E5 Nucleic acid structure and DNA replication Flashcards
what are the bases in DNA nucleotides
adenine
thymine
guanine
cytosine
what are the bases in RNA nucleotides
adenine
uracil
guanine
cytosine
which part of DNA nucleotides keeps DNA stable?
deoxyribose
which is more stable of RNA or DNA and what does this allow for?
- DNA
- means DNA is the predominant carrier of the genetic code
what structural and chemical characteristics of DNA make it a good genetic code carrier?
- structure preserves 4 bases to form base sequence
- base-pairing allows the DNA to be copied accurately
- DNA is a chemically stable molecule
- DNA is double-stranded which ensures that damage to one of the strands can be rectified by copying the information from the other
which ends of the DNA have phosphate group and OH group?
- 5’ end has the phosphate group
- 3’ end has the OH group
which direction are nucleic acid sequences synthesised in?
- 5’ to 3’
- they can be extended on from the OH group
what bond is formed between a phosphate and an OH between nucleotides?
phosphodiester bond
what are the 2 pairs of bases that go together in DNA?
- adenine and thymine (2 hydrogen bonds between)
- guanine and cytosine (3 hydrogen bonds between)
what are the molecules of DNA in a cell referred to as more commonly?
chromosomes
describe chromatin
- DNA has to be packaged in chromatin
- 2 metres of chromatin per cell
- can be broken by tension which would prevent replication or transcription
what is a nucleosome?
- DNA wound twice around a histone
- single units of chromatin
how does winding of DNA around histones affect expression?
- reduces expression
- can’t be reached by transcriptional factors
which direction do DNA polymerases work in?
- 5’ to 3’
- they need the 3’ end to add on to (primer)
describe the requirements of RNA polymerase and its action in replication
- doesn’t require a 3’ primer to add onto like DNA polymerase does
- RNA polymerase replicates a short strand of DNA that is complementary to the single strand of DNA you want to replicate
- DNA polymerase then extends the polymer form the 3’ end of the RNA strand (DNA-RNA hybrid is formed
