DNA and chromosome basics Flashcards
diameter of DNA
2nm
whats on the outside of dna structure
phosphate- -ve charge which attracts polar water
double helix is supported by..
a sugar phosphate back bone which increases the stability of the molecule
the two strands run..
parallel but opposite to each other–> due to 5 prime and 3 prime strand
why do strands run opposite to each other
due to 5 prime and 3 prime strands
intermolecular forces between strands
H bonds- individually weak but together very strong
DNA is a ….. handed double helix
DNA is a RIGHT handed double helix
A + T
2 bonds
C+G
3 bonds
the DNA right handed double helix is made up of..
minor and major grooves
how is DNA faithfully replicated
Semi-conservative replication- otherwise mutations would be very common and this would lead to many disorders and cancers
total DNA in the nucleus
the GENOME - organelles like mitochondria and chloroplasts have their own genomes (circular- majority still found in nucleus
which organelles have their own genomes
mitochondria and chloroplasts - circular
nucleotides are mad cup of..
sugar (deoxyribose); base; phosphate
nucleoside=
sugar and base
what gives rise to minor and major grooves
the fact that A+T and C+G have diff number of hydrogen bonds
Deoxyribose and adenine
deoxy adenosine
Deoxyribose and guanine
deoxy guanosine
deoxyribose and cytosine
deoxy cytidine
deoxyribose and thymine
deoxy thymidine
what does right handed double helix mean
the strand that appear on the top of the molecule will run from right to left
how is 5 prime strand different to the 3 prime strand
5 prime is able to connect with a further phosphate group whereas 3 prime is unable to do so
enzyme work along DNA from the..
5’ to 3’
new strand of DNA is formed from the
3’ to 5’
minor groove
oxygen in deoxyribose points downwards
major groove
oxgen in deoxyribose points upwards
every human has around
2m worth of DNA- each nucleus has around 10 micrometers diameter
what is DNA wrapped around and how many times
DNA wraps twice around 8 core histone proteins to form nucleosomes
why will DNA wrap twice around 8 core histones
DNA is negatively charged due to phosphate group and the histones are positively charged
nucleosome
a structural unit of a eukaryotic chromosome, consisting of a length of DNA coiled around a core of histones.
what does histone H1 do?
brings the nucleosomes together to form chromatin fibres
what forms a chromatin fibre
when histone H1 brings nucleosomes together
what further condenses chromatin
scaffold proteins
net result of DNA folding
each DNA molecule has been packaged into a mitotic chromosome that is 10,000 fold shorter than its fully extended length
interphase chromosomes are organised in the..
nucleus
chromosome territories
chromosomes organise themselves into discrete patches- located near the chromosomes territory boundary
