Transcript How is it inherited

Genetics
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Genetics
What is inherited ?
How is it inherited ?
What is the role of chance in heredity ?
Why do valued traits sometimes
disappear then reappear in only
some offspring?
Genetics – the study of heredity – how
genes or traits are passed to generations
What are some examples of traits?
______________
______________
______________
Our genes code for these traits!!!!!
Alleles
•Distinguishable units of inheritance
•Alternative forms of a single gene
Example of traits:
Examples of Alleles
Eye color
Skin color
Height
Hair texture
Brown or blue
Albino or pigmented
Tall or short
Curly or straight
What is inherited
A Trait!!
Genotype
– units of inheritance
– genetic traits
Phenotype
– observable traits
– What you can see,
hear, taste, smell,
and touch
– “Physical”
Characteristics
Gregor Mendel (1822-1884)
Augustinian monk
Expert plant
breeder
Experiments with
garden peas
Father of Genetics
Mendel studied plants with different
traits. One factor or trait he observed
was tall plants and short plants.
He used pure (true breeding) plants.
He crossed pollinated these plants.
He crossed true breeding tall plants
(TT) with true breeding short (tt)
plants.
Found that all plants in the F1
generation were tall. (Tt)
P (Parental) Generation
F 1 (Filial ) Generation
F 2 Generation
Then Mendel crossed the plants with the Tt
genotype and it produced 75% tall and 25%
short.
From this he formed a law of dominance, because
he knew that one allele was dominant over the
other.
In this case which is dominant, short or tall?
Which is recessive?
IN THE END……
-He concluded that traits are
inherited through the passing
of factors from parents to
offspring.
-He created 3 Laws
1st Law – Law of Dominance – Some
alleles will be shown while some other
alleles will not be shown. In other words
some alleles are shown, while others are
hidden.
- The trait that is shown is considered
dominant because it masked (dominated)
over the other traits.
Trait Characteristics
Dominant
– “‘Stronger’” trait
– The trait you see more
often, or covers
– Expressed by a capital
letter
Y
Recessive
– “‘Weaker’” trait
– The trait you see less
often, or being
masked/covered
– Expressed by a lower
case letter
y
Homo- means same, Hetero – means different
Homozygous is two of the same allele
Heterozygous is two different allele
What would be an example of Homozygous
Dominant? ______
Heterozygous Dominant? _____ ___
Homozygous Recessive? ________
2nd Law – Law of Segregation –
States that during meiosis two alleles
will separate.
Recall Meiosis – you create gametes.
Law of Segregation ensures that
each gamete will have one allele from
the allele pair.
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Law of Independent Assortment – States that
alleles distribute randomly or independently
during meiosis.
YyRr – gametes ____YR______
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_______Yr________
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_______yR________
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_______yr________
Monohybrids are used to view the
outcomes in offspring examining only one
trait
A punnett square is a visual aid that is
used to view traits.
Punnett
Square
The probability is the chance of a certain
outcome.
Example: What is the chance of either having a
girl or boy?
Each outcome will be independent of the
other.
Dihybrids
Looks at the
possibilities of
two
Different traits.