DNA function

Question 1

prokaryotes

Answer 1

no nuclear membrane, DNA arranged often in single chromosome, supercoiled

Question 2

Eukaryotes

Answer 2

DNA is in the nucleus, bound to proteins (chromatin complex). different appearance according to the functional moment. complex packing, 2m linear

Question 3

functions of DNA

Answer 3

template and regulator for transcription and protein synthesis, genetic material

Question 4

History of DNA timeline

Answer 4

Gregor Mendel (1822-1884) → Erwin Chargaff (1905-2002) → Rosalind Franklin (1929-1958) → Crick 1916-2004), Watson (1928 - )

Question 5

DNA replication

Answer 5

1. Prior to cell division DNA opens at the replication fork
2. Base sequence on each parent strand is copied into a complimentary daughter strand
3. The two parental strands separate in front of the fork
4. New DNA is made behind the fork, composed of a new and an old strand: replication is semi-conservative
5. 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)

Question 6

DNA damage

Answer 6

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

Question 7

P53-tumour suppressor gene

Answer 7

keyed or linked to cell cycle control