Download Mendel`s Investigations

Mendel’s Investigations
Mendelian Genetics
Gregor Mendel
• Lived in a monastery
in Vienna during the
1800’s (monk)
• Worked primarily
with pea plants
• His work changed
biology forever with
respect to Genetics
• “Father of Genetics”
Mendel’s Experiment
A. Used pure bred pea
plants (same alleles
from each parent)
B. Most noted for his use
of math to make
conclusions
Experiment and Observations
P1 Pure Tall x Pure Short
↓
F1 Hybrid Tall
↓
Hybrid Tall x Hybrid Tall
↓
F2 ¾ Tall: ¼ Short
Mendel controlled the
fertilization of his pea plants
by removing the male parts,
or stamens.
He then fertilized the female
part, or pistil, with pollen
from a different pea plant.
Mendel drew three important
conclusions.
– Traits are inherited as discrete units. DO
NOT BLEND
– Organisms inherit two copies of each gene,
one from each parent.
– The two copies segregate during gamete
formation.
Alleles
• Alleles are passed from parent to offspring
• One from “mom” and one from “dad”.
• Dominant alleles are the expressed or
observed traits ( brown eyes )
• Recessive alleles are the disappearing or
non-expressed traits (blue eyes)
– Each parent
donates one allele
for every gene.
– Homozygous
describes two
alleles that are the
same at a specific
location.
– Heterozygous
describes two
alleles that are
different at a
specific location.
Phenotype vs Genotype
• Phenotype is the way an organism appears
– Brown hair with blue eyes, tall, thin, etc.
• Genotype is the genetic combination for
the organism. (BB, Bb, bb)
– Heterozygous –
Example: allele from
mom codes for blue
eyes and the allele from
dad codes for brown
eyes.
– Homozygous –Example:
both alleles code for
blue eyes
So, the genotype for a
heterozygous brown
eyed offspring would be
Bb for example.
Let’s Practice
Tell whether the following are heterozygous or
homozygous:
Tt
TT
Hh
Bb
bb
Gg
gg
GG
ff
Mendel’s Laws
1. Law of Segregation
Genes separate when gametes form- sex cells get one
complete set of chromosomes
2.Law of Dominance
When two alleles in a gene pair are different, one allele can
control the trait while the other can be hidden
3.Law of Independent Assortment
Gene pairs separate randomly and independent of each
other during meiosis
*Important when dealing with the inheritance of more
than one trait.*
Punnett Square
Used to
help solve
genetics
problems