SBI4U Chptr 5 MT Exam Review

Name:

Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.

The anticodon for the mRNA codon CGA is GCT. _________________________

Ribosomes move along mRNA in a 5' � 3' direction. _________________________

The genetic change responsible for the disease sickle cell anemia is a point mutation. _________________________

If an X-ray technician suffered genetic damage, it would most likely be due to chemical mutagenic agents. _______________________________________

Ethidium bromide is responsible for induced mutations. _________________________

The mRNA transcript of a gene is made up of the same bases, in the same proportion, as the strand of DNA complementary to the template strand, except the uracil will be replaced by the thymine. __________________________________________________

The tRNA anticodon is complementary to the mRNA codon, which is itself complementary to the DNA bases on the template strand from which it was transcribed. The tRNA anticodon is, therefore,always identical to the base triplet in the template strand of the DNA, except that thymine replaces uracil. _____________________________________________

When Jacob and Monod added lactose to a culture of E.coli cells, they found that lactose was metabolized and that radioactive amino acids were incorporated into the enzyme beta-galactosidase. This was because the inducer prompts the expression of the beta-galactosidase gene, which then started to digests lactose into galactose and glucose. ____________________________________________

Microsatellites often consist of numerous repeats of short sequences of base pairs. _________________________

10.

The fact that the genetic code is very different in almost all organisms indicates that it evolved early in the history of life on earth. _____________________________________________

Multiple Choice
Identify the choice that best completes the statement or answers the question.

11.

The genetic code is

a.	very similar in humans and apes, but different in horses
b.	very similar in monkeys and rats, but different in starfish
c.	very similar in camels and beetles, but different in a geranium
d.	very similar in antelopes, pine trees, and blue-green algae
e.	very similar in all eukaryotes, but different in prokaryotes

12.

Which of the following correctly describes the order in which cell components become involved in protein synthesis?

a.	DNA polymerase, mRNA, ribosome, tRNA
b.	mRNA, RNA polymerase, ribosome, tRNA
c.	RNA polymerase, mRNA, tRNA, ribosome
d.	RNA polymerase, mRNA, ribosome, tRNA
e.	DNA, rRNA, tRNA, mRNA

13.

Line A below shows the peptide synthesized after transcription and translation of a piece of DNA. Line B shows the peptide synthesized after a mutation in this piece of DNA.

A. proline - arginine - aspartic acid - lysine - glycine
B. proline - glutamine - aspartic acid - lysine - glycine

The type of change in the DNA most likely to be responsible for the difference between the peptides is

a.	a frame-shift mutation	d.	a base deletion
b.	a base insertion	e.	a silent mutation
c.	a base substitution

14.

Four genes (A,B,C,D) of a bacterium code for four enzymes (A,B,C,D), which act sequentially to catalyze the production of compound D, as follows.

	enzyme A		enzyme B		enzyme C		enzyme D
precursor �		compound A �		compound B �		compound C �		compound D

A number of mutant strains of the bacterium are isolated, which grow only on supplemented media, as outlined below.

Medium supplemented with
	compound A	compound B	compound C	compound D
strain 1	no growth	no growth	growth	growth
strain 2	no growth	growth	growth	growth
strain 3	no growth	no growth	no growth	growth

The mutations in strains 1, 2 and 3 (respectively) are in genes

a.	C, B, D	d.	B, A, C
b.	C, B, A	e.	A, B, C
c.	D, C, A

15.

A cell in cell culture is briefly immersed in radioactive uracil. After a short time, the radioactive uracil is removed and the cell culture is washed with, and immersed in, nonradioactive uracil. Where would you expect to find the main concentration of radioactive nucleic acid?

I. Immediately after immersion in the radioactive uracil solution.
II. Some time after the cell was returned to nonradioactive uracil.

a.	in the nucleus in both cases
b.	in the cytoplasm in both cases
c.	I. in the nucleus; II. in the cytoplasm
d.	I. in the nucleus; II. in the nucleus and cytoplasm
e.	I. in the nucleus; II. outside the cell

16.

In eukaryotes, introns are removed before mRNA leaves the nucleus because

a.	they do not code for protein
b.	they prevent the movement of ribosomes
c.	they prevent the binding of ribosomes to mRNA
d.	the mRNA would be too long to pass through the nuclear pores if the introns remained in it
e.	they do not consist of the same bases as the rest of the mRNA

17.

If transcription could proceed in both directions along both DNA strands of a gene, how many different polypeptides could be coded for by a single gene?

a.	1	d.	4
b.	2	e.	none
c.	3

18.

There are differences in the amino acid sequence of rabbit and frog haemoglobin polypeptides. If mRNA for rabbit haemoglobin is extracted from rabbit red blood cells, and is then placed in frog eggs, the cells will produce rabbit haemoglobin polypeptides. This shows that

a.	rabbit haemoglobin mRNA is the same as frog haemoglobin mRNA
b.	the genetic code and the machinery of translation are substantially the same in widely-different organisms
c.	the gene for haemoglobin is identical in all organisms
d.	the DNA for rabbit hemoglobin is reverse transcribed into DNA in the frog eggs
e.	frog ribosomes are incapable of binding to mammalian RNA

19.

