Mendel and Mendelian Mendel and Mendelian GeneticsGenetics

Gregor Mendel 1822-1884Gregor Mendel 1822-1884 Published his findings in 1865Published his findings in 1865

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MendelMendel

Considered the Considered the father of modern father of modern geneticsgenetics

Studied inheritance Studied inheritance of pea plantsof pea plants

Said that inheritance Said that inheritance followed certain laws. followed certain laws.

His laws were not His laws were not well accepted at first. well accepted at first.

Why Pea Plants?Why Pea Plants?

Mendel used pea Mendel used pea plants in his plants in his experiments largely experiments largely because of their because of their ability to self ability to self pollinate. pollinate.

Mendel’s laws of Mendel’s laws of inheritanceinheritance

Mendel came up with Mendel came up with two major laws of two major laws of inheritance:inheritance: The law of The law of

segregation (4 parts)segregation (4 parts) The law of The law of

independent independent assortment. assortment.

Law of SegregationLaw of Segregation

There are four parts to this lawThere are four parts to this law1)1) There are alternate versions of genes called There are alternate versions of genes called

alleles. alleles.

2)2) For each characteristic, an organism inherits two For each characteristic, an organism inherits two alleles.alleles.

3)3) Alleles interact in a number of ways. (dominance, Alleles interact in a number of ways. (dominance, incomplete dominance, codominance)incomplete dominance, codominance)

4)4) The two alleles for a trait separate during gamete The two alleles for a trait separate during gamete productionproduction

Law of independent Law of independent assortmentassortment

This law states the This law states the inheritance of one inheritance of one trait will not affect the trait will not affect the inheritance of inheritance of another. another.

This is only true for This is only true for traits that are not traits that are not linked. linked.

The importance of The importance of MendelMendel

Why is Mendel’s work so important?Why is Mendel’s work so important? Before his time no one took the time to Before his time no one took the time to

figure out how traits were passed on.figure out how traits were passed on. Mendel’s work laid the basic framework for Mendel’s work laid the basic framework for

other scientists to build on. other scientists to build on.

After MendelAfter Mendel

Mendel’s work was rediscovered in 1900. Mendel’s work was rediscovered in 1900. Other scientists started to add to his Other scientists started to add to his

ideas to build the current model of ideas to build the current model of genetics as we know it. genetics as we know it.

This is called classical genetics. This is called classical genetics.

CrossesCrosses

Heterozygote: Heterozygote: contains both types contains both types of alleles for a trait. of alleles for a trait. (Aa)(Aa)

Homozygous: Homozygous: contains only one contains only one allele for a trait (AA allele for a trait (AA or aa)or aa)

Generations are Generations are labeled as Flabeled as F##

Monohybrid vs DihybridMonohybrid vs Dihybrid

Monohybrid = Aa X Monohybrid = Aa X AaAa

Dihybrid = AaBb X Dihybrid = AaBb X AaBbAaBb

Law of independent Law of independent assortment says that assortment says that the inheritance of A the inheritance of A will not effect B. will not effect B.

http://www.biology.arizona.edu/mendelian_genetics/mendelian_genetics.html