BIO130H1 Lecture Notes - Genetic Code, Transfer Rna

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21 Feb 2013

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All cells translate rna to protein in same way. From 4-letter alphabet of polynucleotides to 20-letter alphabet amino acids. 20 amino acids but 64 (43) possible combinations. Code read by class of small rna molecules called transfer rnas (trnas) A trna has a specific amino acid at one end and an anticodon at the other - base-pairing lets it recognize a particular subset of codons in messenger rna (mrna) Individual segments (each is a gene) of dna transcribed into mrna. Each segment codes for a specific protein. Once base-pairing complete, protein chain extended and trnas released. Process carried out in ribosomes - made of 2 main chains of rna called ribosomal rnas (rrnas) and more than 50 different proteins. Rna molecules transcribed from the same segment of dna sequence can often be processed in more than. Gene - segment of dna sequence corresponding to a single protein or set of protein variants.

Related Questions

1. _________________________ is the name of the process that produces proteins using RNA molecules.

a.Transcription

b Translation

c. Replication

d. Mutagenesis

2. The peptide bonding site on the ribosome:

a. A site

b. P site

c. E site

d. D site

3. The name given to the bond formed between two amino acids.

a. Hydrogen bond

b. Double bond

c. Peptide bond

d. Negative bond

4. __________________________ is the movement of the mRNA molecule on the ribosome to open up the A-site for the new incoming amino acid.

a. Transformation

b. Mutation

c. Translocation

d. Initiation

5. What does the term semi-conservative mean.

a. Replication of RNA is semi-conservative, each new strand consists of one old strand of RNA and one new strand of RNA.

b. Replication of DNA is semi-conservative, each new strand consists of one old strand of DNA and one new strand of DNA.

c. Replication of DNA is semi-conservative, each new strand consists of new strands of nucleotides.

d. Transcription of RNA is semi conservative.

6. This molecule functions during protein synthesis to recognize the codon and bring the proper amino acid back to the ribosome for translation.

a. mRNA

b. tRNA

c. rRNA

d. DNA polymerase

7. What is meant by the base-pairing rule.

a. Bases on a single strand of DNA are always found as pairs

b. Adenine always base pairs with guanine; cytosine with thymine

c. Adenine always base pairs with thymine; cytosine with guanine

d. Bases on a single strand of RNA are found in pair.

8. In this step of protein synthesis, amino acids are added to a growing polypeptide chain.

a. Initiation.

b. Elongation.

c. Termination.

d. Transpiration.

9. Three complementary bases found in a mRNA are called ____________________.

a. Anti-codon.

b. Triplet.

c. Doublet.

d. Codons.

10. Which statement best describes the job or function of the messenger RNA.

a. Carries the map of the gene sequence in the form of codons to the cytoplasm

for translation of the protein.

b. It transfers amino acids to the ribosome for protein synthesis.

c. It forms the ribosomes.

d. It helps replicate DNA.

ceruleangnat663

Fill in the blank. Elongation during translation does NOT involve ____________.

Question 16 options:

	the translation of codons according to the genetic code
	the formation of bonds catalyzed by the ribosome
	complementary base pairing between RNA molecules
	amino acids being linked together in a polypeptide
	reading the DNA template 3' to 5'

For a given gene, what establishes the reading frame for translation?

Question 17 options:

	the location of the enhancer relative to the gene
	the first three nucleotides at the 5' end of the mRNA
	the first three nucleotides at the 3' end of the mRNA
	the start codon in the mRNA
	the location of the promoter relative to the gene

Which of the following is the LEAST likely direct consequence of a substitution mutation?

Question 18 options:

	changing the length of a protein coded for by a gene
	changing one amino acid in a protein
	creating a stop codon
	eliminating a start codon
	changing the length of the DNA molecule containing a gene

Suppose that the pre-mRNA transcript from a eukaryotic gene is 30,000 nucleotides long, and the gene codes for a sequence of 300 amino acids. What is the best explanation for the relationship between these numbers?

Question 19 options:

	only the first 900 nucleotides of the pre-mRNA transcript are translated
	it takes 100 nucleotides to specify a single amino acid
	300 of the nucleotides in the transcript are important, and the rest are "junk"
	only the last 900 nucleotides of the pre-mRNA transcript are translated
	large portions of pre-mRNA transcripts are cut out during RNA processing

Suppose an individual is born into a population with a novel mutation. Is the new mutation an evolutionary change, and why?

Question 20 options:

	no, because it is not a big enough change to count
	yes, because new mutations are always adaptive
	yes, because the appearance of a new genetic variant is a genetic change in a population
	no, because not enough individuals have the mutation for it to matter
	no, because most mutations are not adaptive

An extraterrestrial organism (ET) is discovered whose basic cellbiology seems pretty much the same as that of
terrestrial organisms except that it uses a different genetic codeto translate RNA into protein. You set out to break the
code by translation experiments using RNAs of known sequence andcell-free extracts of ET cells to supply the necessary
protein-synthesizing machinery. In experiments using the RNAsbelow, the following results were obtained when the 20
possible amino acids were added either singly or in differentcombinations of two or three:
RNA 1: 5?-GCGCGCGCGCGCGCGCGCGCGCGCGCGC-3?
RNA 2: 5?-GCCGCCGCCGCCGCCGCCGCCGCCGCCGCC-3?
Using RNA 1, a polypeptide was produced only if alanine and valinewere added to the reaction mixture. Using RNA 2, a polypeptide wasproduced only if leucine and serine and cysteine were added to thereaction mixture. Assuming that protein synthesis can startanywhere on the template, that the ET genetic code isnonoverlapping and linear, and that each codon is the same length(like the terrestrial triplet code), how many nucleotides does anET codon contain?
(a)2 (b)3 (c)4 (d)5 (e)6

BIO130H1 Lecture Notes - Genetic Code, Transfer Rna

BIO130H1 Full Course Notes

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