DNA Replicaiton

Process of DNA being copied or replicated before every cell division, so one identical copy goes to each daughter cell Occurs during interphase stage of Mitosis

• Replication starts on DNA molecule called replication origin • An enzyme called helicase unzips and unwinds Dna, breaking the hydrogen bonds that joins the base pairs, forming two separate strands • Free nucleotides attach to expose based following complementary base pairings • Dna polymerase enzymes then joins the new nucleotides to each other by strong covalent bonds • New strands wind up forming double helixes with hydrogen bonds connecting them. • creates identical dna molecules

Ribonucleic acid - Made up of nucleotides contain sugar ribose and the base uracil - Single Stranded - RNa is a helper to DNa allowing protein synthesis

Ribosomal RNA - JOins with proteins made in cytoplasm to form subunits ribosomes Messenger RNA - carries genetic information from DNA to ribosomes in cytoplasm where protein synthesis occurs Transfer RNA - transfers amino acids to ribosomes where amino acids are joined

Composed of amino acids - Proteins differ due to the number and order of amino acids - every three bases codes for one amino acid

Adenine + Thymine/Uracil Guanine + Cytosine

Forming bonds between carbon 3 of the sugar and oxygen atom of the phosphate causing a condensation polymerisation reaction

• RNA polymerase attaches to strand of DNA at promoter sequence • DNA strands separate exposing nucleotides • mRNA pairs with DNA base pairs (Following complementary base pairing) • Nucleotides are added til terminator sequence is met • mRNA molecule created and leaves nucleus

• Ribosomes binds with start codon on mRNA • tRNA molecule carry amino acid to mRNA • complementary anti-codon binds with codon • tRNA releases amino acid • amino acids forming together creating a polypeptide chain • polypeptide chain folds onitself to create 3D shape protein

The study of changes in gene expression without affecting or changing the DNA sequence

Addition of acetyl group to the histone Decrease attraction between DNA and Histones as the chromatin more relaxes/unwinds DNA is MORE loosely bounded to histone Enhancing gene Expression RNA polymerase has greater access to gene = Increased transcription

Addition of a methyl group to histones Occuring at CpG sites Blocking access to genes for RNA polymerases Inhibits gene expression Decreasing Transcription

Factors which changes the gene expression influenced by age, environmental/lifestyle

Chromosomes condenses Nuclear membrane breaks down Spindle fibres form

Condensed chromosomes move to the middle of the cell

Centromeres divide/degenerate Chromosomes are moved to opposite ends of spindle

Two sets of chromosomes uncoils Nuclear envelopes reforms Spindle fiber disappears

Cytoplasm of cell divides into two each containing a nucleus