Baker 2003/2004 Whose got Genes? Genes, Heredity, & DNA

Baker 2003/2004 What is GENETICS? The study of how traits are inherited through the interactions of genes.

Baker 2003/2004 What are genes? Genes are a segment of DNA on a chromosome that controls a particular trait. Genes are located on the chromosomes in the nuclei. Each organims has a fixed number of chromosomes. Humans have 23 pairs (46) chromosomes. Genetics is the study of how traits are passed on from one generation to another

Baker 2003/2004 Define TRAIT Ways of looking, thinking, or being Traits that are genetic are passed down through the genes from parents to offspring

Baker 2003/2004 Describe RECESSIVE A trait that is covered over, or dominated, by another form of that trait and seems to disappear Hidden when the other copy of the gene contains the dominant allele. A recessive allele shows up only when there is no dominant allele present Shown with a lower-case letter

Baker 2003/2004 Describe DOMINANT A trait that covers over, or dominates, another form of that trait Trait that always shows up, even when only one of the two alleles is in the dominant form Shown by a capital letter

Baker 2003/2004 Define GENOTYPE An organism's genetic makeup

Baker 2003/2004 Define PHENOTYPE Outward physical appearance and behavior of an organism

Baker 2003/2004 What is a PUNNETT SQUARE? Used to determine the likely hood that the offspring receives a certain trait. An uppercase letter stands for a dominant allele Lowercase letters stand for recessive alleles

Baker 2003/2004 Punnett Squares Sample Problem 1. In roses, red flowers are dominant over white flowers. What are the possible offspring when a homozygous red rose is crossed with a homozygous white rose.

Baker 2003/2004 Red rose = RR white rose = rr Generation 1 (I Do) RR r r R R R R r r r r Genotype 4 Rr Phenotype 100% Red Rose

Baker 2003/2004 Red rose = Rr white rose = rr Generation 2 (We do) R r r r R R r r r r r r Genotype 2 Rr 2 rr Phenotype 50% Red 50% White

Baker 2003/2004 Red rose = Rr Generation 3 (You do) Rr R r R R r r R R r r Genotype 1 RR 2Rr 1 rr Phenotype 75% Red 25% White

Baker 2003/2004 Whose got Genes? Part 2 Genes, Heredity, & DNA

Baker 2003/2004 Who was Gregor Mendel? Austrian monk who studied mathematics and science As a boy he could predict the possible types of flowers and fruits that would result from crossbreeding two plants in his father’s garden Picture taken from biography.com

Baker 2003/2004 Who was Gregor Mendel? Curiosity about the connection between the color of a pea flower and the type of seed that same plant produced inspired him to begin experimenting with garden peas in Made careful use of scientific methods, which resulted in the first recorded study of how traits pass from one generation to the next.

Baker 2003/2004 Define HEREDITY The passing of traits from parent to offspring

Baker 2003/2004 Define ALLELE The different forms of a trait that a gene may have One form of a gene

Baker 2003/2004 What is HOMOZYGOUS? Both alleles [forms of the gene] are the same When offspring inherit two dominant genes, (one dominant gene from each parent) they are said to be homozygous dominant When offspring inherit two recessive genes, (one recessive gene from each parent) they are said to be homozygous recessive AA aa

Baker 2003/2004 What is HETEROZYGOUS? When alleles occur in different forms When offspring inherit one dominant gene and one recessive gene, they are said to be heterozygous Since the dominant gene will be expressed, they are said to be heterozygous dominant Aa

Baker 2003/2004 Generation 1 Heterozygous Homozygous recessive B Brown Eyes are Dominant to b Blue Eyes B b b b B B b b b b b b Genotype 2 Bb 2bb Phenotype 50% Brown 50% Blue

Baker 2003/2004 Generation 2 B Brown Eyes are Dominant to b Blue Eyes Homozygous Dominant Homozygous Recessive BB b b B B B B bb b b Genotype 4 Bb Phenotype 100% Brown Eyes

Baker 2003/2004 Generation 3 B Brown Eyes are Dominant to b Blue Eyes Homozygous Dominant Heterozygous B B B b B B B B B B b b Genotype 2 BB 2 Bb Phenotype 100% Brown Eyes

Baker 2003/2004 References Slideshow adapted from class.net/PowerPoints/Genetics.htm class.net/PowerPoints/Genetics.htm