PSYCH 3102






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

phenotype.                                                                                        ____

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:


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)?