© K. Malone, 2005 Chapter 11 Introduction to Genetics P. 64

© K. Malone, 2005 X First Generation (F1) 100% pink!!! Second Generation (F2) X 3 pink, 1 blue - ¾ pink (75%), ¼ blue (25%) How did this happen?

© K. Malone, 2005 Section 11-1 Genetics!!! Patterns of Inheritance You inherit traits (physical characteristics) from your parents- Heredity! Heredity is what makes you unique –Examples of Traits: Blue, Green, Brown, Black, Hazel Eye color GeneticsGenetics = the scientific study of heredity and its importance in biology

© K. Malone, 2005 Gregor Mendel Gregor Mendel (1822), an Austrian monk who studied inheritance patterns in pea plants, his work is now considered the foundation of modern genetics –He worked with ordinary garden peas, planted in the garden at his monastery.

© K. Malone, 2005 What Mendel Found Mendel studied 7 different pea plant traits that varied from one individual plant to the next (like human traits!) These traits had 2 forms, such as either green seeds or yellow seeds, smooth pods or wrinkled pods –He crossed plants with each of the 7 contrasting characteristics and studied their offspring P = represents the parent generation F (from the Latin word fillius and filia- son and daughter) are the offspring F 1 = first generation F 2 = second generation Hybrids = offspring of crosses between parents with different traits

© K. Malone, 2005 Mendel’s Experiment P generation tallshort

© K. Malone, 2005 Mendel’s Experiment tallshort F 1 generation tall P generation

© K. Malone, 2005 Mendel’s Results Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Flower Height wrinkledgreenwhite roundyellowgray constrictedyellowterminalshort smoothgreen axial tall Round dominant Yellow dominant Gray dominant Smooth dominant Green dominant Axial dominant Tall dominant All the F 1 plants expressed only the dominant trait!

© K. Malone, 2005 Mendel’s Principles of Heredity Mendel learned 2 principles from these experiments: 1.Biological inheritance is determined by factors (we call them genes) that are passed from one generation to the next, Genes = chemical factors that determine traits – each trait is controlled by 1 gene that occurs in 2 contrasting forms or alleles Allele = a different form of a gene Hello! 2. Principle of Dominance: some alleles are dominant and others are recessive

© K. Malone, 2005 Principle of Dominance Eeek! An organism with a dominant allele for a particular form of a trait will always exhibit that form of the trait In other words, if you have the dominant allele, you will express that dominant trait An organism with a recessive allele for a particular form of a trait will exhibit that form only when the dominant allele is not present In other words, you must have 2 recessive alleles to express the recessive trait I’m Dominant!! Tall = TT or Tt Short = tt

© K. Malone, 2005 Where did the recessive traits go? Mendel wanted to know why all his F 1 plants expressed only dominant traits ????? He wondered, “Had all the recessive traits disappeared? Or were they still present in the F 1 plants?” To answer this question, he allowed his F 1 plants to self- pollinate F 1 X F 1 F2F2

© K. Malone, 2005 Mendel’s Experiment P generation tallshort F 1 generation tall

© K. Malone, 2005 Mendel’s Experiment P generation tallshort F 1 generation tall F 2 generation tall short

© K. Malone, 2005 F 1 Cross Mendel thought the results for his F 1 cross were amazing! All the recessive traits re- appeared in the F 2 offspring!