Nucleic acids

DNA

RNA

Shape of DNA molecule, due to coiling of sugar-phosphate backbone strands into a right-handed spiral configuration

Molecule that repeats to make polymer

Molecule consisting of 5 carbon sugar, phosphate group and nitrogenous base

Large molecule containing many nucleotides

Enzyme that catalyses formation of DNA from activated deoxyribose nucleotides, using single stranded DNA as template

Enzyme that catalyses breaking of hydrogen bonds between nitrogenous pairs of bases

How DNA replicates, resulting in 2 new molecules, each containing one old strand and one new. One old strand is conserved in each new molecule

Length of DNA that codes for a polypeptide or for a length of RNA that's involved in regulating gene expression

Polymer made of many amino acids joined together by peptide bonds

Large polypeptide of 100 or more amino acids

Process of making mRNA from a DNA template

Formation of protein, at ribosomes, by assembling amino acids into a particular sequence according to the coded instructions carried from the DNA to the ribosomes from mRNA

Polypeptide of 51 amino acids

Ribose

Single-stranded

Shorter than DNA

Uracil

Thymine

Messenger (mRNA)

Transfer (tRNA)

Ribosomal (rRNA)

Code that determines the sequence of amino acids in a particular polypeptide or protein

75% of organisms dry mass

Sequence of DNA base triplets that determines AA sequence, primary structure, of polypeptide

Complementary to shape of substrate

Complementary to antigen on surface of invading pathogen

Complementary to cell-signalling molecule

Inside cell nucleus

It'll fold correctly and be held in tertiary structure, enabling it to carry out function

Chromosomes

Pass out of nucleus

Copy of gene is transcribed into length of mRNA sequence of base triplets, codons. Passes out of nucleus to ribsomome, ensuring coded instructions are translated and protein assembled correctly from AA

Triplet of bases on a DNA molecule

Triplet of bases on tRNA molecule, complementary to mRNA molecule

Triplet of bases on length of mRNA

Degenerate

Non-overlapping

As for all AA's, except methionine and tryptophan, there's more than one base triplet

Effect of point mutations as change in one base triplet could produce another base triplet that still codes for same AA

From a fixed point in group of 3 bases

Causes frame shift as every base triplet after, hence AA coded for, is changed

Uracil

Transcription

1. Gene unwinds and unzips

2. Hydrogen bonds between complementary nucleotide bases break

3. Enzyme RNA polymerase catalyses formation of temporary hydrogen bonds between RNA nucleotides and their complementary unpaired DNA bases. A with T, C with G, G with C, U with A, on one strand of unwound DNA - template strand

4. Length of RNA that's complementary to template strand of gene is produced. It's therefore a copy of other DNA strand - coding strand

5. mRNA passes out of nucleus, through nuclear envelope and attached to ribosome

In nucleolus, in 2 smaller subunits

2 smaller subunits pass out separately out of nucleus through pores in nuclear envelope and then come together to form nucleus

Mg ions

Ribosomal RNA and protein in roughly equal parts

Catalyse synthesis of polypeptides

In nucleolus and pass out of nucleus into cytoplasm

Single-stranded polynucleotides that can twist into hairpin shape

Trio of nucleotide bases that recognises and attaches to specific AA

Triplet of bases, anticodon, that's complementary to specific codon of bases on mRNA

1. tRNA molecules bring AAs to find place when anticodon binds by temporary hydrogen bonds to complementary codon on mRNA molecule

2. As ribosome moves along length of mRNA, it reads code and when 2 AAs are adjacent to each other, peptide bond forms between them

3. Energy, in form of ATP, is needed for polypeptide synthesis

4. AA sequence for polypeptide is determined by sequence of nucleotide bases on length of DNA - the gene

5. After polypeptide assembled, mRNA breaks down. It's component molecules recycled into new lengths of mRNA with different codon sequences

6. Newly synthesized polypeptide is helped by chaperone proteins to fold into correct 3D, tertiary structure, to carry out it's function

DNA has to repliacate so daughter cells can receive full set of instructions

During interphase, before cell division

Just before organelles divide

Each chromosome has identical copy of itself

Chromosomes first joined together at centrome forming 2 sister chromatids

1. DNA unwinds, catalysed by gyrase enzyme. Then unzips, hydrogen bonds between nucleotide bases broken, catalysed by enzyme helicase. Results in 2 single strands of DNA with exposed nucleotide bases

2. Free phosphorylated nucleotides, present in nucleoplasm, bond to exposed bases, following complementary base rules C and G, A and T

3. Enzyme DNA polymerase catalyses addition of new nucleotide bases in the 5’ to 3’ direction, to the single strands of DNA; using each single strand of unzipped DNA as template

4. Leading strand is synthesised continuously and lagging strand is in fragments (discontinuous) are later joined, catalysed by ligase enzymes

5. Hydrolysis of activated nucleotides, to release extra phosphate groups, supplies the energy to make phosphodiester bonds between sugar residue of one nucleotide and the phosphate group of the next

6. Product of replication is 2 DNA molecules, identical to each other and parent molecule. Each molecule contains one old strand and one new

Strands of DNA molecules contain one old strand and one new strand

Semi-conservative replication

Errors may occur and wrong nucleotide may be inserted

1 in 10⁸ base pairs

Change the genetic code

Point mutation

Some enzymes can proofread and edit out incorrect nucleotides, reducing rate that mutations are produced

Different versions of a particular gene

No

Loop within cytoplasm (not membrane bound)

Naked DNA - not wrapped around histone protein

Naked DNA

Majority in nucleus

Each molecule tightly wound around histone protein into chromosomes

Loop of DNA without histone protein in mitochondria and chloroplasts

1. Macerate tissue, adding stong detergent

2. Add ethanol to precipitate out of solution

3. Further purified of unwanted salts and then concentrated

4

Purine

Pyramidines

adenine and guanine

2

Thymine and cystosine

1

Nucleic acid

Macromolecule

Nuclei of eukaryotic cells

Cytoplasm of prokaryotic cells

Contains hereditary material and carries encoded instructions used in development and functioning of living organisms

Adenosine

AMP

ADP

ATP

Polymer, made of repeating monomers - nucleotides

Consists of 2 polynucleotide strands - antiparallel (run in opposite directions)

Each nucleotide constsis of phosphate group, 5 carbon sugar (deoxyribose) and 1 of 4 nitrogenous bases (A,G,C,T)

Phosphodiester bond (covalent) between sugar and phosphate group

When polynucleotides are broken down (hydrolysis reaction)

When polynucleotides are synthesised (condensation reaction)

Can carry lots of encoded info

Pentose sugars where nitrogenous base is linked to C1 of sugar and phosphate group is linked to C5 or C3 of sugar, linked by covalent bonds formed in condensation

Monomers of nucleic acids, DNA and RNA

Ribose

Deoxyribose

Become phosphorylated nucleotides

Coenzymes

Metabolic pathways

Energy-rich end product of energy-releasing biochemical pathways used to drive most energy-requiring metabolic processes in cells

Thymine

Guanine

Adenine

Cytosine

Uracil

Pyramidines to give equal sized rungs on DNA ladder

Allow the molecule to unzip for transcription and replication

2

3

Form between nitrogenous bases to join antiparallel strands

Sugar-phosphate backbones of antiparallel polynucleotide strands

Complementary bases joined by hydrogen bonds

Direction that the 3rd and 5th molecules on the deoxyribose are facing

Where phosphate group is attached to the 5th carbon

Where the phosphate group is attached to the 3rd carbon

Protect the base sequences and integrity of the encoded info

Stability