2. Genetics
(from Ancient Greek γενετικός genetikos, "genitive"
and that from γένεσις genesis, "origin")
a discipline of biology, is the science of
genes, heredity, and variation in living organisms.
4. Classical Genetics
consists of the technique and methodologies of
genetics that predate the advent of molecular
biology.
A key discovery of classical genetics in eukaryotes
was genetic linkage.
5. FIELDS OF GENETICS
Genetics is a broad discipline
Encompasses molecular, cellular, organismal, and
population biology
Many researchers have training in supporting disciplines
Biochemistry, biophysics, ecology, agriculture, etc.
Traditionally divided into three areas
Transmission genetics
Molecular genetics
Population genetics
6. FIELDS OF GENETICS
Transmission genetics
Oldest field of genetics
Explores inheritance patterns of traits as they are
passed from parents to offspring
Modern understanding began with Gregor Mendel
Provided conceptual framework for transmission
genetics
7. Cytogenetics
is a branch of genetics
that is concerned with
the study of the
structure and function of
the cell, especially the
chromosomes.
It includes routine
analysis of G-Banded
chromosomes, other
cytogenetic banding
techniques, as well as
molecular cytogenetics
such as fluorescent in
situ hybridization (FISH)
and comparative
genomic hybridization
(CGH).
8. Molecular Genetics
is the field of biology and genetics that studies the structure and function of
genes at a molecular level.
The field studies how the genes are transferred from generation to generation.
Molecular genetics employs the methods of genetics and molecular biology.
It is so-called to differentiate it from other sub fields of genetics such as
ecological genetics and population genetics.
An important area within molecular genetics is the use of molecular
information to determine the patterns of descent, and therefore the correct
scientific classification of organisms: this is called molecular systematics
9. Molecular Genetics
Seeks a biochemical
understanding of the
hereditary material
Seek an understanding of
DNA’s molecular features
Seeks an understanding of
gene expression
Interfaces with numerous other disciplines
Biochemistry, biophysics, cell biology, etc.
10. Molecular Genetics
Seeks a biochemical
understanding of the
hereditary material Most work is done on a
few model organisms
Seek an
understanding of Escherichia coli,
DNA’s molecular Saccharomyces
features cerevisiae,
Drosophila
Seeks an melanogaster, and
understanding of Arabidopsis thaliana
gene expression
Often involves the study
Interfaces with of mutant alleles
numerous other
disciplines Especially loss-of-
function mutations
Biochemistry, bioph
ysics, cell
biology, etc.
11. Population Genetics
Foundations of the field arose in the early 1900s
Concerned with genetic variation and its role in
evolution
Links the fields of classical
genetics and evolutionary biology
12. Genomics
a discipline in genetics concerned with the study of
the genomes of organisms.
The field includes efforts to determine the entire
DNA sequence of organisms and fine-scale genetic
mapping
ncludes studies of intragenomic phenomena such
as heterosis, epistasis, pleiotropy and other
interactions between loci and alleles within the
genome. In contrast, the investigation of the roles
and functions of single genes is a primary focus of
molecular biology or genetics and is a common
topic of modern medical and biological research.
14. Proteomics
the large-scale study of proteins, particularly their
structures and functions.
The term "proteomics" was first coined in 1997[3] to make an
analogy with genomics, the study of the genes.
The word "proteome" is a blend of "protein" and
"genome", and was coined by Marc Wilkins in 1994 while
working on the concept as a PhD student
After genomics and transcriptomics, proteomics is
considered the next step in the study of biological systems
It is much more complicated than genomics mostly because
while an organism's genome is more or less constant, the
proteome differs from cell to cell and from time to time.
15.
16. Behavioral Genetics
the field of study that examines the role of genetics in
animal (including human) behaviour.
Often associated with the "nature versus nurture"
debate, behavioural genetics is highly
interdisciplinary, involving contributions from biology,
genetics, ethology, psychology, and statistics.
Traditional research strategies in behavioral genetics
include studies of twins and adoptees, techniques
designed to sort biological from environmental
influences.
Genetics and molecular biology have provided some
significant insights into behaviors associated with
inherited disorders.
17. Sir Francis
Galton
a nineteenth-century intellectual, is
recognized as one of the first
behavioural geneticists.
a cousin of Charles Darwin, studied the
heritability of human ability, focusing on
mental characteristics as well as
eminence among close relatives in the
English upper-class. In 1869, Galton
published his results in Hereditary
Genius.[
18. Psychiatric genetics
subfield of behavioral neurogenetics, studies the
role of genetics in psychological conditions such as
alcoholism, schizophrenia, bipolar disorder, and
autism.
The basic principle behind psychiatric genetics is
that genetic polymorphisms, as indicated by
linkage to e.g. a single nucleotide polymorphism
(SNP), are part of the etiology of psychiatric
disorders.
19. Developmental Genetics
Scientists in the Developmental Genetics Program
study a number of diverse developmental questions
including: Establishment of the body axis by
morphogen gradients, Regionalization of the
embryonic xbrain into different structural and
functional regions, Neural stem cell allocation and
differentiation, Axon navigation and branching,
Development of the embryonic eye, Heart
development and analysis of heart function, Germ
line development.