The repressor protein of the lac operon has two different recognition and binding sites for other molecules. Which of the following pairs of molecules do you think it likely that these sites would bind?

a.	RNA polymerase and lactose
b.	RNA polymerase and DNA
c.	a DNA sequence on the operator and lactose
d.	a DNA sequence on the regulator gene and lactose
e.	lactose and DNA polymerase

20.

In the presence of high cellular concentrations of tryptophan

a.	the repressor attaches to the DNA, but transcription proceeds
b.	the repressor binds to tryptophan and then leaves the operator
c.	tryptophan binds to the operator and prevents transcription
d.	tryptophan binds to the repressor, which than binds to the operator
e.	tryptophan binds to the repressor, which binds to the promoter and prevents transcription

21.

Which of the following is true with respect to the lac operon?

a.	The repressor only binds to the operator when it is bound to the product of the enzymes coded for by the genes of the operon.
b.	The repressor only binds to the operator when it is bound to the mRNA transcript of the lacZ and lacY genes.
c.	The repressor only leaves the operator when it is bound to the protein product of the lacI gene.
d.	The repressor is always bound to the operator, but changes shape when lactose binds to it, allowing RNA polymerase to pass.
e.	The repressor is bound to the operator, except when it is bound to the inducer.

22.

Garrod's work was significant because he proposed that an individual's hereditary makeup might effect that individual's ability to produce an enzyme. He did this by

a.	clarifying the nature of the disease alkaptonuria and investigating the pattern of its inheritance
b.	specifying the structure of the chemical alkapton
c.	investigating the structure of the enzyme which metabolizes alkapton
d.	investigating gene regulation in the operon producing the enzymes of the alkapton synthesis pathway
e.	noticing that alkaptonuria was a disease normally found only in males

23.

If you were shown an electron micrograph of a cell in which mRNA was being translated while it was still being transcribed from the DNA, you would know

a.	the gene product was in high demand at the point in the cell cycle at which the image was captured
b.	the cell was prokaryotic
c.	transcription was occurring extremely fast
d.	the electron micrograph showed the nucleus of the cell
e.	the cell was eukaryotic

24.

Which of the following is not true of prokaryotic cells?

a.	There are no introns.
b.	The methionine that enters the 'P' site at the beginning of translation has a formyl group attached to it.
c.	At least some of the genes are organized into operons.
d.	The ribosomes, which are smaller than those in eukaryotes, bind to the 5' cap of the mRNA.
e.	he genome is circular.

25.

It is thought possible that the evolution of modern eukaryotic cells involved an endosymbiotic relationship between the prokaryotic cell ancestral to mitochondria and a host prokaryotic cell. Which of the following is not true?

a.	Mitochondria have DNA organized into a few tiny chromosomes held in a mini-nucleus.
b.	The sequence of the DNA of mitochondria is similar to that of bacterial DNA.
c.	Mitochondria divide by fission.
d.	The prokaryotes ancestral to mitochondria may have had compartmentalized organelles.
e.	Mitochondria have replication, transcription, and translation systems distinct from those of the host cell.

26.

Which of the following is not accurate?

a.	The DNA in eukaryotes is arranged into chromosomes.
b.	The DNA in eukaryotes contains noncoding regions.
c.	The mRNA transcript of the DNA of eukaryotes has a 5' cap.
d.	The ribosomes of eukaryotes are larger than in prokaryotes.
e.	The spliceosomes are larger in eukaryotes than in prokaryotes.

27.

Which of the following is not an example of noncoding DNA?

a.	VNTRs	d.	SINES
b.	telomeres	e.	histones
c.	LINES

28.

Which of the following statements concerning the infection of human cells by HIV viruses is not accurate?

a.	After entry to the cell, the virus coat is removed, and then the viral DNA is released into the cell.
b.	The virus binds to specific sites on the surface of a human cell.
c.	Single stranded DNA is converted into double stranded DNA.
d.	When viral DNA takes over the protein synthesizing apparatus of the cell, viral proteins are produced by the host cell ribosomes.
e.	New viral particles, containing nucleic acid and structural protein, 'pinch off' from the host cell membrane.

29.

A provirus is

a.	a virus that has not yet infected a human cell
b.	a RNA transcript of viral DNA
c.	viral DNA integrated into a host cell chromosome
d.	newly formed viral protein and nucleic acid just before it pinches off from the host cell membrane
e.	a virus locked on to a binding site on the host cell membrane

30.

Compare the two mRNA sequences below.
AUAUUCGGCAAUCCG
AUAUUCCGCAAUCCG
This change could be the result of a

a.	nonsense mutation	d.	translocation
b.	addition mutation	e.	point mutation
c.	deletion mutation

31.

