Genetics 101

Gregor Mendel (1822-1884) First scientist to apply mathematics to experimentation. Suggested a hypothesis to explain inheritance. His main goal was to find a pattern of inheritance based on observations. Observed patterns of inheritance using pea plants. While Mendel's research was with plants, the basic underlying principles of heredity that he discovered also apply to people and other animals because the mechanisms of heredity are essentially the same for all complex life forms. Mendel chose garden peas (pisum sativum) for genetic experiments. Why is this significant?

Mendel and the Pea Plant

Common Garden Pea

Round vs. Wrinkled Pea Seeds

But, where the heck did Shorty go???? Parental Generation (P) First Filial Generation (F1) But, where the heck did Shorty go????

Where the heck did Shorty come from??? 2nd Filial generation (F2)

Mendel called them tall and short “factors”, we now call them “alleles Alleles are alternate forms of a trait. What two alleles are shown here? Can you identify the generations?

The pair of alleles for any trait comprise the gene for that trait.

Dominant Recessive Trait shown Trait masked, hidden -tt- short -TT- Tall -Tt – tall Trait masked, hidden -tt- short * recessive only show s when homozygous

Punnett Square P P P p p p P p

Punnett Square T t TT Tt Tt tt T t Genotype- TT- 1 Tt- 2 tt- 1 Mendel’s F2 Generation T- tall (dominant) t – short (recessive) Cross - Tt x Tt Punnett Square T t Genotype- TT- 1 Tt- 2 tt- 1 Phenotype Tall- 3 Short-1 T t TT Tt Tt tt

MA- ___________ CA-_________ Bell Ringer # 1 1. The trait that is expressed is known as the ___________ trait. A. recessive B. dominant C. hybrid D. heterozygous R-EOC- Genetics MA- ___________ CA-_________

MA- ___________ CA-_________ Bell Ringer # 1. A human baby boy inherits a recessive allele from his mother. In which circumstance would he most likely show the trait coded for by the recessive allele? A. The baby inherits the dominant allele from his father. B. The allele is on an autosomal chromosome and the baby is a twin. C. The allele is on the X chromosome. D. The allele is on the Y chromosome. R-EOC- Genetics MA- ___________ CA-_________

Mendel’s Experimental Results

Punnett Square Analysis Homozygous dominant (purebred dominant) Heterozygous (hybrid) R RR Rr r Homozygous recessive (purebred recessive) Rr rr Heterozygous (hybrid)

What’s the phenotypic ratio of round to wrinkled peas in this pod? Can you make a prediction about the parents?

Flower Color

Test Cross P p Pp Used by Mendel to determine unknown genotype of a dominant phenotype. How can we tell if a purpe flower plant is heterozgous (Pp) or homozygous dominant (PP)? P p Pp pp

Intro To Genetics http://www.youtube.com/watch?v=B_PQ8qYtUL0

Heredity http://glencoe.mcgraw-hill.com/sites/dl/free/0078695104/161752/00051105.html

Vocabulary Genetics- is the science of genes, heredity, and variation in living organisms. Allele-is one of two or more forms of a gene .

Identical factors- Homozygous -TT,tt Different Factors – Heterozygous Genetic Terms Identical factors- -TT,tt Different Factors – Tt (hybrid) Homozygous Heterozygous

Genotype Phenotype Genes (TT,Tt,tt) Appearance (ex: blue)

A. The environment affects these characteristics after birth. 1. Robert and Susan are married and have two children, one son and one daughter. The children have different hair color and eye color. Which of the following statements explains these differences in the children? A. The environment affects these characteristics after birth. B. There is a lack of variation in the genes of parent sex cells. C. Sexual reproduction produces a fertilized egg that has a unique genetic makeup. D. Hormone changes in a pregnant woman’s body cause traits to develop differently in a fertilized egg. R-EOC- Genetics MA-_______ CA- ______

If red is dominant and white is recessive, where do pink carnations come from??????

Incomplete Dominance Genotype 1 RR 2 Rr 1 rr What’s going on here? R r Rr Genotype 1 RR 2 Rr 1 rr Phenotype 1 Red 2 Pink 1 White What are the genotypes and phenotypes shown?? R r RR Rr rr Incomplete Dominance

Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a combined phenotype. Mixture of traits….

Both traits are visible…. Codominance - is a situation in which both alleles are equally strong and both alleles are visible in the hybrid genotype. Both traits are visible….

Co-dominance in Chickens

ERMINETTE CHICKENS These chickens have feathers that are both white and black, but not grey. BB = black feathers BW = black and white feathers WW = white feathers

Codominance in blood types Universal Recipient Universal Donor

Polygenic traits - Multiple alleles A polygenic trait is one whose phenotype is influenced by more than one gene. Traits that display a continuous distribution, such as height or skin & eye color, are polygenic.

Mendel’s First Law: The Law of Segregation Alleles do not normally enter the same gamete, they are separated from each other during cell division. Germ cell Rr Gametes R r Can you relate this to meiosis?

Mendel’s Second Law: The Law of Independent Assortment In a dihybrid cross, the segregation of one pair of alleles does not affect the segregation of the second pair of alleles.

MA- _________ CA-_______ 1. For the trait being followed in the pedigree, individuals II-1 and II-4 in Figure 12-1 can be classified as _____. SC.F.2.4.1 A) homozygous dominant B) homozygous recessive C) mutants D) carriers R-EOC- ___________ MA- _________ CA-_______

MA- _________ CA-_______ In this pedigree, which family members are carriers of Tay-Sachs? both parents second and fourth offspring first and second offspring mother only R-EOC- ___________ MA- _________ CA-_______

…to be continued…