Gene expression topic Y12 -

Nucleotide

monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base

Purine

Classification of bases such as adenine and guanine(A + G). Has a double ring structure.

Pyrimidine

Bases such as thymine and cytosine (T + C).Has a single ring structure.

RNA

Ribonucleic acid. A single strand nucleic acid important in protein synthesis.

Uracil

Base found in RNA only. Present instead of THYMINE.

Polypeptide

Long chain of amino acids joined together by peptide bonds.

Transcription

Making of mRNA using free nucleotide base pairing against DNA template strand. DNA sequence in a gene is copied.

Coding strand

Strand of DNA where mRNA is an exact copy of this DNA strand ( U instead of T). Not used for transcription.

Template strand

Free nucleotide base pair match this DNA strand during transcription.

Start codon

AUG - 3 nucleotides where transcription starts

Stop codon

UAA, UAG, UGA - 3 nucleotides where transcription stops

Promoter

3 nucleotides on DNA where RNA polymerase attaches and unwinds it.

Terminator

Base sequence where transcription stops

RNA polymerase

Enzyme causes DNA helix to unwind ahead of transcription.

mRNA

Single stranded polynucleotide which copies section DNA sequence to carry out of nucleus for proteins to be made. (messenger RNA)

Translation

Information carried by mRNA is converted into specific sequence of amino acids to form a polypeptide/protein.

tRNA

Transfer RNA. Attaches to amino acids found in cytoplasm based on 3 bases on end of tRNA (anti-codon)

Codon

3 bases on mRNA read by anti-codons on tRNA to make proteins.

Anti-codon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

Redundant code (redundancy):

Genetic code is referred to this as some codons (UUU, UUC..) code for same amino acid.

Only different in last base.