20. Conservation genetics
an interdisciplinary science that aims to apply
genetic methods to the conservation and
restoration of biodiversity.
Researchers involved in conservation genetics
come from a variety of fields including population
genetics, molecular ecology, biology, evolutionary
biology, and systematics.
21. Metagenics
it means "the creation of something which creates.“
the practice of engineering organisms to create a
specific enzyme, protein, or other biochemicals
from simpler starting materials.
22. Ecological Genetics
is the study of genetics in natural populations.
This contrasts with classical genetics, which works
mostly on crosses between laboratory strains, and
DNA sequence analysis, which studies genes at the
molecular level.
23. Evolutionary Genetics
the broad field of studies that resulted from the integration of genetics and
Darwinian evolution, called the ‘modern synthesis’ (Huxley 1942), achieved
through the theoretical works of R. A. Fisher, S. Wright, and J. B. S. Haldane and
the conceptual works and influential writings of J. Huxley, T. Dobzhansky, and H.J.
Muller.
This field attempts to account for evolution in terms of changes in gene and
genotype frequencies within populations and the processes that convert the
variation with populations into more or less permanent variation between species
24. Medical Genetics
is the specialty of medicine that involves the
diagnosis and management of hereditary disorders
medical genetics refers to the application of
genetics to medical care.
Example: gene theraphy
25.
26. Human genetics
describes the study of inheritance as it occurs in
human beings
Human genetics encompasses a variety of
overlapping fields including: classical genetics,
cytogenetics, molecular genetics, biochemical
genetics, genomics, population genetics,
developmental genetics, clinical genetics, and
genetic counseling.
27. Microbial Genetics
a subject area within microbiology and genetic engineering. It studies the genetics of
very small (micro) organisms.
This involves the study of the genotype of microbial species and also the expression
system in the form of phenotypes.It also involves the study of genetic processes taking
place in these micro organisms i.e., recombination etc
28. Archaeogenetics
a term coined by Colin Renfrew, refers to the
application of the techniques of molecular population
genetics to the study of the human past.
the analysis of DNA recovered from archaeological
remains, i.e. ancient DNA;
the analysis of DNA from modern populations
(including humans and domestic plant and animal
species) in order to study human past and the genetic
legacy of human interaction with the biosphere; and
the application of statistical methods developed by
molecular geneticists to archaeological data.
29.
30.
31. Quantitative
Genetics
the study of continuously measured traits (such as height or weight)
and their mechanisms.
It can be an extension of simple Mendelian inheritance in that the
combined effects of one or more genes and the environments in which
they are expressed give rise to continuous distributions of phenotypic
values.
32. Quantitative Traits
Mendel worked with traits that were all discrete, either/or traits: yellow or green, round or
wrinkled, etc. Different alleles gave clearly distinguishable phenotypes.
However, many traits don’t fall into discrete categories: height, for example, or yield of corn
per acre. These are “quantitative traits”.
The manipulation of quantitative traits has allowed major increases in crop yield during the
past 80 years. This is an important part of why today famine is rare, a product of political
instability rather than a real shortage of food. Until very recently, crop improvement
through quantitative genetics was the most profitable aspect of genetics.
Early in the history of genetics is was argued that quantitative traits worked through a
genetic system quite different from Mendelian genetics. This idea has been disproved, and
the theory of quantitative genetics is based on Mendelian principles.
33. Types of Quantitative Trait
In general, the distribution of quantitative
traits values in a population follows the
normal distribution (also known as
Gaussian distribution or bell curve).
These curves are characterized by the
mean (mid-point) and by the variance
(width). Often standard deviation, the
square root of variance, is used as a
measure of the curve’s width.
1. continuous trait: can take on any value:
height, for example.
2. countable (meristic) can take on
integer values only: number of bristles,
for example.
3. threshold trait: has an underlying
quantitative distribution, but the trait
only appears only if a threshold is
crossed.
34. Punchline and Basic Questions
The basic tenet of quantitative genetics: the
variation seen in quantitative traits is due to a
combination of many genes each contributing a
small amount, plus environmental factors.
Or: phenotype = genetics plus environment.
Basic questions (plus answers):
1. What is the genetic basis of quantitative traits? (they
are caused by normal genes following Mendel’s rules).
2. How can we separate the effects of genetics from the
effects of the environment? (by inbreeding to eliminate
genetic variation).
3. How can we predict and control the outcome of a
cross? (by artificial selection).
35. Quantitative Traits are Caused by
Mendelian Genes
In 1909 Herman Nilsson-Ehle from Sweden did a series
of experiments with kernel color in wheat.
Wheat is a hexaploid, the result of 3 different species
producing a stable hybrid, an allopolyploid. There are
thus 3 similar but slightly different genomes contained
in the wheat genome, called A, B, and D.
Each genome has a single gene that affects kernel color,
and each of these loci has a red allele and a white allele.
We will call the red alleles A, B, and D, and the white
alleles a, b, and d.
Inheritance of these alleles is partially dominant, or
“additive”. The amount of red pigment in the kernel is
proportional to the number of red alleles present, from 0
to 6.
