BLY 301 CH 7

What is included in mRNA processing?

• introns removed

• g-caps added to 5’ end

• poly A tail added

What do the G cap and Poly A tail do?

protect from degradation & help w/ transport

Which TF initiates transcription?

TFIIH through phosphorylation

Why is TFIID significant?

it has the TATA box and indicates binding site for RNA Polymerase?

Which direction is mRNA read and translated?

5' to 3’, remember translation begins at start codon (AUG)

What is the starting codon?

AUG

When does transcription start in prokaryotes?

once the sigma factor of RNA Polymerase finds a promoter region

What does a shift in the large subunit of the ribosome cause?

transfer of tRNA from P to E site because of change in protein shape

While codons are found on ___, anti-codons are found on _____

mRNA, tRNA

Overall function of DNA, RNA, and proteins?

DNA stores genetic info, RNA carries genetic info, protein expresses genetic info & performs

What does RNA polymerase do?

chooses template strand, starting point, and binds to promoter to start transcription

What do the types of RNA do?

• mRNA: carries genetic instructions

• rRNA: catalyzes peptide bonds

• tRNA: matches amino acids to mRNA codons

What is RNA splicing?

• removal of introns,

• seals gaps in exons,

• catalyzed by SRNPS

What is the process of transcription? (eukaryotes)

• DNA’s nucleotide sequence copied to mRNA

• RNA Polymerase catalyzes and starts process

• RNA synthesized through base pairing

How does transcription work in prokaryotes?

RNA Polymerase use sigma factor to bind to promoter region

What is the process of translation?

• charged tRNA moves to A site and base pairs w/ mRNA

• c-terminus of growing polypeptide chain is transferred to the new amino acid at A site

• polypeptide chain & tRNA amino acid bind at A site

• large ribosomal unit shifts and tRNA moves P site > E site and A site > P site

• small subunit moves down mRNA, tRNA leaves, A site is free

What do the 3 (APE) sites do?

• A site: origin, receives charged tRNA

• P site: holds tRNA

• E site: releases tRNA

What do ribosomes and their small and large ribosomal subunits do?

• overall: ribosomes decode machinery of cell

• small: matches tRNA & mRNA codons

• large: catalyzes peptide bond formation

• ribozymes: catalyze rxns

• binding sites for mRNA and tRNAs

What are proteolysis?

breakdown of proteins into peptides & amino acids, led by proteasomes

What is the degradation process?

• target protein marked w/ ubiquitin

• ATP hydrolysis powers unfolding

• proteasome/protease break down protein & recycle ubiquitin

What is the RNA World hypothesis?

idea that early life used RNA as genetic material and a catalyst

What evidence backs up the RNA World hypothesis?

RNA can:

• store genetic info

• fold

• catalyze rxns

• form complementary RNA

DNA is:

• more stable because of its sugar

Proteins are:

• catalysts and structural molecules

What are tRNAs special features?

• carry anticodon for specific mRNA codon

• tail-end where amino acid attaches

• can recognize more than 1 codon, only 2 of 3 codons must be accurate

• charged: ATP gives energy that attaches tRNA to amino acid, producing a high energy bond that helps with protein synthesis

Where are proteins made?

on polyribosomes

What do general transcription factors do?