Introduction to genetics that presence the definition of chromosomes, genes and a discussion on the different branches of genetics.

1. Copyright © 2009 Pearson Education, Inc.
1.0 Introduction to genetics
Prepared by Pratheep Sandrasaigaran
Lecturer at Manipal International University

2. Copyright © 2009 Pearson Education, Inc.
Genetics Textbooks
Prepared by Pratheep Sandrasaigaran
1. Concepts of Genetics, Klug, Cummings,
Spencer, Palladino, 2012
2. Human Genetics concepts and Application
9th ed.
3. Crash course: Cell Biology and Genetics, 4th
ed.
4. Genetics for Dummies. Tara. R.R
5. The facts on file Illustrated guide to The
human: body Cells and Genetics

3. Copyright © 2009 Pearson Education, Inc.
Diagram from Internet source
By the end of this
chapter you should
be able to:
• Understand the concept of genetics
in brief
• History of genetics
• Define chromosomes and genes
• Knowing the different branches of
genetics
Prepared by Pratheep Sandrasaigaran

4. Copyright © 2009 Pearson Education, Inc.
1.1 Introduction: What Is Genetics?
Prepared by Pratheep Sandrasaigaran

5. Copyright © 2009 Pearson Education, Inc.
What Is Genetics?
Prepared by Pratheep Sandrasaigaran
• Genetics is the field of science that examines
how traits are passed from one generation to
the next; Blueprint of life.
• An organism’s genes, snippets of DNA that are
the fundamental units of heredity, control how
it looks, behaves, and reproduces.

6. Copyright © 2009 Pearson Education, Inc.
Four major subdivisions Genetics
Prepared by Pratheep Sandrasaigaran
• 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.

7. Copyright © 2009 Pearson Education, Inc.
Four major subdivisions Genetics
Prepared by Pratheep Sandrasaigaran
• 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

8. Copyright © 2009 Pearson Education, Inc.
The four major subdivisions
Genetics
Prepared by Pratheep Sandrasaigaran
Classical
genetics
Population
genetics
Molecular
genetics
Quantitative
genetics

9. Copyright © 2009 Pearson Education, Inc.
Classical genetics: Transmitting traits
from generation to generation
Prepared by Pratheep Sandrasaigaran
• Study of physical traits as a stand-in or the
genes that control appearance, or
phenotype.
• Governed by Mendel’s Laws or Mendelian
genetics.
• Investigates the history of genes inheritance
in human population based on phenotypic
records of a family over several generations

10. Copyright © 2009 Pearson Education, Inc.
Molecular genetics:
The chemistry of genes
Prepared by Pratheep Sandrasaigaran
• Investigate the structures and functions
of genes at the molecular level.
• Investigate the physical and chemical
structures of the double helix, DNA.
• Investigation on how the genetic code
works at the levels of DNA and RNA

11. Copyright © 2009 Pearson Education, Inc.
Population genetics:
Genetics of groups
Prepared by Pratheep Sandrasaigaran
• The use of Mathematics and equations to
describe what goes on genetically is
population genetics.
• So what is population Genetics?
• The use of Mendelian genetics and examine
the inheritance patterns of many different
individuals who have something like
geographic location in common.

12. Copyright © 2009 Pearson Education, Inc.
Population genetics:
Genetics of groups
Prepared by Pratheep Sandrasaigaran
• Population genetics helps scientists understand
how the collective genetic diversity of a
population influences the health of individuals
within the population.
• Population genetics has revealed that all cheetahs
are very, very genetically similar; in fact, they’re
so similar that a skin graft from any animal won’t
be rejected by any other animal.

13. Copyright © 2009 Pearson Education, Inc.
Quantitative genetics: Measuring
the strength of heredity
Prepared by Pratheep Sandrasaigaran
• Quantitative genetics examines traits that vary in
really subtle ways and relates those traits to the
underlying genetics of organisms.
• Quantitative genetics works on a complex statistical
approach to estimate how much variation in a
particular trait is due to the environment and how
much is actually genetic.
• This measure allows scientists to make predictions
about how offspring will turn out based on
characteristics of the parent organisms; agriculture
for plant and animal breeding

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1.2 History of genetics
Prepared by Pratheep Sandrasaigaran

15. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

16. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

17. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

18. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

19. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to
Genetics, Gonick. L. & Wheelis, M.

20. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

21. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

22. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to
Genetics, Gonick. L. & Wheelis, M.

23. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

24. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics,
Gonick. L. & Wheelis, M.

25. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

26. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.

27. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics,
Gonick. L. & Wheelis, M.

28. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Adapted from The Cartoon Guide to Genetics,
Gonick. L. & Wheelis, M.

