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What GENETICS is?
 Some defines says that it is the study of heredity
 But heredity phenomena were of interest to humans long
before biology or genetics existed as the disciplines that
we know today
 Genetics as a set of principles and analytical procedures
did not begin until the 1860s, when Augustinian monk
named Mendel performed a set of experiments that
pointed to the existence of biological elements that we
now call GENES
 The word genetics comes from the word “gene”, and genes
are the focus of the subject
 So we can say that genetics: The study of gene structure
and action and the patterns of inheritance of traits from
parent to offspring.
What is a gene?
A gene is a section of the (DNA) deoxyribonucleic acid
Why study genetics?
There are two basic reasons:
1. Genetics occupies a pivotal position in the entire subject of
biology. Therefore, for any serious student of plant,
animal, or microbial life, an understanding of genetics is
essential.
2. Genetics, like no other scientific discipline, is central to
numerous aspects of human affairs. It touches our
humanity in many different ways. Indeed, genetic issues
seem to surface daily in our lives, and no thinking person
can afford to be ignorant of its discoveries.
The Cell
 A general characteristic of cells is their microscopic size.
 While there are a few exceptions—the marine alga
Acetabularia can be up to 5 centimeters long—a typical
eukaryotic cell is 10 to 100 micrometers.
 Most bacterial cells are only 1 to 10 micrometers in
diameter.
 Hooke observed
compartments.
a
honeycomb
of
tiny,
empty
 He called the compartments in the cork cellulae (Latin,
“small rooms”), and the term has come down to us as cells.
The cell theory includes the following three
principles:
1. All organisms are composed of one or more cells, and the
life processes of metabolism and heredity occur within
these cells.
2. Cells are the smallest living things, the basic units of
organization of all organisms.
3. Cells arise only by division of a previously existing cell.
Before we start, did you know….
 Humans are 99.9% genetically identical – only 0.1% of our
genetic make-up differs.
 Our genes are remarkably similar to those of other life
forms.
 For example, we share 98% of our genes with
chimpanzees, 90% with mice, 85% with zebra fish, 21%
with worms, and 7% with a simple bacterium such as E.
coli.