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Chapter 16 & 17 (Key Proteins (Helicase (Unwinds and splits double…
Chapter 16 & 17
Key Proteins
Helicase
Unwinds and splits double helix
Single-Strand Binding Protein
Stablizes split DNA before Synthesis
Topoisomerase
Breaks swivels and reattaches DNA ahead of Helicase
Primase
Synthesizes RNA Primer
DNA Polymerase III
Adds nucleotides to RNA Primer or DNA strand
DNA Polymerase I
Replaces RNA nucleotides of primer with DNA nucleotides
DNA ligase
bonds new nucleotides together (leading or lagging)
Nuclease
Cuts damaged DNA to be replaced with new nucelotides
Transcription
RNA Polymerase
follows same rules as DNA polymerase
substitue Uracil for Thymine
RNA synthesis
Inside nucleus (first, before RNA modification)
Initiation
RNA pol binds to promoter (specific DNA sequence)
DNA unwinds
RNA pol initiates RNA Synthesis
Elongation
RNA pol moves down unwinding DNA
RNA is transcribed from unwound DNA
DNA rejoins behind transcription/RNA pol
Termination
RNA transcript is released
RNA pol detaches
Translation
Synthesis of polypeptide (protein)
Outside nucleus (last)
through a ribosome
Transfer RNA (tRNA)
attaches amino acids from cytoplasm
to proteins being built in the ribosome
Ribosome
Ribosomal rRNA
proteins
binding sites
mRNA
forms peptide bonds with tRNA to elongate amino acid chain
tRNA
In
A & P sites
Out
E site
recognizes mRNA and binds based on recognitions
stages of translation (coordinated by the Ribosome)
Initiation
Small ribosomal subunit binds to mRNA
Large ribosomal subunit with tRNA completes initiation complex
Elongation
Amino Acids are added to chain by tRNA
Termination
a specific mRNA sequence (stop codon) reaches the A site
water is added to polypeptide
amino acid chain breaks off from ribosome
Molecular structure of DNA
chemical composition
nucleotide
Phosphate Group
Deoxyribose (a pentose sugar)
Ntirogen base
Thymine
Guanine
Cytosine
Adenine
container of genetic information
Inheritance by DNA replication
Instructions for life encoded in nitrogen bases
Double Helix Shape
Twisted rope ladder
DNA replication
Semi-Conservative Model
double helix splits and replicates itself by individual strands
Origins of Replication
RNA Primer
initial site of replication
short section of RNA in DNA double helix
Split strands
Antiparallel Elongation
Leading strand
1 RNA primer
DNA Polymerase III (DNA pol III)
Lagging strand
Sequence of RNA primers
Okazaki fragments
segments of DNA in between RNA primers
Replication at replication fork
Helicase splits helix
Lagging strand
Primase synthesizes RNA primer
DNA pol III synthesizes DNA immediately after RNA primer
DNA pol I replaces RNA primer with DNA nucleotides (fragment)
DNA ligase bonds new DNA with fragment DNA
Leading strand
Continually synthesized by DNA pol III
RNA Proccessing
Inside nucleus (after Transcription)
Eukaryotic cell transcript (pre-mRNA) modification
of transcript ends or cutting of transcript
RNA splicing
Large portions of pre-mRNA removed and reconnected
Introns
Part that is cut out
Exons
Part expressed
Spliceosome
complex of small RNAs and proteins
Cuts intron and rejoins transcript
Ribozymes
RNA molecule which functions as an enzyme
transcript cut its own introns
alternative RNA splicing
different proteins arising depending on which exons are cut
Chromosome
Chromosome
Prokaryotic
Circular DNA molecule which makes up the nuceloid
Eukaryotic
Chromatin
DNA
histones
DNA wraps around this; part of chromatin packing
nucleosomes
"bead on a string"
DNA wound around core of histones
Eukaryotic Chromosomes consists of many nucleosomes
packed into chromatin
DNA
chemical makeup of genetic material