29. Copyright © 2009 Pearson Education, Inc.
1.3 Chromosomes and Genes
Prepared by Pratheep Sandrasaigaran

30. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
The Chromosome Theory of
Inheritance
• Mendel conducted his experiments before the
structure and role of chromosomes were
known.
• About 20 years after his work was published,
advances in microscopy allowed researchers to
identify chromosomes.
• Chromosomes in diploid cells exist in pairs,
called homologous chromosomes (identical in
size and location of the centromere).

31. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
The Chromosome Theory of
Inheritance
• In mitosis, chromosomes are copied and
distributed so that each daughter cell receives
a diploid (2n) set of chromosomes.
• Meiosis is associated with gamete formation.
• How many chromosome do you see in human
gamete?

32. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
The Chromosome Theory of
Inheritance
• Walter Sutton and Theodor Boveri noticed that
genes and chromosomes exist in pairs,
• They also notice that members of a gene pair
and members of a chromosome pair separate
from each other during gamete formation.
• Based on these parallels, Sutton and Boveri
independently proposed that genes are carried
on chromosomes
A drawing of chromosome
X of D. melanogaster
Adapted from Concepts of Genetics, Klug, Cummings, Spencer, Palladino, 2012
.

33. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
The Chromosome Theory of
Inheritance
• The theory- Inherited traits are controlled by genes
residing on chromosomes faithfully transmitted
through gametes, maintaining genetic continuity
from generation to generation.
• Why there are variations in eye colour human?
• Due to allele (alternative forms of a gene) of a gene
controlling eye colour.

34. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Phenotype and Genotype.
• Different alleles may produce differences in the
observable features, or phenotype, of an
organism.
• The set of alleles for a given trait carried by an
organism is called the genotype.
• Knowing gene control the phenotype and
genotype, what is the chemical nature of Genes?
• By the 1920s, scientists were aware that proteins
and DNA were the major chemical components of
chromosomes.
DNA
Protein

35. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
DNA is carrier of genetic
• DNA was the carrier of genetic information
came from work of Oswald Avery, Colin
MacLeod, and Maclyn McCarty with bacteria
and other experiments with viruses that infect
and kill cells of the bacterium Escherichia coli.
• DNA makes RNA, which most often makes
protein “central dogma”.
• How proteins can be responsible for imparting
the properties of living systems?
An electron micrograph showing T phage infecting
a cell of the bacterium E. coli
Adapted from Concepts of Genetics, Klug,
Cummings, Spencer, Palladino, 2012
.

36. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Protein control the biological
functions
• Lets do Maths..!
• proteins are made from combinations of 20
different amino acids.
• Presume a protein is made of 3 bases of amino
acid polypeptide. How many different type of
protein can be derived?
• Now, if a Protein is made of 100 bases of amino
acid polypeptide. How many different type of
protein can be derived?
203
= 8000
20100
= ????

37. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Timeline of genetics
timeline showing the development of genetics from Gregor Mendel’s work on pea plants to the current era of genomics
and its many applications in research, medicine, and society.
Adapted from Concepts of Genetics, Klug, Cummings, Spencer, Palladino, 2012
.

38. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Gene expression consists of transcription of DNA into mRNA
(top) and the translation (center) of mRNA (with the help of
a ribosome) into a protein (bottom).
Adapted from Concepts of Genetics, Klug, Cummings, Spencer, Palladino, 2012
.
Central dogma
of genetics

39. Copyright © 2009 Pearson Education, Inc.
1.3 Knowing the different branches
of genetics
Prepared by Pratheep Sandrasaigaran

40. Copyright © 2009 Pearson Education, Inc.
• Behavioural genetics
• Developmental genetics
• Conservation genetics
• Ecological genetics
• Evolutionary genetics
• Genetic engineering
• Genomics
• Human genetics
• Microbial genetics
• Molecular genetics
• Population genetics
• Quantitative genetics
Prepared by Pratheep Sandrasaigaran
Branches of genetics
Dolly, a Finn Dorset sheep cloned from the genetic
material of an adult mammary cell, shown next to her
first-born lamb, Bonnie.
Adapted from Concepts of Genetics, Klug, Cummings, Spencer, Palladino,
2012
.

41. Copyright © 2009 Pearson Education, Inc.
Prepared by Pratheep Sandrasaigaran
Diagram of the human chromosome set, showing
the location of some genes whose mutant forms
cause hereditary diseases. Conditions that can be
diagnosed using DNA analysis are indicated by a
red dot
Adapted from Concepts of Genetics, Klug, Cummings, Spencer, Palladino,
2012
.