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