Download Genetics and Sex-Linked Inheritance Test Review

Genetics and Evolution Test Review
Matching:
__G___ 1. “This allele is only seen when paired with itself”
A. genotype
__C___ 2. JJ or jj
B. phenotype
__B___ 3. “An organism’s physical appearance or behavior”
C. homozygous
__H___ 4. “An allele that has more than one effect on an organism”
D. heterozygous
__I___ 5. “Several alleles, each contributing a small amount to the
final appearance of the trait”
E. allele
__D___ 6. “One dominant and one recessive allele”
F. dominant allele
__A___ 7. “An organism’s genetic makeup”
G. recessive allele
__F___ 8. “An allele that is always seen”
H. pleiotropy
__E___ 9. “A variation of a gene”
I. polygenic trait
__J___ 10. These are why there are 4 different blood types
J. multiple alleles
11. Mendel spoke of observing “true breeding” and “non-true breeding” plants. What did he
mean by this? How would modern geneticists explain what Mendel observed?
Mendel’s true breeding plants passed their traits on to their offspring unchanged while his nontrue breeding did not. True breeding plants are now recognized as being homozygous (dominant
or recessive) and non-true breeding is heterozygous.
12. Explain Mendel’s two Rules of Heredity.
(Rule of Independent Assortment and Rule of Segregation).
Rule of Segregation – alleles from each parent separate and are rejoined randomly in the offspring.
Rule of Independent Assortment – alleles of each gene pair are passed independently (randomly) to
offspring AND different allele pairs are also separated and passed on randomly.
Complete a Punnett Square to support your answers for questions #13 – 16.
13. When Mendel crossed two purple-flowered pea plants, he obtained a phenotypic ratio of 3:1 (purple- flowered
pea plants to white-flowered pea plants). What were the genotypes of the parents?
PP
Pp
Pp
Pp
Pp x Pp
14. All the polar icecaps have melted, covering the world in water. If a man with webbed fingers and webbed toes
marries and has children with a woman that is heterozygous for both webbed fingers and webbed toes, what
genotypes will their children have? (Webbed fingers and toes are both recessive traits).
FfTt
FfTt
FfTt
FfTt
Fftt
Fftt
Fftt
Fftt
ffTt
ffTt
ffTt
ffTt
fftt
fftt
fftt
fftt
Non-webbed fingers and non-webbed toes
Non-webbed fingers and webbed toes
Webbed fingers and non-webbed toes
Webbed fingers and webbed toes
4/16
4/16
4/16
4/16
15. A cartoon mouse with 3 fingers mates with another cartoon mouse with 4 fingers. Predict the phenotypes of
their offspring if 5 fingers plus 3 fingers makes 4 fingers.
F3F3 x F3F5
F3F3
F3F3
F3F5
F3F5
2 offspring with 3 fingers
2 offspring with 4 fingers
16. If mom has blood type AO and dad has blood type AB, what are the possible blood types of their children?
AO x AB
AA
AO
AB
BO
2 offspring with blood type A
1 offspring with blood type AB
1 offspring with blood type B
17. Is it possible for any of their grandchildren to be blood type OO? If so, how? If not, why not?
If either of the children with the AO or BO blood type marry a person that is either blood type OO
or carries the recessive O gene, they can have a child with the OO blood type.
18. Use the Rule of Multiplication to determine how many children in question #14 will be heterozygous for
webbed fingers and have webbed toes.
fftt (father)
f = 2/2
2/2 * 2 /2 = 4/4
t = 2/2
FfTt (mother)
F = 1/2
T = 1/2
1/2 * 1/2 = 1/4
4/4 * 1/4 = 4/16
19. One of the newest areas of genetic research is epigenes. What is an epigene? What does it do?
An epigene is a chemical tag found on the DNA strand and the histone proteins within the DNA strand that
modify the genes. They are what provide variation within the genes. Epigenes can also silence or inactivate a
gene so it isn’t expressed.
20. What do I mean when I say that a gene has been ‘imprinted’? How does imprinting affect an
individual? How, if at all, does it affect an individual’s offspring?
A gene that is imprinted has been turned off by an epigene. This means that for the individual with an
imprinted gene, they are operating as if they were haploid for that gene. In other words, they have only one
working gene for that particular trait. If the silenced gene is passed on to the offspring, they also have only
working gene for that particular trait.
21. Explain the process of DNA methylation. Include in your answer, when this process happens.
During protein synthesis, a methyl molecule is attached to the DNA’s strand’s backbone. This molecule
prevents the gene from being accidently transcribed (turned into a protein). If the protein isn’t made, the trait
isn’t expressed.
22. What does siRNA do? How would using siRNA as a treatment cure a disease?
SiRNA increases or decreases the amount of protein that a particular gene makes. Scientists think that it can
be used to treat disease by increasing or decreasing the production of the protein(s) that allow the gene(s) for
the disease to be expressed.
Matching:
__G___ 23. One gene modifies the effects of another gene
A. Autosome
__D___ 24. Proved that genes are carried on the sex chromosomes
B. Sex Chromosome
__H___ 25. The gain or loss of a chromosome
C. Nondisjunction
__A__ 26. Chromosomes that control the characteristics of the body
D. Thomas Morgan
__C___ 27. Chromosome pairs that don’t separate during meiosis
E. Walter Sutton
__F___ 28. An inactivated X chromosome
F. Barr body
__E___ 29. Credited with the chromosomal theory of inheritance
G. Epistasis
__B___ 30. Chromosomes responsible for gender characteristics
H. Aneuploidy
31. What is mitochondrial DNA? How does it affect inheritance?_
Mitochondrial DNA are small pieces of DNA found in the mitochondria (and in the chloroplasts). This DNA is
different from the DNA found in the nucleus. It is usually passed from mothers to offspring and often carries
genetic information unique to the mother. Mitochondrial DNA can be used to determine family lines – but only
that certain individuals are related through a specific female in that female line.
32. What is a Barr body? Why are they created?
In a female, one of the X chromosomes becomes condensed and inactivated, becoming a Barr body. This is
done so that there isn’t conflicting information between the two X chromosomes. Which chromosome that’s
inactivated is varies randomly from cell to cell. If a female is heterozygous for a sex-linked trait some of her
cells will express one gene and some will express the other – randomly. They call these females genetic
mosaics.
33. A child is born with the genotype XXY. What caused this? Is this child male or female? How do you know?
During meiosis, the sex chromosomes experienced nondisjunction, meaning they weren’t separated properly
between the gamete cells. The child is male because of the presence of the Y chromosome.
34. A male grasshopper’s chromosome #3 has an inverse mutation. (This mutation causes the wings to be
misshapen). If the female has a normal but imprinted chromosome #3, describe the phenotype of the offspring.
Then explain why this happened.
The offspring will have misshapen wings. This happened because the mother’s normal gene has been
inactivated by an epigene. Although the offspring have a gene from each parent, the gene from the mother has
been turned off, making the offspring haploid from wing shape. This means that the only working gene in the
offspring is the mutated gene belonging to the father.