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 rolling- dominant Widow’s peak- dominant Free ear lobe- dominant Attached ear lobe- recessive Hitch-hiker’s thumb- recessive Bent little finger- dominant

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 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 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 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 T= Tall t= short Tt T Tt t tt tt

In pea plants tall height is dominant to short height 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 Genotype Tt=2 and tt=2 Phenotype Tall=2 and short =2 t t T= Tall t= short T Tt Tt t tt tt

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/genetics-puppets.gif “Cartoon”. April 18, 2007. http://www.cartoonstock.com/newscartoons/cartoonists/bgr/lowres/bgrn968l.jpg “Mendel”. April 19, 2007. http://www.micro.utexas.edu/courses/levin/bio304/genetics/mendel.gif “Mendel Cartoon”. April 19, 2007. http://eebweb.arizona.edu/courses/ecol320/Mendel'sPeaSoupSmall.jpg “Punnett square”. April 19, 2007. http://www.usd.edu/med/som/genetics/curriculum/fig1-13.JPG