Revision notes Flashcards
What are nucleic acids
Nucleic acids are linear aggregations of nucleotide building blocks, forming RNA/DNA (gives a double helical conformation when 2 antiparallel strands come together).
describe structures of DNA
10 bp per helical turn
width is 2 nm
Regarding the packaging and structure of nucleosomes
the octamer of histones in a nucleosomes are wrapped around by DNA in a left-handed superhelix
Histones are positively charged hence are able to interact with the negatively charged DNA strand. The core region of DNA winds round the octamer while the linker is found between nucleosomes. The total condensation of DNA is approximately 10000-fold shorter than its extended length. Only 1 histone is located between nucleosomes in addition to the octamer.
Source: Nucleic acids and chromosomes lecture.
how many genes in the human genome
In humans each cell nucleus contains over 1 metre of DNA
There is about 23,000 genes in the human genome.
A DNA strand must be unwound before it can undergo semi-conservative replication. Which of the following is FALSE
energy used to break hydrogen bonds come from the hydrolysis of GTP
Energy for the breakage of hydrogen bonds come from the hydrolysis of ATP.
cell cycle
need to phases!!!
Chiasma formation happens in meoisis, not in S-phase of the cell cycle. Condensation of chromatin occurs during late prophase of mitosis. Cells leave the cell cycle at G0 while M is the shortest phase in the cell cycle.
Concerning the proof-reading mechanism following DNA replication,
phosphodiester bonds are hydrolysed prior to the replacement of incorrect nucleotides with the correct nucleotides
Errors occur with an approximate frequency of 1 in 10^9 base pairs. Phosphodiester bonds are cleaved using a 3’ to 5’ exonuclease activity of DNA polymerase. Incorrect bases and primer sequences are removed and replaced.
DNA replication on the template strand with 3’ at its unwound end
referring to leading strand
Thalassaemia
is characterised by hepatosplenomegaly=is a disorder where both the liver and spleen swell beyond their normal size.
Thalassaemia may be associated with endocrinopathies (e.g. diabetes mellitus and thyroid disorders). It is the imbalance of haemoglobin chains and results in darkening of the skin due to melanin overproduction and overstimulation. High quantities of iron are absorbed to due to chronic anaemia.
when do we say triplet
There are 64 codons for 20 amino acids, the rarer amino acids have fewer codons. In an mRNA reading frame, 3 bases are known as a codon (triplet referring to 3 bases in a DNA sequence). Met can be removed from the polypeptide sequence after translation, hence is not always the first amino acid. There are no STOP amino acids, only STOP codons.
Source: Protein synthesis and post-translational modification lecture.
antibiotic and what they do?
streptomycin inhibits the initiation stage
erythromycin inhibits translocation
puromycin terminates elongation
restriction endonuclease
This is an enzyme that cleaves DNA at specific sites, where the base sequence is usually a palindrome. The restriction endonuclease only cleaves non-host DNA since they are not protected i.e. unmethylated DNA.
This molecule anneals with DNA at above 50 degrees and the DNA chain is extended.
This molecule anneals with DNA at above 50 degrees and the DNA chain is extended.
This molecule is required in the detection of specific nucleic acid sequences in which homologous SS DNA or RNA combine to form double stranded molecules.
Hybridisation probes can be DNA, RNA or oligonucleotides and they are radioactively or fluorescently labelled.
Which of these is NOT a type of non-coding RNA? rRNA tRNA mRNA piRNA snRNA
mRNA
Non-coding RNAs are functional molecules that are not translated into proteins. They are highly abundant and functionally important
