Download Mendel noted

Genetics
A Monk and his Methods
Gregor Mendel
• In 1865 he
published his
observations of
pea plants.
• His work went
unnoticed for
several decades,
before the
realization of his
genius set in.
What did he do?
• He worked with Pea plants.
• He noted several variations in the
characteristics of his plants
• Variations such as
– Flower color (Purple or White)
– Seed Texture (Round or Wrinkled)
Careful Observations
• Mendel did several experiments
where he cross-bred (mated) plants
of various characteristics.
• He took careful notes and recorded
all of his observations
• Mendel made some astounding
conclusions
The Conclusions
• Mendel noted that some traits
seemed to prevail over others…..
• An example:
– Mendel cross bred a pea plant with
white flowers and a pea plant with
purple flowers. The majority of plants
produced had purple flowers, few had
white flowers.
Why is this important?
• These
observations lead
to the conclusion
that certain traits
are DOMINANT
over other traits.
• The traits that are
not DOMINANT
are called
RECESSIVE.
Patterns of Inheritance
• Mendel noted
these patterns of
inheritance among
pea plants.
• Today we can
apply these ideas
to human
inheritance.
This family inherited the “Cat-face gene”.
Let’s Take a Closer Look
• What is actually happening when
traits are inherited????
• Remember traits (genes) are carried
on CHROMOSOMES.
• You have TWO copies of EACH
chromosome.
• This means you have TWO copies
of EACH gene.
Your Genes
• You received one half of your genes
from your mother and the other half
from your father.
• These genes complement each
other and express themselves as a
PHENOTYPE.
• PHENOTYPE- physical
characteristic of an organism (What
you see)
Phenotype Vs. Genotype
• Your phenotype (what you see) may
be different than your GENOTYPE
• GENOTYPE- the combination of
ALLELEs that an organism has for a
trait
• ALLELE- a variation of a trait
Let’s Check it Out
Dominant Vs Recessive
• Some alleles are
Dominant and
some are
Recessive
Homozygous and
Heterozygous
• Genotypes can be Heterozygous or
Homozygous.
• A Heterozygous genotype has one
of each allele. (Aa)
• A Homozygous genotype only has
one type of allele (aa or AA)
Recessive
• Only those
individuals who
have the
homozygous
recessive
genotype will have
the recessive
phenotype.
References
• http://www.jic.bbsrc.ac.uk/germplas/pisum/zgs4f
1.gif
• http://www.laskerfoundation.org/rprimers/gnn/tim
eline/images/first_second_generation.gif
• http://www3.sympatico.ca/the_adams_family/catfamily.png
• http://www.awa.com/norton/figures/fig1307.gif
• http://library.thinkquest.org/C0118084/Gene/Gen
etic_variation/dominant_recessive_files/homolog
ous_chromosomes.gif
• http://site.voila.fr/bioafb/loismend/genelapi.GIF
• http://www.glasgowzoo.co.uk/images/warmblood
ed/wal2.jpg