Transcript Mendel`s Law of Genetics

Mendel’s Law of Genetics
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http://www.brainpop.com/health/geneticsgro
wthanddevelopment/heredity/preview.weml
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In 1856, Gregor Mendel was the first to trace one
trait through several generations.
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He was an Austrian monk. He did a number of
experiments on inheritance in pea plants. He did
not know about genes and chromosomes: what
he called “factors” we now call genes. Mendel
did not know about cell division so he had not
seen diagrams or slides of mitosis and meiosis.
 It
was this study of passing
traits from one pea plant to
the next that lead us to a
new branch of science
called genetics. (heredity)
Heredity
The
passing of traits from
parents to offspring on
chromosomes.
 Genes
are carried from parents
to offspring on chromosomes
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The pea plant experiment involved
mathematical problems that showed how
often a trait showed up in a generation.
Mendel gathered that information and
calculated the probability of a trait showing
up in each generation.
Probability
 The
mathematical chance
that something will happen
Mendel’s
laws of genetics:
 The
Law of Dominance
 The
Law of Segregation
 The
Law of Independent
Assortment
Law of Dominance
 States
that when an organism has
two different alleles for a trait, the
allele that is expressed,
overshadowing the expression of
the other allele is said to be
dominant. The gene whose
expression is overshadowed is said
to be recessive.
Law of Segregation
 States
that the alleles for a
trait separate when gametes
(egg and sperm) are formed.
These alleles pairs are then
united at fertilization.
Law of Independent Assortment
States the alleles for
different traits are
distributed to sex
cells independently
of one another.
 Applications
of Mendel’s Laws
provide opportunities for
treatment and prevention of
genetic disorders.
 Mendel
took plants that always
produced the same characteristics
in every generation (true breeding)
and cross pollinated them with a
different kind of true breeding
plant. Allowing the offspring to
have either dominant or recessive
alleles.
Dominant
 A trait
that always shows up
in the organism when the
allele is present.
Recessive
 Are
traits that are masked
when the dominant allele is
present. They can only
appear when both alleles
are recessive.
True breeding
Always
produce the
same characteristics in
every generation. A
pure breed.
Cross pollination
 To
allow plants of different
alleles to fertilize each other.
 Example: mixing a red allele
plant with a white allele plant
will produce a plant with pink
flowers.
The offspring from this type of breeding
is called hybrid
 We also refer to them as being
Heterozygous.
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 Heterozygous-
having
different alleles.
 Homozygous- having identical
or the same alleles
Self pollinating
 To
allow plants of the same
allele traits to fertilize
themselves.
 If
humans did this we would
call it inbreeding.