L1: Genetics

Genetics

Etymology: Greek word “Gen”

• to become or grow into something

William Bateson

The word “genetics” was coined by __ in 1905

Genetics

Branch of biology that studies heredity and variation

Heredity

• transmission of traits from parents to offspring

• similarity of parents and offspring

Variation

• differences between parents and offspring

• differences among offspring

• differences among individuals in the population

Gene

is a unit of heredity that controls a trait

Gene

are the principal determinants of life processes

1. Transmission genetics

2. Molecular genetics

3. Population genetics

Three interrelated fields in genetics:

Transmission genetics

• also known as classical genetics

• encompasses the basic principles of genetics

• How are traits passed on from one generation to the next?

Transmission genetics

• chromosomes as bearers of genes

• arrangement of genes on chromosomes

• map the genes on chromosomes

Molecular genetics

• chemical nature of the gene

• how genetic information is replicated, encoded, and expressed?

Population genetics

• studies the genetic composition of groups of individuals of the same species (population)

• how the composition changes over time

• it is the study of evolution (genetic changes)

1. Molecular genetics

2. Cytogenetics

3. Developmental genetics

4. Evolutionary genetics

5. Biochemical genetics

6. Behavioral genetics

7. Population genetics

8. Quantitative genetics

Branches of genetics

Molecular genetics

• structure and functions of genes at the molecular level

• processes in the Central Dogma of Molecular Biology

Cytogenetics

• behavior of chromosomes – carrier of genes

Developmental genetics

• gene regulation during development

• switching on and off of genes

Evolutionary genetics

• genetic change within and between species

Biochemical genetics

• role of enzymes and proteins

• products of genes

• genetic basis of metabolic disorders e.g. albinism

Behavioral genetics

• behavioral traits that are inherited

• genetic basis of behavioral disorders - e.g. schizophrenia, alcoholism, manic depressive psychosis, criminality

Population genetics

• fate of genes in the population

• factors affecting gene frequencies

Quantitative genetics

• inheritance and expression of quantitative traits

• role of genetic and environmental factors

Blending theory of inheritance

• Before 1860s

• Offspring are intermediate between the parents

• But not true if offspring is similar to one of the parents

Hippocrates, Aristotle, Darwin

Theory of Pangenesis

(initially Greek Theory of Inheritance)

- All structures and organs of the body

contribute copies of themselves to sex cells

Golden Age of Greek Culture (500 – 300 BC)

Attention was given to:

- reproduction

- heredity

Jean Baptiste de Lamarck

Theory of Inheritance of Acquired Characteristics

• Acquired body modifications are inherited

August Weismann

Germplasm Theory

• Plans of the entire body are contributed only by the sex cells

Kolreuter, Gardner, Naudin, Charles Darwin, Dzierson (around

1800s)

• uniformity in F1 (first filial gen.)

• variations in F2 (second filial gen.)

Gregor Mendel

• Beginning of Classical Genetics

• concept of the gene presence of discrete hereditary unit

• explains similarities & differences among parents & offspring

Gregor Mendel

• Father of Genetics

• responsible for two important principles of genetics:

• Principle of segregation

• Principle of independent assortment

Carl Correns (Germany)

Erick von Tschermak (Austria)

Hugo de Vries (Netherlands)

• duplicated Mendel’s experiments on other plants

• re-discoverers of the work of Mendel

William Bateson, Saunders, Lucien Cuenot

observed Mendel’s principles on animals

Walter Sutton (USA) and

Theodor Boveri (Germany)

Chromosome Theory of Inheritance

• Chromosomes contain the genes.

Thomas Hunt Morgan and Calvin Bridges

association between specific genes and specific chromosomes ~ Linkage

Oswald Avery, Colin MacLeod, & Maclyn McCarty

DNA as hereditary material

James D. Watson and Francis H. Crick

• Elucidation of the DNA structure

• DNA double helix

Francis Galton

Eugenics was coined by __ in 1883 in England

Eugenics

• application of genetic knowledge for the improvement of human race

• ethical issues

Euphenics

• replaced eugenics

• Medical and /or genetic intervention

• designed to reduce the impact of defective genotypes on individuals

Euphenics

• insulin for diabetes

• dietary control