INTRODUCTION TO BEHAVIOR GENETICS
PRACTICE EXAM 1
Match the following definitions to the terms they define:
1. Any chromosome other than the X or Y chromosomes ____
2. Structure composed of chromatin, found in the nucleus of a cell ____
3. An allele that produces a particular phenotype even when present in
the heterozygous state ____
4. The genetic constitution of an individual, or the combination of
alleles at a particular locus. ____
5. The presence of the same allele at a locus on both members of a
homologous pair. ____
6. Type of cell division that occurs in germ cells, producing gametes. ____
7. "Building blocks" of DNA. ____
8. Describes the situation when a gene has multiple effects on
9. 90% of the cell cycle is spent in the phase. ____
10. The phenotype of an individual with only one X and no Y chromosome____
(the following may be used once, more than once, or not at all)
allele amino acid autosome centromere
chromosome DNA dominant Down syndrome
gamete genotype heterozygosity homozygosity
interphase Klinefelter syndrome meiosis mitosis
non-disjunction nucleotides phenotype
pleiotropy recessive RNA crossing-over
monosomy trisomy Turner syndrome X-linkage zygote
Match the following events to the terms below:
11. When DNA is replicated . ____
12. When crossing-over occurs ____
13. When pairing of homologous chromosomes occurs ____
14. When separation of sister chromatids occurs. ____
15. When genes are able to be expressed . ____
17. Splicing out of introns ____
(each term can be used once, more than once, or not at all)
mitosis meiosis I meiosis II interphase transcription
translation replication RNA processing polymerization
Distinguish between the following terms
16. codominance and incomplete dominance
17. phenotype and genotype
18. Explain the term "non-disjunction".
Give an example of a disorder caused by non-disjunction and briefly explain how this disorder arises.
How it arises_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
19. If the following sequence shows the codons in part of an RNA molecule:
a. show how a nonsense mutation might result in no polypeptide being produced on translation of this part of the sequence:
AAA CAG UUA GAC AAA CUA UAA
lys glu leu asp lys leu stop
b. show a CAG (trinucleotide) 5 repeat mutation and its consequences in terms of amino acid sequence for the same sequence
20. Define the term ‘penetrance’. Give an example of an allele that is fully penetrant and an example of an allele that shows incomplete penetrance.
21. A man who is heterozygous for familial hypercholesterolemia (caused by an incompletely dominant allele) marries a normal women and they have children.
a. What is the probability that the first 2 children will have the trait?
b. What is the probability that the first 3 children will have the trait?
c. What is the probability that the first 2 or 3 children will have the trait?
22. A mouse geneticist discovers 2 autosomal recessive alleles, each of which , when homozygous, causes blindness. How could the geneticist determine whether the alleles occur at the same locus (ie are alleles of the same gene)?