Genetics 3.2

Genome size Genome size varies by organisms. Smallest genomes are in viruses even though they are not regarded as living organisms. Unlike the number of genes the genome size is directly proportional to the complexity of the organism Organism Description Genome Size (million bp) T2 phage Virus that attacks E. coli 0.18 Escherichia coli Gut bacteria 5 Drosphilia melanegaster Fruit fly 140 Homo sapiens Humans 3,000 Paris japonica Woodland plant 150,000

Autoradiography Collecting quantitative data on the number of bases in a genome. John Cairns first produced images of DNA E.coli was used in the first experiment 1. cells were grown for 2 generations in a solution containing thymidine. Radioactive isotope 2. Cell membranes were digested using lysozyme 3. During the next 2 months the radioactive DNA decayed and emitted high energy electrons 4. These electrons were captured on a photographic film and measured using microscopes

Ploidy Haploid - One set of chromosomes (n) Diploid - Two sets of homologous chromosomes (2n) Polyploid - More than two sets of chromosomes

Haploid and Diploid The advantage of having diploid cells is that the effects of harmful recessive mutations can be avoided if a dominant allele is also present. One of the most fundamental characteristics of a species is the number of chromosomes they have in each of their cells This number can change due to evolution!

Who has more chromosomes?