Ch1 introduction to genetics

Copyright © 2009 Pearson Education, Inc.

1.0 Introduction to genetics

Prepared by Pratheep SandrasaigaranLecturer at Manipal International University


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


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


http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http%3A%2F%2Fdiscovermagazine.com%2F2013%2Fmay%2F13-grandmas-experiences-leave-epigenetic-mark-on-your-genes&ei=9SL5VKq8BI2HuAT-oYHYDA&psig=AFQjCNELIQSln_mCFL6vYEW9yXBbCIT08Q&ust=1425699618390172


1.1 Introduction: What Is Genetics?



What Is Genetics?


• 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.


Four major subdivisions 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.


Four major subdivisions Genetics


• 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


The four major subdivisions Genetics


Classical genetics

Population genetics

Molecular genetics

Quantitative genetics


Classical genetics: Transmitting traits from generation to generation


• 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


Molecular genetics:The chemistry of genes


• 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


Population genetics: Genetics of groups


• 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.


Population genetics: Genetics of groups


• 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.


Quantitative genetics: Measuringthe strength of heredity


• 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


1.2 History of genetics


Copyright © 2009 Pearson Education, Inc.Prepared by Pratheep Sandrasaigaran

Adapted from The Cartoon Guide to Genetics, Gonick. L. & Wheelis, M.




























1.3 Chromosomes and Genes



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).



• 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?



• 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.



• 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.


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


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

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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 = ????


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.



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).


Central dogma of genetics


1.3 Knowing the different branches of genetics



• Behavioural genetics• Developmental genetics• Conservation genetics• Ecological genetics• Evolutionary genetics• Genetic engineering• Genomics• Human genetics• Microbial genetics• Molecular genetics• Population genetics• Quantitative genetics


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.


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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


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Science

Ch1 introduction to genetics