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Biochemistry I - Transcription, Translation, and DNA Repair

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T/F Ribosomes are made up of only one subunit.

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Date created

Mar 1, 2020

Cards (47)

Section 1

(47 cards)

T/F Ribosomes are made up of only one subunit.

Front

F They have small and large subunits

Back

Post-translational modification often occurs after translation. What are the function of chaperone proteins? Give two examples of common modifications.

Front

Chaperone proteins help the nascent polypeptide fold correctly Glycosylation (addition of sugars) Prenylation (addition of lipids)

Back

Translation can be separated into three phases: initiation, elongation, and termination. What occurs in the termination phase (three steps)?

Front

A release factor binds to the termination codon, causing hydrolization of the protein from the tRNA and the ribosome subunits disassociate.

Back

The RNA strand will be synthesized in which direction? What does this mean the abut the direction of the DNA strand?

Front

5'→3' it is synthesized, so the template strand is read 3'→5' The mRNA strand is parallel to the CODING strand

Back

Transcription begins with the unwinding of DNA and binding so it does create supercoils. Which enzymes assist in this process?

Front

Helicase Topoisomerase

Back

What is the start codon? What amino acid does this code for?

Front

AUG methionine

Back

What is the function of rRNA?

Front

These molecules assist in the transfer of peptide bonds in the ribosome during translation.

Back

How does DNA polymerase look for DNA replication errors?

Front

Mismatches bases are more unstable due to unfavorable hydrogen bonding, so it can detect this discrepancy.

Back

What is a frameshift mutation?

Front

This is where a number of nucleotides are added or deleted for a code, resulting in a different codon reading of the strand. These are typically more serious than point mutations.

Back

Differentiate between introns and exons.

Front

Introns are NON coding and stay in the nucleus during excision. Exons are coding and will be combined in the spliceosome.

Back

What is the function of tRNA? Where is it found? What region bind to the mRNA?

Front

It converts the language of nucleic acids into proteins through amino acids and peptides. Mature tRNA is found in the cytoplasm, and its anticodons bind to mRNA.

Back

What are the two, primary tumor suppressing genes?

Front

p53 and Rb (retinoblastoma)

Back

RNA is synthesized by which enzyme? What does it search for to initiate transcription?

Front

DNA-dependent RNA polymerase (RNA polymerase II in eukaryotes) It searches for a promoter region

Back

Where does transcription occur?

Front

In the nucleus (translation occurs in the cytoplasm)

Back

RNA polymerase travels in which direction on the template (antisense) strand?

Front

It travels 3'→5' in order to produce mRNA in the 5'→3' direction.

Back

T/F The excision endonuclease makes nicks in the anhydride backbone to remove the thymidine dimers.

Front

F Nicks are made in the phosphodiester bonds. Anhydride bonds are not present in DNA or RNA.

Back

Differentiate between monocistronic and polycistronic mRNA.

Front

Monocistronic is where one strand of mRNA codes for ONE protein. This occurs in eukaryotes. Polycistonic is where one strand may code for multiple proteins. This occurs in prokaryotes.

Back

What is the relationship between the mRNA and the coding strand?

Front

They would be parallel to each other and the RNA would have T bases replaced with U bases

Back

In which direction is mRNA synthesized? In which direction is mRNA read?

Front

5'→3' (template is read 3'→5')

Back

What is a mutation that affects one of the nucleotides in the codon that is expressed?

Front

Expressed point mutation

Back

What occurs in the E site of the ribosome?

Front

The uncharged tRNA transiently waits and then leaves to become charged again

Back

T/F In translation, the mRNA moves along the ribosome.

Front

F The opposite of this is true

Back

What is the function of the 3' poly-A-tail?

Front

This tail protects the mRNA from degradation in the cytoplasm. It will be degraded, however, the longer it is the more time the mRNA has to reach the ribosome.

Back

What is the central dogma of molecular biology/biochemistry state?

Front

DNA↔RNA→Protein

Back

Alternative splicing allows one hnRNA transcript to do what?

