Name: Ellie Mullins
Date: 1/9/15
Lab Report: 4.04 & 4.05 Genetic Crosses
** Before beginning this assignment, please read the slides
in your Biology course for lessons 4.04 and 4.05.**
Here are some notes to help you:
Alleles – versions of the same gene – individuals inherit 2 alleles for each gene, 1 from each parent
Dominant Allele - the allele associated with a trait which is expressed even if only 1 copy of the allele
is present (so this dominant trait will show up even if a recessive trait is present)
Recessive Allele - the allele associated with a trait which is expressed only if 2 copies of the allele are
present (this recessive trait will not show up if there is a dominant trait present)
Genotype – an organism’s genetic makeup – the set of alleles for a specific trait
Phenotype – an organism’s physical appearance – how it looks based on the genotype
Homozygous Genotype – organism has 2 identical alleles for a gene
Heterozygous Genotype – organism has 2 different alleles for a gene
P generation (parents)  F1 generation (offspring from parents)  F2 generation (offspring from F1)
Setting up a Punnett Square:
If you need more help with these concepts, here is an instructional video for you. It
introduces important vocabulary and explains Punnett Squares.
https://www.youtube.com/watch?v=i-0rSv6oxSY
Part 1: Monohybrid Cross - Predicting Freckles in an F1 Generation
Some characteristics in people are inherited as simple dominant and recessive traits. One
example is freckles. The allele for having freckles (F) is dominant over the allele for not having
freckles (f), which is recessive. So, having freckles is a dominant trait, and the lack of freckles
is a recessive trait.
In this example, a person with freckles would have the genotype of either FF or Ff because the
dominant F is present. A person with no freckles is represented with the genotype ff.
genotype for freckles: FF or Ff
genotype for no freckles: ff
(2 points)
1. Imagine a mother and a father who both have freckles and are
heterozygous for the trait, (have the genotype Ff). They are the P (parent)
generation. Complete the Punnett square to show their offspring, the F1
generation. Be sure to write the letter for an allele on each bold line.
Example
Parent
2 Allele
#1
Parent
2 Allele
#2
Score
Punnett Square for #1
Parent 1
Allele #1
Parent 1
Allele #2
Offspring
genotype
#1- 25%
chance
Offspring
genotype
#3 – 25%
chance
Offspring
genotype
#2 – 25%
chance
Offspring
genotype
#4 – 25%
chance
_F_
_F_
_F _F
_f_
F
_f_
f
F
f
f
f
(2 points)
2. What are the possible genotypes (both alleles) and phenotypes (physical
appearances) of the offspring (F1 generation)?
Genotypes:
Score
__F_ _F__
Phenotypes:
(1 point)
3. What is the percent chance the offspring will have freckles?
(Hint: Each square is 25%, so add together 25% for each
square that will produce a phenotype with freckles.)
Score
Part 2: Incomplete Dominance—Predicting Flower Color in Snapdragons
Snapdragons are popular plants that produce brightly colored flowers. When a plant that is
homozygous with white (WW) flowers is crossed with a plant that is homozygous with red
flowers (RR), all offspring are heterozygous (WR) with pink flowers. Snapdragons are an
example of a plant that exhibits an inheritance pattern called incomplete dominance.
(1 point)
4. Write the genotype of each parent plant below. Use W to indicate the allele
for white flowers and R to indicate the allele for red flowers.
Score
Genotype of homozygous parent plant with white flowers:
Genotype of homozygous parent plant with red flowers:
(2 points)
5. The two parent plants above in #4 are the P generation, or parent generation.
Create a Punnett square to show their offspring, the F1 generation. Use the
parent genotypes you determined from question 3 above.
Score
(2 points)
6. What are the genotypes and phenotypes of the F1 generation?
Score
Genotypes:
Phenotypes (color of snapdragons):
(4 points)
7. Now create a Punnett square showing a cross between 2 of the F1 plants
from above (genotypes from question 6). Their offspring are the F2 generation.
What are the genotypes and phenotypes of the F2 offspring?
Score
Genotypes:
Phenotypes (colors of snapdragons):
Part 3: Multiple Alleles - Codominance in ABO blood types
As you read in the online lab, human blood type is determined by multiple alleles that show a
type of inheritance called codominance. Recall that the alleles that determine blood type are IA,
IB, and i. IA and IB are both dominant over i, while neither IA nor IB is dominant when they
combine. Use this table to help you determine the genotypes associated with each blood type.
Possible
Genotypes
IA IA or IA i
IB IB or IB i
IA IB
ii
Alleles
IA
IB
A
I IB
i
Blood Type
(Phenotypes)
A
B
AB
O
(4 points)
8. Cross 2 parents, one that has the genotype IAi and the other that has the
genotype IBi. Complete this Punnett square to calculate the possible genotypes
of their children. (To type the A or B click on “Superscript” under “Font.”)
IA
IB
Score
i
Genotypes:
Phenotypes (blood types):
i
Part 4: Sex-Linked Inheritance - Predicting Color Blindness in Offspring
Recall that females have two X chromosomes (XX): one each from the mother and father.
Males have one X chromosome from mother and one Y chromosome from father (XY).
Traits associated with genes located on the sex chromosomes are called sex-linked traits.



Individuals with red-green color blindness do not perceive the colors red and green.
The dominant allele, B, for normal color vision is on the X chromosome (written XB)
The recessive allele, b, causes red-green color blindness (written Xb)
o So a female with normal vision could have the genotype XBXB or XBXb.
 When a female is XBXb, she is a carrier of the color blindness allele.
o A female with color blindness would have the genotype XbXb.
o A male with normal vision would have the genotype XBY.
o
A male with color blindness would have the genotype XbY.
(4 points)
9. A man who is color-blind marries a woman who has normal vision and is
not a carrier of the allele for color blindness. Create a Punnett square to
predict the possible genotypes of their children.
Score
Genotypes:
Phenotypes (male or female AND normal or
color blind vision):
Your Score
/ 22