Chapter 10 Section 1 Mendels Experiment In the mid 19 th century a monk named Mendel studied how traits are passed from one generation to another Experimented on garden peas green pea plants reproduce sexually produce gametes ID: 380967
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Slide1
Mendel’s Laws of Heredity
Chapter 10 Section 1Slide2
Mendel’s Experiment
In the mid 19
th
century, a monk named Mendel studied how traits are passed from one generation to another.
Experimented on
garden peas
.
green pea plants reproduce sexually (produce gametes)
fertilization
is observable when the male
gamete
meets the female gamete to produce a
zygote
. In this case, Mendel focussed on
pollination
.
green pea plants contain
both male and female gametes
and are therefore capable of
self-pollination
. Mendel was able
to take gametes from different
plants and experiment on the
effects of cross-pollination.Slide3
Mendel’s Monohybrid Crosses
Mendel cross-pollinated with one tall and one short pea plant.
Result:
-
Hybrid offspring
(coming from parent’s of differing traits)
-First generation of offspring were all as tall as the tall parent plant, as if the shorter parent plant had never existed!
Mendel then allowed the first generation offspring to self-pollinate.Result:-75% of 2nd generation plants were as tall as the original tall parent plant.-25% of the 2nd generation plants were as short as the original short parent plant. The trait had reappeared!Slide4
Mendel did similar monohybrid crosses with 7 different traits from the pea family.
He noticed that one trait disappeared in the first generation and reappeared, unchanged, in the second generation.Slide5
Mendelian Genetics Vocabulary
Character
: a heritable feature, such as flower color
Trait
: a variant of a character, such as purple
or white
flowers
P generation: The true-breeding parents F1 generation: the hybrid offspring of the P generation
F
2
generation
: results when F
1
individuals self-pollinateSlide6
Alleles
A gene is expressed in 2 forms in each organism capable of meiosis. These 2 forms are called alleles.
In Mendel’s experiment,
each plant had 2 alleles
for height, the tall allele
being dominant (observable)
and the short allele being
Recessive (non-observable).Slide7
The Law of Segregation
States that each individual has 2 alleles (2 forms) of each gene.
When gametes are produced, each gamete receives one of these alleles.
During fertilization, these gametes randomly pair up. There are 4 different ways these alleles can pair up.Slide8
Phenotypes and Genotypes
Phenotype
: An organism’s physical appearance
Genotype
: An organism’s genetic makeup
Mendel noticed that two plants could have the same phenotype but have different genotypes. How is this possible?
An organism that is
heterozygous for a particular gene has a pair of alleles that are different for that gene - Example: Tt, tTAn organism that is homozygous for a particular geneHas a pair of identical alleles for that gene
Exhibits
true-breeding
Example: TT,
ttSlide9