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The Work of Gregor Mendel 11-1 Every living thing has a set of characteristics inherited from its parents Scientists realize that heredity holds the key to understanding what makes us unique As a result, genetics is at the core of a revolution in understanding biology Genetics - scientific study of heredity Gregor Mendel’s Peas Gregor Mendel Austrian monk, born 1822 Studied science and math Worked in a monastery - in charge of the garden Taught at the high school His work in the garden changed biology forever Mendel conducted his famous genetic experiments with garden peas Pea plants have flowers that contain both male and female parts Male - stamen (anthers & filament), pollen Female - carpel( stigma, style, ovary), eggs When pollen fertilizes an egg cell, a seed for a new plant is formed Pea plants normally reproduce by selfpollination Seeds that are produced by selfpollination inherit all of their characteristics from a single plant Known as a true breeding plant Produces offspring identical to parent Mendel had a supply of true-breeding pea plants Basis for his experiments Noted that pea plants have 7 contrasting traits Height, seed shape, seed color, seed coat color, flower position, pod shape, pod color Plants can also cross-pollinate Mendel manipulated this concept during his experiments He removed the male plant parts from several plants, that had a contrasting traits Carefully dusted pollen from one plant onto stigma of plant with contrasting trait Studied the offspring of the crosses Genes & Dominance In Mendel’s cross-breeding experiments, he was studying the traits of the pea plants Trait - a specific characteristic, like seed color, that varies from one individual to another The offspring that resulted from Mendel’s cross-breeding were known as hybrids Have parents with different traits Ex: tall x short The first set of offspring are called the F1 generation, or first filial Offspring in the F1 generation only showed traits from one of the parents Mendel made 2 conclusions from these experiments: Biological inheritance is determined by factors that are passed from one generation to the next Today, those factors are called genes Mendel’s studies involved genes that had two contrasting forms The different forms of a gene are called alleles His second conclusion is the principle of dominance Some alleles are dominant and others are recessive Dominant alleles are always expressed Recessive alleles are only expressed when paired up with another recessive allele Segregation Mendel wondered what happened to the recessive traits in the F1 crosses Mendel allowed all of the plants of the F1 to self-pollinate, creating the F2 or second filial generation The F1 Cross In the F2 generation, the recessive trait appeared in about 1/4 of the offspring The remaining 3/4 still showed the dominant trait Explaining the F1 Cross Mendel assumed that at some point, the contrasting alleles were separated, or segregated He believed that this happened during the formation of gametes - sex cells Tt x Tt T t T t TT Tt Tt tt