molecular biology 1 Flashcards
what is the difference between deoxyribose and ribose
deoxyribose is missing an oxygen hydroxy group on carbon 2
how are the sugars joined together
sugars are joined together via a 5’-3’ phosphodiesterase bond which are strong covalent bonds
how are the sugars joined together
sugars are joined together via a 5’-3’ phosphodiesterase bond which are strong covalent bonds
nucleoside
base and 5 carbon sugar
nucleotide
nucleoside and phosphate group
purines
adenine and guanine
pyrimidines
cytosine, thymine, uracil
describe the DNA structure
- antiparallel double helix
- phosphate sugar backbone
- base pairs on the inside are held together with hydrogen bonds.
primary structure of DNA?
sequence of nucleotides
secondary structure of DNA?
spatial arrangement of the nucleotide chains
how are base pairs held together
hydrogen bonds
A-T
2 hydrogen bonds
G-C
3 hydrogen bonds
chromatin =
histone + DNA
genetics
the tern used t describe inheritance of changes in base sequences
why does the double helix normally exist in the B-helix form
because there are major and minor grooves formed by the structure
what is the polarity of DNA?
this is the direction that DNA will run, the way which they are lined together, give DNA polarity.
how can chromosomes be distinguished between each other
size and G banding
what is a karyotype and what technique is used to find it
- a karyotype is a full set of chromosomes
- G banding
what reaction is chromosomes pulled apart
condensation
what forms the phosphate sugar backbone?
the joining of the sugars via a phosphate
what is the charge of the phosphate sugar backbone
negative
biggest and smaller chromosome?
1- biggest
21- shortest
how does fluorescent marking work for identifying chromosomes?
- complementary probes of DNA can be made that will match the DNA being analysed
- these probes have fluorescent markers on them
- When the DNA strands are separated, they naturally want to be in a double helix so they bind to the fluorescent probe which allows for the image of chromosomes to be made.
what are the 2 parts of the chromosome
telomere and centromere
what does the centromere allow
it allows for separation of DNA to opposite ends during mitosis
what is a nucleosome consist of
147 base pairs of DNA double helix wrapped around a histone core (DNA wrapped around histones)
what allows histone and DNA to bind
the fact that the histone is positively charged and the DNA is negatively charged
what does histone H1 do?
it provides a unique role in anchoring the DNA to the histone and telling it to keep folding in the right direction, this helps the nucleosome to become more condensed.
how is the chromosome made
the nucleosome continues condensing.
how are proteins condensed in the cell cycle?
enzymes called condensins allow the proteins to adopt a very tight structure
why do chromosomes need to be remodelled and how is it done
- chromosomes need to be remodelled to allow protein access in order to use the genetic info.
- done using a remodelling complex and requires energy
what is epigenetic modification and what are examples
changes in gene expression that do not cause changes in the DNA sequence.
methylation, acetylation, phosphorylation
acetylation
this removes the positive charge from the histone which decreases the binding of the positively charged DNA, causing relaxation of the structure.
what % of our genome codes for proteins?
approx 1.5% with the rest being junk proteins
why are repetitions in DNA important in forensics?
as consecutive repeats at different locations will be different for different people
this sample can be used in gel electrophoresis to identify the matching repeats.
what is myotonia
this is the inability to relax muscles at will
what causes myotonic dystrophy
this is caused by a trinucletide repeat that occurs many times in a row at a particular location.
for most people a trinucleotide repeat is not going to cause any problems, but id the repeat is very large this can lead to muscular dystrophy.
structure of mitochondrial DNA
17000 base pairs long
circular
2-10 copies in mitochondrion with several mitochondria per cell.
why can mitochondria be good for forensics
because there are more copies and their smaller culcular structure makes them more stable allowing it to be purified while DNA can’t.
where are mitochondria dna inherited and what is this implication on disease?
- inherited from mother
- this means if there is a defect in the mitochondria it will only come from the mother.
(it is also useful to see lineage)
what are the 2 types of repeat in DNA
- interspersed repeats
- tandem repeats
what is an example of interspersed repeats?
SINE and LINE which are often derived from retroviruses
what is an example of TANDEM repeats
satellites, mini satellites and micro satellites
