Transcript Chapter 26
Chapter #26 Inheritance of Traits Chapter 26.1 Notes • Genetics is the study of how traits are passed from parents to offspring. • Body cells have 2 of each chromosome. • Sex cells have 1 of each chromosome (sperm and egg). • Gene is a small section of chromosome that determines a trait. Example eye color, hair color, ear shape. Human Traits Tongue rollingdominant Widow’s peakdominant Free ear lobedominant Attached ear loberecessive Hitch-hiker’s thumbrecessive Bent little fingerdominant • Dominant genes that keep other genes from showing their traits. • Pure dominant or homozygous dominant (FF) has 2 dominant (BIG) genes. • Pure recessive or homozygous recessive (ff) has 2 recessive (lower case) gene • Heterozygous (Ff) 1 dominant gene and 1 recessive gene. Chapter 26.2 Notes • Punnett square is a way to show which genes can combine. • Gregor Mendel- 1865 Austrian monk who studied the genetics of pea plants “The father of Genetics”. • Genotype is the actual genetic make up of an organism…the letters (TT, Tt, tt) • Phenotype is what the organism look like (TT=tall, Tt=tall, tt= short) • Monohybrid cross only 1 trait at a time is crossed (4 squares) Example • In pea plants tall height is dominant to short height. If you cross a pure recessive short plant and a heterozygous tall plant what are the genotype and phenotype??? • In pea plants tall height is dominant to short height. If you cross a pure recessive short plant and a heterozygous tall plant what are the genotype and phenotype??? • Step #1, write the key for the letters. • T= tall • t= short • In pea plants tall height is dominant to short height. If you cross a pure recessive short plant and a heterozygous tall plant what are the genotype and phenotype??? Step #2, figure out each parents letters • T= tall • t= short • Parent #1 tt • Parent #2 Tt In pea plants tall height is dominant to short height. If you cross a pure recessive short plant and a heterozygous tall plant what are the genotype and phenotype??? Step #3, Draw the punnett square t T= Tall t= short t T Tt Tt t tt tt • In pea plants tall height is dominant to short height. If you cross a pure recessive short plant and a heterozygous tall plant what are the genotype and phenotype??? Step #4, Figure out the geno and phenotypes t t T Tt Tt t tt tt T= Tall t= short Genotype Tt=2 and tt=2 Phenotype Tall=2 and short =2 • Dihybrid cross is when 2 traits are crossed at the same time (16 squares) • Example in pea plant round and yellow seeds are dominant over wrinkled and green seeds. If a pure dominant round, yellow seed plant is crossed with a pure recessive wrinkled, green seed plant are crossed what are the geno and phenotype? Work Cited “Mouse Genes”. April 18, 2007. http://www.uga.edu/srel/kidsdoscience/images/geneticspuppets.gif “Cartoon”. April 18, 2007. http://www.cartoonstock.com/newscartoons/cartoonists/b gr/lowres/bgrn968l.jpg “Mendel”. April 19, 2007. http://www.micro.utexas.edu/courses/levin/bio304/geneti cs/mendel.gif “Mendel Cartoon”. April 19, 2007. http://eebweb.arizona.edu/courses/ecol320/Mendel'sPea SoupSmall.jpg “Punnett square”. April 19, 2007. http://www.usd.edu/med/som/genetics/curriculum/fig113.JPG