DNA function Flashcards
prokaryotes
no nuclear membrane, DNA arranged often in single chromosome, supercoiled
Eukaryotes
DNA is in the nucleus, bound to proteins (chromatin complex). different appearance according to the functional moment. complex packing, 2m linear
functions of DNA
template and regulator for transcription and protein synthesis, genetic material
History of DNA timeline
Gregor Mendel (1822-1884) → Erwin Chargaff (1905-2002) → Rosalind Franklin (1929-1958) → Crick 1916-2004), Watson (1928 - )
DNA replication
- Prior to cell division DNA opens at the replication fork
- Base sequence on each parent strand is copied into a complimentary daughter strand
- The two parental strands separate in front of the fork
- New DNA is made behind the fork, composed of a new and an old strand: replication is semi-conservative
- Many proteins are involved in DNA replication, binding proteins and enzymes
It happens about 700-1000 bp per second
6 billion base pairs
Human DNA
• Origins of replication – multiple points of origin
• Enzymes involves: Polymerases (5” to 3”), Helicase, ligase, nuclease, primase, topisomerase
DNA Polymerase – reads 3” to 5” prints 5” to 3”, substrates are deoxyribonucleotides triphosphates, enzyme stays on the strand, at the same time extends and proof-reads
Has editing function, detects incorrect insertion of base and will excise and repeat
Opening the strands – Helicase - single stranded binding proteins (SSB) keep it open, Troisomerase unwinds it (relieves supercoiling)
DNA damage
Benzopyrene - product of incomplete combustion of hydrocarbons. it is a DNA-adduct - it reacts with bases to form a bulky group that disrupts replication
ionising radiation - can damage bases, cause breaks in phosphate backbone
UV - damages bases, in particular the formation of thymine dimers
P53-tumour suppressor gene
keyed or linked to cell cycle control
