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The Inner workings and Purpose of DNA (DNA Broken Down (Differentiation…
The Inner workings and Purpose of DNA
DNA Broken Down
Key Proteins
DNA Replication
Origin of Replication - where replication of chromosomal DNA begins
DNA Helicase
Enzymes that untwist the double helix at the replication forks, separating the parental strands, making them available template strands
Single Strand Binding Proteins
Bind to the unpaired DNA strands, preventing them from re-pairing
Replication Fork
A y-shaped region where the parental strands of DNA are being unwound
Topoisomerase
Enzyme that helps relieve strain on replication fork by breaking, swiveling and rejoining DNA strands
Primer
RNA chain initially produced during DNA synthesis
Primase
Enzyme that starts a complementary RNA chain with a single RNA nucleotide and adds them one at a time, using parental DNA as a template
DNA Polymerase
Enzymes that catalyze the synthesis of new DNA by adding nucleotides to the 3' (prime) end of an already existing chain
DNA Ligase
Enzymes that joins the sugar phosphate backbones of all Okazaki fragments into a continuous DNA strand
DNA Repair
Mismatch Repair
Other enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors
Nuclease
DNA cutting enzyme that generally cuts out damaged DNA
Nucleotide excision repair
An important function of this system in skin cells it to repair genetic damage caused by UV rays from sunlight
Finds the damaged DNA, isolating it and removing it from the strand to replace it with the correct bases
Differentiation between:
Chromatin
Complex of DNA and protein, fitting into the nucleus through an elaborate multilevel system of packing
Chromosomes
Compacted chromatin that holds most if not all of the genetic material in an organism, made
DNA
Deoxirobonucleic Acid, a double helix, lives inside the nucleus like chromatin, the smallest of the three, binds with proteins to form the other two (Chromatin and Chromosomes)
DNA Structure
Codes for proteins to be made and produced in organisms, making unique individuals with proteins produced and expressed
Phosphate
Phosphate group that attaches itself to the sugar to form the 'backbone' of DNA
Nitrogenous Base (5)
C
Cytosine pairs with Guanine
G
Guanine pairs with Cytosine
T
Thymine pairs with Adenine
U
Uracil (RNA) pairs with Adenine
A
Adenine pairs with Thymine
Sugar
Pentose sugar known as Deoxiribose, hence the name Deoxiribonucleic Acid (DNA)
How DNA works and products
RNA Processing
Enzymes in the nucleus modify pre-mRNA in specific ways before the message is sent into the cytoplasm
RNA Processing takes place after transcription to edit the mRNA and alter it before it is sent out into the cytoplasm
RNA processing works through 5 different steps
3' Poly-A tail
Discovery of Introns
5' capping
Intron processing and removal
pre-mRNA processing
RNA Processing takes place in the nucleus of the cell following Transcription
Important Parts
Introns
Noncoding segments of nucleic acid that lie between coding regions,
Intervening sequences
Exons
Regions that are eventually
expressed
, usually by being translated into amino acid sequences
Splicosomes
A large complex made of proteins and small RNA's
Removes introns by binding to several short nucleotide sequences along the intron
Ribosymes
RNA molecules that function as enzymes
Domain
Modular architecture consisting of discrete structural and functional regions in proteins
Translation
Synthesis of a polypeptide using the information in the mRNA
Translation takes place at the very end of DNA replication, following RNA processing
mRNA is decoded and turned into a ribosome to create a specific polypeptide that later folds into an active protein and goes to work in the cell
Translation takes place in the cytoplasm of the cell
Important Proteins
Ribosomes
Facilitate the specific coupling of tRNA anticodons with mRNA codons during protein synthesis
Consists of a large subunit and a small subunit, each made up of proteins and one or more
Ribosomal RNA
Enzymes
aminocyl-tRNA synthase
A family of related enzymes that match up the tRNA and amino acids correctly
20 different synthases, one for each amino acid and tRNA
Joins a given amino acid to an appropriate tRNA
tRNA
'Transfer RNA' translator for the series of codons along a mRNA molecule
Anticodon
The particular nucleotide triplet that base-pairs to a specific mRNA codon
Active Sites
P SIte
Peptidyl-tRNA binding site, holds the tRNA carrying the growing poly
Peptide
chain
E Site
Exit
site, where discharged tRNA leave the ribosome
A Site
Aminoacyl-tRNA binding site, holding the tRNA carrying the next amino acid to be added to the chain (Assembly)
Wobble
A flexible base pairing at the third position of an mRNA codon
Transcription
Synthesis of RNA using information in the DNA
Transcription occurs, coupled with translation in Eukaryotic cells, during Interphase of cell replication, when the DNA begins to replicate
Works through 3 stages to synthesize DNA into RNA
Elongation
DNA unwinds and elongates the RNA transcript, in 5' to 3'
Termination
RNA transcript is released and the polymerase detaches from the DNA
Initiation
After RNA polymerase binds to the promoter, DNA unwinds and RNA synthesis begins at the start point on the template
Transcription takes place inside the nucleus of the cell
Important Enzymes and Other
RNA Polymerase
Enzyme that pries the coupled DNA strands apart and joins together RNA nucleotides to it's complementary DNA strand
Transcription factors
A collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription
Promoter
DNA sequence where RNA polymerase attaches and initiates transcription
Terminator
Sequence that signals the end of transcription (in bacteria)
Transcription Unit
Stretch of DNA downstream from the promoter that is transcribed into an RNA molecule
Start Point
The nucleotide where RNA polymerase begins the synthesis of mRNA
TATA Box
A crucial promoter DNA sequence consisting of Thymine Adenine Thyme Adenine