DNA and Genes

3.2.2 You should know: Of evidence for the semi-conservative model for replication of DNA That a gene occupies a locus on a particular strand of DNA That genes contain a code as a specific sequence of bases to determine a polypeptide How DNA is organised for both eukaryotic and prokaryotic cells. A sequence of three bases (triplet) denotes 1 amino acid The base sequence of a gene determines the amino acid sequence in a polypeptide. Not all DNA codes for polypeptides How Wales is contributing to the global pool of genomic research.

DNA structure replication Genes and chromosomes

Choose 12 answers from the list below and write into your bingo card. helicase identical 40% antiparallel 20% semiconservative DNA polymerase deoxyribose cytosine TAG double helix phosphate GGC bases nucleotides hydrogen Crick and Watson

N 14 N 15 1 st Generation 2 nd generation Results-centrifuged DNA samples from E.coli bacteria

hill.com/sites/ x/student_view0 /chapter12/animation_quiz_- _meselson_and_stahl_experiment.html

A gene A gene is a section of DNA which holds the genetic information to instruct a cell how to build one poly peptide chain. Each gene codes for a polypeptide chain which could be an enzyme or part of a larger protein molecule.

sph.bu.edu A reminder of protein structure. Remember the primary structure is the key to the other levels

Genes One-gene-one-enzyme theory  Production of a given peptide is under control of a single gene

Genes and proteins The nucleus acts as the control centre of a cell because the DNA it contains govern the production of enzymes for the cell and thereby which reactions can take place. Genes work in pairs Genes can exist in different forms called alleles

A locus The position a gene holds on a chromosome is its locus

Cell typeNature of DNA Prokaryotic The DNA molecules are: They are not chromosomes. EukaryoticThe DNA molecules are: They are called chromosomes DNA in cells

Chromosome structure

DNA Double stranded, coiled molecule

The genetic code A triplet of bases codes for one amino acid DNA is used to build up a copy as RNA RNA can leave the nucleus and join with a ribosome The information is interpreted and used to build a polypeptide chain

Introns and exons

multiple repeats- These are DNA sequences that repeat over and over. E.g. CCTTCCTTCCTT. They are found inbetween genes. These areas don’t code for amino acids either.

Alleles Alternative forms of a gene Genes work in pairs If a new allele arises due to a change in BASE sequence it is called a mutation Not all mutations are harmful but sometimes the poly peptide formed cannot fold correctly so has an altered shape and becomes non functional

Suggested viewing: Meselsohn and Stahl animation MCGrawHill hill.com/sites/ x/student_view0/chapter12/animation_quiz_- _meselson_and_stahl_experiment.html How DNA is packaged(basic) DNA learning center