Introduction to Genetics Chapter 9 Introduction to Genetics

List as many traits as you can that could be inherited

Who was Gregor Mendel? He was known as the “Father of Genetics” He discovered how traits were inherited Genetics – study of heredity Heredity – the passing of traits from parents to offspring Trait – a genetically determined characteristic

Mendel’s Peas Mendel did his study on pea plants Pea plants have many traits (tall/short, purple flowers/white flowers) Pea plants can be self-fertilized or cross-fertilized

Purple True-Breed x White True-Breed = Hybrid Types of Plants True-Breeding - these plants always create plants that look like themselves Hybrids – offspring of true-breeding plants Purple True-Breed x White True-Breed = Hybrid

Dominance Some factors are dominant over others. Purple true-breed x White true-breed = all purple offspring (hybrids) - Therefore, purple is the dominant factor - White is the recessive factor

Types of Inheritance (dominance) Complete - the dominant allele's trait masks the recessive allele's trait Incomplete - the trait seen is a blend of the two allele's traits Codominant - both alleles' traits are fully expressed

Genes and Alleles Genes – a short segment of DNA that contains the instructions for a single trait - remember at the time Mendel was experimenting DNA was unheard of so he knew genes as factors that determine a trait Mendel discovered that each trait is controlled by two factors (alleles) - allele: is an alternative form of a gene. - ex. purple vs white flower color

Mendel’s Experiments Draw the crosses (it will take up all this space)

Mendel’s Experiments The 'F' stands for filial, which in Latin means “of a son or daughter” Draw the crosses

Mendel’s Experiments Draw the crosses

Mendel’s Experiments Draw the crosses

Explaining the Crosses Principle of segregation - When a parent makes sperm or eggs, their genes separate The gametes (egg or sperm) contain either a P allele (purple) or a p allele (white) P p

Recall: Law of Independent Assortment Chromosomes separate independently of one another during the formation of gametes

Below is an example of a complete dominance trait: height Vocab Genotype - what gene alleles (letters), the organism has - ex. TT, Tt, tt Phenotype - what it looks like - ex. tall or short Below is an example of a complete dominance trait: height Genotype Phenotype TT tall Tt tt short

Describing Genotypes Homozygous: two types Homozygous dominant: TT Homozygous recessive: tt Heterozygous: Tt

Let's review what you know about genetics...... www.youtube.com/watch?feature=player_embedded&v=d4izVAKhMPQ

Types of Crosses Testcross – an individual with unknown genotype crossed with a homozygous recessive individual Why did I put one dominant allele for the individual of the unknown genotype? t T Tt ? ?t

Polygenic Traits a compound word poly meaning many genic refering to genes Polygenic - a trait that is controlled by more than one gene Medel was lucky and studied traits that were not polygenic. Polygenic traits (human eye color) are much more complicated than single gene traits (pea flower color)

Check for understanding 1.  A one-eyed purple people eater is crossed with a two eyed purple people eater.  All of their offspring have two eyes.   Which trait is dominant? 2.  If you use the letter T for this gene.   What is the genotype of the offspring?  3.  Are these offspring the F1 or F2 generation? 4.  If you crossed the offspring with each other?  How many of the new offspring would you expect to have two eyes?

5.   The passing of traits from parents to offspring is known as  ___________________________ 6.  Who was the father of genetics?  __________ 7.  A single gene will code for a _______________, such as flower color. 8.  Every gene is made of two ______________