www sciencequeen net Whose got Genes Genes Heredity

www. sciencequeen. net 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

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

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

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

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 1856. 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? AA aa 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 Baker 2003/2004

What is HETEROZYGOUS? Aa 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 Baker 2003/2004

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

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

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

References Slideshow adapted from http: //www. scienceclass. net/Power. Points/Genetics. htm Baker 2003/2004