Punnett Squares and Probability

Allele

Different forms of the same gene. Ex) T or t

dominant

When the genotype consists of a dominant and a recessive allele, the phenotype will be like _________________ allele.

ratio

a comparison of two quantities

Dominant

a trait that is always expressed. It prevents a recessive from being expressed.

Punnett Square

used to determine all the possible genotypes and phenotypes that offspring can inherit from their parents

Recessive

A gene that his hidden by a dominant gene. Need two recessive gene for it to be expressed. (ex. bb)

The probability is 0%

A homozygous red (RR) flower is crossed with a homozygous white (rr) flower. Use a Punnett square to determine the probability of one of their offspring having a white color.

The probability is 100%

A homozygous red (RR) flower is crossed with a homozygous white (rr) flower. Use a Punnett square to determine the probability of one of their offspring having red color.

carrier

A person who has one recessive allele for a trait, but does not have the trait.

Genotype

An organism's genetic makeup, or allele combinations.

Phenotype

An organism's physical appearance, or visible traits. Ex.( tall, brown eyes, etc)

Homozygous

"Purebread" having two identical alleles for a trait Ex) BB

The probability is 50%

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

The probability is 75%

One flower is heterozygous red (Rr) and it is crossed with a heterozygous red (Rr) plant. Use a Punnett square to determine the probability of one of their offspring having a red color.

The probability is 25%

One flower is heterozygous red (Rr) and it is crossed with a heterozygous red (Rr) plant. Use a Punnett square to determine the probability of one of their offspring having a white color.

physical appearance

Phenotype refers to the ______________________ of an individual.

What do Punnett Squares show?

They show the probability of offspring inheriting particular genetic combinations.

Heterozygous

Two different alleles for a trait. Ex) Bb

probability

likelihood that a particular event will occur