Genetics Exam 3

a ____ is a inherited change in the DNA sequence of genetic information

mutation

____ are the source of all genetic variation, the base of evolution, and many diseases and disorders.

mutations

geneticists use mutuations for ___ ____

genetic dissection

____ is figuring out how a car works by breaking different parts and observing the effects

genetic dissection

____ mutations that do not pass to gametes

somatic

______ mutations that do pass to gametes

germline

____ mutations affect a single gene or locus

gene

_____ mutations of the number or structure of chromosomes.

chromosome

_____ _____ is a gene mutation when a single pair of bases in DNA is altered.

base substitution

____ is a gene mutation when one or more nucleotide pairs is added or deleted. can be ____ or ____

indel , insertions or deletions

frameshift mutations are mutations that alter the ___ ___ of a gene

reading frame

insertions and deletions are mutations that alter the ___ ____.

reading frame

a ____ mutation changes a amino acid

missense slide 10

a ____ mutation results in a shortened protein.

nonsense

a ____ mutation changes into another codon for the same amino acid.

silent

True or False: all missense mutations disrupt the functions of proteins. slide 12

false bc a missense mutation can change the amino acid for one similar to it with similar function so that would disrupt function

True or False: Most nonsense mutations disrupt the function of proteins. slide 12

true, they shorten the protein so function is lost

a ____ is a group of structural genes, their promoter and additional sequences that control their transcription

operon slide 3

a _____ is a site for transcription initiation, binds to the RNA polymerase enzyme

promoter

a ______ protein binds to another DNA sequence and controls the transcription of one or more structural genes.

regulator

can a operator sequence have a missense mutation? why?

no, missense occurs in protein coding regions but this sequence is made of noncoding DNA

regulatory region of DNA, near the promoter is the ____ ____

operator sequence

the operator sequence does not experience mutations. T/F

False, it can have a frame shift mutation to a base substitution mutation

the operator sequence affects the ___ of transcription of the _____ genes

rate, structural

the negative control RP is a activator or repressor?

repressor

a _____binds to DNA & inhibits transcription

repressor RP

RP

regulatory protein

the positive control RP is a activator or repressor?

activator

binds to DNA and promotes transcription

activator RP

what are the 2 types of transcriptional control in bacteria?

negative (repressor) and positive (activator)

does transcription start on or off in negative Inducible operons?

transcription starts off and something has to happen for it to be turned on

what’s going on in negative inducible operons with no inducer present?

active repressor RP binds to the operator of an operon which physically blocks the RNAP from binding to the operator slide 7 so no transcription

what’s going on in negative inducible operons with the inducer present?

a small molecule binds to the active RP to change its shape making it unable to bind to the operator and block RNAP so transcription takes place slide 8

what is a co-repressor

small molecule that binds to the inactive repressor protein change its shape so that can bind to DNA and inhibits transcription ex: purple molecule slide 8

does transcription start on or off in negative repressible operons?

transcription is starts on but but something must happen to turn it off

what’s going on in negative repressible operons with no Product U present?

inactive repressor RP cant bind to the operator and block RNAP so transcription takes place slide 9

what’s going on in negative repressible operons with Product U present?

product u binds to the inactive repressor RP and prevents transcription slide 10

product u is an example of a ____

co-repressor

______ is a active transport protein for lactose

lactose permease

what 2 molecules does lactose break down into?

glucose and galactose slide 11

______ is the enzyme that breaks down lactose and turns it into allolactose.

beta-galactosidase slide 11

lactose metabolism is a example of ___ ___ _____

negative inducible operon

what’s going on during lactose metabolism when lactose is absent?

starts with a active repressor RP that binds to the lacO operator and blocks RNAP so the structural genes aren’t expressed slide 13

what’s going on during lactose metabolism when lactose is present?

starts with a active repressor RP that becomes inactive when allolactise binds to it, so the inactive RP doesnt bind to lacO and transcription and translation happens

the goal of E.coli metabolism is do _____ energy with as little ___ as possible

produce, waste

what sugar is preferred over other sugars for metabolism?

glucose

if there’s a lot of glucose you dont need lactose so the genes involved in the metabolism of lactose will be off. this explains _______ _______

catabolite repression

in E.coli metabolism, when glucose is high, cAMP is ___? result?

low, little transcription

a ____ is a transcription factor that helps RNAP bind DNA but only when attached to cAMP.

cap slide 17 & 18

in E.coli metabolism, when glucose is low, cAMP is ___? result?

high, transcription and translation happens

does transcription start on or off in negative repressible (Trp) operons?

transcription starts on and needs to be turned off

what’s going on in negative repressible (Trp) operons when trp is low?

inactive repressor RP cant bind to the operator and block RNAP so transcription and translation takes place slide 22

what’s going on in negative repressible (Trp) operons when trp is high?

