protein synthesis and chromosomes

a base sequence (a section) of DNA, which occupies a locus (a fixed position), that codes for: • the amino acid sequence of a polypeptide (therefore determining the proteins of an organism) • a functional RNA (including ribosomal RNA and tRNAs )

mitochondria and ribosomes

genome - the complete set of genes in the cell proteome= the full range of proteins that the cell is able to produce -

carry the same genes which code for the same characteristics at the same locus, half from mum, other half from dad can be different alleles

sister chromatids are identical copies of chromosomes formed during DNA replication homologous chromosomes could be different alleles

an alternative form of a gene

three bases on mRNA that codes for a single amino acid

messenger RNA ,transfer RNA, ribosomal RNA

• single polynucleotide strand • the groups of three bases in mRNA is called a codon

• single polynucleotide folded into a cloverleaf shape • held by hydrogen bonds which occur between complementary base pairs within the polynucleotide • a sequence of three bases = anticodons • it has an amino acid binding site on the opposite end of where the anticodons are

carries genetic code from the DNA in the nucleus to the cytoplasm

carries amino acids to the ribosome during protein synthesis

the process of making an RNA copy of a gene sequence

occurs in the nucleolus of the nucleus hydrogen bonds between complementry base pairs break and the DNA helix unwinds to expose the bases to act as a template only one chain of the DNA acts as a template free RNA nucleotides align by complementary base pairing in RNA uracil base pairs with adenine RNA polymerase joins adjacent nucleotide by phosphodiester bonds between adjacent nucleotides RNA polymerase reaches a stop codon and then detaches, resulting in the formation of pre-MRNA. pre-mRNA is spliced to form mRNA mRNA then leaves the nucleus through the nuclear envelope pores -

ONLY HAPPENS IN EUKARYOTES In the nucleus: introns are removed from the pre-mRNA and exons are joined together through splicesome.

the process in which the mRNA is ‘read’ and translated into a protein.

A molecule of mRNA leaves the nucleus via a nuclear pore mRNA is attached to a ribosome in the cytoplasm the ribosome attaches at the start codon the tRNA molecule brings a specific amino acid and then the complementary anti codon binds to complementary mRNA codons the ribosome will move along the mRNA molecule to enable another complementary tRNA to attach to the next codon on the mRNA the two amino acids that have been delivered by the tRNA molecules are joined by a peptide bond. this is catalyzed by an enzyme and requires ATP trna is released after amino acid joined to polypeptide the ribosome moves along the mRNA to form polypeptide until it reaches a stop codon the polypeptide chain is now created and will enter the Golgi body for folding and modification

each amino acid has more than one triplet code if a point of mutation occurs, even though the triplet bases will be different, it may still code for the same amino acid and therefore have no effect

each base is part of only one triplet code if a point of mutation occurs, it will only affect one codon and therefore one amino acid

each triplet codes for the same amino acid in all organisms (indirect evidence for evolution) his is an advantage as it means genetic engineering is possible