2.1.3 nucleotides and nucleic acids Flashcards
what is DNA made from
deoxyribose sugar
phosphate group
nitrogenous bases (thymine, adenine, guanine and cytosine)
what is RNA made from
ribose sugar
phosphate group
nitrogenous bases (uracil, adenine, guanine and cytosine)
why is RNA single-stranded
it transfers info so doesn’t need to be replicated
explain the process of transcription
DNA helicase breaks H bonds between complimentary bases
RNA polymerase uses antisense strand as template to make mRNA
free nucleotides line up and join to complementary bases by phosphodiester bonds made by RNA polymerase
mRNA detaches and moves out nucleus by pore
explain the process of translation
mRNA attaches to ribosome
tRNA collects amino acids and transfers them from cytoplasm to ribosome
tRNA attaches to mRNA by base pairing
amino acids attached to 2 tRNA molecules join by peptide bond and tRNA detaches to leave them behind
repeats, forms polypeptide chains until stop codon
how many H bonds do A and T have
2
how many H bonds do C and G have
3
which bases are purines
adenine and guanine
which bases are pyrimidines
cytosine and thymine
how is a chromosome formed
DNA double helix
wrapped round histones to make nucleosome
nucleosome makes coil that wraps round others to make supercoil
tightly wound supercoil = chromatin fibre
chromosome made of chromatin
describe DNA replication
DNA helicase breaks H bonds between base pairs
free nucleotides bind to complementary bases
DNA polymerase forms phosphodiester bonds
2 identical daughter molecules of DNA formed with one original parent strand and one new strand
what proves semi-conservative replication
15N and 14N centrifugation
what is the sense strand
sequence of bases that code for amino acid sequence
what is the antisense strand
used to make copies of coding strand
what does universal mean
code applies to all organisms
