MEDS2013 - Frontiers of Human Health

DNA bases

ATCG

RNA bases

AUGC

DNA

double stranded, more stable, stays in nucleus, has one job

RNA

single stranded, moves all around cell, has many jobs

DNA stays in the nucleus because

it is bulky and precious

transcription

small portion of DNA is copied into RNA

translation

ribosomes convert RNA code into amino acids

mRNA processing

introns removed, add 5’ cap and 3’ polyAtail to mRNA

introns

portion of DNA in a gene that is not expressed as a protein

exons

portion of DNA in a gene that is translated and expressed as a protein

3 nucleic acids is

a codon = amino acid

translation

tRNA brings amino acid to ribosome that reads mRNA sequence and links the amino acid into a polypeptide chain that folds into protein

gene

small piece of DNA that is transcribed as mRNA and translated as a protein

genome

all of the genetic material in an organism

histone proteins

DNA is wound around structural proteins that make up a nucleosomes and these are packaged into chromsomes

haploid

1 set, gametes

diploid

2 sets

why cells need to regulate transcription

no reason to express entire genome at all times where only a small portion of DNA is expressed as proteins

closed chromatin

heterochromatin is densely packed where transcription cannot occur

open chromatin

euchromatin is loosely packed where transcription can occur

allele

versions of a gene

diploid organism

have two copies of each allele

autosomal

alleles encoded on chromosomes 1-22

sex linked

alleles encoded on X/Y chromosome

autosomal traits

widows peak, earlobe attached, eye colour, hair colour

sex linked traits

colourblindness, haemophilia, webbed toes, ear hair

nucleotide composition

base, sugar, phosphate

DNA structure

chains antiparallel, sugar phosphate backbone on outside and base pairs inside

double helix has

wide major groove and narrow minor groove

RNA can form

secondary structures via base pairing

absorption spectrum for DNA

1 for 50ng/uL

absorption spectrum for RNA

1 for 40ng/uL

gene

DNA sequence that encodes products that carry out functions in the cell, can be protein coding or RNA coding

transcription

producing nucleotide-for-nucleotide copy of an RNA molecule from a DNA template

translation

producing a polypeptide chain from a mature mRNA transcript

two DNA strands in transcription

coding strand that codes for gene of interest and is the same as RNA produced and the template strand

mRNA in translation is read in

triplets (codons) to produce a polypeptide chain

the genetic code

used to translate RNA sequence into an amino acid sequence

standard number of amino acids in genetic code

20, 64 codons where 61 code for an amino acid and 3 serve as stop codons

Met (AUG)

start codon to initiate translation

structure of protein coding genes

RNA polymerase synthesises mRNA precursors (pre mRNA) where introns are removed to produce mature transcript comprised of exons

mutations within exons

affect protein structure/function

mutations within introns

affect protein expression as introns contain regulatory regions