Punnett Squares & calculating percentages

Pg 125

Punnett Squares

• What are punnett squares?

• What do the letters in a punnett square mean?

• What is a genotype?• What is a phenotype?

• A tool used to predict Mendelian genetics.

• An uppercase letter is a dominate allele, and a lower case letter is a recessive allele.

• A genotype is its genetic makeup

• A phenotype is its how the organism looks as a result of its genotype

Punnett Square

• One dog carries heterozygous, black-fur traits (Bb), and its mate carries homogeneous, blond-fur traits (bb). Use a Punnett square to determine the probability of one of their puppies having black fur.

• What you know: dominant allele is B Recessive allele is b

•What do we need to find: What is the probability of a puppies fur being black

Punnett Square

Black dog (Bb)Blonde dog (bb)

B bb Bb bbb Bb bb

Black dog

Blondedog

Punnett Square

Black dog (Bb)Blonde dog (bb)

There are two Bb genotypes and four possible outcomes%(black fur)= number of ways to get black fur

number of possible outcomes

B bb Bb bbb Bb bb

Black dog

Blondedog

%502

1

4

2

Punnett Square practice

1. In peas, the color yellow(Y) is dominant to the color green (y). According to the Punnett square, what is the probability of an offspring being yellow?

Y yYy

Parent (Yy)

Parent (Yy)

Punnett squares

2. What was the probability of an offspring having the yy genotype?