Introduction to genetics

BS-Genetics 1st
Introduction to Genetics

 The word genetics was derived from the Greek root gennō,
γεννώ
 which means to give birth or to grow into
 It was coined by British biologist William Bateson in 1905/6
for the study of physiology of heredity and variations.
Introduction

Definition
 Genetics is the branch of science/Biology
 Concerned with genes, heredity, and variation in living
organisms
(viruses, bacteria, plants and animals).

Genetics
 It seeks to understand the process of trait inheritance from
parents to offspring,
including
 Molecular structure and function of genes
 Gene behaviour in the context of a cell or organism,
 Gene distribution, and variation
 Change in populations.

Genes:
 Nucleotide sequence that stores the information
which specifies the order of the monomers in a final
functional polypeptide or RNA molecule.
Genes, heredity, and variation

Heredity
 The process of transmission of characters from one generation to next,
either by gametes – in sexual reproduction or
by the asexual reproductive bodies in asexual reproduction,
is called inheritance or heredity.
 Heredity is the cause of similarities between individuals.
 This is the reason that brothers and sisters with the same parents resemble
each other and with their parents.
Heredity and variation

Cont.
Variation
Any difference between cells, individual organisms, or groups
of organisms of any species
Is the cause of differences between individuals.
This is the reason that brothers and sisters who do resemble
each other are still unique individuals

Divisions of Genetics
Traditionally, the study of genetics has been divided into
three major sub disciplines:
1. Transmission genetics
2. Molecular genetics, and
3. Population genetics

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1. Transmission genetics / classical genetics
encompasses the basic principles of genetics and how
traits are passed from one generation to the next
This area addresses the relation between chromosomes
and heredity, the arrangement of genes on chromosomes,
and gene mapping.

Cont.
Here the focus is on the individual organism —
how an individual organism inherits its genetic makeup
and how it passes its genes to the next generation.

2. Molecular genetics
 concerns the chemical nature of the gene itself:
 how genetic information is encoded, replicated, and expressed
 It includes the cellular processes of replication, transcription,
and translation — by which genetic information is transferred
from one molecule to another — and gene regulation —
the processes that control the expression of genetic information.
The focus in molecular genetics is the gene — its structure,
organization, and function.

3. Population genetics
 explores the genetic composition of groups of individual
members of the same species (populations) and how that
composition changes over time and space. Because evolution is
genetic change, population genetics is fundamentally the study
of evolution.
 The focus of population genetics is the group of genes found in a
population.

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 t is convenient and traditional to divide the study of genetics into
these three groups, but we should recognize that the fields
overlap and that each major subdivision can be further divided
into a number of more specialized fields, such as chromosomal
genetics, biochemical genetics, quantitative genetics, and so
forth.
 Genetics can alternatively be subdivided by organism (fruit fly,
corn, or bacterial genetics), and each of these organisms can
be studied at the level of transmission, molecular, and
population genetics.

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Replication
 Modern genetics is an extremely broad field, encompassing
many interrelated sub disciplines and specializations.
In recent years, the science of genetics has proliferated into
numerous distinctive sub disciplines.
Some of the significant branches of genetics are the
following:

1. Plant genetics. The genetics of plants.
2. Animal genetics. The genetics of animals.
3. Human genetics. It involves the study of heredity of human
traits, human disorders, betterment and correction of human
disorders.
4. Microbial genetics. It deals with the genetics of microorganisms
(viz., viruses, bacteria, unicellular plants and animals).

5. Fungal genetics or mycogenetics. The genetics of fungi.
6. Viral genetics. Genetics of virus.
7. Mendelian genetics. It involves study of heredity of both
qualitative (monogenic) and quantitative (polygenic) traits and
the influence of environment on their expressions.
8. Quantitative genetics. It involves the study of heredity of
quantitative traits such as height, weight and IQ in human
beings and milk production in cattle.

9. Clinical genetics. Genetics involved in the detection of causes of
diseases such as haemophilia, colour blindness, diabetes,
phenylketonuria.
10. Immunogenetics. It deals with genetics of production of
different types of antibodies; the diversity of antibodies has
been found to be under control of genetic regulation.

Introduction to genetics

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