Bio 107 Exam 2 Ch 15

What is the relationship between coding strand, template strand, and RNA?

Coding & template: complementary

RNA & coding: same

RNA & template: complementary

How is RNA read?

In groups of 3 (codons)

What determines which nucleotides starts protein synthesis?

There’s a starting sequence AUG, from there it codes in 3 starting after that

What is the start codon?

AUG (Met)

Stop codons

UAA, UGA, UAG

What is the protein responsible for protein synthesis?

rRNA, ribosomal RNA

All RNA is synthesized from a ___ template by ____.

DNA, transcription

What are the different kinds of RNA?

mRNA, rRNA, and tRNA

Messenger RNA (mRNA)

Intermediate form of information from nucleus to cytoplasm for processing

Ribosomal RNA (rRNA)

Class of RNA found in ribosomes, is essential for their function in protein production

Transfer RNA (tRNA)

intermediary adapter molecule between mRNA and amino acids during protein synthesis

Transcription requirements

Promoters, start sites, and terminator

Promoter

forms recognition and binding site for RNA polymerase

Start site

actual site where RNA synthesis begins

Terminator

Signal to end transcription

Transcription unit

Region from promoter to the terminator

What allows the polymerase to recognize the promoter?

The sigma subunit, it recognizes the promoter, brings the polymerase and then leaves it once the DNA is opened.

What allows the terminator to stop transcription?

An RNA-DNA hybrid in the transcription bubble is dissociated, this lets the RNA polymerase release the DNA so the DNA can rewind. The simplest terminator is a hairin, which cuases RNA polymerase to pause at uracil (the U-A bonds are the weakest which results in the dissociation of RNA from DNA).

What is the purpose of transcription factors?

Transcription factors get the RNA Pol 2 enzyme to a promoter to initiate gene expression. They interact with RNA polymerases to form initiation complexes at the promoters. 

What is 5’ capping?

In eukaryotes, the primary transcription must be modified to become mature mRNA. GTP is added to the 5’ end, with a methyl group is called methyl-G cap. It’s involved in translation initiation, RNA stability and further processing

What is 3’ Adenylation?

It’s an addition of a 3’ poly-A tail created by poly-A polymerase. Other termination mechanisms exist using other factors

What is removed during splicing?

Introns

Splicing process

A number of modifications are made while the mRNA is in the nucleus: introns are removed and exons are spliced together, a 5’ cap is added; a poly-A tail is added

Introns

They’re invening sequences, non-coding sequences

Exons

Expressed sequences, sequences that will be translated

Which does the spliceosome consist of?

Small ribonucleoprotein particles (snRNPs), they cluster with other proteins to make the spliceosome. They’re responsible for removing introns via splicing

______________ _______________ refers to genes being spliced together in different patterns. The number of proteins and pre spliced mRNA is not the same. Why do you think this is?

he same mRNA transcript can be spliced in different ways. Different proteins can be yielded from the same gene, it just depends on what you decide to cut out. There’s different pol-A sites on the different 3’ Poly-A tails for different proteins

What does tRNA do?

Interact with mRNA and amino acids, carry amino acids to the riibosome for incorportaion into a polypeptide

What is the purpose of the ribosome?

A key machine used for translation, needs mRNA, and tRNA.

tRNA binding sites

A (aminoacyl) site, P (peptidyl) site, E (exit) site

A (aminoacyl) site

binds the tRNA carrying the next amino acid

P (peptidyl) site

binds the tRNA attached to the growing peptide chain

E (exit) site

binds the tRNA that carried the previous amino acid added

Eukaryotic genes contain ___ and ___.

Introns, Exons

Splicing

When non-coding DNA/introns are removed, and coding are connected

Why is there non-coding DNA?

RNA can be spliced into many different ways, and each has it’s own function so having more introns that can be removed at different parts will allow for a wide range of proteins to be made.

Splicing is recognized by the ___

Spliceosome

The spliceosome..

Recognizes non-coding DNA/introns, and cuts it out

tRNA

adaptor RNA, recognizes RNA’s message and turns it into proteins by bringing the correct amino acids together (recognized by complementary RNA)

Anticodon

Complementary RNA

Ribosome has a ___ and a ___.

Large, small. The small one has the RNA, and proteins are made in the large subunit. 

Silent mutation

same amino acid inserted, no net effect

Missense mutation

changes amino acid inserted

Nonsense mutations

Changed to a stop codon