Translation + Transcription

structure of a dna strand

sugar phosphate backbone and a base

purine

double ringed bases include adenine and guanine

pyrmidines

single-ringed bases that include thymine and cytosine

number of hydrogen bonds between adenine and thymine

2

number of hydrogen bonds between guanine and cytosine

3

2 strands of dna run in ? direction

antiparallel

stages of dna replication

1. separation of 2 dna strands

2. each parental strand now serves as a template that determines the order of nucleotides along a new complementary strand

3. nucleotides are connected to form the sugar oghosphate backones of the new strands. each daighter dna molecule consists of one parental strand and one new strand

topoisomerase

beaks, swiwels, and rejoins the parental DNA ahead of the replication fork, relieving the strain caused by unwinding

helicase

unwinds and separates the aprental dna strands at the replication forks

primase

synthesizes rna primers using the parental dna as a template

single strand binding proteins

stabilize the unwound parental strands

dna ligase

joins okazaki fragments of lagging strand; on leading strand, joining 3’ end of dna that replaces primer to rest of leading strand DNA

origin of replication

a specific DNA sequence where DNA replication begins.

replication fork

a Y-shaped structure formed during DNA replication where the double-stranded DNA helix is separated, allowing for n

5’ end of strand

phosphate group

3’ end

OH side

during replication new nucleotides must be added to an existing ? end of a sugar in DNA

3’

FREE THREE

lagging strand

the strand of DNA that is replicated discontinuously, in short fragments called Okazaki fragments

synthesized away from the replication fork, which is where DNA replication begins

moves from 5’ to 3’

leading strand

the newly synthesized strand that is built continuously in the 5' to 3' direction, moving towards the replication fork

priming dna synthesis with rna

1. primase joins rna nucleotides into primer

2. dna polymerase adds dna nucleotides to primer

3. a different dna polymerase replaces the rna with dna

synthesis of leading and laggin strands during dna replication

? protect the ends of dna

teleomere

transcription

involves turning dna base sequence for a polypeoptide into an rna copy of the sequence

differences in transcription in prokaryotes v eukaryotes

pro:

• mrna is made and can immediately be translated in the ribosome

euk:

• mrna is made in the nucleus. it undergoes rna processing before leaving the nucleus

how gene info flows

dna → rna → protein

codon

triplet rna bases

promoter

segment of dna that is that the rna polymerase enzyme binds to. located upstream

rna polymerase

adds new nucleotide bases of rna making an mrnaa molecule in 5’ to 3’ direction

termination

after transcribing the transcription unit, a terminator sequence is reached… the mrna will dissociate from the dna shortly afterward

tata box

he TATA box helps initiate the transcription process by specifying where the RNA polymerase should begin reading the DNA to create an RNA molecule. 

stages of transcription

1. initiation

   1. rna polymerase binds to a specific dna region called a promoter, marking the staert of the gene to be transcribed

2. elongation

   1. rna polymerase moving along the dna template, synthesizing the complementary rna strand

3. termination'

   1. occurs when rna polymerase reaches a termination sequence

rna processing

adds a 5’ cap that includes a guanine triphosphate

adds a poly a tail

this is to protect the mrna as it exits the nucleus and aid its exit

rna splicing

introns are removed and exons are spliced together

splicosome

a big structure that removes introns and splices exons together

translation

occurs in the cytoplasm in ribosomes

stages of translation

• mrna enters and binds to the small subunit of the ribosome

• iniation codon (aug) binds to methionine amino acid in the p site

• trna will bring in the appropriate amino acids to add in the appropriate position the polypeptide chain

trna

plays catalytic roles and structural roles in ribosomes

rrna

pl

mrna

carries infromation specifiying amino acid sequences of proteins from dna to ribosomes

point mutation

• substitution

• deletion

• insertion

frameshift mutation

when insertions or deletions of not triplets happen

• missense - which codes for the wrong amino acid

• nonsense - which codes for an early STOP codon

differences in transcription between prokaryotes and eukaryotes

prokaryotes - no transcription factors or tata box on promoter

eukaryotes - transcription factors, tata box on promoter, mrna editing, 5’ cap and polyA tail, intron removal, spliciing of exons

differences in translation between prokaryotes and eukaryotes

prokaryotes - almost simultaneous transcription and translation

eukaryotes - translation begins after the mrna has been modified and leaves the nucleus