Transcription and Translation

Where does transcirption occur

in nucleus

Where does translation occur

in cytoplasm

What happens to the RNA strand that is created from transcription

It is read and creates a polypeptide chian

The instructctions for reading the RNA strand are in…

groups of three called codons

Total codons

64

How many codons are for amino acids

61

how many stop codons

3

What is Met

one of the most popular start codons

What is tRNAs role in translation

connects mRNA codons into the amino acids they encode, one end has an anticodon to bind to specefic codons

Wobble Hypothesis

some tRNA can bind to mutiple codons, the first 2 base paris are precise but the third has a “wobble”

Wobble pairing allows…

the same tRNA recognize multiple codons for the amino acid it carries

what do the The rules of wobble pairing ensure?

ensure that a tRNA does not bind to a wrong codon

Role of Ribosomes in translation

where polypeptides are built and they are made of rRNA and three slots for tRNA

what subunits of ribosomes are

small and large

three site for tRNA binding to ribosome

aminoacyl site, peptidyl site, exit site

Stage 1: Initiation

Initiart tRNA bind to small riobosomal subunite and it starts at the 5 prime end and goes to the 3 prime end to find a start codon, once it does a large ribosomal subunit joins to make a initation complex

Stage 2: elngation

Initiator tRNA moves to P site and the next tRNA goes to a site, ribosome moves down and the initiator tRNA leaves at E site

Stage 2: elngation: peptide bond forms…

bewteen the amino acids produce by tRNA

Stage 3: Termination

Occurs when a stop codon enters the A site, which is recognized by release factors and release polypeptide chain

the 3 stop codons

UAA, UAG, UGA

What is the fundemental princple of molecular gentics

Central dogma

Central Dogma

states that genetic information flows from DNA to RNA to proteins, i gues you could also call this protein synthsis

Major steps of central dogma

replication, transcription, translation

Transcription summary

Information is coded in DNA and is copied into RNA

three types of RNA

mRNA, tRNA, rRNA

mRNA

encodes proteins

tRNA

carries amino acids

rRNA

forms the ribosome

Why are there so many steps central dogma or proteins synthesis or whatever the fuck

DNA is housed in the nucleus and proteins synthesis happens outside it in the cytoplasm, DNA is too valuable for the functioning of a cell to leave for protein synthesis. so we need to make a complementary strand that can leave the nucleus

Main enzyme invloved in transcription

RNA polymerase

RNA polymerase function

uses a single DNA strand to synthesize a complementary RNA strand, and it builds in the 5 prime to 3 prime direction

Stage 1: Initiation

RNA polymerase binds to a promote reigon near the beginning of a gene and the DNA strand is seperate

Promoter

Specifc DNA sequence located upstream (5 prime direction), each gene has one

Ine eukaryotes whats the promoter reigon called

TATA box

Stage 2: Elongation

RNA polymerase reads the DNA and makes a RNA molecule made out of complementary nucletides

The RNA molecules contains the same information as what

the coding strand

Stage 3: Termination

Sequences called terminators signal the completion of the RNA transcript and RNA releases from template strand, termintaion involves a hairpin (to detach RNA from DNA squence)

In bacteria…

RNA can act as mRNA straight away

In Eukaryotse…

the RNA starts off as a pre-mRNA molecule

what process does pre-mRNA need to go through

splicing

Introns

intervening sequnces that need to be removed

Exons

expressed seuqences which are useful for coding reigons

Splicing

small nuclear ribonucleoproteins (snRNPS) combine with pre-mRNA and they form a spliceosome to remove introns

Alternative splicing

Exons can be joined in different combinations and increase the variety of proteins