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Lecture 3

HLTB20H3 Lecture Notes - Lecture 3: Genetic Recombination, Melanin, Meiosis


Department
Health Studies
Course Code
HLTB20H3
Professor
Lianne Tripp
Lecture
3

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Lecture 3 Notes
Contemporary Human Evolution & Variation
Week 4
LECTURE 3 — THE BASIS OF INHERITANCE: THE BASICS OF HUMAN GENETICS
Gregor Johann Mendel
-father of genetics
-austrian monk
-amateur botanist who experimented with pea plants
Mendel’s Work Received Little Recognition…Why?
-simple mathematics
-well controlled botanical experiments, that just happened to have simple mode of inheritance
-no physical evidence for heritable factors (cellular structures and their functions were just
being discovered)
Mendelian Models for Heredity
-characteristics that we observe = phenotype
-if that characteristic is inherited — believe it is influenced by genetics (genotype)
-origins of the study of “genetics” not the study of chromosomes/genes, but the study of
phenotypes
After Mendel…
-gene = segment of DNA molecule that codes for a single polypeptide chain
-polypeptide chain - a chain of amino acids
-initial focus: protein molecules
-allele = alleleomorphs = alternative forms of gene occupying the same locus on a homologous
chromosome
-46 chromosomes in total — 23 pairs
Mendel’s Approach
-experimented with 34 varieties of peas
-through controlled pollination, observed changes in pea phenotypes from generation to
generation
-observed that expected proportions of phenotypes could be predicted
Law of Particulate Inheritance
-inheritance is equal, bi-parental and particulate:
-characteristics of parents are passed on to descendants unchanged as units
-these units occur in pairs/alternate forms
-there is no blending of parental characteristics
Mendel’s First Principle: Law of Segregation
-a pair of alleles control one character in the parent
-these alleles from the parent separate (are packaged in separate gametes) and only one from
each parent passes to the offspring
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