Basic Genetics - the Study of Heredity - Betsy Sanford 7th Life Science Lost Mountain Middle School

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

Gregor Mendel: The Father of Genetics

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

Reginald Punnett English zoologist and geneticist created a table that predicts number and variety of genetic possibilities in offspring the Punnett square is still used today in genetic counseling

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