Genes and How They Work Computer Filename: genes1.ppt Developed by Hugh B. Fackrell

Overview Genes are composed of DNA within the chromosome Genes code for proteins DNA is transcripted into RNA RNA is translated into protein by ribosomes Genes regulated by control of RNA production

Lecture Outline Genes and How They Work Genetic Code Gene Expression transcription translation Protein Synthesis Gene Regulation Gene Architecture

Concepts from OAC Structure & Function of DNA & RNA Genetic code Transcription & translation Protein synthesis Gene Regulation: operators, promotors , repressors

Background Terms & Concepts Structure of DNA & RNA Ribosomes Enzymes Structure of Eukaryotic chromosomes

The Genetic Code Genetic information is stored in DNA sequences found in Chromosomes Mitochondria: 16 KB, 13 genes Chloroplasts: 120-160 KB, 120 genes

Structure of the Genetic Code DNA : sequences of four nucleotides A,T,G,C CODONS : blueprint for the polypeptide Start & Stop Signals: Where to read the blueprint Regulatory Sequences: When to read the blueprint promotors operators enhancers

CODONS sequences of three adjacent nucleotides that code for one amino acid or polypeptide termination 64 codons encrypt of ~ 20 amino acids degenerate RNA: ACU, ACC,ACA, ACG threonine degenerate DNA: TGA, TGG,TGT, TGC threonine

Start Codon RNA: AUG DNA: TAC also codes for methionine

Stop Codon Nonsense Codons RNA: UAA,UAG,UGA DNA: ATT, ATC, ACT

Alternate Genetic Codes Sequence Chromosome Mitochondrion TGA Stop Trypt ATA Isoleucine Methionine AGA Arginine Stop AGG Arginine Stop

Interpreting the Genetic Code Two step process : Transcription DNA --> RNA Translation RNA--> protein

RNA Ribosomal RNA Transfer RNA Messenger RNA

Ribosomal RNA called rRNA found in Ribosomes probably catalytic site provides site for protein assembly ribosomal structure different in eukaryotes and prokaryotes

Prokaryotic Ribosomal RNA large subunit 5s(120), 23s (2900) Small subunit 16s (1540)

Eukaryotic Ribosomal RNA Large subunit 5s(120) 28s (4700) 5.8s (160) Small subunit 18s(1900) Ribosomal RNA 18 S 5.8 S 28 S Transcribed Spacer RNA

Ribosomal RNA

Transfer RNA called tRNA Smaller than mRNA or rRNA found in cytoplasm 40 different kinds of tRNA transports amino acids to ribosome positions amino acids on elongating polypeptide

tRNA

Messenger RNA called mRNA long single strand of RNA copy of the DNA to be decoded transfers information from the nucleus to the cytoplasm for decoding

Transcription Production of an RNA copy of the gene occurs in nucleus of eukaryotes cytoplasm of prokaryotes DNA unravels- single strand RNA Polymerase binds to Promotor site Reads from start sequence(TAC) assembles complementary single strand of RNA (primary RNA) Disengages when reaches stop codon

RNA being read from DNA

Prokaryotic Transcription and Translation

Antibody Structure

Eukaryotic Transcription & Translation

Intron Splicing Regulated at DNA level by restriction endonucleases Regulated at RNA level by SPLICEOSOMES GU....AG sequences thalassemia syndromes

Splicing of DNA

Gene Rearrangement & Processing

mRNA Splicing

DNA Loops