Appendix D
BIO/100 Version 3 / 2

Associate Level Material

Appendix D

Punnett Square Worksheet

Use this worksheet to practice using Punnett Squares to solve genetic problems in preparation for this week’s labs.

Trait, eye color: B = brown eyes, dominant and b = blue eyes, recessive

1.  Father is homozygous dominant

Mother is homozygous recessive

Father’s Alleles
Mother’s Alleles
/ How many children will be:
·  Homozygous, dominant?
·  Heterozygous?
·  Homozygous, recessive?
What is the genotypic ratio?
How many will have brown eyes?
How many will have blue eyes?
What is the phenotypic ratio?

2.  Father is heterozygous

Mother is heterozygous

Father’s Alleles
Mother’s Alleles
/ How many children will be:
·  Homozygous, dominant?
·  Heterozygous?
·  Homozygous, recessive?
What is the genotypic ratio?
How many will have brown eyes?
How many will have blue eyes?
What is the phenotypic ratio?

3.  Father is heterozygous

Mother is homozygous, dominant

Father’s Alleles
Mother’s Alleles
/ How many children will be:
·  Homozygous, dominant?
·  Heterozygous?
·  Homozygous, recessive?
What is the genotypic ratio?
How many will have brown eyes?
How many will have blue eyes?
What is the phenotypic ratio?

Trait, height: T = tall, dominant and t = short, recessive

1.  Mother is homozygous recessive

Father is homozygous dominant

Mother’s Alleles
Father’s Alleles
/ How many children will be:
·  Homozygous, dominant?
·  Heterozygous?
·  Homozygous, recessive?
What is the genotypic ratio?
How many will be tall?
How many will be short?
What is the phenotypic ratio?

2.  Mother is heterozygous

Father is heterozygous

Mother’s Alleles
Father’s Alleles
/ How many children will be:
·  Homozygous, dominant?
·  Heterozygous?
·  Homozygous, recessive?
What is the genotypic ratio?
How many will be tall?
How many will be short?
What is the phenotypic ratio?

3.  Mother is homozygous, dominant

Father is heterozygous

Mother’s Alleles
Father’s Alleles
/ How many children will be:
·  Homozygous, dominant?
·  Heterozygous
·  Homozygous, recessive?
What is the genotypic ratio?
How many will be tall?
How many will be short?
What is the phenotypic ratio?

Traits dimples and curly hair: D = dimples, dominant and d = no dimples, recessive and C = curly hair, dominant and c = straight hair, recessive

1.  Mother is heterozygous for dimples and heterozygous for curly hair

Father is heterozygous for dimples and heterozygous for curly hair

Mother’s Alleles
Father’s Alleles

How many children will be:

·  Homozygous, dominant for dimples?

·  Homozygous, dominant for curly hair?

·  Heterozygous for dimples?

·  Heterozygous for curly hair?

·  Homozygous, recessive for dimples?

·  Homozygous, recessive for curly hair?

How many will have dimples?

How many will have curly hair?

How many will not have dimples?

How many will have straight hair?

2.  Mother is homozygous, recessive for dimples and heterozygous for curly hair

Father is homozygous, dominant for dimples and homozygous, dominant for curly hair

Mother’s Alleles
Father’s Alleles

How many children will be:

·  Homozygous, dominant for height?

·  Homozygous, dominant for eye color?

·  Heterozygous for height?

·  Heterozygous for eye color?

·  Homozygous, recessive for height?

·  Homozygous, recessive for eye color?

How many will be tall?

How many will have brown eyes?

How many will be short?

How many will have blue eyes?

What is the phenotypic ratio?


Answers

Trait: B = brown eyes, dominant and b = blue eyes, recessive

1.  Father is homozygous dominant

Mother is homozygous recessive

Father’s Alleles: BB
B / B
Mother’s Alleles: bb / b / Bb / Bb
b / Bb / Bb
/ How many children will be:
·  Homozygous, dominant? 0
·  Heterozygous? 4
·  Homozygous, recessive? 0
What is the genotypic ratio? 0:4:0
How many will have brown eyes? 4 = 4/4 = 100%
How many will have blue eyes? 0
What is the phenotypic ratio? 4:0

2.  Father is heterozygous

Mother is heterozygous

Father’s Alleles: Bb
B / b
Mother’s Alleles: Bb / B / BB / Bb
b / Bb / bb
/ How many children will be:
·  Homozygous, dominant? 1
·  Heterozygous? 2 or 2/4 = 1/2 = 50%
·  Homozygous, recessive? 1
What is the genotypic ratio? 1:2:1
How many will have brown eyes? 3 = 3/4 = 75%
How many will have blue eyes? 1 = 1/4 = 25%
What is the phenotypic ratio? 3:1

