bio chapter 17

Whaat is a ribozyme? a. an enzyme that uses RNA as a substrate b. an RNA with enzymatic activity c. an enzyme that catalyzes the association between the large and small ribosomal subunits d. an enzyme that synthesizes RNA as part of the transcription process e. an enzyme that synthesizes RNA primers during DNA replication

B. An RNA with enzymatic activity

Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because a. RNA is much more stable than DNA. b. RNA acts as an expendable copy of the genetic material. c. only one mRNA molecule can be transcribed from a single gene, lowering the potential rate of gene expression. d. tRNA, rRNA and others are not transcribed. e. mRNA molecules are subiect to mutation but DNA is not.

B. RNA acts as an expendable copy of the genetic material

• Generally speaking, how many genetic codes are there? A. 20 B. one C. four D. one for each organism E. three

B. one

The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except  a. a gene from an organism could theoretically be expressed by any other organism. b. all organisms have a common ancestor. c. DNA was the first genetic material. d. the same codons in different organisms usually translate into the same amino acids. e. different organisms have the same number of different types of amino acids.

C. DNA was the first genetic material

Which of the following statements is true? A. Each DNA base codes for three amino acids. B. Each gene codes for three proteins. C. It takes three genes to code for one protein. D. Each triplet has many different meanings. E. Each amino acid in a protein is coded for by three bases in the DNA.

E. each amino acid in a protein is coded for by three bases in the DNA

Sickle-cell disease is probably the result of which kind of mutation? a. point b. frameshift c. nonsense d. nondisiunction e. both B and D

a. point

23. The anticodon of a particular tRNA molecule is a. complementary to the corresponding mRNA codon. b. complementary to the corresponding triplet in rRNA. c. the part of tRNA that bonds to a specific amino acid. d. changeable, depending on the amino acid that attaches to the tRNA. e. catalytic, making the tRNA a ribozyme.

a. Complementary to the corresponding mRNA codon

24. Which of the following is not true of RNA processing? a. Exons are cut out before mRNA leaves the nucleus. b. Nucleotides may be added at both ends of the RNA. c. Ribozymes may function in RNA splicing. d. RNA splicing can be catalyzed by spliceosomes. e. A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.

a. Exon are cut out before mRNA leaves the nucleus

13. What are polyribosomes? a. groups of ribosomes reading a single mRNA simultaneously b. ribosomes containing more than two subunits c. multiple copies of ribosomes associated with giant chromosomes d. aggregations of vesicles containing ribosomal RNA e. ribosomes associated with more than one tRNA

a. groups of ribosomes reading a single mRNA simultaneously

Which of the following statements is FALSE? A. In bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter sites of genes. B. In bacteria, transcription of a gene is initiated when the RNA polymerase by itself recognizes and binds to the promoter of the gene. C. The initiation of gene transcription in eukaryotes requires the binding of proteins called transcription factors to the TATA box in the promoter region of a gene. D. In eukaryotes, transcription factors generally bind to a specific DNA region containing the sequence TATA before RNA polymerase can bind to the promoter. E. All of the listed responses are correct.

a. in bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter site of genes.

Introns are significant to biological evolution because a. their presence allows exons to be shuffled. b. they protect the mRNA from degeneration. C. they are translated into essential amino acids. d. they maintain the genetic code by preventing incorrect DNA base pairings. e. they correct enzymatic alterations of DNA bases.

a. their presence allows exons to be shuffled

2. If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides? a. 1 b. 2 c. 3 d. 4 e. 12

b. 2

25. Which component is not directly involved in translation? a. mRNA b. DNA c. tRNA d. ribosomes e. GTP

b. DNA

17. Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product? a. a deletion of a codon B a deletion of 2 nucleotides c. a substitution of the third nucleotide in an ACC codon d. a substitution of the first nucleotide of a GGG codon e. an insertion of a codon

b. a deletion of 2 nucleotides

14. When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by a. a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes. b. a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane. c. moving through a specialized channel of the nucleus. d. a chemical signal given off by the ER. e. a signal sequence of RNA that precedes the start codon of the message.