a co repressor binds to the inactive repressor RP allowing it to bind to the operator and block RNAP so transcription does not takes place

_____ is when transcription begins at the start site but terminates before RNAP can get to the strcutural genes.

attenuation

attenuation produces the ___ ___ which encodes right next to trp codons.

leader peptide

what are the 2 secondary structures that the mRNA for the leader peptide can adopt?

attenuator and antiterminator

the _____ terminates transcription when trp is high.

attenuator

regions 1+2 and 3+4 together slide 26 left

the _____ allows transcription to continue when trp is low.

anti terminator

regions 2 + 3 together slide 26 right

in a trp operon, when too much trp is being made it can “___ ___” on its self to end transcription

feed back

during the process of attenuation, when trp is ___, the ribosome is covering region _ when region 3 is transcribed, and the __ terminates transcription.

high, 2, attenuator slide 28

during the process of attenuation, when trp is ___, the ribosome is covering region _ when region 3 is transcribed, and the __ allows transcription_.

low, 1, anti terminator

_____ RNA is s small molecule that base pairs w a complimentary DNA/RNA sequence and blocks translation

antisense

codon

the set of nucleotides that encode a specific amino acid

sense codons (61) code for…

specific amino acids

stop codons (3) code for …

UAA, UAG, UGA

do not encode for a specific amino acid

there are ____ essential amino acids

20

degenerate

containing more information than needed

because there are ___ essential amino acids and ___ potential codons for them, the potential codons are

degenerate - know too much

what are synonymous codons?

Different codons coding for the same amino acid.

what do codons do?

bind to tRNA anti codons

what are isoaccepting tRNAs?

different tRNAs that accept the same amino acid but have different anticodons slide 7

how many anti codons are there?

30-50

explain what the wobble position is

when the 1st and 2nd position is complimentary and the third position can be wrong or “wobble” slide 8

what is the reading frame?

the way a nucleotide sequence is read (start code . stop codon)

replace base pair T with ___ for mRNA transcription

U Uracil

what are the 3 major components of translation?

mRNA, charged tRNA and ribosome

what makes a tRNA molecule “charged”?

if it has a amino acid attached slide 10

what is (enzyme) aminoacyl-tRNA Synthetase’s function? slide 11

attaches each amino acid to the correct tRNA.

ribosome structure

large subunit (50S) and small subunit (30S) slide 12

what are ribosome’s 3 main tasks? slide 12

1. bind mRNA and identify the start codon

2. enable base paring of mRNA codons & tRNA anticodons

3. catalyze peptide bond formation as the polypeptide chain grows

what is peptidyl transferase’s (enzyme in the ribosome) responsible for?

responsible for peptide bond formation during translation.

what is IF-3’s function? slide 13

initiation factor 3 prevents the large subunit from biting during initiation

mRNA can only bond to the small unit of the ribosome when

the subunits are separated slide 13

Shine Dalgarno sequence

DNA sequence that is complementary to nucleotides at the 3' end of the RNA component in a small subunit slide 13

IF2 and GTP role

both are required for the attachment of the initiator tRNA slide 15

IF 1 and 3 role slide 15

keep the large and small subunits separated

whats going on at the end of initation (translation steps)?

the ribosome is assembled on the mRNA and the first tRNA us attached to the initation codon

what are the 3 major steps of translation?

tRNA charging, initiation, elongation, & termination slide 10

after transcription pre-mRNA will need changes to the ___ , ____ and the _____

5’ cap

3’ end

protein coding region

mature eukaryotic mRNA does not have a _____ sequence like prokaryotes.

SD sequence

what is this? (eukaryotes) slide 19

5’ untranslated region (start codon)

what is this? (eukaryotes) slide 19

3’ untranslated region (stop codon)

what is this? (eukaryotes) slide 19

ply A tail

what is this? (eukaryotes) slide 19

poly A binding protein

what is this? (eukaryotes) slide 19

cap binding protein

what does the ribosome look for in eukaryotes?

the kozak sequence

whats going on @ the E site? (elongation translation)

tRNA moves away from the P site to the E site, then it just exits the ribosome from there slide 20

whats going on @ the P site? (elongation translation) aside 20

tRNA moves away from the A site into the P site where a peptide bond is formed between 2 amino acids (p site & a site) slide 20

whats going on @ the A site? (elongation translation) slide 20

all charged tRNAs (except the initiator tRNA) enter the A site

what happens during step 1 of eukaryotic elongation? (during translation) slide 21

slide 21 EF-Tu (pink) binds w GTP (yellow) and the charged tRNA to form the 3 part complex we see in the second diagram then once the complex is in the a site, GTP is cleaved which then forms GDP and the EFTuGDP is released and gets regenerated back to EFTuGTP by the elongation factor