Properties of DNA Flashcards
1
Q
DNA melting & hybridisation
A
- Although the secondary structure of DNA is stable, it can denature by treating it by alkali/acid or by heating
- Temperature of melting varies from 65-80 degrees depending on G=C content (since most H bonds, 3, are broken)
- If cooled slowly, DNA renatures (hybridises)
2
Q
The Dimensions Of DNA
A
- Diameter of helix is 2 nm
- Adjacent bases are separated by 0.34nm + related by a rotation of 36 degrees
- Helical structure repeats every 10 residues, 3.4nm ( 1 complete twist = 10 base pairs)
3
Q
How to determine length of DNA molecules
A
By multiplying the number of base pairs by 0.34nm
4
Q
Base pairs in human genome
A
3 x 10 ^9 bp
5
Q
Chromosome sizes
A
50 x 10^6 to 250 x 10^6 bp
6
Q
How is DNA packaged?
A
Into chromosomes using histone proteins 5 types)
- 2 copies of each come together to form a histone ocular
- Which forms a nucleosome , a cylinder that DNA can wrap around
7
Q
How Chromosomes are folded
A
- Folds into 30 nm fiber then to 300 nm fiber - is highly compacted
- To replicate/transcribe DNA in the cell, it is in an organised compacted form
8
Q
Epigenetics
A
- DNA and histones can be modified
e.g. DNA methylation of C residues or histones modified by also acetylation (silenced sequences to specify the cell type - genes not required for cell is methylated)
9
Q
The effect of epigenetics
A
- Doesn’t change DNA sequence but can regulate gene transcription
- Changes can be passed during cell division and to future generations (epigenetic inheritance)
- Key roles: development, aging (from methylation), cancer, behaviour + addiction
