Chapter 13

Question 1

What is the central dogma?

Answer 1

DNA is used as instructions to make RNA, and RNA is used as instructions to make proteins

Question 2

Define transcription

Answer 2

Use of DNA nucleotide sequences as instructions to make an RNA sequence

Question 3

Define translation

Answer 3

Use of the RNA sequence as instructions to make the amino acid sequence of a protein. Triplets of nucleotides determine the amino acid.

Question 4

Define a codon

Answer 4

Every 3 nucleotides (triplet) of an RNA sequence to specify an amino acid

Question 5

What 5 characteristics does the genetic code have?

Answer 5

-unambiguous
-degenerate/redundant
-universal
-nonoverlapping
-ordered

Question 6

What does it mean that the genetic code is unambiguous?

Answer 6

A given codon specifies for only ONE amino acid

Question 7

What does it mean that the genetic code is degenerate/redundant?

Answer 7

A given amino acid can be specified by multiple codons

Question 8

What does it mean that the genetic code is universal?

Answer 8

Almost all species use the same genetic code
*Exceptions apply

Question 9

What does it mean that the genetic code is non-overlapping?

Answer 9

A given nucleotide is only part of one codon. (The RNA sequence is read in groupings of 3)

Question 10

Define start codon

Answer 10

Genetic code only has 1 start codon - the first codon to be translated. AUG, aka methionine

Question 11

Define stop codon

Answer 11

Genetic code has 3 stop codons - causing translation to end but do NOT code for an amino acid. UGA , UAA, and UAG

Question 12

What is an example of altered codon-amino pairing (exception to the universal characteristic)

Answer 12

In most species AGA codes for aginine, but in the human mitochondria it is instead a stop codon.

Question 13

Define open reading frames

Answer 13

ORFs are the 3-letter groupings read by the ribosome.

Question 14

Define alternative ORFs

Answer 14

Shifting the start position up or down a nucleotide results in a different ORF, which creates a different protein.

Question 15

How can alternative reading frames happen?

Answer 15

mRNAs being initiated at different positions. They can use or ignore start codons dependent on different environmental conditions and needs.

Question 16

Define a gene

Answer 16

What is transcribed to produce an RNA molecule. It is a few thousand base pairs long.

Question 17

Define RNA polymerase

Answer 17

Enzyme that transcribes the gene to produce an RNA molecule.

Question 18

Define promoter

Answer 18

A few dozen base pairs that is before the gene, helping RNA polymerase to bind.

Question 19

What does bacterial RNA polymerase consist of?

Answer 19

Core enzyme and sigma factor

Question 20

What does the core enzyme of bacterial RNA polymerase do?

Answer 20

Catalyzes RNA production and has multiple protein subunits

Question 21

Whats the sigma factor of bacterial RNA polymerase?

Answer 21

Helps to initiate transcription and binds to the promoter

Question 22

Define holoenzyme

Answer 22

The core enzyme + the sigma factor (the entire enzyme)

Question 23

Define template binding (bacterial)

Answer 23

Transcription begins at this point with the sigma factor binding to the template strand of DNA and scanning for the promoter.

Question 24

Define template strand

Answer 24

Strand of DNA that RNA polymerase reads

Question 25

Define coding strand

Answer 25

Strand of DNA that is NOT being read

Question 26

Define antisense strand

Answer 26

AKA template. Reading strand

Question 27

Define sense strand

Answer 27

AKA coding. NON-reading strand

Question 28

Define consensus sequence

Answer 28

The nucleotide sequence of the promoters that is the average/most similar among these many sequences. This is how the sigma factor recognizes promoters, as it is designed to bind to the consensus sequence.

Question 29

What happens once the sigma factor binds to the promoter? (bacterial)

Answer 29

DNA strands are then unraveled, and then the sigma factor leaves. RNA polymerase then reads the template strand to create a complementary RNA sequence.

Question 30

Define proofread

Answer 30

3'->5' exonuclease ability. RNA polymerase recognizes its mistakes, excises them, then adds the right nucleotide.

Question 31

How does transcription end in bacteria?

Answer 31

The new RNA forms a hairpin structure at the 3' end. Then, either intrinsic or Rho-dependent termination occurs

Question 32

What does the rho protein do? (Rho-dependent termination) (bacterial)

Answer 32

Binds to RNA and detaches it from DNA to help end transcription. It does this by binding to the 5' side and moving in the 3' direction, breaking RNA-DNA base pairing.

Question 33

What are the 3 steps of bacterial transcription?

Answer 33

1. Initiation - binding to DNA 2. Elongation - reading of DNA 3. Termination - detaching from DNA