Basic Genetics - the Study of Heredity -
trait – are hereditary (passed from parent to offspring through DNA) DNA – the chemical code for building proteins proteins – create cell structure and function chromosomes – threadlike strands of DNA genes – sections of chromosomes that code for specific proteins humans – about 20-25,000 genes on 46 chromosomes
DNA Diagrams
DNA Diagrams
DNA Diagrams
Human Chromosomes 23 pair = 46 total the last pair determines gender
Gregor Mendel: The Father of Genetics born 1822 in Austria college & monastery; worked in gardens wondered why similar plants had different characteristics. decided to study pea plants because they grow fast, are self-pollinating, and come in many varieties. did not know about DNA; made his theories based on the results of his experiments. in eight years (1856-1864), he grew over 30,000 pea plants
cross-pollination - occurs when pollen from one plant pollinates the egg of another plant
true-breeding – when a plant self-pollinates and always shows the same trait as the parent Mendel crossed true-breeding plants
Alleles the different forms of a gene flower color = purple or white purple flower color stronger, dominant represented with a capital letter white flower color recessive, weaker represented with a lower case letter
Mendel’s Pea Plants
Punnett Square the letters on the inside of the square show the possible offspring
Genes you get genes from each parent each pair of genes is represented by a two letter combination the letter combination shows the possible alleles (forms) of the genes two capitals, PP two lower case pp or one capital and one lowercase Pp always write the capital letter first
Genotype the exact genetic make up of the gene (the exact 2 alleles) represented by the letter combinations PP, Pp, pp
Phenotype the results of the genotype what the letters show what you can see of the trait PP = purple flower color Pp = purple flower color pp = white flower color
Homozygous the alleles of a gene are exactly the same PP = homozygous dominant pp = homozygous recessive also called purebred
Heterozygous the alleles of the gene are different Pp = heterozygous dominant also called hybrid