ChromosomesChromosomes

GenesGenes

Where do you find DNA?Where do you find DNA?All mature cells contain DNA except the red blood cellsAll mature cells contain DNA except the red blood cells

DNA is found in the nucleus DNA is found in the nucleus Small amounts of DNA are also present in the chloroplasts Small amounts of DNA are also present in the chloroplasts

and mitochondriaand mitochondria

Nucleus

Source: Source: http://www.tokyo-med.ac.jp/genet/picts/cell-e.jpghttp://www.tokyo-med.ac.jp/genet/picts/cell-e.jpg

Chloroplast

Mitochondrion

Mitochondrial DNAMitochondrial DNA Represented as mtDNARepresented as mtDNA

Double-stranded circular molecule Double-stranded circular molecule made up of 16,568 base pairs, made up of 16,568 base pairs, coding for 37 genescoding for 37 genes

• 13 genes code for proteins involved in 13 genes code for proteins involved in cellular respirationcellular respiration

• 2 genes code for ribosomal RNA 2 genes code for ribosomal RNA (rRNA)(rRNA)

• 22 genes code for transfer RNA (tRNA)22 genes code for transfer RNA (tRNA)

Mitochondrial DNAMitochondrial DNA

Representing DNARepresenting DNA

5’…A C G T T C G A A G C T A G G T T A T C G A…3’

3’…T G C _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ G C T…5’

If this represents the sequence of bases on one strand of DNA, what would the sequence of the other

strand be?

This is the principle used in This is the principle used in gene-sequencinggene-sequencing

5’…A C G T T C G A A G C T A G G T T A T C G A…3’

…T

DNA sample is heated to separate strands forming a template

Nucleotides are added to the mix with each of the 4 DNA bases. Additional fluorescent dye-labelled nucleotides are also added to the mix

The mixture is cooled allowing the added nucleotides to attach to the template strand according to base-pair rules

…A C G T T C G A A G C T A G G T T A T C G A…

…T G…T G C…T G C A

Varying lengths of complementary strands are produced. At the end of each strand, a nucleotide with the fluorescent dye attaches, causing the synthesis of the strand to stop

The dyes are detected by an electronic analyser which records the result

Human Genome ProjectHuman Genome Project This technique of DNA sequencing has This technique of DNA sequencing has

made it possible for scientists to made it possible for scientists to collaboratively map the entire Human collaboratively map the entire Human GenomeGenome

Began in 1990 and fully completed in Began in 1990 and fully completed in 20032003

Aims:Aims:• Improve diagnosis of genetically inherited Improve diagnosis of genetically inherited

disordersdisorders• Improve treatments for a range of diseasesImprove treatments for a range of diseases• Prevent diseases that have a genetic Prevent diseases that have a genetic

predispositionpredisposition

Interesting facts about the Interesting facts about the Human GenomeHuman Genome

Flanking regionsFlanking regions

Coding RegionUpstreamFlankingRegion

DownstreamFlankingRegion

Comparative GenomicsComparative Genomics The sequences of many other The sequences of many other

genomes have been sequencedgenomes have been sequenced

This allows scientists to compare This allows scientists to compare the genomes of a variety of species the genomes of a variety of species and determine degrees of and determine degrees of relatedness between themrelatedness between them