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Nucleotides & nucleic acids - Coggle Diagram
Nucleotides & nucleic acids
nucleic acids
DNA - deoxyribonucleic acid
RNA - ribonucleic acid
they're info molecules
eukaryotes - DNA found in nucleus
monomers of all nucleic acids = nucleotides
only difference so far is in RNA the sugar will be ribose & for DNA its deoxyribose
nitrogenous bases
DNA - 4 bases
Thymine
Cytosine
Adenine
Guanine
RNA - 4 bases
Uracil
Cytosine
Adenine
Guanine
joining nucleotides together
condensation reaction
phosphodiester bonds
how DNA is organised
eukaryotic cells - DNA within nucleus
inside nucleus nucleoplasm - within that are dark granules called chromatin (made up of DNA)
DNA is wound around histone proteins
they keep the DNA stable, stop it tangling & keep it compact (found in chromatin)
during division the chromatin condenses chromosomes are visible (bunches of histones & DNA)
prokaryotic cells - DNA is in a loop within cytoplasm
DNA isn't enclosed in a nucleus & not would around histone proteins (sometimes referred to as naked DNA)
virus - DNA is naked & in a loop
nucleotides in DNA
the phosphate & the sugar are always the same but the organic/nitrogenous base differs
Adenine & Guanine
larger
have a double ring
purines
Cytosine & Thymine
smaller
have a single ring
pyrimidines
so when A+T & C+G bind they are complementary base pairs joint by H bonds
A+T
2 H bonds
C+G
3 H bonds
Uracil - pyrimidine & has 2 H bonds with Adenine in RNA
liver breaks down purines into uric acids & if you eat too much meat (contains lots) it will crystallise in your joints
DNA
made up of nucleotides - its a double stranded polynucleotide
H bonds hold the 2 strands together
is very stable or info would have errors
2 polynucleotide chains run in opposite direction to form antiparallel chains to allow for complementary base pairing
in a double helix
DNA vs RNA
sugar making up the nucleotides
DNA - deoxyribose
RNA - ribose
nitrogenous base Uracil in RNA replaces Thymine in DNA
RNA is normally single stranded - DNA is always double stranded
3 types of RNA
tRNA
rRNA
mRNA
DNA replication
new cells need copies of instructions from old cells cause they will do the same functions
process;
2) DNA molecule unzips - H bonds between the bases are broken - controlled by DNA helicase enzyme. - result = 2 single strands with exposed bases
3) free nucleotides are present in the nucleus bind to complementary exposed bases - enzyme DNA polymerase catalyses the addition which seals the sugar phosphate backbone - nucleotide join in 5' to 3' direction
1) each DNA molecule unwinds - controlled by gyrase enzyme
products are 2 DNA molecules & they're identical to each other & the parent molecule
Semi-conservative replication
one old parent strand & one new daughter strand makes up the new molecule of DNA
codons & anti-codons
showing codons for amino acids
a codon is a triplet of bases that code for 1 amino acid
all the bases for an entire protein are called a gene
mRNA codons
64 possible codons
during translation 3 bases of mRNA are a codon & the 3 bases of the amino acid coming from the tRNA are an anti-codon (complementary to the codon)
RNA in protein synthesis
1) transcription (mRNA)
DNA unzips - using DNA helicase
mRNA forms along the DNA template strand - using RNA polymerase
DNA unwinds - using gyrase
the mRNA will leave the nucleus via the nuclear pore
mRNA moves towards a ribosome in the cytoplasm
2) translation (tRNA)
tRNA collects the correct amino acids & transports it to the ribosome
peptide bonds link one amino acid to the rest
eventually the polypeptide chain will twist & fold forming a proteins
the sequence of bases on the mRNA strand determine which amino acids are collected & in which sequence
the tRNA molecules are specific in which amino acids they collect
the 3 types of RNA
mRNA
made as a strand which is complementary to the template strand of a DNA molecule
rRNA
found in ribosomes
tRNA
carries amino acids to the ribosomes where they're bonded together to form polypeptides (peptide bonds)
the genetic code
its universal
in almost all living organisms the same triplet codes for the same amino acid
its degenerate
all amino acids except methionine & tryptophan have more than 1 base triplet
this could reduce the effect of mutations as a change in 1 base of a triplet could still code for the same amino acid
its non-overlapping
meaning that the genetic code is read starting from a fixed point of 3 bases
if a base is added or deleted it will cause a frame shift - every amino acid will then be different
types of mutation & their effects
Duplication
ATT TCC GTT ATC
becomes
ATT TTC CGT TAT C
--> frame shift = huge difference (totally different protein made)
Deletion
ATT TCC GTT ATC
becomes
ATT CCG TTA TC
<-- frame shift - huge difference
Substitution
ATT TCC GTT ATC
becomes
ATG TTCC GTT ATC
point mutation - many have no or little significant difference
Inversion
ATT TCC GTT ATC
becomes
ATT CCT GTT ATC
point mutation - minor effect
negative consequences of mutation - cancerous cells/cancer
negative consequences of mutation is gametes - genetic disease
advantage of mutation - new adaptation/advantageous feature
mutagen = anything that can cause a mutation
e.g. ionising radiation, UV light, cigarette smoke, chemicals, electromagnetic radiation, cosmic rays, diesel fumes
ATP & ADP as phosphorylated nucleotides
ATP, it is described as a phosphorylated nucleotide because it has three phosphate groups attached
ADP has 2 phosphate groups & when joined with P it makes ATP
