gen test 4

what is the central dogma of biology

DNA. RNA, protein

what is transcription

making RNA from DNA

what is translation

making protein from mRNA

why is mRNA called a copy of DNA

it has the same sequence but has U instead of T

what strand is used in transcription

the template strand

what are the 3 stages of transcription

initiation, elongation, termination

what happens during initiation

transcription machinery assembles at a promoter

what happens during elongation

RNA polymerase builds RNA by adding nucleotides

what happens during termination

RNA polymerase stops at the end of the gene

what is RNA polymerase

a enzyme thhat catalyzes the synthesis of RNA from DNA

what enzyme performs transcription in bacteria

RNA polymerase

what is a consensus sequence

a DNA sequence recognized by proteins

what is the Pribnow box

TATAAT

what is the -35 sequence

TTGACA

what is Rrho dependent termination

use rho protein to stop transcription

what is rho independent termination

hairpin loop and uracil sequence stops transcription

how many RNA polymerases do eukaryotes have

three (I, II, III)

which polymerase makes mRNA for eukaryotes

RNA polymerase II

what must happen before transcription for eukaryotes

chromatin must be modified/unwound from histones

what is the TATA box

a promoter sequence where transcription begins

what are enhancers

DNA sequences that increase transcription

what proteins help start transcription

transcription factors

what is RNA processing

modifying pre-mRNA before it becomes mRNA

what is added to the 5’ end

5’ cap (7-methylguanine)

what is added to the 3’ end

poly-A tail

what are introns

noncoding regions

what are exons

coding regions

what removes introns

spliceosome

what is a codon

a 3-base sequence that codes for amino acids

why are codons 3 bases long

allows for enough combinations for 20 amino acids

what is the start codon

AUG

why do silent mutations occur

because multiple codons code for the same amino acid

what does the ribosome do

builds proteins from mRNA

where does translation start

at the 5’ end of mRNA

what scans for the start codon

the ribosome

what does tRNA do

matches codons with amino acid

why cant one base code for one amino acid

not enough combinations

why is DNA considered storage

it holds instructions for proteins

differnce between DNA and RNA

DNA has thymine and is double stranded and RNA has uracil and is single stranded

difference between prokaryotes and eukaryotes

eukaryotes have introns and exons and prokaryotes dont

how does DNA determine traits?

DNA to mRNA to protein to trait

what is the role of mRNA

middleman between DNA and protein

why must gene expression be regulated

replication, translation, and transcription is energetically expensive

what is reversible gene regulation

genes can be turned on and off

when does bacteria make amino acids

when there is none in the environment

what is a gene

DNA sequence transcribed into RNA

what are structural genes

encoded proteins for metabolism, biosynthesis, or structure

what are regulatory genes

genes that encode proteins that control other genes

how do regulatory proteins work

bind to DNA to activate or repress transcription

what are constitutive genes

genes that are always on

what is a protein domain

a 60-90 amino acid region that binds DNA

what is a motif

repeating ATCG sequence

where do most DNA binding proteins bind?

major groove of DNA

what type of operon is the lac operon

negative inducible

what does the lac operon do

breaks down lactose

what is a inducible operon

kept off and must be altered to be expressed

what are repressible operons

kept off and must be turned on

what is a negative inducible operon

The regulatory protein is a repressor, and so the gene’s natural, unregulated state is on

Negative repressible operons

The regulatory protein is also a repressor, and so the gene’s natural, unregulated state is on

Positive inducible operons

The regulatory protein is an activator, and so the gene’s natural, unregulated state is off

Positive repressible operons

The regulatory protein is also an activator, and so the gene’s natural, unregulated state is off ( must turn on)

what are lac structural genes

lacZ, lacY, and lacA

what is the inducer

allolactose

what happens when there is no lactose

repressor binds and transcription turns off

what happens when lactose is present

allolactose inactivates repressor and transcription is turned on

what happens when glucose is present

lac operon is off

what happens when glucose is low

cAMP increases

what does cAMP do

activates CAP (catabolite activator protein)

when do you get max lac operon expression

when lactose is present and glucose is low

when lactose is present and glucose is high what happens

lac operon turns off

Lactose present, glucose low → what happens?

lac operon turns on

No lactose (any glucose level) → what happens?

lac operon is off because repressor is bound

what type of operon is trp

negative repressible

what does trp operon do

synthesize tryptophan

when is the trp operon on

when tryptophan is low

when is the trp operon off

When tryptophan is HIGH

what is attenuation

Premature termination of transcription

why can attenuation happen in bateria

transcription and termination happen at the same time

what structure stops transcription in trp operon

3-4 hairpin

what structure allows transcription to continue

2-3 pairing

what is a mutation

a change in DNA sequence. can be caused by cellular errors or environmental reasons

why are mutations important

good source of variation and can cause deceases

what are somatic mutations

mutations to body cells

what are germ-line mutations

mutations in gametes

what is a base substitution

a mutation where one nucleotide is replaced by another

difference between transition and transversion

transition changes purine into pyrimidine or purine while transversion changes purine to pyrimidine

what are insertions or deletions

adding or removing nucleotides in dna

what is a frameshift mutation

a mutation caused by INDELs that change the reading frame

what are expanding nucleotide repeats

increase in repeated dna sequence

why are repeat expansion dangerous

they are linked to over 30 diseases

what is a forward mutation

changes wild-type phenotype to a mutant phenotype

what is a reverse mutation

restores mutant phenotype to wild type

what is a missense mutation

no change in amino acid due to redundancy

what is a nonsense mutation

converts a codon to a stop codon

what is a neutral mutation

changes amino acid but does not affect protein function

what is a loss of function mutation

mutation that reduces or eliminates protein function (recessive)

what is a gain-of-function mutation?

mutation that creates new function (dominate)

what is reversion

mutation that restores original DNA sequence

what is a suppressor mutation

a second mutation that restores phenotype without fixing og mutation

what are the two main sources of mutations

spontaneous (internal) or induced (environment)