chapter 10: gene expression

Question 0

why diseases occur

Answer 0

mutant phenotype arises from a change in the protein’s amino acid sequence

Question 1

archibald garrod

Answer 1

an early 1900s physician who applied mendelian genetics to patients and proposed that one gene codes to one enzyme
“inborn error of metabolism” (genetically determined biochem disease)

Question 2

one gene - one polypeptide hypoth

Answer 2

one gene codes for one polypeptide (although they dont have to)
(modification of te one gene on protein hypoth)

Question 3

molecular bio

Answer 3

the study of nucleic acids and proteins, focusing on gene expressiob

Question 4

to translate genes into proteins

Answer 4

1. transcription: the info in a dna sequence is copied into a complementary rna seq
2. translation: rna sequence creates amino acid seq of a polypeptide

Question 5

messenger rna

Answer 5

travels from nucleus to cytoplasm to be translated into a polypeptide

Question 6

ribosomal rna

Answer 6

catalyzes peptide bond formation between amino acids fo form a polypeptide

Question 7

transfer rna

Answer 7

mediates between mrna and protein; can 1. bind to a specific amino acid and 2. recognize a specific seq of nucleotides in mrna through complementary base pairing; recognizes which base should be added next to polypeptide chain

Question 8

requirements for transcription

Answer 8

1. dna template
2. nucleotide triphoephates (atp, gtp, ctp, utp)
3. an rna polymerase enzyme

Question 9

promoter

Answer 9

dna sequence that initiates transcription by binding to the rna polymerase. they tell rna polymerase:

1. where to start
2. which two dna strands to transcribe

Question 10

transcription initiation site

Answer 10

on the promoter; where transcription begins

Question 11

elongation

Answer 11

rna polymerase unwinds 13 base pairs of dna and begins ro add new nucleotides to the growing strand

Question 12

termination

Answer 12

base sequences that specify where to terminate transcription

Question 13

coding regions

Answer 13

expressed as proteins; usually continuous

Question 14

introns

Answer 14

noncoding sequences in genes that interrupt the coding region

Question 15

exons

Answer 15

the regions between introns on genes; they are still expressed

Question 16

nucleic acid hybridization

Answer 16

1. dna denatured by heat to break hydrogen bonds and separate the strands
2. a probe (single stranded nucleic acid from another source) is incubated with the dna. if complementary, the strands will join through hydorgen bonding
   RESULT: a hybrid

Question 17

rna splicing

Answer 17

removes introns and splices exons together

Question 18

consensus sequences

Answer 18

• short stretches of dna that appear with little variation, despite the gene
• at boundaries of introns/exons
• bound by small nuclear ribonucleoprotein particles (snRNPS), ehich have complementary bases to the consensus sequence

Question 19

spliceosome

Answer 19

rna-protein complex that cuts the pre-mRNA, releases the introns, and joins the exons
RESULT: mature mRNA

Question 20

alternative splicing hypothesis

Answer 20

• not all exons are inclided in every mRNA; some are spliced out
• results in different mRNAs and diff polypeptides from a single gene

Question 21

5’ cap

Answer 21

• added to the 5’ end of the pre-mRNA as it is transcribed
• facilitates the binding of mRNA to the ribosome for translation and protects mRNA from being digested by ribonucleases (enzymes)

Question 22

poly A tail

Answer 22

• added to the 3’ end of pre-mRNA
• helps exit from nucleus
• mRNA stability

Question 23

redundant code

Answer 23

many diff codons for each amino acid

Question 24

ambiguous code

Answer 24

***genetic code is NOT ambiguous | would mean that a single codon codes for diff amino acids

Question 25

silent mutation

Answer 25

- genetic code is redundant | - no change in amino acid sequence

Question 26

missense mutations

Answer 26

change in amino acid sequence

Question 27

nonsense mutation

Answer 27

result in premature stop codon

Question 28

frame shift mutation

Answer 28

result in insertion or deletion

Question 29

how to ensure right protein is made

Answer 29

1. transfer rnas (tRNAs) must chemically read each mRNA codon correctly 2. tRNA must deliver the amino acid that corresponds with the codon

Question 30

tRNAs

Answer 30

- specific to each of the 20 amino acids (when carrying it, the trna is "charged") - bind to mRNA: rhe anticodon on trna is complementary to the mrna codon for the amino acid - trnas interact with ribosomes

Question 31

aminoacyl-tRNA synthetases

Answer 31

family of enzymes specific to amino acid/corresponding trna

Question 32

ribosome sites where trna can bind

Answer 32

1. a (amino acid) site: charged trna anticodon binds to mrna codon 2. p (polypeptide) site: trna adds its amino acid to the polypeptide chain 3. e (exit) site: trna rests before picking up another amino acid and restarting

Question 33

fidelity function

Answer 33

- ensures charged trna with correct anticodon binds to right codon on mRNA - hydrogen bonds will form

Question 34

initiation complex

Answer 34

1. charged trna and small ribosomal subunit bind to mRNA 2. small subunit moves slong mRNA until it reaches start codon 3. anticodon binds to start codon

Question 35

peptidyl transferase activity

Answer 35

- large subunit breaks bond between methionine and its tRNA in P site - large subunit catalyzes the formation of oeotide bond between methionine and anino acid

Question 36

release factor

Answer 36

protein that allows hydrolysis of bond between polypeptide chain and tRNA in p site stops elongation cycle

Question 37

polyribosome/polysome

Answer 37

an assemblags of a strand of mRNA and its beadlike ribosomes + their growinf peptide chains

Question 38

posttranslational aspects of protein synthesis

Answer 38

proteins can be modified after translation (adding new chem groups that contribute to fuction of mature protein)

Question 39

signal sequence (aka signal peptide)

Answer 39

short stretch of amino scids thst indicates where in the cell the polypeptide belongs (diff signals depending on where proteins are destined to go)

Question 40

proteolysis

Answer 40

- modification of protein post translation - cutting of the polypeptide chain - some proteins are actually polyproteins (long polypeptides of distinct proteins) and can be cut into proteases

Question 41

glycoslation

Answer 41

- modification of protein post translation | - addition of carbohydrates to proteins --> form glycoproteins

Question 42

phosphorylation

Answer 42

- modification of protein post translation - addition of phosphate groups - change the conformstion of the protein, exposing binding site for another protein or active site for an enzyme - caralyzed by protein kinases: important in cell signalling