If there are “CUES” listed within the question, please USE them and UNDERLINE them in your answer!
Chapter 17
1) Fill in the following chart using Figure 5.20 and what you’ve learned about protein structure.
Structure
Bond(s) or interactions holding
the structure together
Description
Primary
Secondary
Tertiary
Quaternary
Then, answer the following:
a) Which of the four levels of protein structure is maintained after denaturing? Explain.
b) When people get their hair chemically straightened, one chemical is put on the hair to break the disulfide bridges that give the hair
strands their (curled) shape, and a second chemical is used to reform the disulfide bridges to hold the hair in a new (straight) position.
What levels of protein structure are affected by this treatment? Why doesn’t the hair stay straight forever after this treatment?
2) Using Figures 5.17 and 5.18, draw the two amino acids, glutamic acid and lysine. Which has two carboxyl groups? (circle and label.) Which has
two amino groups? (circle and label) Also, draw a dipeptide made up of lysine and glutamic acid bound together by a peptide bond. Identify the
peptide bond with an arrow.
3) Use Figure 5.17 to answer the following: Suppose you have placed a protein in an aqueous environment. After consulting Figure 5.17, where
would you expect to find a region that is rich in the amino acids leucine, isoleucine & valine? Why? A region rich in serine, threonine & glutamine?
Why? (CUES: polar, non-polar, interior, exterior)
4) Edwin said to Clare, “The amino acid sequence of the proteins in your hair determines how curly or straight your hair will be.” Clare replied,
“I don’t think that’s right. Your genes determine whether your hair is curly or straight. That’s why it’s inherited.” Who is right? Explain.
(CUES: genotype, phenotype, nucleotide sequence, transcription, translation)
5) Explain how it is that humans have only about 24,000 genes but at least 85,000 different mRNA sequences. (CUES: intron, exon,
spliceosome, alternative mRNA splicing)
6) A dog was taken to a veterinary clinic because it had become increasingly inactive and lethargic. A blood test determined that the dog had
very low levels of the steroid hormones produced by the adrenal glands, especially cortisol. The veterinarian told the owner that the dog has “a
mutation in its cortisol gene.” Explain why this characterization is inaccurate, given that steroid hormones such as cortisol are lipids. Speculate
on a way that a genetic mutation could result in low levels of steroid hormones. (CUES: proteins, transcription, translation)
7) Explain the relationship between codons and anticodons, and describe where they interact. (CUES: complementary, mRNA, tRNA, ribosome,
amino acid, protein)
8) What would be the consequences of the following:
a) A mutation of a promoter sequence such that the promoter is deleted. (CUES: transcription, RNA polymerase, expression)
b) A mutation of the gene that encodes RNA polymerase, such that the polymerase is not made. (CUES: transcription, promoter,
expression)
c) An error in mRNA processing that allows the inclusion of an intron sequence in the final copy of the mRNA strand. (CUES:
translation, protein structure, function)
9) The double-stranded DNA sequence for the coding region of a short polypeptide is:
5’- A T G T T T T C G A C G T G C G A T T G A -3’
3’- T A C A A A A G C T G C A C G C T A A C T -5’
1
5
10
15
20
a) Which strand of DNA (top or bottom) is transcribed into mRNA? Explain. (CUES: start, stop, codon)
b) What is the amino acid sequence of the peptide coded for by the DNA?
c) A mutant strain has a C-G base pair at position 5 instead of the T-A pair shown here. What is the amino acid sequence of the
peptide? Explain.
d) A mutation at base pair 15 results in a peptide that is not full length. What point mutation would cause this? Explain.
10) In the April 30, 2010, issue of Science, J.C. Roach reported that the mutation rate for humans is approximately 1.1 x 10-8 mutations per
base pair in the haploid genome. Humans have a diploid genome of 6 x 109 base pairs. Based on this evidence, calculate the number of mutations
in each new human child. Show your work. Also, explain why the majority of these mutations have no effect on most children.
11) A gene mutation is a change in the sequence of nucleotides that occurs during cell division (mitosis and meiosis) within a single coding section
of DNA. Mistakes can also occur in the transcription of mRNA or the translation of a polypeptide. However, these changes are not considered
to be mutations, because they are not permanent changes to the cell. Explain why “mistakes” in transcription and translation are not as serious
as mutations in a gene. (CUES: inherited, replication)
12) Use Figure 17.26 to summarize transcription & translation. Include all the events shown. (CUES: codon, anticodon, mRNA, tRNA, 5’, 3’,
peptide bond, polypeptide, transcription, intron, exon, nucleus, ribosome, amino acid)
Chapter 19
1) Use Figure 19.3 to describe the 8 methods of regulation of gene expression. Please include regulation at the DNA, RNA & protein levels.
2) Explain how, in a eukaryotic cell, a gene on one chromosome might affect the expression of a gene on a different chromosome. How might a
gene in a certain cell affect expression of a gene in a different cell? (CUES: repressor, activator, RNA polymerase, transcription, transcription
factor, epistasis)
3) What is the difference between epigenetic regulation and gene regulation by transcription factors? (CUES: transcription, methylation,
histone acetylation, activators, repressors, promoter, RNA polymerase)
4) Use Figure 19.5 to answer the following: A biochemist found that an organism produced a pre-mRNA molecule consisting of 1,452 nucleotides
and translated this mRNA into a polypeptide containing 233 amino acids. How many nucleotides in the mRNA message would actually be needed
to carry the message for the polypeptide, and how many were “extras”? How would the organism know which nucleotides made up the message?
(CUES: splicing, stop codon, intron, start codon, coding segment, exon, UTR, 5’ cap, poly-A tail)
5) If the mRNA being degraded in Figure 19.9 coded for a protein that promotes mitosis in a multicellular organism, what would happen if a
mutation disabled the gene encoding the miRNA that triggers this degradation? (CUES: cell division, transcription, translation, tumor, cancer)
6) Explain how the types of mutations that lead to cancer are different for a proto-oncogene and a tumor-suppressor gene in terms of the
effect of the mutation on the activity of the gene product. (CUES: overactive, underactive, stimulation, inhibition)
7) Use p. 380-381 in your textbook to answer the following: What are 3 ways that transposable elements are thought to contribute to a
genome’s evolution?