Organisms are made up of cells, cells are largely protein Organisms are made up of cells, cells are largely protein and DNA carries the instructions for the synthesis of those and DNA carries the instructions for the synthesis of those

proteinsproteins

DNA is made up of subunit building blocks called DNA is made up of subunit building blocks called nucleotidesnucleotides

Nucleotides are joined into chains and two such chains Nucleotides are joined into chains and two such chains associate with eachother by base pairingassociate with eachother by base pairing

The sequence information in DNA is copied into RNA The sequence information in DNA is copied into RNA (mRNA) which then directs protein synthesis(mRNA) which then directs protein synthesis

Amino acid assembly during translation occurs on Amino acid assembly during translation occurs on ribosomes; tRNA serves as the crucial adaptor moleculeribosomes; tRNA serves as the crucial adaptor molecule

Proteins are composed of subunits called amino acids; Proteins are composed of subunits called amino acids; mRNA directs the synthesis of an amino acid polymermRNA directs the synthesis of an amino acid polymer

Rare mutations in DNA are changes in its nucleotide Rare mutations in DNA are changes in its nucleotide sequence, leading to an altered mRNA and an altered sequence, leading to an altered mRNA and an altered

proteinprotein

A brief overview of the human genomeA brief overview of the human genome

Size = 3x10Size = 3x109 9 base pairs (bp), A paired with T and G paired with C, base pairs (bp), A paired with T and G paired with C, distributed over 23 chromosomes (this is for a haploid, or germ cell; distributed over 23 chromosomes (this is for a haploid, or germ cell; double those numbers for a diploid somatic cell)double those numbers for a diploid somatic cell)

Nucleotide changes occur in DNA via mutations; the spontaneous Nucleotide changes occur in DNA via mutations; the spontaneous mutation rate is approx. 10mutation rate is approx. 10-8-8 per germ cell per year per germ cell per year

Base composition: 40% GC base pairs; less than 2% in the format Base composition: 40% GC base pairs; less than 2% in the format CpG; this is b/c of mutation at such sites, CpG -> TpG, especially so CpG; this is b/c of mutation at such sites, CpG -> TpG, especially so when C is methylatedwhen C is methylated

Genic content of our genome: 3-5% of genome = “genes”; this Genic content of our genome: 3-5% of genome = “genes”; this represents about 1.5x10represents about 1.5x1077 bp and includes approx. 40,000 genes bp and includes approx. 40,000 genes

What’s in the remaining 95% of the genome? About 40% is What’s in the remaining 95% of the genome? About 40% is retroelements, remnants of retroviruses (much like computer viruses). retroelements, remnants of retroviruses (much like computer viruses). Retroelements are usually highly methylated at the C in CpG doubletsRetroelements are usually highly methylated at the C in CpG doublets

About 30% of the genome = variable, simple repeat sequences in About 30% of the genome = variable, simple repeat sequences in DNADNA

Genes include both coding regions as well as control Genes include both coding regions as well as control regionsregions

Consensus sequences identify evolutionarily conserved Consensus sequences identify evolutionarily conserved sequences that are likely to be important; eg, the sequences that are likely to be important; eg, the

promoterpromoter

-10TATAa

Promoter

+1 ATG

Met

Overview of the Prokaryotic Promoter Region

TATAaA A ATG

ACCATGG

-30 +1

+50

Met

Eukaryotic Promoter Structure

Alternative promoter structures

Initiator (Inr) YY A N T/A YYY+1

CpG Islands (CpG)20-50-----+1

Some general landmarks that characterize transcription Some general landmarks that characterize transcription and translationand translation

Short, conserved sequences delimit exon/intron Short, conserved sequences delimit exon/intron boundariesboundaries

mRNA

aa1-aa2-aa(n)

cDNA

Genomic DNA

TATAa……..ATG G GU…..AG

G

Intron #1

GU………AGG UAA……..AAUAAAG UAA

Intron (n) STOP Poly A tail

Start

Repetitive DNA sequences comprise much of the non-Repetitive DNA sequences comprise much of the non-coding segment of the genomecoding segment of the genome

1-3%30%

A brief overview of the human genomeA brief overview of the human genome

Size = 3x10Size = 3x109 9 base pairs (bp), A paired with T and G paired with C, base pairs (bp), A paired with T and G paired with C, distributed over 23 chromosomes (this is for a haploid, or germ cell; distributed over 23 chromosomes (this is for a haploid, or germ cell; double those numbers for a diploid somatic cell)double those numbers for a diploid somatic cell)

Nucleotide changes occur in DNA via mutations; the spontaneous Nucleotide changes occur in DNA via mutations; the spontaneous mutation rate is approx. 10mutation rate is approx. 10-8-8 per germ cell per year per germ cell per year

Base composition: 40% GC base pairs; less than 2% in the format Base composition: 40% GC base pairs; less than 2% in the format CpG; this is b/c of mutation at such sites, CpG -> TpG, especially so CpG; this is b/c of mutation at such sites, CpG -> TpG, especially so when C is methylatedwhen C is methylated

Genic content of our genome: 3-5% of genome = “genes”; this Genic content of our genome: 3-5% of genome = “genes”; this represents about 1.5x10represents about 1.5x1077 bp and includes approx. 40,000 genes bp and includes approx. 40,000 genes

What’s in the remaining 95% of the genome? About 40% is What’s in the remaining 95% of the genome? About 40% is retroelements, remnants of retroviruses (much like computer viruses). retroelements, remnants of retroviruses (much like computer viruses). Retroelements are usually highly methylated at the C in CpG doubletsRetroelements are usually highly methylated at the C in CpG doublets

About 30% of the genome = variable, simple repeat sequences in About 30% of the genome = variable, simple repeat sequences in DNADNA

Gene identification can begin with mRNA isolation and Gene identification can begin with mRNA isolation and formation of copy DNA (cDNA)formation of copy DNA (cDNA)

Large-scale gene analysis can be performed using DNA Large-scale gene analysis can be performed using DNA microarrays, or chipsmicroarrays, or chips

Human CF gene, approx. 250kb

4kb

Approx. 1 mutation per 1kb in noncoding regions; if 80% of the genome is noncoding:3x109bp x 0.8 = 2.4x109 x 1/1,000 = 2.4x106 mut.differing between any two individuals