Gene Expression

Question 1

gene expression definition

Answer 1

process by which DNA directs protein synthesis

Question 2

Archibald Garrod

Answer 2

1902
suggested that genes dictate phenotypes via enzymes catalyzing reactions
symptoms of disease = inability to produce an enzyme

Question 3

George Beadle and Edward Tatum

Answer 3

exposed bread mold to X-rays creating mutants that couldn’t survive on minimal medium
mutant cells only grew in medium with added arginine suggesting they couldn’t produce arginine themselves

Question 4

Adrian Srb and Norman Horowitz

Answer 4

investigated 3 classes of arginine deficient mutants from Beadle and Tatum’s experiment
each mutant lacked different enzyme in 3 step arginine production pathway

developed 1 gene 1 enzyme hypothesis, which later became 1 gene 1 polypeptide hypothesis

Question 5

central dogma definition

Answer 5

the flow of information in a given cell
cells are governed by a chain of command

Question 6

genetic code is

Answer 6

redundant but not ambiguous
multiple codons for 1 amino acid, but only 1 amino acid per codon
correct reading frame required
universal from prokaryotes to eukaryotes

Question 7

differences between eukaryotic and prokaryotic central dogma

Answer 7

prokaryotes: translation can begin before transcription has ended

eukaryotes: nuclear envelope separates transcription/translation
primary RNA transcripts are modified (pre-mRNA) to form mRNA for translation

Question 8

RNA pol attaches to the
function

Answer 8

promoter to transcribe the transcription unit
signal transcriptional start point

Question 9

in bacteria, sequence signaling end of transcription is

Answer 9

the terminator

Question 10

transcription factors function

Answer 10

mediate binding of RNA pol and initiation of transcription

Question 11

transcription initiation complex includes

Answer 11

transcription factors, RNA pol II bound to promoter

Question 12

TATA box

Answer 12

promoter element in eukaryotes

Question 13

elongation rate in eukaryotes

Answer 13

transcription bubble opens 10-20 nucleotides at a time
transcription rate of 40 nucleotides per second in eukaryotes
gene can be transcribed simultaneously by multiple RNA pol

Question 14

termination of transcription in prokaryotes and eukaryotes

Answer 14

prokaryotes: transcription ends at terminator, no modifications to mRNA
eukaryotes: RNA Pol II transcribe poly adenylation signaling sequence and released 10-35 nucleotides after

Question 15

pre-mRNA processing
function

Answer 15

5’ cap with guanosine residue
3’ poly A tail 50-250 nucleotides long

facilitate export into cytoplasm
protect mRNA from hydrolytic enzymes
ribosomes attach to 5’ cap

Question 16

snRNPs

Answer 16

small nuclear ribonucleoproteins recognize splice sites
catalytic RNAs (ribozymes) catalyze splicing reaction

Question 17

how can RNA function as enzymes

Answer 17

can base pair with itself and form 3D structures
functional groups that can participate in catalysis
RNA can H bond with other nucleic acid molecules

Question 18

exon shuffling

Answer 18

changes in orders of exons resulting in evolution of new proteins
often exons code for a specific domain

Question 19

aminoacyl-tRNA synthetase

Answer 19

matching of aminoacyl with correct tRNA by recognizing anti-codon

Question 20

ribosome function

Answer 20

facilitate coupling of tRNA anti-codons with mRNA codons
ribosomes made up of rRNA and proteins

Question 21

antibiotic drugs and ribosomes

Answer 21

differences in prokaryotic and eukaryotic ribosomes allows targeting of prokaryotic ribosomes in antibiotics

Question 22

completion of translation initiation complex

Answer 22

initiation factors bring large subunit to small subunit bound to mRNA
GTP hydrolyzed to attach large subunit
moves tRNA(Met) to P site

Question 23

AA added to which end of growing polypeptide?

Answer 23

C terminal end

Question 24

when is energy used in translation elongation?

Answer 24

codon recognition and translocation

Question 25

translation termination

Answer 25

stop codon signals release factor protein binding
release factor causes addition of water instead of AA, releasing polypeptide
disassembly of complex driven by GTP

Question 26

types of post-translational modification

Answer 26

hydroxylation - OH addition
methylation - CH3 addition
lipidation - fatty acid addition
acetylation - acetyl group to N terminus
disulfide bond
SUMOylation - small ubiquitin like modifier, protein
ubiquitination - signals degradation
glycosylation - sugar added
phosphorylation

Question 27

free vs bound ribosomes

Answer 27

found in cytosol
mostly synthesize proteins for cytosol

found attached to ER
make proteins for endomembrane system, and proteins for secretion

can switch from free to bound

Question 28

SRP

Answer 28

signal recognition particle
binds to signal peptide portion of peptide being translation and escorts ribosome to dock at ER
translation finishes into the ER
for proteins destined for ER or for secretion

Question 29

polyribosome/polysome

Answer 29

multiple ribosomes translating a single mRNA simultaneously
amplifies protein products

Question 30

point mutation

Answer 30

change in 1 base pair
can lead to abnormal protein
nucleotide pair substitution, deletion or insertion

Question 31

genetic disorder or hereditary disease

Answer 31

mutation with an adverse effect on phenotype

Question 32

nucleotide pair substitutions types

Answer 32

silent - no effect on phenotype
missense - coding for wrong AA
nonsense - coding for stop codon

Question 33

nucleotide pair insertion/deletion

Answer 33

can cause frameshift mutation - disastrous effect on protein more so than substitution mutations
3 nucleotide deletion - reading frame stays valid

Question 34

sources of mutation

Answer 34

spontaneous during DNA replication, repair and recombination
mutagens are physical or chemical agents that cause mutations
ex. UV, X rays, carcinogens, processed foods/preservatives, cosmetics, cleaning products, viruses, bacteria

Question 35

definition of a gene

Answer 35

region of DNA that can be expressed to produce a final functional product either polypeptide or RNA