b. a signal-recognition particle that brings ribosome to a receptor protein in the ER membrane

4. Which of these is the function of a poly (A) signal sequence? a. It adds the poly (A) tail to the 3' end of the mRNA. b. It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10---35 nucleotides away. c. It allows the 3' end of the mRNA to attach to the ribosome. d. It is a sequence that codes for the hydrolysis of the RNA polymerase. e. It adds a 7-methy|guanosine cap to the 3' end of the mRNA.

b. it codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10 ---35 nucleotides away

Use the following information to answer the following questions. A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. 15. The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following? a. polypeptide factors plus ATP b. polypeptide factors plus GTP c. polymerases plus GTP d. SRP plus chaperones e. signal peptides plus release factor

b. polypeptide factors plus GTP

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptidecan form. 11. The dipeptide that will form will be a. cysteine-alanine. b. proline-threonine. c. glycine-cysteine. d. alanine-alanine. e. threonine-glycine.

b. proline-threonine

&. During splicing, which molecular component of the spliceosome catalyzes the excision reaction? a. protein b.DNA c. RNA d. lipid e.sugar

c. RNA

Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of a. proteins b. lipids c.RNA d. carbohydrates e. DNA

c. RNA

5. In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? a. ligase b. RNA polymerase I c. RNA polymerase II d. RNA polymerase III e. primase

c. RNA polymerase II

10. A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is a. TTT. b. UUA. c. UUU. d. AAA. e. either UAA or TAA, depending on first base wobble.

c. UUU

22. Of the following, which is the most current description of a gene? a. a unit of heredity that causes formation of a phenotypic characteristic b. a DNA subunit that codes for a single complete protein c. a DNA sequence that is expressed to form a functional product: either RNA or polypeptide d. a DNA RNA sequence combination that results in an enzymatic product c. a discrete unit of hereditary information that consists of a sequence of amino acids

c. a DNA sequence that is expressed to form a function product: either RNA or polypeptide

During the transcription of a given portion of a DNA molecule A. mRNA is synthesized on both chains of the DNA molecule at once B. mRNA is synthesized on both chains of the DNA molecule, but first on one side and then the other C. mRNA is synthesized on only one of the chains D. half of the mRNA is synthesized on half of one chain; then the other half of the mRNA is made on the other half of the DNA E. All of the listed responses are correct.

c. mRNA is synthesized on one of the chain

12. What is the most abundant type of RNA? a. mRNA b. tRNA c. rRNA d. pre-mRNA e. hRNA

c. rRNA

9. In the structural organization of many eukaryotic genes, individual exons may be related to which of the following? a. the sequence of the intron that immediately precedes each exon b. the number of polypeptides making up the functional protein c. the various domains of the polypeptide product d. the number of restriction enzyme cutting sites e. the number of start sites for transcription

c. the various domains of the polypeptide product

16. Why might a point mutation in DNA make a difference in the level of protein's activity? a. It might result in a chromosomal translocation. b. It might exchange one stop codon for another stop codon. c. It might exchange one serine codon for a different serine codon. d. It might substitute an amino acid in the active site. e. It might substitute the N terminus of the polypeptide for the C terminus.

d. It might substitute an amino acid in the active site

18. Each of the following options is a modification of the sentence THECATATETHERAT. Which of the following is analogous to a frameshift mutation? a. THERATATETHECAT b. THETACATETHERAT c. THECATARETHERAT d. THECATATTHERAT e. CATATETHERAT

d. THECATATTHERAT

The number of nucleotide bases "read" together on the mRNA to designate each amino acid is _______; this unit is called a(n) ________ a. two... dipeptide b. three ... triose c. two... anticodon d. three....codon e. one ... amino acid

d. three...codon

21. Gene expression in Archaea differs from that in other prokaryotes. It shares features with which of the following? a. eubacteria only b. eukaryotes only c. protists only d. fungi only e. bacteria and eukaryotes

e. bacteria and eukaryotes

20. A frameshift mutation could result from a. a base insertion only. b. a base deletion only. c. a base substitution only. d. deletion of three consecutive bases. e. either an insertion or a deletion of a base.

e. either an insertion or deletion of a base