3.  Father is heterozygous

Mother is homozygous, dominant

Father’s Alleles: Bb
B / b
Mother’s Alleles: BB / B / BB / Bb
B / BB / Bb
/ How many children will be:
·  Homozygous, dominant? 2
·  Heterozygous? 2
·  Homozygous, recessive? 0
What is the genotypic ratio? 2:2:0
How many will have brown eyes? 4 = 4/4 = 100%
How many will have blue eyes? 0
What is the phenotypic ratio? 3:1

Trait: T = tall, dominant and t = short, recessive

1.  Mother is homozygous recessive

Father is homozygous dominant

Mother’s Alleles: tt
t / t
Father’s Alleles: TT / T / Tt / Tt
T / Tt / Tt
/ How many children will be:
·  Homozygous, dominant? 0
·  Heterozygous? 4
·  Homozygous, recessive? 0
What is the genotypic ratio? 0:4:0
How many will be tall? 4 = 4/4 = 100%
How many will be short? 0
What is the phenotypic ratio? 4:0

2.  Mother is heterozygous

Father is heterozygous

Mother’s Alleles: Tt
T / t
Father’s Alleles: Tt / T / TT / Tt
t / Tt / tt
/ How many children will be:
·  Homozygous, dominant? 1
·  Heterozygous? 2
·  Homozygous, recessive? 1
What is the genotypic ratio? 1:2:1
How many will be tall? 3 = 3/4 = 75%
How many will be short? 1
What is the phenotypic ratio? 3:1

3.  Mother is homozygous, dominant

Father is heterozygous

Mother’s Alleles: TT
T / T
Father’s Alleles: Tt / T / TT / TT
t / Tt / Tt
/ How many children will be:
·  Homozygous, dominant? 2
·  Heterozygous? 2
·  Homozygous, recessive? 0
What is the genotypic ratio? 2:2:0
How many will be tall? 4 = 4/4 = 100%
How many will be short? 0
What is the phenotypic ratio? 4:0

Traits dimples and curly hair: D = dimples, dominant and d = no dimples, recessive and C = curly hair, dominant and c = straight hair, recessive

1.  Mother is heterozygous for dimples and heterozygous for curly hair

Father is heterozygous for dimples and heterozygous for curly hair

Mother’s Alleles: DdCc
DC / Dc / dC / dc
Father’s Alleles: DdCc / DC / DDCC / DDCc / DdCC / DdCc
Dc / DDCc / DDcc / DdCc / Ddcc
dC / DdCC / DdCc / ddCC / ddCc
dc / DdCc / Ddcc / ddCc / ddcc

How many children will be:

·  Homozygous, dominant for dimples? 4

·  Homozygous, dominant for curly hair? 4

·  Heterozygous for dimples? 8

·  Heterozygous for curly hair? 8

·  Homozygous, recessive for dimples? 4

·  Homozygous, recessive for curly hair? 2

How many will have dimples? 12 or 12/16 = 3/4= 75%

How many will have curly hair? 12 or 12/16 = 3/4= 75%

How many will not have dimples? 4 or 4/16 = 1/4 = 25%

How many will have straight hair? 4 or 4/16 = 1/4 = 25%

How many will have dimples and curly hair? 12 or 12/16 = 3/4= 75%

How many will have dimples and straight hair? 3 or 3/16 = 18.75%

2.  Mother is homozygous, recessive for dimples and heterozygous for curly hair

Father is homozygous, dominant for dimples and homozygous, dominant for curly hair

Mother’s Alleles: ddCc
dC / dc / dC / dc
Father’s Alleles: DDCC / DC / DdCC / DdCc / DdCC / DdCc
DC / DdCC / DdCc / DdCC / DdCc
DC / DdCC / DdCc / DdCC / DdCc
DC / DdCC / DdCc / DdCC / DdCc

How many children will be:

·  Homozygous, dominant for dimples? 0

·  Homozygous, dominant for curly hair? 8

·  Heterozygous for dimples? 8

·  Heterozygous for curly hair? 8

·  Homozygous, recessive for dimples? 8

·  Homozygous, recessive for curly hair? 8

How many will have dimples? 16 or 16/16 = 1 = 100%

How many will have curly hair? 16 or 16/16 = 1 = 100%