Download Genes and How They Work

Genes and How They Work
Computer Filename: genes1.ppt
Developed by Hugh B. Fackrell
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Overview
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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
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Lecture Outline
Genes and How They Work
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Genetic Code
Gene Expression transcription translation
Protein Synthesis
Gene Regulation
Gene Architecture
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Concepts from OAC
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Structure & Function of DNA & RNA
Genetic code
Transcription & translation
Protein synthesis
Gene Regulation: operators, promotors ,
repressors
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Background Terms & Concepts
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Structure of DNA & RNA
 Ribosomes
 Enzymes
 Structure of Eukaryotic chromosomes
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The Genetic Code
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Genetic information is stored in DNA
sequences found in
– Chromosomes
– Mitochondria: 16 KB, 13 genes
– Chloroplasts: 120-160 KB, 120 genes
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Structure of the Genetic Code
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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
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CODONS
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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
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Start Codon
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RNA: AUG
 DNA: TAC
 also codes for methionine
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Stop Codon
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Nonsense Codons
 RNA: UAA,UAG,UGA
 DNA: ATT, ATC, ACT
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Alternate Genetic Codes
Sequence
TGA
ATA
AGA
AGG
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Chromosome
Stop
Isoleucine
Arginine
Arginine
Mitochondrion
Trypt
Methionine
Stop
Stop
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Interpreting the Genetic Code
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Two step process :
– Transcription DNA --> RNA
– Translation RNA--> protein
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RNA
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Ribosomal RNA
 Transfer RNA
 Messenger RNA
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Ribosomal RNA
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called rRNA
found in Ribosomes
probably catalytic site
provides site for protein assembly
ribosomal structure different in
eukaryotes and prokaryotes
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Prokaryotic Ribosomal RNA
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large subunit 5s(120), 23s (2900)
 Small subunit 16s (1540)
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Eukaryotic Ribosomal RNA
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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
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Ribosomal RNA
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Transfer RNA
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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
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tRNA
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Messenger RNA
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called mRNA
 long single strand of RNA
 copy of the DNA to be decoded
 transfers information from the nucleus to
the cytoplasm for decoding
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Transcription
Production of an RNA copy of the gene
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occurs in nucleus of eukaryotes
– cytoplasm of prokaryotes
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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
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RNA being read from DNA
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Prokaryotic Transcription
and Translation
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Antibody Structure
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Eukaryotic Transcription &
Translation
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Intron Splicing
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Regulated at DNA level by restriction
endonucleases
 Regulated at RNA level by
SPLICEOSOMES
 GU....AG sequences
 thalassemia syndromes
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Splicing of DNA
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Gene Rearrangement &
Processing
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mRNA Splicing
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DNA Loops
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