Chapter 17

Question 1

Gene expression

Answer 1

the process b which DNA directs the synthesis of proteins (sometimes RNA)

Question 2

One Gene- One Polypeptide Hypothesis

Answer 2

Each gene codes for a polypeptide, which can constitute part of a protein

Question 3

Transcription

Answer 3

Synthesis of RNA under the direction of DNA. Produces mRNA

Question 4

mRNA

Answer 4

Messenger RNA that is produced during transcription

Carries the genetic message of the DNA to the ribosome (protein making machinery)

Question 5

mRNA differences in Prokaryotes and Eukaryotes

Answer 5

Eukaryotes- Nuclear envelope separates transcription from translation
mRNA is modified through RNA processing to yield finished mRNA
Prokaryotes- mRNA produced by transcription is immediately translated without further processing

Question 6

Translation

Answer 6

Production of a polypeptide chain using the mRNA transcript

Occurs in the ribosomes in the cytosol

Question 7

Template Strand

Answer 7

The strand of DNA that is transcribed in transcription

mRNA is complementary to this strand of DNA

Question 8

Codons

Answer 8

mRNA nucleotide triplets

Smallest units are uniform length that can code for all the amino acids

Question 9

Genetic Code

Answer 9

Redundant because more than one codon codes for an amino acid , but they are never vague

Question 10

Reading Frame

Answer 10

The correct groupings in order for the specific polypeptides to be produced

Question 11

RNA polymerase

Answer 11

Catalyzes the RNA synthesis, which follows the same base pairing rule, except uracil substitutes for thymine

Question 12

Promoter

Answer 12

DNA sequences where RNA polymerase attaches

Question 13

Terminator

Answer 13

Sequence signaling the end of transcription in bacteria

Question 14

Transcription Unit

Answer 14

Entire stretch of DNA that is transcibed

Question 15

Transcription Initiation Complex

Answer 15

The completed assembly of transcription factors and RNA polymerase II bound to a promoter

Question 16

Steps of Transcription

Answer 16

1. Initiation- Transcription factors bind to the promoter which helps the RNA polymerase II be able to bind to the promoter, creating a transcription initiation complex
2. Elongation- RNA polymerase II untwists the DNA and adds complementary RNA bases
3. Termination- After RNA polymerase transcribes the terminator sequence in the DNA, the RNA transcript is released and the RNA polymerase detaches

Question 17

Differences in Transcription between Prokayotes and Eukaryotes

Answer 17

RNA polymerase can bind to the promoter by itself in prokaryotes,
Prokaryotic polymerase stops transcription at the end of the terminator
Eukaryotes continues transcription after the pre-RNA is cleaved from the growing RNA chain, polymerase eventually falls of the DNA

Question 18

TATA box

Answer 18

Promoter that is crucial in forming the initiation complex in eukaryote

Question 19

Alteration of mRNA ends

Answer 19

Adds a 5’ cap to the 5’ end
The 3’ end receives a poly-A tail
Help to facilitate the export of mRNA, protects the mRNA from hydrolytic enzymes, and help ribosomes to attach to the 5’ end

Question 20

RNA Splicing

Answer 20

Removes introns and joins exons together creating a mRNA molecule with a continuous coding sequence

Question 21

Spliceosome

Answer 21

Consists of a variety of proteins and several small nuclear ribonucleicproteins that recognize splice sites

Question 22

Ribozyme

Answer 22

Catalytic RNA molecules that function as enzymes and cal splice RNA
Rendered obsolete the belief that all biological catalysts are proteins

Question 23

tRNA

Answer 23

Each tRNA carries specific amino acids on one end

Each has an anti codon on the opposite end that pairs with a codon on the mRNA

Question 24

Acute Translation

Answer 24

1. A correct match between the tRNA and an amino acid (joined by the enzyme aminoacyl-tRNA synthetase)
2. Correct match between tRNA anti codon and mRNA codon

Question 25

wobble

Answer 25

Flexible pairing at third base of a codon

Allows some tRNA to bind more than one codon

Question 26

Ribosomes

Answer 26

Made out of rRNA
Facilitate the specific coupling of tRNA anti codons with mRNA codons in protein synthesis
Two ribosomal subunits (large and small) that are made of proteins and rRNA

Question 27

3 Binding Sites

Answer 27

P- holds the tRNA that carries the polypeptide chain
A- holds he rRNA that carries the next amino acid to be added
E- Exit site, where discharged tRNA leave the ribosome

Question 28

Steps of Translation

Answer 28

initiation- a small ribosomal subunit binds to mRNA , anticodon matches up with the start codon on the mRNA, and the large subunit attaches, allowing tRNA to attach to the P site
Elongation- Amino acids are added to the preceding amino acid
Termination- Stop codon is reached and translation stops

Question 29

Signal Peptide

Answer 29

The sequence of the leading 20 or so amino acids that direct proteins to their final destination

Question 30

Point Mutations

Answer 30

alterations of just one base pair in a gene

Question 31

Missense mutation

Answer 31

substitutions that still allow for the codon to code for an amino acid

Question 32

Nonense mutation

Answer 32

subsitutions that change a regular amino acid codon into a a stop codon, ceasing translation

Question 33

Insertion/ Deletions

Answer 33

Additions and losses of nucleotide pairs in genes

Question 34

Frameshift Mutation

Answer 34

causes mRNA to be read incorrectly