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Genetics Unit - Test Review
This test will cover genetics, genetic disorders, and chromosomal disorders. First and foremost, study the
notes given in class! Second, look over the two quizzes on genetics. Review the worksheets covering
incomplete dominance (spongebob), codominance (blood typing), and sex-linked traits. Just because
something is not on the review guide does not mean that it will not be on the test.
1. Describe Mendel’s work. You should know what he worked with and what he discovered.
He worked with pea plants. Discovered patterns of inheritance, dominant
and recessive traits
2. List Mendel’s 3 Laws of Inheritance:
1) Principal of Dominance
2) Law of Segregation
3) Law of Independent Assortment
3. Solve the following types of genetic problems:
1 trait crosses involving a dominant and a recessive gene.
(Tt X Tt)
T=Tall t=short
T
t
Genotypic Ratio= TT:Tt:tt
T
TT
Tt
1:2:1
Phenotypic Ratio= Tall:short
t
Tt
tt
3:1
2 trait crosses involving 2 dominant and 2 recessive genes.
(TtGg X TtGg) T=Tall t=Short
G=Green g=yellow
TG
Tg
tG
tg
TG TTGG
TTGg
TtGG
TtGg
Tg
TTGg
TTgg
TtGg
Ttgg
tG
TtGG
TtGg
ttGG
ttGg
tg
TtGg
Ttgg
ttGg
ttgg
Genotypic Ratio=TTGG:TTGg:TTgg:TtGG:TtGg:Ttgg:ttGG:ttGg:ttgg
1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1
Phenotypic Ratio=Tall/Green : Tall/Yellow : Short/Green : Short/Yellow
9
:
3
:
3
:
1
1 trait cross that is sex-linked. (in this case, pretend that the disorder is caused by a recessive allele)
(XHXh X XHY)
XH
Xh
XH
Y
XH XH XH Xh
XHY
Xh Y
Describe the possible offspring:
3 “normal” 1 with disorder
1 normal male, 1 male w/ disorder, 1 normal female, 1 carrier female
A cross involving 2 genes that are codominant.
(IAi X IBi) also known as AO blood crossed with BO blood.
A
O
List all of the possible genotypes: AB, AO, BO, OO
B
AB
BO
List all of the possible phenotypes:
O
AO
OO
Type AB Blood, Type A Blood,
Type B Blood, Type O Blood
4. Which individuals are:
I
Male: I- 1, 3; II- 2, 4, 6; III-1
Female: I- 2, 4; II- 1,3,5; III-2
3
4
II
1
Carriers: I- 2,4; II- 3
Affected: III- 1
2
1
2
3
4
5
6
III
1
2
5. What is a karyotype and identify some of the problems that can be identified by a karyotype.
Karyotype- a picture of a person’s chromosomes. Can be used to check
for chromosome abnormalities, like Down Syndrome & shows the sex
chromosomes.
6. Explain how an autosomal trait is different from a sex-linked trait and provide examples of each.
Autosomal traits are passed on from parents to offspring on genes that do
not determine sex of offspring. EX- Hair Color
Sex-linked traits are carried on the X-chromosome. EX- Hemophilia
7. Define the following terms:
Trait: similar genes, example – eye color
Pure-bred: offspring that are the result of mating between genetically
similar kinds of parents--the opposite of hybrid. Purebred is the same as
true breeding
Hybrid: offspring that are the result of mating between two genetically
different kinds of parents--the opposite of pure-bred.
Homozygous: Homozygous refers to a genotype consisting of two identical
alleles of a gene for a particular trait. EX.- TT or tt
Heterozygous: a genotype consisting of two different alleles of a gene for a
particular trait. EX.- Tt
Dominant Trait: a gene, that when present, is always expressed (shows up)
Recessive Trait: a gene that is only shown when the individual is homozygous
Alleles: Different versions of the gene. EX.- T, t, B, b
Genotype: The actual genetic make-up of an organism, combo of alleles.
EX.- Tt, TT, or tt
Phenotype: The observed traits (what is seen) in an organism. EX.- Tall or
Short
Monohybrid Cross: A genetic cross involving only 1 genetic trait. EX. TT x Tt
Dihybrid Cross: A genetic cross involving 2 genetic traits. EX. TtGG x ttGg
Codominance: Neither allele is dominant or recessive, so that both appear in
the phenotype or influence it. EX.- Type AB Blood
Incomplete Dominance: When neither allele is dominant over the other, so you
get a blending of traits expressed in phenotype. EX.- Red flower crossed
with a White flower produces a Pink flower. RR x WW = RW (Pink)
Sex Chromosome: A chromosome that determines sex of offspring
Autosome: Any chromosome that is not a Sex Chromosome.