Academic Genetics Review
KEY
1. What is a trait?
A characteristic an organism has such as hair color (inherited) or
riding a bike (learned)
2. What is a dominant trait?
The stronger trait that masks the other (hides) represented by a
capital letter in the genotype. Example T=tall
3. What is a recessive trait?
The weaker trait that is masked by the other (hidden)
represented with a lower case letter in the genotype. Example t=
short
4. What is a genotype?
The genetic makeup of an organism; each trait is represented by
2 alleles in the genotype. Example Tt not visible, what’s inside
5. What is a phenotype?
The physical appearance or action that can be observed in an
organism. Example rolling your tongue or tall plant
6. If blue eyes are dominant to green eyes, what genotypes would
give someone blue eyes? What genotypes would give someone
green eyes?
B=blue b=green
BB =blue Bb=blue bb=green
The only way to see the (green eyes) is homozygous recessive
genotype (bb).
7. How many genes do we have for each trait?
1 gene for each trait
8. How many alleles do we get for each trait from each parent?
Each gene is made of 2 alleles: one from mom and one from dad.
For questions 9, 10, and 11, tall is dominant to short.
Tall=T short=t
9. What would a heterozygous genotype be? What would its
phenotype be?
Tt would be tall because it has at least one dominant allele
10. What would a homozygous dominant genotype be? What would
its phenotype be?
TT would be tall because it has at least one dominant allele
11. What would the homozygous recessive genotype be? What would
its phenotype be?
tt would be short because there is no dominant allele
12.What is the difference between a purebred and a hybrid?
Purebred genotypes has either two dominant or two recessive
alleles (TT or Tt=homozygous), hybrid genotypes have one
dominant and one recessive allele (tt=heterozygous)
13.Why do we use a Punnett square in genetics?
To predict the probability of offspring traits (genotypes and
phenotypes from 2 parents –sexual reproduction
14. Determine the probability that two parents who are
heterozygous for eye color will have a blue-eyed child. Brown
eyes are dominant to blue eyes.
Brown=B blue=b
Bb X Bb
Genotypes
BB=25%
Bb=50%
bb=25%
Phenotypes
Brown
Blue
there is a 25% chance of blue
eyes in the offspring
15.A homozygous black rabbit is crossed with a heterozygous white
rabbit. White is dominant to black. Set up the Punnett square
cross. Show all your work. Then use the Punnett square to fill
out the genotypes and phenotypes, and probability of each.
Don’t forget the KEY.
w
w
W
Ww
Ww
w
ww
ww
White=W
Black=w
Ww X ww
Genotypes:
Ww
50%
ww 50%
Phenotypes: white 50%
black =50%
16. What are the base pairs in DNA and how do they go together?
Adenine-Thymine (A-T) and Cytosine-Guanine (C-G)
17. Where is DNA found in an organism?
In the nucleus of a cell wrapped into a chromosome
18. What is the function of DNA?
It encodes or carries information needed to create and direct
the chemicals that produce the diversity of living organisms or
the instructions for the traits.
19. What does DNA look like? Make a sketch in the space below
(hint: how did we make the ladder).
Sugar and phosphate sides to the ladder and base pair rungs
This ladder shape is then twisted
20. Compare and contrast asexual and sexual reproduction. Include
2-3 facts about each one and 2 examples of each.
Sexual Reproduction
Asexual Reproduction
two parents (egg and sperm)
more diversity in offspring
more time invested in offspring
one parent
identical clone of parent
faster
21. What are the levels of organization from organism to gene?
22. What is the difference between how you get a contagious
disease compared to a genetic disorder?
You get contagious diseases such as the flu, by coming in contact
with someone that has the disease. You come in contact with the
virus, bacteria, or whatever carries the “bug”. In a genetic
disorder, the problem is in the genetic makeup carried through
genes (chromosomes/dna) of the parents and inherited by the
offspring through their parents.