Download Genetics

Genetics
BACKGROUND
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Genetics is the branch of biology that deals with
heredity and the expression of inherited traits.
 Charles Darwin did not know anything about
how traits (like flower color) where passed-on
from parent to offspring.
 But that did not stop Darwin from studying
change through time of species. (evolution)
Background cont.
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Ironically, Mendel was working on the very mechanism
that would have greatly supported Darwin's theories.
 But what neither one knew about - nor anyone until the
early 20th century (1900's) was the mechanism of
inheritance.
 While we don't know when people first recognized the
existence of heredity, there is evidence that suggests the
successful domestication of animals and cultivation of
plants thousands of years ago.
 8000-1000 B.C.: horses, camels, oxen, dogs.
 5000 B.C.: maize (corn) wheat, rice, date palm.
Background cont.
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Preformation: a theory first put forward in the
17th century (1600's). Stating that sex cells
contain a complete miniature adult called a
homunculus
 This theory was popular well into the 18th
century (1700's).Later scientific discoveries by
Casper Wolff (1733-1794) and others clearly
disproved this ideal.
 During same time: atomic theory and cell theory
were being developed.
Homunculus
CONCEPTS
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What's the center of heredity in a cell?
In eukaryotic organisms it is the nucleus, in
prokaryotes it is the nucleoid region.
What is the genetic material?
In eukaryotes & prokaryotes it is DNA, in viruses
it can be either DNA or RNA.
What do DNA & RNA stand for?
DNA: deoxyribonucleic acid / RNA: ribonucleic
acid.
How is DNA organized to serve as the genetic
material?
DNA, although single-stranded in a few viruses,
is usually a double-stranded molecule organized
as a double helix.
General Animal Cell
Location of genetic
material: DNA
General Bacteria Cell (prokaryote)
In bacteria, since
they don’t have a
nucleus, the DNA is
found in an area
called the nucleoid
region
Concepts cont.
 Contained
within each DNA molecule are
hereditary units called genes, which are
part of larger elements, the chromosomes.
 What is a gene? The functional unit of
heredity.
 A segment of the DNA molecule that
codes for a characteristic/trait.
 There are many genes in a chromosome.
CENTRAL DOGMA OF GENETICS
 Expression
of the stored genetic
information is a complex process.
 DNA  transcription  mRNA 
ribosomes  translation  PROTEIN
 Proteins were 1st thought to be the
genetic material for hereditary traits.
 Later research pointed to nucleic acids
(DNA) Frederick Griffith ~ Medical officer
in the British Ministry of Health.
MOLECULAR STRUCTURE
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DNA is a chemical strand made-up of repeating
nucleotides.
Nucleotides are the building blocks of nucleic acids DNA/RNA.
These units are made-up of 3 parts: a nitrogenous base,
a pentose sugar (5-carbon sugar), and a phosphate
group.
There are 2 kinds of nitrogenous bases: purines &
pyrimidines
In nucleic acids, the purines are ADENINE & GUANINE,
the pyrimidines are CYTOSINE, THYMINE, & URACIL
MOLECULAR STRUCTURE cont.
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These chemicals are arranged into double-stranded
helixes.
 This helix is referred to as chromatin during interphase of
the cell cyce & as chromosomes during mitosis and
meiosis.
 In the double helix, complemetary strands match-up in a
specific way.
 Think of it as a latter that got sawed down the middle.
 When you put it together again, each step connects to a
step on the other side.
 In DNA, it is as follows: A - T and G - C / in RNA T is
replaced by U.
Questions?