Transcript Mendel`s Contributions

What we know?
All forms of life
have their own
DNA
DNA is the unit
of inhertance
DNA blueprint
for our bodies
Know structure
of DNA and how
it replicates
Know how DNA
is distributed
evenly in Mitosis
When a cell is dividing, DNA winds up tightly and forms
chromosomes in the nucleus of the cell.
The genes are contained
within the chromosome.
• During the
1800s most
people believed
that traits were
caused by a
blending of
traits from our
parents.
• Mendel did not
believe this and
set out to find
out how we
inherit our
traits.
DNA is the basis for inheritance….
• What are traits?
• How are traits inherited
Inheritance of Traits through
Sexual Reproduction
• Male and female reproductive cells join to
form the new zygote or embryo. .
Fertilization:
When sperm with half the
genetic information join with
an egg containing half the
genetic information form a
whole new
??? o zygote. '' Zz ???
Unique Individual.
Fig. 3.9b
Important Concepts to take away
from this presentation.
• Who was Mendel and what were his
contributions?
• What is the unit of heredity?
• What is the difference between fertilization
and pollination?
• Know the flower parts and the function of
each part.
Gregor Mendel
• Gregor Johann Mendel was born on July 22, 1822 to
peasant parents in a small farm village in Czechoslovakia.
• As a monk, Mendel used Math and Scientific method to
study inherited characteristics of garden peas.
• Mendel, the first person to trace the characteristics of
successive generations of a living thing,
Mendel Grew Generations and Generations of
Garden Peas to observe inherited characteristics.
Mendel picked common garden pea plants
because
1. they can be grown easily in large
numbers and their reproduction can
be manipulated.
2. Inexpensive and many generations can
be grown in short period of time in
small place
3. Pea plants have both male and female
reproductive organs. As a result, they
can either self-pollinate themselves or
cross-pollinate with another plant.
Mendel observed
seven traits that are
easily recognized and
apparently only occur
in one of two forms:
Two Processes you need to understand:
Pollination
The transfer of pollen (male gamete) to the female
structure of the flower. to reach the egg.
Fertilization:
When sperm with half the genetic information join with
an egg containing half the genetic information form a
whole new
Unique Individual.
What happened to the gene for white flowers?
He did not stop there!
• But took the First Generation (F1) and
crossed them…
In cross-pollinating plants that either produce yellow or
green peas exclusively, Mendel found that the first offspring
generation (f1) always has yellow peas. However, the
following generation (f2) consistently has a 3:1 ratio of
yellow to green.
Mendel came to three important conclusions from these
experimental results:
1. that the inheritance of each trait is determined by
"units" or "factors" (now called genes) that are
passed on to descendents unchanged
2. These units come in different forms called alleles
3. His Second conclusion was the principle of
dominance. Some alleles are dominant over
others.
4. His Third conclusion was the law of segregation.
When the white flower showed up again in the next
generation he knew that the units must separate
independently so they can show up in the next
generation.
(In plants and animals… )
Somatic cells (cells of the body) are diploid.
This means that each cell has two chromosomes
of each type. They are in PAIRS.
Biologists use “2N” to symbolize diploid.
Gamete cells (egg, sperm) are haploid. This
means that each cell has only one of each type
of chromosome.
Biologists use “1N” to symbolize haploid.
DNA is the molecule that transfers hereditary
information from one cell to the next.
This is a model of the double helix shape of DNA.
A karyotype is a picture showing the arrangement
of a full set of chromosomes.
Humans have 46 (or 23 pairs) of chromosomes
A karyotype is a picture showing the
arrangement of a full set of chromosomes.
Humans have
46 (or 23
pairs) of
chromosomes
Why are the chromosomes in pairs?
- One set of chromosomes
from the female parent
- One set of chromosomes
from the male parent
This means that each
individual contains
TWO COPIES of every
gene in their genome!
If an individual is made by the fusing together of a
sperm and an egg cell, how many copies are in the
sperm and the egg cell?? Can there be two??
He wondered what it was that gave
organisms their characteristics.
Why is this flower so different from
the first?
• Most people believed that traits or
characteristics are blends from the parents.
• Mendel did not accept this idea.
• During his childhood he worked as
a gardener and learned quite a lot
about flowering plants.
He decided to work with pea
plants, not only because of his
knowledge of them but also
• .
because
 They were inexpensive
 He could grow lots in a small space and
 He could control which plants pollinated
another
Important Concepts to take away
from this presentation.
• Who was Mendel and what were his
contributions?
• What is the unit of heredity?
• What is the difference between fertilization
and pollination?
• Know the flower parts and the function of
each part.
Pollination
• Transfer of Pollen from male part to female
part of the plant.
Mendel’s Contributions
• Using the garden peas for his subject,
Mendel's studies in "plant hybridization"
proved the existence of paired units of
heredity (now called genes).
• He also established the statistical laws
governing them.
• But his work was so brilliant and
unprecedented at the time it appeared that it
took thirty-four years for the rest of the
scientific community to catch up to it.
• What information should you take
away from this presentation?
Quiz Yourself
• Who was Mendel and what were his
contributions?
• What is the unit of heredity?
• What is the difference between fertilization
and pollination?
• Know the flower parts and the function of
each part.
What is Next?
• We will look at Mendel’s observations to
understand how he came up with his
conclusions.