Genetics – Introduction & History
Genetics
Unit 1
B.Tech Biotechnology
Sem IV
Science of Genetics
Image courtesy: http://www.ige3.unige.ch/wp-content/themes/parallelus-salutation/assets/images/illustrations/genetics-cloud_1_big.jpg
Quotes
Genetics is all about showcasing human beauty along with high-quality
performance.
Bela Karolyi
Mild autism can give you a genius like Einstein. If you have severe autism,
you could remain nonverbal. You don't want people to be on the severe
end of the spectrum. But if you got rid of all the autism genetics, you
wouldn't have science or art. All you would have is a bunch of social 'yak
yaks.'
Temple Grandin
Quote reference:
http://www.brainyquote.com/quotes/keywords/genetics_2.html#HcdJUtj7UbbxIWYx.99
Genetics : Definition
• The branch of biology that deals with heredity, especially the
mechanisms of hereditary transmission and the variation of
inherited characteristics among similar or related organisms.
• Genetics is the study of heredity, the process in which a
parent passes certain genes onto their children. A person's
appearance -- height, hair color, skin color, and eye color -- are
determined by genes.
• Genetics in simple word is studying about Gene and their
effect and interaction in families. How a gene behaves and
interacts?
Genetics: Terminology
• Diploid Number
– Number of chromosomes in pair (2n)
• Haploid Number
– Number if chromosomes alone (n)
• Alleles
– Two form of Gene
– Wild type & Mutant type
• Genotype
– Set of alleles for a given trait
• Phenotype
– Observable features
WHY GENETICS IS IMPORTANT ?
• Same nucleic acid
• Same genetic code
• Undergirds the study of many other biological
disciplines
• Genetic variation = Foundation of evolution
• The study of almost any field of biology or
medicine is incomplete without a thorough
understanding of genes and genetic methods.
Cell, Chromosome & DNA
Cell Cycle – Mitosis & Meiosis
Image Courtesy : Adèle L., Marston, and Amon Angelika. 'ERRATUM: MEIOSIS: CELL-CYCLE CONTROLS
SHUFFLE AND DEAL'. Nature Reviews Molecular Cell Biology 6.10 (2005): 818-818, Web. 7 Mar. 2015.
Transmission of Genetic Material
Image source: Open.edu,. 'SK195_1_2.1: 3 The Transmission Of
Genetic Material - SK195_1_2.1'. N.p., 2015. Web. 7 Mar. 2015.
Gametogenesis
The stages of gametogenesis in vertebrates: In both sexes, a relatively small population of
primordial germ cells present in the embryo proliferates by mitosis to form a population of
gonial cells (spermatogonia or oogonia) from which the gametes differentiate. In the male (a),
meiosis occurs before differentiation, hereas in the female (b), both meiotic divisions occur after
differentiation. Each primary spermatocyte generally gives rise to four viable gametes, whereas
each primary oocyte forms only one fertilizable egg and two or three polar bodies.
Genetics & History - Ancient
Time Line
Events
8000 – 10000 BC
Domestication of Horses, Camels and Dogs
5000 BC
Cultivation of maize, wheat, rice & date palm
5000 BC
Maize dating in caves in the Tehuacan Valley of Mexico
500 – 400 BC
Hippocratic treatise On the Seed argued that active
“humors” in various parts of the male body served as
the bearers of hereditary traits.
384 – 322 BC
Aristotle proposed that the generative power of male
semen resided in a “vital heat” contained within it that
had the capacity to produce offspring of the same
“form”
Less than 100 year
Mendel’s Theory to Chromosomal theory of Inheritance
History of Genetics - Before 1860
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Development of Light microscopy
The elucidation of cell theory
Findings of Charles Darwin The Origin of species
Cell – coined by Robert Hook, Microscopy came into
existence
Anton van Leeuwenhoek discovered living organisms
Discovery of Nuclei – Robert Brown
Mitosis described – Hugo von Mohl – 1835 – 1839
Cell Theory – Rudolf Virchow – All cells come from
preexisting cells
History of Genetics - 1860-1900
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1866 – Gregor Mendel’s work on pea published
1900 – Rediscovery of Mendel’s work
1888 - W.Waldeyer - coined the term chromosome.
1875 - O. Hertwig - Fusion of sperm and egg to form the zygote.
1880s - Theodor Boveri, as well as K. Rabl and E. van Breden,
hypothesized that chromosomes are individual structures with
continuity from one generation to the next despite their
“disappearance” between cell divisions.
• 1885 - August Weismann - Inheritance is based exclusively in the
nucleus.
• 1887 - Reductional division, meiosis.
• 1890 - O.Hertwig and T. Boveri - described the process of meiosis
in detail.
History of Genetics - 1900-1944
• Development of the chromosomal theory
• In 1903, Walter Sutton hypothesized that the behavior of chromosomes
during meiosis explained Mendel’s rules of inheritance, thus leading to the
discovery that genes are located on chromosomes.
• In 1913, Alfred Sturtevant created the first genetic map, using the fruit fly.
He showed that genes existed in a linear order on chromosomes.
• In 1927, L. Stadler and H. J. Muller showed that genes can be mutated
artificially by X rays.
• 1930 and 1932, R. A. Fisher, S. Wright, and J. B. S. Haldane developed the
algebraic foundations for our understanding of the process of evolution.
• In 1943, S. Luria and M. Delbrück demonstrated that bacteria have normal
genetic systems and thus could serve as models for studying genetic
processes.
