Warm- Up # 4

1. What is a dominant trait?2. What is a recessive trait?3. Is “Bb” genotype or phenotype?4. Is black hair genotype or phenotype?5. Which of these is heterozygous:

A. TT B. Tt C. tt

Learning Target 1/31

• I can determine the genotype and phenotype of a monohybrid cross using a Punnett Square

Vocab Review

• Genotype - the genetic make-up of an organism

HH: homozygous dominantHh: heterozygous dominanthh: homozygous recessive

• Phenotype: the way an organism looks or behaves based on the genotype (trait)

Examples: left-handed, brown eyes, long nose

CH 11 Punnett Squares Notes

Mendel’s Law of Segregation

Rr

R r

R r SpermSperm

Alleles separate during meiosis

Mendel’s Law of Independent Assortment

RrGg

RG Rg rG rg

An individual can give lots of combinations of alleles

Punnett Squares

• Punnett Square - a tool used to predict the genotype of an organism’s offspring

Bb

Bb

Male

Female

Example Punnett Square• Trait: Body Color

dominant = green body (G)recessive = blue body (g)

Parent #1: GgParent #2: Gg

G g

G

g

GG Gg

Gg gg

Example Punnett Square• Possible Offspring Genotypes:

1 GG 25%2 Gg 50%1 gg 25%

G g

G

g

GG Gg

Gg gg

dominant = green body (G)recessive = blue body (h)

Possible Offspring Phenotypes:3 green body 75%1 blue body 25%

Practice Problem #1• Trait: Human Eye Color

dominant = brown eyes (B)recessive = blue eyes (b)

Parent #1: BBParent #2: Bb

B B

B

b

BB

Bb

BB

Bb

Practice Problem #1• Possible Offspring Genotypes:

2 BB 50%

2 Bb 50%

Possible Offspring Phenotypes: 4 brown eyes 100%0 blue eyes 0%

B B

B

b

BB BB

Bb Bb

Practice Problem #2

• In many animals black fur is dominant (B) and brown fur is recessive (b).

• Complete the Punnett Square for Female dog-BbMale dog- bb

B

b

b

b

Bb bb

Bb bb

Practice Problem #2

• Possible genotypes:2 Bb 50%2 bb 50%

• Possible phenotypes: 2 Black fur dog 50%2 Brown fur dog 50%

B

b

b

b

Bb bb

Bb bb

Practice Problem #3

• In people right-handed is dominant (R) and left-handed is recessive (r)

• Complete the Punnett Square for:Heterozygous parentHomozygous recessive

parent

R

r

r

r

Rr rr

Rr rr

Practice Problem #3

• Possible genotypes:2 Rr 50%2 rr 50%

• Possible phenotypes: 2 Right-handed 50%2 Left-handed 50%

R

r

r

r

Rr rr

Rr rr

Monohybrid cross

• Homozygous dominant + homozygous recessive• Example: BB x bb, HH x hh

B

b

b

B

Bb Bb

Bb Bb