module 2.1.3 - nucleotides and nucleic acids Flashcards
what are the 3 components of a nucleotides
a phosphate group, a pentose sugar and an organic nitrogenous base
what are the purine bases (2 rings) in RNA and DNA
adenine and guanine for both RNA and DNA
what are the pyrimidine bases (1 ring) in RNA and DNA
cytosine and uracil in RNA
cytosine and thymine in DNA
what are the pentose sugars in RNA and DNA
ribose in RNA and deoxyribose in DNA
what are the 3 types of RNA
messenger RNA, transfer RNA and ribosomal RNA
what does mRNA do
it carries the copy of the gene out of the nucleus and transfers it to the ribosomes where the code is for protein synthesis
what does tRNA do
it transports amino acids to the ribosomes
what does rRNA do
it make up the ribosomes
what is the structure of RNA
it is a polynucleotide, non - helical, usually single stranded and much shorter than DNA
bases are complementary: adenine to uracil (2 H bonds), cytosine to guanine ( 3 H bonds)
what is the structure of DNA
it is found in the nucleus. the 2 polynucleotide strands lies in opposite directions (anti-parallel) and are joined together to form double helix. each purine is paired to a pyrimidine
what is the structure of ATP and ADP
they both contain a pentose sugar (ribose), a nitrogenous base (adenine)
ADP has 2 phosphate groups but ATP has 3 phosphate groups
what is a polynucleotide and how is it formed
formed when nucleotides bind together in a long chain
- the bonds are formed by condensation and are called phosphodiester bonds. they can be broken by hydrolysis
- these bonds form between the sugar of one nucleotide and the phosphate group of another, making a sugar–phosphate ‘backbone’
- leaves the organic base of each nucleotide sticking out to the side of the chain
explain the process of semi conservative replication
- one double-stranded molecule untwists and the hydrogen bonds between the base pairs break —-> catalysed by the enzyme helicase
- the two polynucleotide chains separate, exposing the bases
- each strand is then used as a template to make two new double strands
- new nucleotides pair to the exposed bases on both strands, using their complementary shapes to pair correctly
5 each new chain of nucleotides is bonded together by the enzyme DNA polymerase to form the second half of each DNA molecule - the enzyme also checks that the pairing of the bases is correct
- each new molecule then twists to form its double helix
what is a mutation
when an incorrect base may be bonded into place
what is the pattern of mutation
random and spontaneous