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Mendel and the Gene Idea Mendel’s Discoveries Extending Medelian Genetics Mendelian Inheritance in Humans

Mendel and the Gene Idea Mendel’s Discoveries Extending Medelian Genetics Mendelian Inheritance in Humans

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Page 1: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Mendel and the Gene Idea

Mendel’s DiscoveriesExtending Medelian GeneticsMendelian Inheritance in

Humans

Page 2: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Mendel’s Discoveries

Experimental and quantitative approach

Law of segregation Law of independent

assortment Roles of probability Discovered the

behavior of genes

Page 3: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Law of Segregation

Allele pairs segregate during gamete formation and randomly recombine during fertilization

Predicted by Punnett square

Page 4: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Some useful genetic vocabulary Homozygous Heterzygous Phenotype Genotype Monohybrid cross Dihybrid cross

Testcross Dominant Recessive P F2

F1

Page 5: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Law of Independent Assortment

Each pair of alleles segregates independently of other gene pairs during gamete formation

Page 6: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Roles of Probability

Role of multiplication

The probability that two independent events will occur simultaneously is the product of their individual probabilities

Role of addition The probability of an

event that can occur in two or more independent ways is the sum fo the separate probabilities of of the different ways

Page 7: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Beyond Mendel

Incomplete dominance Codominance Multiple alleles Pleiotropy Epistasis Polygenetic inheritance

Page 8: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

What is a dominant allele?

Dominance does NOT determine relative abundance!

Recessive alleles have no message Recessive product is overwhelmed by

product of dominant allele Recessive product inhibited by

dominant product

Page 9: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Mendelian Inheritance in Humans

Difficult to study Few offspring Generation-20 yrs Breeding

experiments frowned upon

Understanding comes from family pedigrees

Page 10: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Human Disorders

Recessive lethals Dominant lethals Multifactorial

disorders

Page 11: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Sickle Cell Disease-Video

http://www.hhmi.org/biointeractive/media/DNAi_sicklecell-lg.mov

Page 12: Mendel and the Gene Idea  Mendel’s Discoveries  Extending Medelian Genetics  Mendelian Inheritance in Humans

Technology and Genetics

Role of genetic counseling

Carrier recognition Newborn screening Fetal testing

1) chorionic villus sampling

2) amniocentesis