Genetics is the study of heredity and the variation of inherited traits. The document outlines the major subdivisions and branches of genetics and provides important milestones in the field. It notes that genetics began with Mendel's experiments on pea plants in 1865 which demonstrated that heredity is transmitted in discrete units. Later discoveries include identifying DNA as the genetic material in 1944, determining the double helix structure of DNA in 1953, cracking the genetic code in 1966, and completing the first draft of the human genome in 1990. The future of genetics involves continued research to understand all the information contained in the human genome to better understand diseases and develop new treatments.

1. Genetics-
Historical
Highlights

2. Genetics- Definition
“ Genetics is that branch of biological
sciences which deals with the transmission of
characteristics from parent to off spring.”
“Genetics is the field of science that
examines how traits are passed from one
generation to the next; Blueprint of life.”

3. Major Subdivisions of Genetics
 Classical genetics: Describes how traits (physical
characteristics) are passed along from one generation to
another.
 Molecular genetics: The study of the chemical and physical
structures of DNA, its cousin RNA, and proteins
 Population genetics: Takes Mendelian genetics (that is, the
genetics of individual families) and ramps it up to look at the
genetic makeup of larger groups.
 Quantitative genetics: A highly mathematical field that
examines the statistical relationships between genes and the
traits they encode

4. Branches of Genetics
 Behavioral genetics
 Developmental genetics
 Conservation genetics
 Ecological genetics
 Evolutionary genetics
 Genetic engineering
 Genomics
 Human genetics
 Microbial genetics
 Molecular genetics
 Population genetics
 Quantitative genetics

5. Important Milestones in Genetics
Present knowledge in genetics dates
back to the Johann Gregor Mendel
(1822-1884) who found out that both the
parents contributed equally to their
offsprings.

6. 1859 Discovery: Natural Selection
Charles Darwin wrote “On the Origin
of Species by Means of Natural
Selection, or the Preservation of
Favored Races in the Struggle for
Life.”

7. 1865 Discovery: Heredity Transmitted in Units
Gregor Mendel’s experiments on peas demonstrate
that heredity is transmitted in discrete units. The
understanding that genes remain distinct entities
even if the characteristics of parents appear to
blend in their children explains how natural
selection could work and provides support for
Darwin’s proposal.

8. 1869 DNA Isolated: Frederick
Miescher isolates DNA from cells for the
first time and calls it “nuclein”.
1900 Rediscovery of Mendel’s work:
Botanists DeVries, Correns, and von
Tschermak independently rediscover
Mendel’s work while doing their own
work on the laws of inheritance.

9. 1902 Chromosome Theory of Inheritance: Walter
Sutton observes that the segregation of chromosomes
during meiosis matched the segregation pattern of
Mendel’s .
1902: William Bateson Coined the term Genetics
for the science deals with hereditary
1909 The Word Gene is Coined: Wilhelm
Johannsen coins the word “gene” to describe the
Mendelian unit of heredity. He also uses the terms
genotype and phenotype to differentiate between the
genetic traits of an individual and its outward
appearance.

10.  1911 Chromosomes Carry Genes: Thomas Hunt Morgan
and his students study fruit fly chromosomes. They show that
chromosomes carry genes, and also discover genetic linkage.
 1943 DNA Has a Regular Periodic Structure: William
Astbury, a British scientist, obtains the first X-ray diffraction
pattern of DNA, which reveals that DNA must have a regular
periodic structure. He suggests that nucleotide bases are
stacked on top of each other.
 1944 DNA Transforms Cells: Oswald Avery, Colin
MacLeod, and Maclyn McCarty show that DNA (not proteins)
can transform the properties of cells -- thus clarifying the
chemical nature of genes.

11. 1952 Genes Are Made of DNA : Alfred Hershey &
Martha Chase show that only the DNA of a virus
needs to enter a bacterium to infect it, providing
strong support for the idea that genes are made of
DNA
1953 DNA Double Helix : Francis H. Crick and
James D. Watson described the double helix
structure of DNA. They receive the Nobel Prize for
their work in 1962.
1955 46 Human Chromosomes: Joe HinTjio
defines 46 as the exact number of chromosomes in

12.  1959 Chromosome Abnormalities Identified: Jerome
Lejeune and his colleagues discover that Down Syndrome is
caused by trisomy 21.
 1961 First Screen for Metabolic Defect in Newborns:
Robert Guthrie develops a method to test newborns for the
metabolic defect, phenylketonuria (PKU).
 1966 Genetic Code Cracked: Marshall Nirenberg and
others figure out the genetic code that allows nucleic acids
with their 4 letter alphabet to determine the order of 20 kinds
of amino acids in proteins.
 1972 First recombinant DNA
 1975 DNA Sequencing: Two groups, Frederick Sanger and
colleagues, and Alan Maxam and Walter Gilbert, both
develop rapid DNA sequencing methods.

13. 1983 PCR Invented: The polymerase chain
reaction, or PCR, is used to amplify DNA.
1987 First Human Genetic Map
1990 Launch of the Human Genome
Project.
1996- Dolly(sheep) the first mammal
cloned from an adult somatic cell using
the process of nuclear transfer.

14. Future
It will take decades of research for scientists to
understand all of the information that is contained
within the human genome. In time, more human
diseases will be understood at the level of the
molecules that are involved, which could
dramatically change the practice of medicine by
leading to the development of new drugs, as well as
to genetic testing to improve and individualize
treatments.

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