Genetics: An Introduction

Genetics: An Introduction
A little motivational video:
What is Genetics?
 The science that studies heredity
Heredity is the passing of traits from parents to offspring
Joke of the day:
 Genetic variation describes naturally occurring
genetic differences among individuals of the same
 Why?
 Recombination of chromosomes that occurs during sexual
reproduction (called independent assortment)
 Crossing over during meiosis
Some vocabulary:
 Genes
 Humans have ~21,500
 Chemical instructions for building proteins
 Locus/loci: specific location on a chromosome
 Diploid cells contain two copies of each gene on pairs
of homologous chromosomes
 Allele: each version of a gene
Video: ABC News: All in the family: Mixed race twins
The color of skin is genetically very complicated!
 Skin color comes from the
pigment melanin
Produced by melanocytes in skin
More than 100 genes directly or
indirectly influence amount of
melanin in an individual’s skin
Lead to many variations in skin color
History of Genetics
 People have known about inheritance for a long
children resemble their parents
domestication of animals and plants, selective breeding for
good characteristics
Sumerian horse breeding records
Egyptian data palm breeding
Mid 1800’s Discoveries
 Major events in the mid-1800’s
led directly to the development
of modern genetics.
1859: Charles Darwin publishes The
Origin of Species, which describes
the theory of evolution by natural
selection. This theory requires
heredity to work.
1866: Gregor Mendel publishes
Experiments in Plant Hybridization,
which lays out the basic theory of
genetics. It is widely ignored until
History of Genetics:
 Pioneer of Genetics: Gregor Mendel
 Born in 1822 in Czechoslovakia.
 Became a monk at a monastery in
 Taught biology and had interests in
 Also studied at the University of
Major Events in the 20th Century
 1900: rediscovery of Mendel’s work by Robert Correns, Hugo de
Vries, and Erich von Tschermak .
1904: Gregory Bateson discovers linkage between genes. Also
coins the word “genetics”.
1910: Thomas Hunt Morgan proves that genes are located on the
chromosomes (using Drosophila).
1944: Oswald Avery, Colin MacLeod and Maclyn McCarty show
that DNA can transform bacteria, demonstrating that DNA is the
hereditary material.
1953: James Watson and Francis Crick determine the structure
of the DNA molecule, which leads directly to knowledge of how it
1966: Marshall Nirenberg solves the genetic code, showing that 3
DNA bases code for one amino acid.
1972: Stanley Cohen and Herbert Boyer combine DNA from two
different species in vitro, then transform it into bacterial cells:
first DNA cloning.
2001: Sequence of the entire human genome is announced.
To do :
 Read pages 130 and 131.
 Read Mendel biography articles and answer the
questions at the bottom based on both readings!