1. Three major types of RNAs were discussed in some detail: mRNA, rRNA,
and tRNA. For each of the conditions below predict the consequences in
terms of the population of proteins being synthesized in a particular cell.
What qualitative and quantitative changes, if any, are expected in the
individual protein involved (if one is involved) and in the population of
proteins produced in that cell?
(a) An acridine dye-induced mutation in mRNA. The condition is
heterozygous in the involved cell.
(b) A deletion (homozygous) that removes approximately half of the rRNA
genes.
Separate and clearly label your answers for parts a-b in the box below.: (a)
Population of proteins: Half of the protein products of that gene will be defective,
and the other half will be normal. Individual protein: The protein should show
multiple amino acid substitutions "downstream" from the point of the mutation. If a
nonsense triplet is introduced, the protein would be shortened in the substituted
region.
(b) Population of proteins: There would be an overall reduction in protein
synthesis. Individual protein: All of the proteins would be made in their normal
form, but at reduced levels.
2. Describe what is meant by the term forward genetics.: Forward genetics
involves the isolation of mutants that show differences in a particular phenotype of
interest. Mutant isolation is usually followed by an analysis of gene pathways
through epistasis and/or complementation analyses. Then the gene is usually
mapped and cloned and studied by a variety of molecular and developmental
approaches.
3. Complementation analysis can be used to determine whether two
mutations are in the same gene. Explain how to test for complementation
and how one would interpret the results.: A cross is made between the two
homozygous strains. If the F1 progeny are wild type, complementation has
occurred and the two mutations must lie in two separate genes.
4. What are the basic regulatory elements in a strand of DNA that allow for
genes to be regulated? Are these different in eukaryotes and prokaryotes? If
so, how?: Promoters, operators in prokaryotes.
, genetics module 4 exam
Promoters, proximal promoter elements, enhancers, and silencers in eukaryotes.
Eukaryotic transcription is different in a few ways, most notably in that prokaryotic
genes are transcribed as operons, while eukaryotic genes are not. In addition, the
role of the nucleosome is different in eukaryotic transcription.
5. Explain why mutations in the lacI gene are trans in their effects, but
mutations in the lacO gene are cis in their effects.: The lacI gene encodes the
lac repressor protein, which can diffuse within the cell and attach to any operator.
It can therefore affect the expression of genes on the same or different molecules
of DNA. The lacO gene encodes the operator. It affects the binding of DNA
polymerase (OR the lacI repressor) to the DNA, and therefore affects only the
expression of genes on the same molecule of DNA.
6. The _________________, which binds to a core promoter, consists of
general transcription factors and RNA polymerase: basal transcription
apparatus 7. What symbols are used to describe constitutive mutations in
the lac operon: I-, O^c
8. High-throughput technologies such as DNA and protein expression
_________ are often used to provide a global picture of gene expression:
microarrays
9. Approximately 5% of the cytosine residues are methylated in the genome
of any given eukaryote. In what way is DNA methylation related to
genetic regulation?: There is an inverse relationship between the degree of
methylation of eukaryotic DNA and the degree of gene expression
10. Constitutive mutations may occur in various components of the lac
operon. Name two genes of the lac operon in which constitutive
mutations could occur.: lacI and lacO
11. What are the approximate positions (in bp) of each type of consensus
sequence (modular element) found at the 5' end of eukaryotic genes?: TATA
is -30 bp relative to transcription start site
GC box -110 bp
CAAT box -70bp
12. Regions of chromosomes that are inactivated through methylation are
termed this.: silent chromatin
13. A __________ is a DNA stretch of 180 bp that specifies a 60 amino acid
homeodomain.: homeobox
, genetics module 4 exam
14. One type of mutation involves the replacement of a purine with a purine.
What general term is associated with this mutational phenomena?: transition
15. This process moves a nucleosome from the TATA box of a gene's
promoter so that transcription can occur.: chromatin remodeling
16. The lac repressor binds to:
promoter and lactose.
lactose and DNA.
RNA polymerase and DNA.
d-galactosidase, permease and transacetylase.
RNA polymerase.: lactose and DNA
17. Which of these is a level or type of genetic regulation in eukaryotes?
Select all that apply:
transcriptional co-
transcriptional RNA
splicing
DNA methylation post-translational: transcriptional, DNA methylation,
and post-translational
18. A conditional mutation is one that allows a mutant gene product to
function normally under the ________ condition, but to function
abnormally under the ________ condition. Such mutations are especially
useful for the study of ________ mutations.
restrictive; permissive; dominant permissive;
restrictive; dominant dominant; recessive;
semidominant recessive; dominant; codominant
permissive; restrictive; lethal: permissive, restrictive, lethal
19. Conditional mutations are more likely to result from which of the
following alterations to the coding region of a gene. a mutation caused
by a deletion a mutation caused by a base addition a mutation caused
by X rays
a mutation caused by a tautomeric shift a mutation caused by a base
addition or deletion: a mutation caused by a tautomeric shift
20. LINES differ from retrotransposons in that LINES:
do not contain LTRs.
do not contain the transposase gene. do not
encode reverse transcriptase. do not transpose
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