CH 17

Question 1

Gene expression

Answer 1

-process by which DNA directs protein synthesis
-2 stages transcription and translation

Question 2

Transcription

Answer 2

-the synthesis of RNA using information in DNA

Question 3

messenger RNA (mRNA)

Answer 3

-attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein

Question 4

Translation

Answer 4

-the synthesis of a polypeptide, using information in the mRNA

Question 5

Ribosomes

Answer 5

-sites of translation

Question 6

primary transcript

Answer 6

-the initial RNA transcript from any gene prior to processing

Question 7

triplet code

Answer 7

-a series of nonoverlapping, three-nucleotide words

Question 8

template strand

Answer 8

-DNA strand that provides template/pattern for complimentary base pairing

Question 9

codons

Answer 9

-mRNA base triplets
-read in the 5′ → 3′ direction

Question 10

reading frame

Answer 10

-how they are grouped

Question 11

RNA polymerase

Answer 11

-catalyzes RNA synthisis
-pries the DNA strands apart and joins together the RNA nucleotides

Question 12

promoter

Answer 12

-The DNA sequence where RNA polymerase attaches

Question 13

terminator

Answer 13

-the sequence signaling the end of transcription in bacteria

Question 14

transcription unit

Answer 14

-stretch of DNA that is transcribed

Question 15

Transcription factors

Answer 15

-mediate the binding of RNA polymerase and the initiation of transcription

Question 16

transcription initiation complex

Answer 16

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

Question 17

TATA box

Answer 17

-crucial in forming the initiation complex in eukaryotes

Question 18

5’ cap

Answer 18

-modified form of guanine added on to end of 5’ strand

Question 19

poly-A tail

Answer 19

-enzyme adds 50-250 adenine at the end of the 3’ strand

Question 20

introns

Answer 20

-noncoding regions

Question 21

exons

Answer 21

-other regions
-eventually expressed, usually translated into amino acid sequences

Question 22

RNA splicing

Answer 22

-removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

Question 23

Spliceosomes

Answer 23

-consist of a variety of proteins and several small RNAs that recognize the splice sites

Question 24

Ribozymes

Answer 24

-catalytic RNA molecules that function as enzymes and can splice RNA

Question 25

alternative RNA splicing

Answer 25

-Some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during splicing

Question 26

domains

Answer 26

-Proteins often have a modular architecture consisting of discrete regions

Question 27

transfer RNA (tRNA)

Answer 27

-transfer amino acids to the growing polypeptide in a ribosome

Question 28

anticodon

Answer 28

-base-pairs with a complementary codon on mRNA

Question 29

aminoacyl-tRNA synthetase

Answer 29

-carries out the correct matching of tRNA and amino acids

Question 30

wobble

Answer 30

-Flexible pairing at the third base of a codon -allows some tRNAs to bind to more than one codon

Question 31

ribosomal RNA (rRNA)

Answer 31

-RNA molecules (and proteins) that make up ribosomes

Question 32

P site

Answer 32

-holds the tRNA that carries the growing polypeptide chain

Question 33

A site

Answer 33

-holds the tRNA that carries the next amino acid to be added to the chain

Question 34

E site

Answer 34

-the exit site, where discharged tRNAs leave the ribosome

Question 35

signal peptide

Answer 35

-marks Polypeptides destined for the ER or for secretion

Question 36

signal-recognition particle (SRP)

Answer 36

-binds to the signal peptide -escorts the ribosome to a receptor protein built into the ER membrane

Question 37

polyribosome/polysome

Answer 37

-formed by Multiple ribosomes that translate a single mRNA simultaneously

Question 38

Mutations

Answer 38

-changes in the genetic information of a cell

Question 39

Point mutations

Answer 39

-changes in just one nucleotide pair of a gene

Question 40

nucleotide-pair substitution

Answer 40

-replaces one nucleotide and its partner with another pair of nucleotides

Question 41

Silent mutations

Answer 41

-have no effect on the amino acid produced by a codon because of redundancy in the genetic code

Question 42

Missense mutations

Answer 42

-still code for an amino acid, but not the correct amino acid

Question 43

Nonsense mutations

Answer 43

-change an amino acid codon into a stop codon; most lead to a nonfunctional protein

Question 44

Insertions/deletions

Answer 44

-additions or losses of nucleotide pairs in a gene

Question 45

frameshift mutation

Answer 45

-produced by the Insertion or deletion of nucleotides may alter the reading frame

Question 46

Mutagens

Answer 46

-physical or chemical agents that can cause mutations