Genetic_crosses_lab_6 Fall 2014

Lab 6: Genetic
Crosses

Name: ______________________________
Lab
section: ____________
Lab Instructor’s
name: _____________________
Last
4 digits of your CUNYFirst Empl ID #:
_____________
Fall 2014

Read Chapter 7 and
print out the sample genetic cross posted below the lab on the portal, to use
as a guide.

Below
is a list of the phenotypes used in this lab.
These are all single gene traits that show complete dominance. Use this information to set up and analyze
your crosses.

Trait

Dominant
phenotype

Recessive
Phenotype

Flower
color

Purple
flowers

White
flowers

Plant
Height

Tall
plants

Short
Plants

Seed
Shape

Smooth
seeds

Wrinkled
seeds

Seed
Color

Yellow
seeds

Green
seeds

Part I: Symbols
and definitions:

1.
a) What is an allele? What is a gene? Give an example of 2 alleles of a human
gene. (0.5 pts)

b) What is the difference between an organism
that is a homozygote and one that is a heterozygote? (0.25 pts)

c) What is the difference between an
organism’s genotype and its phenotype? (0.25 pts)

2.
For each trait in the table below, indicate ALL OF THE GENOTYPESthat are possible.
Use the first letter of the dominant trait to indicate the trait. (2pts)

Trait

Dominant genotype(s)

Recessive genotype(s)

Flower
color

Purple
=

White
=

Plant
Height

Tall
=

Short
=

Seed
Shape

Smooth
=

Wrinkled
=

Seed
Color

Yellow
=

Green

Pick three of the
crosses to complete using any 3 of the last 4 digits of your CUNYFirst BC student
Empl ID. If there are repeats, pick
random numbers, so you are doing 3 different crosses. Circle the numbers of the crosses you are
doing in column 1 below.
You must pick 3 different
crosses. If there are multiple repeated
numbers in your ID, pick additional numbers of your choice.

Cross Number

Male parent traits

Female parent traits

0

Heterozygous for flower color
Heterozygous for height

Homozygous dominant for flower
color
Heterozygous for height

1

Heterozygous for flower color
Homozygous dominant for height

Heterozygous for flower color
Homozygous dominant for height

2

Heterozygous for flower color
Heterozygous for seed color

Heterozygous for flower color
Heterozygous for seed color

3

Homozygous recessive for flower
color
Heterozygous for seed color

Homozygous dominant for flower
color
Heterozygous for seed color

4

Homozygous recessive for seed
shape
Homozygous recessive for height

Heterozygous for seed shape
Heterozygous for height

5

Heterozygous for seed shape
Heterozygous for height

Heterozygous for seed shape
Homozygous recessive for height

6

Homozygous dominant for flower
color
Homozygous recessive for seed
shape

Homozygous recessive for flower
color
Homozygous dominant for seed
shape

7

Heterozygous for flower color
Homozygous recessive for seed
shape

Heterozygous for flower color
Homozygous recessive for seed
shape

8

Heterozygous for seed shape
Heterozygous for seed color

Homozygous recessive for seed
shape
Homozygous dominant for seed
color

9

Heterozygous for seed shape
Homozygous recessive for seed
color

Homozygous recessive for seed
shape
Homozygous recessive for seed
color

Now you can use the charts and
Punnett squares on each of the following pages to complete your crosses. You can use the sample of a genetic cross
posted on the BioPortal directly below the lab for a guide in doing these
crosses.

Cross 1: Please write the
number of the cross you are performing:
______________
Then fill in the genotype and
phenotype for each parent below. Use the sample of a genetic cross posted on
the portal directly below the lab for a guide.

Sex

Genotype

Phenotype

Male

Female

Step 1: Determine the different gamete combinations
that each parent can contribute to the offspring. Check the hint from the
sample problem when you are doing this.

Sex

Gamete 1

Gamete 2

Gamete 3

Gamete 4

Male

Female

Step 2: Fill in the Punnett Square
below

Male gametes place across à
Female
Gametes:
Place
below: ?

Step 3: Find the Phenotype of
each of the 16 combinations in your Punnett Square page.

Phenotype you’ve found in offspring

Number of offspring with this phenotype

Cross 2: Please write the
number of the cross you are performing:
______________
Then fill in the genotype and
phenotype for each parent below.

Sex

Genotype

Phenotype

Male

Female

Step 1: Determine the different gamete combinations
that each parent can contribute to the offspring.

Sex

Gamete 1

Gamete 2

Gamete 3

Gamete 4

Male

Female

Step 2: Fill in the Punnett Square
below

Male gametes place across à
Female
Gametes:
Place
below: ?

Step 3: Find the Phenotype of
each of the 16 combinations in your Punnett Square page.

Phenotype you’ve found in offspring

Number of offspring with this phenotype

Cross 3: Please write the
number of the cross you are performing:
______________
Then fill in the genotype and
phenotype for each parent below.

Sex

Genotype

Phenotype

Male

Female

Step 1: Determine the different gamete combinations
that each parent can contribute to the offspring.

Sex

Gamete 1

Gamete 2

Gamete 3

Gamete 4

Male

Female

Step 2: Fill in the Punnett Square
below

Male gametes place across à
Female
Gametes:
Place
below: ?

Step 3: Find the Phenotype of
each of the 16 combinations in your Punnett Square page.

Phenotype you’ve found in offspring

Number of offspring with this phenotype

Questions:
1. Are gametes haploid or diploid?
What about the offspring, are they haploid or diploid? (1pt)

2. a) Can two purple flowered and yellow seeded parents produce offspring that have
white flowers and green seeds?
Explain using a Punnett square why
you think this outcome is possible or not. (1 pt)

b) Can two short and green seeded parents produce offspring
that are tall and have yellow seeds?
Explain using a Punnett square why you think this outcome is possible or
not. (1 pt)