BIOLOGY 12 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:

Variation: Genetic variation describes naturally occurring genetic differences among individuals of the same species 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 parents-stirs-issues/story?id= parents-stirs-issues/story?id=

The color of skin is genetically very complicated! Skin color comes from the pigment melanin  Produced by melanocytes in skin cells  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 time.  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 1900.

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 statistics.  Also studied at the University of Vienna

Major Events in the 20 th 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 replicates 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!