Biology 1002B Lecture 13: Lecture 13 – Where do we get the gene

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1 Apr 2016

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Transcription is the first step of gene expression, in which a particular segment of dna is copied into rna by the enzyme rna polymerase. Both rna and dna are nucleic acids, which use base pairs of nucleotides as a complementary language. The two can be converted back and forth from dna to rna by the action of the correct enzymes. During transcription, a dna sequence is read by an rna polymerase, which produces a complementary, antiparallel rna strand called a primary transcript. In molecular biology and genetics, translation is the process in which cellular ribosomes create proteins. In translation, messenger rna (mrna) produced by transcription from dna is decoded by a ribosome to produce a specific amino acid chain, or polypeptide. The polypeptide later folds into an active protein and performs its functions in the cell. The ribosome facilitates decoding by inducing the binding of complementary trna anticodon sequences to mrna codons.

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5. Alpha amanitin is a drug that binds RNA polymerase andprevents it from functioning in the cell (this is the compound thatis found in poison mushrooms). The reason people die when theyconsume alpha amanitin is:

a) Alpha amanitin prevents gene expression from occurring in thecell

b) DNA replication is directly inhibited by alpha amantin

c) Alpha amanitin binds tightly to the messenger RNAs that aremade in the cell, preventing translation

d) Alpha amanitin binds to nuclear pores preventing thetransport of messenger RNA into the cytoplasm

6. In order for transcriptional initiation to begin in E. colithe following elements are needed:

a) an origin and RNA polymerase

b) initiator protein and a promoter

c) the sigma subunit of RNA polymerase and an RNA template

d) RNA polymerase and a promoter

e) helicase and primase

Questions 7 and 8. You are studying two species of closelyrelated snakes, one species lives in sandy desert area and has paletan skin and the species lives in a volcanic rock area and has darkbrown skin. You a sequence the DNA from each type of snake anddiscover a gene encoding a protein that transports pigment into theskin cells. The pigment transporter protein is responsible for skincolor. When you analyze the DNA coding sequence of the pigmenttransporter from each snake you find these two DNA sequences (hashmarks have been added to indicate the reading frame):

pale tan snake: GCG/TTG/GAC/TGC/ACC (DNA template strand)CGC/AAC/CTG/ACG/TGG (complementary strand) dark brown snake:ACG/TTG/GAC/TGC/ACC (DNA template strand) TGC/AAC/CTG/ACG/TGG(complementary strand)

7. From these sequences you conclude:

a) that the amino acid sequence of the pigment transporters forthe two proteins are almost identical

b) that the amino acid sequence of the pigment transporters forthe two proteins are very dissimilar

c) that the amino acid sequence of the pigment transporters forthe two proteins are identical

8. Since the skin color is different in each snake, you concludefrom the sequence data above that:

a) the genetic code in the skin cells in each of these snakes isdifferent

b) the DNA sequence encoding the entire gene for pigmenttransporters in these two snakes is different

c) that one of the codons in the gene for the pigmenttransporter in these two snakes is different

9. You are analyzing eukaryotic cells that have been exposed tothe radioactive uracil. In most cells the radioactive uracil isinitially localized in the nucleus and then moves from the nucleusto the cytoplasm. However, you observe that in some cells theradioactive molecules stay in the nucleus and never arrive in thecytoplasm. This is most likely a defect in:

a) the transcription of the DNA

b) the processing of the mRNA

c) the translation of the RNA

d) the labeling of the RNA

e) the replication of the DNA

10. Which of the following is true of both eukaryotic andbacterial transcription? (select all that are true)
a) Transcription factors must bind the promoter before RNApolymerase initiates transcription

b) Messenger RNAs must be spliced before translation begins inorder to produce the appropriate gene product

c) During transcription only one DNA strand is used as atemplate to make the messenger RNA

d) Termination of transcription occurs when the RNA polymerasetranscribes a hairpin structure in the RNA followed by a string ofU

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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.

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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

Biology 1002B Lecture 13: Lecture 13 – Where do we get the gene

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