Function? Cell nucleus chromosome double helix gene Context.
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Transcript of Function? Cell nucleus chromosome double helix gene Context.
Function? http://www.youtube.com/watch?v=d1UPf7lXeO8&feature=related
Cell nucleus
chromosome
double helixgene
Context
Double helixDeoxyriboseA - T pair
Single helixRibose sugarA - U pair
DNA vs RNA : Structure
segments of the sequence - genes - code for polypeptides
rewrites and translates the code into polypeptides(proteins)
DNA vs RNA : Function
Types of RNA
Ribsomal, rRNA, combines with protein in the cytoplasm to form a ribosome.
Types of RNA
Messenger, mRNA, is synthesized from a gene and carries the code into the cytoplasm for protein synthesis
Types of RNA
Transfer (tRNA) a loop of nucleotides three of which form an anticodon. Also contains the amino acid coded for by the mRNA codon complement. The polypeptide is built by linking the amino acids of adjacent tRNA.
anticodon
amino acid
The Ribosome• The ribosome serves as the site for protein synthesis. Made of rRNA and protein, ribsomes are synthesized in two sub units.
ribosome
tRNA sites
mRNA site
• The ribosome attaches itself to m-RNA and provides the stabilizing structure to hold all substances in position as the protein is synthesized.
The Central Dogmagene expression
Reading & expressing genes
Genes in the DNA are transcribed into RNA which is translatedinto a sequence of amino acids
Fundamental & universal to life on Earth
mRNA carries the code from the nucleus; tRNA base pair with mRNA at ribosomes to string the amino acids together
https://www.youtube.com/watch?v=u9dhO0iCLwwwww.youtube.com/watch
Transcription is initiated when RNA polymerase binds at DNA ‘upstream’ of the gene, called the promoter
Elongation – polymerase adds nucleotides to transcribe the gene. Termination sequences near the end of the gene communicate a stop-transcription message
Template & Direction
Since DNA is antiparallel, the template is always the 3’-5’ helix
mRNA is ‘written’ 5’-3 as it can only be built by adding a 5’ C to a 3’C in the chain (mnemonic: write has 5 letters)
coding strand
anti-sense strand
The code is redundant6 codons for serine!but never ambiguousCCC = proline, only
Eukaryote genes are modified before translation
Introns are excised
Exons are spliced together
Splicing can occur in multiple ways, creating many mRNA from one gene
Ex: 30,000 genes, +100,000 proteins
Caps and tails are added to the mRNA, slowing destruction by enzymes
CAP at 5’ end
Poly–A TAIL
STARTcodon
STOP Codon
Summary of Differences
Replication Transcription & Translation
Point mutation/substitutionPotentially changes one amino acid - missense
Mutations change the codeand sometimes the protein
Frameshift mutations result from insertion or deletion of nucleotides
http://www.youtube.com/watch?v=kp0esidDr-c
Alters the codons from that point down