transcription The first step of gene expression synthesis

transcription The first step of gene expression – synthesis of RNA molecule

Some nomenclature conventions RNAP

RNA DNA

Similarities and Differences Between DNA and RNA • Similar strand structure • Can define a 5’ and 3’ end • 2’ hydroxyl in RNA: causes stability differences) • Uracil in RNA takes the place of Thymine in in DNA

Secondary structure of RNA Stem & loop

Difference between DNA and RNA. – DNA – Double Helix, RNA – Single Stranded – DNA --- A-T, RNA ---A-U – DNA ---Deoxyribose Sugar, RNA---Ribose • What is a similarity of DNA and RNA? – G binds with C in both DNA and RNA – Both have sugar and phosphate backbone

The pathway of gene expression

CAP

Conserved seqences Polypyrimidine tract

Splice sites can be included in the exons

m. RNA splicing lariat

Systemic Lupus Erythematosus (SLE) Lupus is a type of immune system disorder known as an autoimmune disease. In autoimmune diseases, the body harms its own healthy cells and tissues. This leads to inflammation and damage of various body tissues. Lupus can affect many parts of the body, including the joints, skin, kidneys, heart, lungs, blood vessels, and brain. Although people with the disease may have many different symptoms, some of the most common ones include extreme fatigue, painful or swollen joints (arthritis), unexplained fever, skin rashes, and kidney problems. Lupus is also known as a rheumatic disease. The rheumatic diseases are a group of disorders that cause aches, pain, and stiffness in the joints, muscles, and bones.

15% of the mutation leading to genetic disorders effect splicing activity Untreated β thalassemia

Treatment of thalassemia major

antisense

Human genome 2. 91 billion base pairs 24, 500 genes 1. 5% exons (127 nucleotides) 24% introns (~3, 000 nucleotides) 75% intergenic (no genes) Average size of a gene is 27, 894 bases Contains an average of 8. 8 exons Titin contains 234 exons.

Gene number C. elegans ~19, 000 Homo Sapiens ~24, 000 Drosophila melanogaster ~13, 600 Mouse ~24, 000 Arabidopsis thaliana ~25, 500 Rice (Oryza sativa) ~50, 000

Compared to worm and fly, human has shorter exons and longer introns on the extremes of the distribution 150 nt – drosophila 125 nt – Ciona intes. 119 nt - human

5000 genes 234 introns Multi-introns genes 7. 8 introns per gene

Sequences of humanmouse homologous exons are 88% conserved

Alternative splicing טראק פוליפרימידין 40% 18% 8% ? 3% isoform

Alternative splicing regulate pro or anti apoptotic pathways. pro-apoptotic anti-apoptotic

translation The last stage in gene expression – synthesis of protein

Amino acid

N C

N to C terminal 5’ to 3’

CDS

Aminoacyl t. RNA

t. RNA Aminoacyl-t. RNA • 20) synthetase (diffrent one for each amino – acid NEEDS ENERGY! –

64 combinations for 20 amino acids 3 termination codons

טרנסלציה סרט מלאי ספירת Met one codon LEU 6 codons, 4 of which are CUN

Disease-Associated Mutations A mutation is a change in the normal base pair sequence Commonly used to define DNA sequence changes that alter protein function

Polymorphism DNA sequence changes that do not alter protein function (common definition, not technically correct) Functional protein

Single nucleotide polymorphisms (SNP) (in the coding sequence) m. RNA Normal Protein Sequence variant A U G Met A A G U U U GGC GC A U UG C A A Lys Phe Gly Ala Leu Gln m. RNA A U G Protein Met A A G U U U GGU GC A U UG C A A Lys Phe Gly Ala Silent DNA sequence polymorphism Leu Gln

Missense Mutations Normal m. RNA Protein A U G Met A A G U U U GGC GC A U UG C A A Lys Phe Gly Ala Leu Gln m. RNA Missense A U G Protein Met A A G U U U AGC GC A U UG C A A Lys Phe Ser Ala Leu Missense: changes to a codon for another amino acid (can be harmful mutation or neutral polymorphism) Gln

Nonsense Mutations Normal m. RNA Protein m. RNA Nonsense Protein A U G Met A U G A A G U U U GGC GC A U UG C A A Lys Phe Gly Ala Leu Gln U A G U U U GGC GC A U UG C A A Met Nonsense: change from an amino acid codon to a stop codon, producing a shortened protein

Frameshift Mutations Normal m. RNA Protein A U G Met A A G U U U GGC GC A U UG C A A Lys Phe Gly Ala Leu Gln U Frameshift m. RNA Protein A U G A A G U U G GC G C A U UGC A A Met Lys Leu Ala Frameshift: insertion or deletion of base pairs, producing a stop codon downstream and (usually) shortened protein Pre-mature stop codon

mutation Missense mutation

Translation II A peptide – a chain of amino acids A protein – a stretch of one or more amino acid chains with biological function

+e. IF 3

e. IF 3

Translation

טרנסלציה סרט Life cycle of m. RNA movie