Double helix Deoxyribose A - T pair Single helix Ribose sugar A - 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 Dogma gene expression Reading & expressing genes Genes in the DNA are transcribed into RNA which is translated into 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=u9dhO0iCLww
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 3C in the chain (mnemonic: write has 5 letters) coding strand anti-sense strand
The code is redundant 6 codons for serine! but never ambiguous CCC = 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 START codon STOP Codon
Summary of Differences Copies both DNA helices Uses template strand of DNA to create RNA Leads to more cellsLeads to proteins (gene expression) Entire molecule copiedSingle gene transcribed, exons spliced together DNA polymerase adds nucleotideRNA polymerase adds nucleotides RNA primer initiates sequencingPromotor on DNA initiates sequencing Replication Transcription & Translation
Point mutation/substitution Potentially changes one amino acid - missense Mutations change the code and sometimes the protein
Frameshift mutations result from insertion or deletion of nucleotides Alters the codons from that point down