Front

Code for multiple proteins

Back

Differentiate between missense and nonsense mutations.

Front

Missense is where one codon now codes for a different amino acid than originally coded. Nonsense is where a codon now has a premature stop codon (UAA, UGA, UAG)

Back

T/F The most efficient route to remove a single base pair mutation is using AP endonuclease.

Front

T

Back

Translation can be separated into three phases: initiation, elongation, and termination. What occurs in the elongation phase (three steps)?

Front

1. first tRNA binds to the A site while M is already bound in the P site from initiation. 2. Peptidyltransferase transfers amino acids (only M in this case) from P to A site. 3. Translocation of growing chain from A site to P site

Back

What is DNA mismatch repair? When does this occur?

Front

This is where in the G₂ cell cycle phase cells can detect and repair mismatches missed by DNA polymerase

Back

Will GTP or GDP be utilized by peptidyltransferase while transferring amino acids from the P to A site?

Front

GTP

Back

What is the purpose of the signal sequence in translation?

Front

This designates the ribosome to move the lengthening chain to the endoplasmic reticulum so the protein can be directly translated into the lumen of the ER.

Back

When a codon is recognized by an anticodon, are the tRNA and mRNA parallel or antiparallel?

Front

Antiparallel

Back

How does DNA polymerase recognize which strand is the daughter strand in DNA repair?

Front

The template strand will be more heavily methylated

Back

There are three codons that code for the termination of protein translation. What are these three?

Front

UAA UAG UGA

Back

UV light (from the sun) can cause what to occur to thymidine residues that are adjacent to each other? What is the process to correct this?

Front

They can form dimers. Nucleotide excision repair removes these dimers using an excision endonuclease that makes nicks in the phosphodiester backbone to remove the bulging dimer.

Back

Differentiate between the sense and antisense strand.

Front

Sense=coding Antisense=template

Back

What is the function of AP endonuclease?

Front

It removes specific base pairs that are causing non-helix distorting mutations via base excision repair.

Back

mRNA has what function? What are the three base-pair coding regions called?

Front

Carries information regarding amino acid sequence of a protein to the ribosome. Can be post-translationally modified. Codons

Back

Translation can be separated into three phases: initiation, elongation, and termination. What occurs during initiation?

Front

The ribosome binds to the mRNA and the charged initiator tRNA binds to the P site on the ribosome.

Back

In both prokaryotes and eukaryotes, translation occurs in the cytoplasm. How does it differ?

Front

Ribosomes begin translating before the mRNA is complete in prokaryotes. Transcription and translation occur in different areas for eukaryotes.

Back

The promoter region is defined to have what types of bases?

Front

This region on DNA (template strand) should have TATA

Back

In which direction is DNA synthesized?

Front

5'→3'

Back

Differentiate between RNA polymerase I, II, and III.

Front

I = synthesizes rRNA II = synthesizes hnRNA III = synthesizes tRNA

Back

What is the difference between oncogenes and a mutation in tumor suppressing genes? Are the net outcomes the same?

Front

Oncogenes are simply mutated genes that cause cancer while a mutation in a tumor suppressing gene inhibits the process designed to STOP cell proliferation. The net result is the same for both, cancer.

Back

The first product of primary transcription is heterogenous nuclear RNA (hnRNA). What are the three post-translational modifications necessary to produce mature mRNA?

Front

Splicing of introns and exons 5' cap 3' poly-A-tail

Back

What is the function of aminoacyl-tRNA synthetase?

Front

This enzyme activates tRNA by placing a specific amino acid on the 3' end. ATP is used to supply energy to this bond.

Back

How do silent mutations relate to the degeneracy of the genetic code?

Front

Since more than one codon codes for a protein, the genetic code is known to be degenerate. A silent mutation is in the "wobble" position (third base in a codon). Some amino acids only require the first two bases in a codon to be correct because any third base would still produce the same protein. This process is an evolutionary design to protect from mutations.

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