Lab 6: Genetic Crosses

26 Jun Lab 6: Genetic Crosses

Question
Lab 6: Genetic Crosses
Name: Marcus Bannister______________________________
Lab section: ____________
Lab Instructor’s name: Natasha LaMont_____________________
Last 4 digits of your CUNYFirst Empl ID #: _____________
Fall 2015

Read Chapter 7 and print out the sample genetic cross posted below the lab on
launchpad 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
Flower color
Plant Height
Seed Shape
Seed Color

Dominant phenotype
Purple flowers
Tall plants
Smooth seeds
Yellow seeds

Recessive Phenotype
White flowers
Short Plants
Wrinkled seeds
Green seeds

Part I: Symbols and definitions:
1. a) What is a gene? What is an allele? Give an example of 2 alleles of a human gene. (0.5
pts)
A gene is the basic physical and functional unit of heredity.
Allele is one of a number of alternative forms of the same gene or same genetic locus.
Attached earlobe allele and Window peak allele.

b) What is the difference between an organism that is a homozygote and one that is a
heterozygote? (0.25 pts)
Heterozygote has two kind allele for specific-Aa
Homozygote organism has one kind allele for specific gene-AA

c) What is the difference between an organism’s genotype and its phenotype? (0.25 pts)
Genotype is an organism’s full hereditary information. For AA

Phenotype is an organism’s actual observed properties, for example red-colored flowers
2. For each trait in the table below, indicate ALL OF THE GENOTYPES that are possible. Use
the first letter of the dominant trait to indicate the trait (for example, use the letter P for purple).
(2pts)
Trait
Flower color
Plant Height
Seed Shape
Seed Color

Dominant genotype(s)
Purple = AA
Tall = BB
Smooth = CC
Yellow = DD

Recessive genotype(s)
White = aa
Short = bb
Wrinkled = cc
Green= dd

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 flower color
Homozygous recessive for seed shape
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. Use the sample of a genetic cross posted on Launchpad directly below the lab
for a guide in doing these crosses.
Cross 1: Please write the number of the cross you are performing: __6____________
Then fill in the genotype and phenotype for each parent below. Use the sample of a genetic
cross posted on launchpad directly below the lab for a guide.
Sex

Genotype

Phenotype

Male

AaCc

Purple Flower
and Wrinkled
seed

Female

AaCc

White flowers
and smooth seed

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

AC

Ac

aC

ac

Female

AC

Ac

aC

ad

aC

ac

Step 2: Fill in the Punnett Square below
Male gametes
place across

AC

Ac

Female Gametes:
Place below: ↓
AC

AACC

AACa

AaCC

AaCc

Ac

AACa

AAcc

AaCc

Aacc

aC

AaCC

AaCc

aaCC

aaCa

ac

AaCc

Aacc

aaCd

aadd

Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page.
Phenotype you’ve found in offspring
Purple flower, wrinkle seed
Purple flower, smooth seed
White flower, wrinkle seed
White flower, smooth seed

Number of offspring with this phenotype

Cross 2: Please write the number of the cross you are performing: _____1_________
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

Male
Female

Step 2: Fill in the Punnett Square below
Male gametes
place across
Female Gametes:
Place below: ↓

Gamete 3

Gamete 4

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: _____9_________
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

Male
Female

Step 2: Fill in the Punnett Square below
Male gametes
place across
Female Gametes:
Place below: ↓

Gamete 3

Gamete 4

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)
Gametes are haploid and the offspring are diploid

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

b) 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)
It is possible if the parent has heterozygote for purple flowers and yellow seeded
Male gametes placed across

AD

Aa

aD

ad

Female Gametes placed below:
AD

AADD

AADa

AaDD

AaDd

Ad

AADd

AAdd

AaDd

Aadd

aD

AaDD

AaDd

aaDD

aaDd

ad

AaDd

Aadd

aaDd

aadd