Transcript Mendelian Genetics

Mendelian Genetics
11.1 Gregor Mendel
Who was Gregor Mendel?
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Austrian monk
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Also “high school”
science/math teacher
One of the first to use
statistics to analyze results
Studied garden peas
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Attempted to refute
Blended Inheritance belief
What was Mendel’s experimental design?
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Create true-breed strains
Selected for phenotypic traits
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Genotype vs. phenotype
Crossed true-breed plants
Kept track of offspring
phenotypes
What is Mendel’s law of segregation?
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Traits segregate
independently
Today we now know
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What alleles are
What a locus is
How genotype
influences phenotype
Why traits segregate
independently
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Remember
independent
assortment in meiosis
I?
What is the difference between dominant and
recessive?
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Dominant is
phenotypically
expressed
To be expressed,
a recessive must
be paired with
________
How can I describe an individual’s genotype?
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Use capital letter for ____________ allele
Use small case letter for _________ allele
Homozygous dominant____________
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Homozygous recessive_____________
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Heterozygote_________________
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If a disease, then is a CARRIER
What’s the relationship of genotype to phenotype?
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Genotype _________ phenotype
If T = tall and t = short, then
TT is a _________ plant
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Tt is a _________ plant
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Tt is a _________ plant
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Mendelian Genetics
11.2 Mendel’s experiments
So can you tell me more about Mendel’s monohybrid
cross?
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F1 and F2
generations
showed
something
interesting
Ratio: _______
Punnett square
What were the F2 offspring like?
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Ratio:
What did Mendel think about this ratio?
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He determined
traits (AKA alleles)
are either
________ or
_______
What happened when
Mendel followed two traits?
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Dihybrid cross
Ratio of cross of two
heterozygotes is:
Thus, the traits assort
___________ of each
other when making
gametes
Mendelian Genetics
11.3 Solving genetics problems
How do we know a trait is dominant (or recessive) in
humans?
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Can’t do breeding experiments like Mendel!
Pedigrees
Carriers
So what do I do with all this information?
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Solve genetics problems!
Use the five steps to solving a genetics problem…
What are the five steps to solving a genetics
problem?
1.
2.
3.
4.
5.
Code the alleles and identify which is
dominant/recessive
Determine parental (or given) genotypes
Determine parental (or given) gametes
Draw Punnett square
Re-read problem to be sure you are answering the
question correctly.
Let’s try it!
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In humans, being able to roll your tongue is dominant (R).
If a heterozygous woman marries a man who can’t roll his
tongue, what are the chances a child of theirs also won’t
be able to roll its tongue?
First step…
Step 1
Code the alleles and identify which is dominant/recessive
In humans, being able to
roll your tongue is
dominant (R). If a
heterozygous woman
marries a man who can’t
roll his tongue, what are
the chances a child of
theirs also won’t be able to
roll its tongue?
Step 2
Determine parental (or given) genotypes
In humans, being able to
roll your tongue is
dominant (R). If a
heterozygous woman
marries a man who can’t
roll his tongue, what are
the chances a child of
theirs also won’t be able to
roll its tongue?
Step 3
Determine parental (or given) gametes
In humans, being able to
roll your tongue is
dominant (R). If a
heterozygous woman
marries a man who can’t
roll his tongue, what are
the chances a child of
theirs also won’t be able to
roll its tongue?
Step 4
Draw Punnett square
In humans, being able to
roll your tongue is
dominant (R). If a
heterozygous woman
marries a man who can’t
roll his tongue, what are
the chances a child of
theirs also won’t be able to
roll its tongue?
Step 5
Re-read problem to be sure you are answering the question
correctly.
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In humans, being able to roll your tongue is dominant
(R). If a heterozygous woman marries a man who can’t
roll his tongue, what are the chances a child of theirs
also won’t be able to roll its tongue?
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Answer:
Now you try!
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If a homozygous tongue roller and a non-tongue roller
marry, what are the chances their child will be able to roll
its tongue?
USE THE 5 STEPS!!!!
Here’s the solution:
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If a homozygous tongue roller and a non-tongue roller marry, what are
the chances their child will be able to roll its tongue?
Now practice with the genetics problems…
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You will be expected to know and use the 5 steps on your
exam!
Mendelian Genetics
11.4 Human genetic disorders
What are autosomal recessive disorders?
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Autosome = ________
Examples
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Tay-Sachs disease
Cystic fibrosis
Phenylketonuria
What are autosomal dominant disorders?
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Only need one
copy of the allele
to have the disease
Examples
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Neurofibromatosis
Huntington’s
disease
Achondroplasia
Mendelian Genetics
11.5 Beyond Mendelian genetics
Is complete dominance the only kind of dominance?
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No!
Incomplete dominance
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Dominant allele cannot fully
mask the recessive allele
Sickle cell anemia
Curly vs. straight hair
Is complete dominance the only kind of dominance?
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Codominance
Multiple alleles
Blood types
demonstrates both
What is polygenic inheritance?
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More than one gene affects phenotype
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Skin color in humans
Human height
Eye color
Seed color in wheat
What is epistasis?
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One gene affects many traits
Marfan Syndrome
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Defective collagen gene
Affects tendons, ligaments, bone, heart tissue, etc.
Can environment affect phenotype?
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Yes!
Himalayan rabbits
Epigenetics