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enzyme function
enzyme function
enzyme function
enzyme function
enzyme function
Protein Function
Enzyme Function
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function of ORI
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DNA includes
Structure
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Occurs
after termination
key enzyme
phase 3
phase 1
phase 2
location
location
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step 2
begins phase 2
2nd step of expression
Next modification
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GENE EXPRESSION

Translation

mRNA to Protein

Proteins

Chemical components

Amino Acyl tRNA synthetase
this is the enzyme that helps ADD the amino acid to the 3’ end of the tRNA.

Ribosomes
-small subunit and large subunit: where the amino acids are assembled into a polypeptide

tRNA: transfer RNA: the amino acid is attached to the 3’ end of the tRNA
tRNAs have an ANTICODON. This anticodon matches the codon of the mRNA nucleotide

mRNA : contains codons which code for a specific amino acid

Amino Acids: Brought to the ribosome by tRNA and is attached to the growing chain of polypeptides.

Peptidyl transferase: Formation of peptide bonds between amino acids

Initiation Factors

Elongation Factors

Release Factors

Transcription

DNA to mRNA

RNA

Prokaryotes

occur simultaneously in the cytoplasm, and the mRNA is simultaneously converted into amino acid sequences of a polypeptide by the ribosomes.

Eukaryotes

occurs in the nucleus, and the final mRNA is transported to the ribosomes in the cytoplasm.

ELONGATION

• Pre-mRNA nucleotides bind with the exposed DNA template strand.
• The RNA polymerase II moves downstream, unwinding the DNA for pairing with RNA nucleotides
• RNA polymerase II adds nucleotides to the 3’ end of the growing pre-mRNA molecule. (that means the template strand runs from 3’-5’)
• DNA strands are also formed back into a double helix

RNA polymerase I: yields pre-MRA and MRNA during transcription

•RNA nucleotides bind with the exposed DNA template strand.
•RNA polymerase moves downstream, unwinding the DNA for pairing with RNA nucleotides
•RNA polymerase adds nucleotides to the 3’ end of the growing pre-mRNA molecule. (that means the template strand runs from 3’-5’)
•DNA strands are also formed back into a double helix

INITIATION

Transcription factors, a collection of proteins, mediate the binding of RNA polymerase II and the initiation of transcription. *transcription factors MUST attach to the promoter first before RNA polymerase II can bind to it. *

RNA polymerase II binds to the promoter. In Eukaryotes, the promotor is typically a TATA box upstream from the transcription start point.

DNA strands unwind

RNA polymerase II initiates pre-mRNA synthesis at the transcription start point on the template strand

mRNA is transcribed at the start point on the template strand

TERMINATION

•At the end of the DNA sequence, RNA polymerase reads through and transcribes the terminator sequence
•Transcription is halted
•RNA polymerase disassociates from the DNA sequence, releasing mRNA

•RNA polymerase II transcribes a sequence of DNA called the polyadenylation signal sequence. This sequence specifies a polyadenylation signal (AAUAAA) in the pre-mRNA which causes the RNA polymerase II to cut the pre-mRNA transcript free

Eukaryote Modifications

First Modification

50-250 adenine nucleotides are added to form a poly-A-tail.

after the polyadenylation signal is transcribed (after transcription ends)

Second Modification

50-250 adenine nucleotides are added to form a poly-A-tail.

after the polyadenylation signal is transcribed (after transcription ends)

occurs in the nucleus

mRNA

Main topic

Replication

DNA to DNA

DNA

Structure: double helix, phosphate-sugar backbone outside the DNA molecule, each strand is anti-parallel to one another.

Nitrogenous Bases:adenine (A) with thymine (T), and guanine(G) with cytosine (C).

ORI sequences

short stretches of DNA that have a specific sequence of nucleotides.

Eukaryotic Chromosome

linear stretch of DNA and have hundreds or even thousands of origins of replication

ENZYMES/PROTEINS IN DNA REP

Helicases

BREAK HYDROGEN BONDS. It untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands.

Single Stranded Binding Protein

bind to each UNPAIRED DNA strand and keep them from forming back into the double helix

Topoisomerase

relieves the tight strain from the untwisting of the DNA strand

Primase

synthesizes the RNA primer at the 5’ end of leading strand and at 5’ end of Okazaki fragment of lagging strand.

DNA pol I

Removes RNA nucleotides of the primer from the 5’ end and replaces them with DNA nucleotides added to the 3’ end of adjacent fragment

DNA pol III

Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to the 3’ end of the primer OR a pre-existing DNA strand

DNA ligase

joins Okazaki fragments of lagging strand

Prokaryotic Chromosome

circular and has a SINGLE origin.

Proteins that initiate DNA replication recognize this sequence and attach to the DNA, separating the two strands and opening up a replication “bubble”

*replication is BIDIRECTIONAL*

RNA Splicing

Removing Introns

Spliceosome: a complex region of small RNAs and proteins

Ribozyme: attaches to pre-mRNA sequences and remove introns