Genetics powerpoint for AQA Biology Unit 2

Genetics

GeneticsNucleotidesPhosphateSugarBaseStays the sameVariesNucleotidesMade up of:A Phosphate GroupPentose SugarNitrogenous BaseSugarIs a deoxyribose - one less oxygenBases can vary- 4 variationsAdenine (A)Thymine (T)Guanine (G)Cytosine (C)Polynucleotide StrandsSugar Phosphate BackboneOne NucleotideBond forms between sugar and phosphate Polynucleotide StandsMany nucleotide join to form Polynucleotide strands.The nucleotides join between the phosphate group of one and the sugar of anotherCreates phosphate-sugar backboneen

Specific Base PairingCAGTGCPhosphate GroupPhosphate GroupDeoxyribose sugarDeoxyribose sugarBasesSpecific Base PairingTwo DNA polynucleotides strands join together by hydrogen bonds between the basesEach base has one particular partnerA and T (Adenine and Thymine)G and C (Guanine and Cytosine)CausesAll factors stated previously causes DNAs structure.

Polynucleotide strand with sugar phosphate backboneBasesHydrogen bonding between the bases, keeping the strands coiled togetherStructure vs. FunctionDouble Helix SturctureMakes DNA very stable in the cell. Means DNA does not break down or damage easily. So information is not lost easilyDNA molecules are long and coiled upThey are coiled very tightly so a lot of information can fit into a small cell nucleusDNA molecules have a paired structure So able to copy itself Semi-conservative replication DNA storage in Eukaryotic cellsThese cells contain linear DNA molecules that exist as chromosomes Chromosomes are made up of one long molecule of DNAThe molecule is wound to fit in the nucleusIt is wound around histone proteins and coiled further to create the chromosome structure. DNA storage in Eukaryotic cells

DNA wound around histone proteinsDNAHistone ProteinsDNA with the protein is coiled up repeatedlyA single ChromosomeDNA storage in Prokaryotic cellsProkaryotes also carry DNA as chromosomes- but DNA molecules are shorter and circularNot wound around proteins Fit in the cell by supercoilingDNA storage in Prokaryotic cells

Circular ChromosomeCoiled ChromosomeSupercoiled to fit into the cellGenesSections of DNAFound in chromosomesCode for proteins Contain instructions to make them Making proteins using genesProteins are made from amino acids The order of nucleotide bases determine the order of amino acids in a protein Each amino acid is coded by 3 bases A tripletDifferent sequences form different amino acids GTC: ValineTCA: Serine CCC: Proline

Making proteins using genesThe code in DNA is degenerateMeans more than one base triplet can code for the same amino acid.Here are more possible combinaios of three bases than there are amino acids 64 triplets and only 20 amino acids

Eg. Proline (Pro) can be coded by CCT, CCC, CCA and CCGGlutamine (Gln) can be coded by CAA and CAGNon Coding DNAGenes in eukaryotic DNA contain sections do not code for amino acids.These are introns (if they code theyre exons) Introns are removed during protein synthesis DNA also contains sections of multiple repeats outside of genes.Areas that repeat over and overThese areas dont code for amino acids.Genes and DevelopmentAll enzymes are proteins- which are built for the instructions within genesThe order of the bases in the genes decides amino acids in proteinThis determines the enzyme that is madeSo, genes help determine the development and nature because they contain the informationGenes and DevelopmentAllelesA gene can exist in more than one formOrder of the bases in each allele is slightly different So they code different versions of the same characteristic Eg. Eye Colour: Blue or brownHomologous ChromosomeHumans have 23 pairs of chromosomes46 in totalPairs of matching chromosomes are called homologous pairs.In this the chromosomes are the same size and have the same genesBut different alleles The alleles coding for the same gene will be in the same position (locus) on each chromosome. Homologous ChromosomesPosition of gene Allele for type BAllele for type ASame size and same genes but different alleleGene MutationsMutations are changes in the base sequence of an organisms DNA.Mutations can produce new alleles of genesA gene codes for a specific protein.So if a sequence of bases in a gene changes a non functional or different protein could be producedAll enzymes are proteins.So if there is a mutation in a gene that codes for an enzymes, then that enzyme may not form properly.Can produce and active site that does not match substrate.