DNA Structure & Function

You Tube IndexDNA Structure (in order of usefulness)• DNA Structure– http://glencoe.mcgraw-hill.com/sites/9834092339/student

_view0/chapter14/dna_structure.html

• Good (factual, but dry)– http://www.youtube.com/watch?v=tknYrU98rBk&feature=

fvwrel

• Structure & Prot synthesis– http://www.youtube.com/watch?v=FUA6_Ucw3i4For history of discovery of DNA and structure see the Powerpoint “DNA History”

Watson & Crick(credited with discovery of STRUCTURE of DNA, though

their work relied heavily on the work of others)

DNA Functions• Carries genetic code for life processes• Can replicate to continue life…• Lengths of DNA (genes) code for

production of proteins that are– structural– functional– & are 95% of human body!

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DNA Packaging!!!

Role of DNA Terms(over the course of this AS & others you will understand all of these terms)

• Genome – all the DNA in a cell• Genes – sections of DNA coding for

the production of proteins• Chromosomes - • Chromatid• Nucleus - • Nuclear Membrane• Chromatin• DNA• Nucleotides - the repeating unit of

DNA• Protein• mRNA

• Prokaryote – cells / organisms without a nucleus

• Eukaryote – cells / organisms with a nucleus

• Protein synthesis – process where protein is manufactured

• Mitochondria – organelle (“little organ”) in a cell where energy (ATP) is produced

• Cytoplasm • Enzymes• Metabolism• Cell division• Centromere

Nucleic Acids• Two types:– DNA – Deoxyribose nucleic acid (location: nucleus)– RNA – Ribose nucleic acid (location: nucleus +

cytoplasm)• Made of repeating units: nucleotides• Nucleotide made of:– Nitrogen base– A 5-carbon sugar(deoxyribose in DNA,ribose in RNA)– Phosphate group

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Sweet Difference

DNA Structure

The two strands are “anti parallel”One strand runs from 3’ to 5’ the other 5’ to 3’

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DNA Structure• Shape: double helix (like a twisted ladder)

DNA Structure• 4 bases:

– A – Adenine T – Thymine – G – Guanine C – Cytosine

• “Rungs” - Bases held together by hydrogen bonds– A pairs with T (two bonds)– G pairs with C (three bonds)

• “Backbone”– Sugars joined to phosphates* by “phosphodiester” bonds!

• Complementary vs template– Since you find a C opposite a G… etc thesecond strand is said to be complementaryto the first.- And: the first strand can be used as a template to make a new complementary strand

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In RNA the base U (Uracil) replaces thymine

* Pyrimidines vs Purines

• The “pyrimidine bases” are:– C & T (one ring

structure)• The “purines” are:– A & G (double ring

structure)

To remember: purines = two rings

http://upload.wikimedia.org/wikipedia/commons/e/e4/DNA_chemical_structure.svg

Length of DNA in organisms

• Only 4 bases BUT one DNA molecule = millions of bases long

• Human: 6 billion base pairs• Bacteria: ~ 4.3 million bases• Viruses…..

ΦX174 Bacteriophage DNA SequenceBacteriophage = virus affecting bacteria

9 genes, each codes for one protein.

Genes overlap, one genes is highlighted.

Human genome = 1 million times longer

How much DNA in humans?

• ~ 100,000,000,000,000 cells in the human body

• 2m of DNA in each cell (3-5cm per chromosome)

• DNA length in kilometres:– 200,000,000,000 km

• How many times to the moon? (moon = 184,000km)– 1,086,957 times

• How many times to the sun & back? (= 300,000,000km)– 667 times

DNA Structure END