History of Genetics - 1944-Present
• 1944 - O. Avery and colleagues—DNA—was
the genetic material.
• 1953 - James Watson and Francis Crick - the
structure of DNA
• 1968 – 1973 - W. Arber, H. Smith, and D.
Nathans – discovered restriction
endonucleases,
• 1972 - Paul Berg – first recombinant DNA
• 1997 - First mammal cloned, Dolly the sheep
• 2003 – Human Genome Project completed
Genetics Time Line
• Pre – Mendelian Genetics
• Mendelian Genetics
• Post – Mendelian Genetics
Ancient Times
Humans have long
understood that
offspring tend to
resemble parents, and
have selectively bred
animals and plants for
many centuries and
the genetics started
from the same
moment.
Assyrian relief with cuneiform: "A winged deity pollinating stylized trees,
symbolizing fertility. This is an alabaster relief from the Northwest Palace of
King Assur-nasir-pal II at Nimrud." Brooklyn Museum. Image Courtey: Link
Molecular Genetics
• Structure & Function of gene at molecular level
• Helps in understanding developmental biology, genetic
mutations that cause disease
• Using molecular techniques we can discover the reason why
traits are carried on and how and why genes may mutate.
• Techniques in Molecular Genetics – PCR, Cloning, Cell culture,
Separation & Detection of DNA, mRNA isolation, phage
display, knockout technology, siRNA technology.
Website: Wikipedia,. 'Molecular Genetics'. N.p., 2015. Web. 7 Mar. 2015.
Forward v/s Reverse
Forward Genetics
• Phenotype first gene
second.
• We generate phenotypically
distinct organism and then
further study.
• Mode of inheritance and
interaction studied.
• Mutant gene then identified
• Relating observed
phenotype to biochemical
mechanism
Reverse Genetics
• Gene first phenotype
second
• Gene mutate or excised by
molecular biology
techniques
• Mutated gene inserted to
genome and absence or
change in phenotype
recorded
The Human Genome Project
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Began in 1990
Proposed completion – 2005 but completed in 2003
Started by the U.S. Department of Energy and the National Institutes of Health in
an effort to reach six set goals.
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These goals included:
1.
2.
3.
4.
5.
6.
identifying 20,000 to 25,000 genes in human DNA (although initial estimates were
approximately 100,000 genes),
determining sequences of chemical base pairs in human DNA,
storing all found information into databases,
improving the tools used for data analysis,
transferring technologies to private sectors, and
addressing the ethical, legal, and social issues (ELSI) that may arise from the projects.
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The project was worked on by eighteen different countries including the United
States, Japan, France, Germany, and the United Kingdom.
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The collaborative effort resulted in the discovery of the many benefits of
molecular genetics.
1. Web: Genome.gov,. 'An Overview Of The Human Genome Project'. N.p., 2015. Web. 7 Mar. 2015.
2. Wikipedia,. 'Human Genome Project'. N.p., 2015. Web. 7 Mar. 2015.
Human Chromosome Set - Location of genes on chromosomes, whose
mutant form causes Disease.
Model Organisms
1. Escherichia coli: Bacterium
2. Dictyostelium discoideum: Amoeba
3. Neurospora crassa: Bread Mold
4. Saccharomyces cerevisiae: Yeast
5. Arabidopsis thaliana: Mustard Plant
6. Caenorhabditis elegans: Roundworm
7. Drosophila melanogaster: Fruit Fly
8. Danio rerio: Zebrafish
9. Mus musculus: Mouse
10. Rattus norvegicus: Rat
Gregor Johann Mendel
• “Father of modern genetics“
• Mendel studied seed shape, flower color,
seed coat tint, pod shape, unripe pod
color, flower location, and plant height.
• Law of Segregation and the Law of
Independent Assortment
Other Experiments
• Mendel began his studies on heredity using mice. He was at St.
Thomas's Abbey but his bishop did not like one of his friar
studying animal sex, so Mendel switched to plants.
• Mendel also bred bees in a bee house that was built for him, using
bee hives that he designed
• He also studied astronomy and meteorology, founding the
'Austrian Meteorological Society' in 1865.
• He had a fondness for the bees, and refer to them as "my dearest
little animals"
Web Resources
• http://www.dnaftb.org/#classical
(experiments)
• http://sciencecases.lib.buffalo.edu/cs/collecti
on/results.asp?subject_headings=genetics%20
/%20heredity (Case study)
• Image Sources:
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http://news.bbcimg.co.uk/media/images/51032000/jpg/_51032029_zebrafishspl.jpg
http://upload.wikimedia.org/wikipedia/commons/8/83/Arabidopsis_thaliana_JdP_2013-04-28.jpg
http://upload.wikimedia.org/wikipedia/commons/b/bc/E_coli_at_10000x,_original.jpg
http://static.diffen.com/uploadz/6/62/Rat-2.jpg
http://genomics.nimr.mrc.ac.uk/online/dicty-fl-db.html (Copyright, M.J. Grimson & R.L. Blanton. Biological
Sciences Electron Microscopy Laboratory, Texas Tech University)
Book Reference
• Gupta, P. K. Genetics. Meerut, India: Rastogi
Publications, 2007. Print.
• Gupta, P K. Genetics. Meerut: Rastogi Publications,
2011. Print.
• Karp, Gerald. Cell And Molecular Biology. Hoboken,
NJ: John Wiley, 2010. Print.
• Klug, William S., and Michael R. Cummings. Concepts
Of Genetics. 7th ed. India: Pearson Education, 2007.
Print.