The 'Central Dogma' states that the flow of genetic information is in the direction

a.	protein, RNA, protein	d.	RNA, DNA, protein
b.	RNA, DNA, RNA	e.	DNA, RNA, protein
c.	protein, RNA, DNA

32.

Which of the following statements is inaccurate concerning the deoxyribose sugar in a DNA nucleotide?

a.	It has an oxygen atom attached to its 2' carbon.
b.	It has an oxygen atom attached to its 3' carbon.
c.	It has a base attached to its 1' carbon.
d.	It has an oxygen atom attached to its 5' carbon.
e.	It is found in chloroplasts and mitochondria.

33.

There are three kinds of RNA polymerase in eukaryotes�RNA polymerases I, II, and III. RNA polymerases I, II, and III are used, respectively, to transcribe

a.	mRNA, tRNA, rRNA	d.	tRNA, rRNA, mRNA
b.	tRNA, mRNA, rRNA	e.	all transcribe mRNA
c.	rRNA, mRNA, tRNA

34.

The function of the polyadenine tail that is added to mRNA in eukaryotic cells is to

a.	prevent degradation of the mRNA
b.	initiate the binding of the mRNA to the ribosome
c.	help the mRNA to bind to a pore in the nuclear membrane
d.	add a specific amino acid sequence to the polypeptide produced
e.	act as a signal for the termination of translation

35.

In a eukaryotic cell, the sizes of the large and small ribosome subunits are, respectively

a.	50S, 40S	d.	80S, 60S
b.	60S, 50S	e.	80S, 70S
c.	60S, 40S

Completion
Complete each statement.

36.

The sequence of ____________________ in DNA determines the sequence of ____________________ in the polypeptide for which the DNA codes.

37.

After transcription, the first-formed mRNA is modified in eukaryotic cells. A ____________________ is added at the 5' end and a _____________________ made up of many ____________________ nucleotides is added at the 3' end.

38.

In eukaryotic cells, the first-formed mRNA transcript is processed by ____________________ made up of ____________________ and RNA, which remove the introns.

39.

Excess of tryptophan ____________________ synthesis of the enzymes coded for by the genes of the trp operon. The trp repressor protein only ____________________ to the operator of the trp operon when it is bound to tryptophan. Therefore, tryptophan is a ____________________.

40.

HIV viruses bind to specific _________________________ on the helper T-cell surface. After this, the viral and cell _________________________ fuse and the entire virus enters the cell.

41.

Mutations that involve long sections of DNA are called ____________________ mutations. A kind of mutation that involves the movement of a piece of one chromosome to another (often nonhomologous) chromosome is called a ____________________. ____________________ are mutations in the course of which a segment of a chromosome breaks off, turns through 180�, and then joins up again with the chromosome.

42.

____________________ elements are pieces of DNA that constantly move from one location in the genome to another.

43.

The DNA of the ____________________ strand of a gene is ____________________ into mRNA, then ____________________ into protein.

44.

There are different kinds of RNA in a cell. ____________________ is always comparatively short, ____________________ is variable in length, while ____________________ forms part of the ribosome.

45.

At the end of translation, a ______________________________ protein causes the dismantling of the ______________________________ complex.

Matching

Match each item with the correct statement below.

a.	SINES	e.	pseudogenes
b.	LINES	f.	nucleosomes
c.	telomeres	g.	centromeres
d.	histone

46.

DNA sequences homologous with genes that are never transcribed.

47.

noncoding DNA at the end of chromosomes.

48.

groups of eight proteins enveloped by coiled DNA.

49.

positively charged protein.

50.

points of contact of two replicated chromosome strands.

51.

repeated DNA sequences about 5000�7000 base pairs long.

52.

repeated DNA sequences about 300 base pairs long.

Short Answer

53.

It has been demonstrated that the memories of mice can be improved by genetically engineering their genomes to include an extra copy of a gene called NR2B. The protein product of this gene functions as a receptor in the neurons of many vertebrates. For which type of human diseases might this discovery prove important in the development of a therapy?

54.

Recent research indicates that in some bacteria, when an anticodon attempts to hydrogen bond to a codon, two parts of the ribosome (called A1492 and A1493) change shape and check that the match is correct (i.e., that the bases of the codon and anticodon are complementary�at least as far as the first two bases of the codon are concerned). The amino acid from the tRNA is only added to the growing polypeptide chain if the bases are complementary. There is also evidence that an antibiotic, paromycin, causes the same kind of shape change in A1492 and A1493 as complementary base pairs do, no matter what bases are present. Hypothesize how paromycin might kill bacteria.

55.

Two mutations of the lacI (repressor) gene have different effects. The I^smutation results in constant beta-galactosidase and permease production, even in the absence of lactose. The I^s mutation prevents any production of these enzymes, even in the presence of lactose. Provide a possible explanation for the different effects of these two mutations on the repressor protein molecule.