Final Exam

Question 1

To get from DNA (nucleic acids) to protein
(amino acids) requires two major stages:

Answer 1

1. TRANSCRIPTION
2. TRANSLATION

Question 2

Transcription

Answer 2

is the process of making RNA (copy gene to send to ribosome)

Question 3

Prokaryotic vs Eukaryotic Transcription

Answer 3

• In bacteria, all transcription is performed by a single type of RNA polymerase
  – polymerase contains four catalytic subunits and a single regulatory subunit known as sigma factor
• In eukaryotes, there are 3 different RNA polymerases
  – RNA polymerase I transcribes rRNA
  – RNA polymerase II transcribes mRNA and some snRNA
  – RNA polymerase III transcribes tRNA and some other small RNA

Question 4

The two constituents of chromosomes

Answer 4

proteins and DNA

Question 5

Translation

Answer 5

(synthesize protein at ribosome)

Question 6

Transcription occurs in 3 stages

Answer 6

• Initiation
• Elongation
• Termination

Question 7

Initiation

Answer 7

– RNA polymerase (RNAP) complex binds to DNA at a given “start” signal
– The RNAP unwinds the DNA helix, separating the strands and creating a transcription bubble

Question 8

Elongation

Answer 8

RNA synthesized in the 5’-to-3’ direction as ribonucleotides are added by RNAP

Question 9

Termination

Answer 9

– Marked by sequence that signals “stop” to polymerase
– RNA–DNA hybrid within the transcription bubble dissociates
– RNAP releases the DNA and DNA rewinds into helix

Question 10

introns

Answer 10

Eukaryotic genes have regions of non-coding information

Question 11

RNA editing

Answer 11

splicing of the mRNA transcript

Question 12

Why have introns?

Answer 12

• Introns may help regulate gene expression
  – Splicing process itself necessary for export of mRNA out of the nucleus
  – Some introns contain sequences that control gene activity
• Alternative splicing
  – By changing pattern of splicing, different variations of a protein can be formed
  – Clear illustration of why the proteome is more complex than the genome

Question 13

Alternative splicing

Answer 13

can produce different forms of a protein from the same gene

Question 14

Transcription is carefully regulated by the cell

Answer 14

Even the simplest cells are finely tuned to both internal and external signals that affect the rate of expression (transcription) of each gene
* In order to optimize the use of resources, cells carefully regulate transcription, expressing genes only when they are needed at a particular moment
* Some genes, however, are so important to a cell’s survival that they are expressed all the time. these are called housekeeping or constitutive genes

Question 15

Transcription is carefully regulated by the cell

Answer 15

Even the simplest cells are finely tuned to both internal and external signals that affect the rate of expression (transcription) of each gene
* In order to optimize the use of resources, cells carefully regulate transcription, expressing genes only when they are needed at a particular moment
* Some genes, however, are so important to a cell’s survival that they are expressed all the time. these are called housekeeping or constitutive genes

Question 16

key players in interpreting the code

Answer 16

the ribosome (made of two subunits) and tRNAs that bring amino acids to the ribosome

Question 17

tRNA – the decoder

Answer 17

The “interpreter” of translation is an RNA molecule
* Bring correct amino acid to the ribosome
* Correct amino acid added based on “read” of codons on
mRNA
– Base-pairing interactions with anticodon loop

Question 18

ribosome

Answer 18

is the catalytic machine that actually builds the peptide from the mRNA message

Question 19

tRNA synthetases

Answer 19

• Catalyze the esterification of a specific amino acid to its compatible cognate tRNA to form an aminoacyl-tRNA
  – requires energy in the form of ATP
• “Match and attach” enzymes
• Have specific identity elements
  – Some recognize anticodon loop sequence
  – Some recognize acceptor arm sequence
• Specifically, closing base-pair

Question 20

Peptidyl transferase

Answer 20

– Enzymatic component of the ribosome
– Forms peptide bonds between amino acids

Question 21

The ribosome has two primary functions

Answer 21

– Decode the mRNA
– Form peptide bonds

Question 22

In eukaryotes, transcription and translation are spatially and temporally separated

Question 23

mutation

Answer 23

a change in the normal base-pair sequence

Question 24

Point mutations

Answer 24

alter a single base
– deletions, insertions

Question 25

Base substitutions

Answer 25

substitute one base for another