Download File - Chapter 14: Mendel and the Gene idea

CHAPTER 14:
MENDELIAN GENETICS AND
INHERITANCE
GREGOR MENDEL
• Born July 20, 1822 in
Heinzendorf (Austria)
• As a child, gardened
and kept bees to
entertain himself
• Joined Abbey of St.
Thomas (Brno) in
1843; occupied spare
time with gardening
• Mendel soon
discovered that
crossing different
varieties of pea plants
would produce
characteristic traits of
both varieties in the
offspring. He dubbed
these traits as
“dominant” and
“recessive” in
correspondance to
their appearance
frequency.
The Gene Idea
THE BASIC IDEA
• Mendel concluded
from his studies that
some traits have a
disposition which
favors them over
other traits. These
traits are Dominant. A
dominant trait is
marked by a capital
letter.
RECESSIVE TRAITS
• While the dominant traits (marked in grey
on the previous slide) are more likely to be
displayed than the recessives, if an
organism carries 2 recessive alleles (gene
types) then it cannot display the dominant
(because it does not carry it). Therefore,
an organism with this genotype (xx) would
be considered homozygous recessive.
HETEROZYGOUS TRAITS and
INCOMPLETE DOMINANCE
• Organisms carrying a
dominant and recessive
allele (Xx) are considered
heterozygous (one of
each). An organism in this
situation usually displays
the dominant allele,
except in cases of co- or
incomplete dominance, in
which an organism
displays either both traits
in competition or a
compromise between the
traits.
Applying Mendel’s Ideas
• Mendelian genetics
are the precursor to
modern scientific
projects such as
Mapping the Human
Genome and
determining
predisposition to
disease via family
history.
Mendel’s Studies, applied
• Ever wondered if your going to develop a
disease in your family’s history? Due to
the research of Mendel, this takes a little
simple studying (no expensive testing
necessary, at least initially).
• Ever wonder what color eyes your baby
will have? Due to the work of Mendel, trait
mapping is possible when a spouse’s traits
are known.
Later life and decline
• First publishing his works
in a paper titled
Experiments on Plant
Hybridization, Mendel
was ridiculed by the
scientific community.
When a reading at the
Natural History Society of
Brunn went awry,
Mendel retired from the
public eye, tending his
garden in order to further
his research on his own.
Death and Works
• When Mendel died in
Brno, Austria in 1884
of a Kidney Infection,
the monastery burned
all of his papers, and
it was not until the
1900’s that the
importance of his
discoveries were
realized, and he
became a figure of
the modern scientific
circuit.
THE END