square is a chart which shows/predicts all possible gene combinations in a cross of parents (whose genes are known).

Punnett square Dad has a detachable head, mom does not. If we wanted to predict whether or not the kids would have detachable heads, we would use a punnent square.

Punnett square  Mom

has two alleles

 Dad

H

h

h

h

What will there baby get?

has two alleles

Punnett square h h

Hh

Hh

hh

hh

H h When alleles are combined in the squares you are able to see what the child could inherit

Punnett squares

Their child could inherit “Hh” or “hh” H is dominant and the baby will have a normal head h is recessive and the baby will have a detachable head

Hh

Hh

hh

hh

Punnett squares

What are the chances the baby will have a detachable head?

Hh

Hh

hh

hh

Terms to know  Phenotype

– what you see (detachable

head)

 Genotype

type)

– the genes inherited (head