Transcript The Work of Gregor Mendel

The Work of Gregor Mendel
Think About It!
What is an inheritance?
– It is something we each receive from our
parents – a contribution that determines blood
type, hair color, and much more.
Every living thing has a set of
characteristics that are inherited from its
parent or parents.
Heredity is the delivery of characteristics
from parent to offspring.
Think About It!
Genetics
scientific
heredity.
is
the
study of
– It is the key to
understanding
what
makes each organism
unique.
– Was founded by an
Austrian monk named
Gregor Mendel.
Experiments of Gregor Mendel
Mendel
– Performed his work in
a monastery garden.
– Carried out his work
with ordinary garden
peas, because peas
are small and easy to
grow.
These peas
represented a
“model system”
Experiments of Gregor Mendel
Mendel was able to
carry out experiments
that would have been
impossible or taken
years to do.
Experiments of Gregor Mendel
Studied seven different pea plant traits. Each
trait had two contrasting characteristics.
Pea Plant Traits, Contd.
The Role of Fertilization
Fertilization is a process that produces a new
cell when male and female reproductive cells
join.
– Male reproductive cells are called sperm.
– Female reproductive cells are called eggs.
The Role of Fertilization
In
seed
plants,
fertilization
occurs
through self- or crosspollination.
Pollination
transfers
pollen (sperm) from
the male reproductive
organ to the female
reproductive
organ
(stigma).
The Role of Fertilization
In self-pollination, sperm
cells fertilize eggs cells
from within the same
flower.
– Peas flowers are selfpollinating, because of
this they
Produce a seed
that inherits all of
the characteristics
(traits)
of
its
parents.
Are “true breeding”
because
they
produce offspring
with identical traits.
The Role of Fertilization
In cross-pollination, pollen from the anther of a
flower goes to the stigma of a different flower.
– Mendel utilized this process to learn more about
traits.
A trait is a specific characteristic of an individual that may
vary from one individual to another.
The Role of Fertilization
(Cross-Pollination, Continued)
– First, Mendel prevented self-pollination by
removing the male part of a flower.
– Then, Mendel dusted the female part of the
flower with pollen from a different plant.
– These plants produced a seed that inherited
different characteristics of its parent.
The offspring of these plants are called
hybrids.
Mendel’s Conclusions
An individuals
characteristics are
determined by genes
that are passed from
parent to offspring.
– Genes are
segments of DNA
that determine a
trait.
Mendel’s Conclusions
– Each individual has
two factors for each
trait, one from each
parent.
– Alleles are forms of a
gene for a specific
trait.
They are a single
member of a pair of
genes, responsible for a
single trait.
Mendel’s Conclusions
Some alleles are dominant and others are
recessive.
– This is called the principle of dominance.
Mendel’s Conclusions
An organism with one dominant allele for a
particular trait will exhibit the trait.
– A dominant allele is represented by a capital
letter.
An organism with a recessive allele for a
particular trait will exhibit the trait when the
dominant allele is not present.
– A recessive allele is represented by a
lowercase letter.
Segregation
Mendel
that
assumed
– A dominant allele
masks a recessive
allele in an F1
generation.
Segregation
In F2 generations the
recessive
trait
reappeared indicating
that the dominant and
recessive alleles had
separated.
- Segregation explains
how this occurred.
Segregation
Is the separation of alleles
during gamete formation.
– Gametes are sex cells
– When
gametes
are
formed,
allele
pairs
separate leaving each
cell with a single allele
for each trait.
– When fertilization occurs
alleles randomly unite to
form a gene for a
specific trait
Practice Quiz for Mendel's Genetics
http://anthro.palomar.edu/mendel/quizzes/
mendqui1.htm