Download The Genetics of Inheritance

The Genetics of Inheritance
Why do we look the way we do?
• All organisms are made of cells.
• Inside of these cells, a chemical called
DNA contains the “instructions” that
control the way we look.
DNA
DNA: the instruction manual
• The segments in the DNA that carry the
“instructions” are called GENES.
• Every individual has two of every gene.
• There is more than
one version of
each gene. The
different versions
are called alleles.
Dominant & Recessive Human Traits
Earlobes:
Free
# Students w/
free lobes
Widow’s peak:
Attached
# Students w/
attached lobes
# Students w/ a
widow’s peak
# Students w/out a
Widow’s peak
One allele is dominant and the other allele is recessive.
The dominant allele covers the expression of the recessive allele.
Genotype & Phenotype
•
The observable traits of an organism is called the phenotype.
# Students w/ free lobes
# Students w/ attached lobes
• The genotype is the combination of all of the different alleles
that make up an individual
Incomplete Dominant Traits
Blood types:
Flower color:
In incomplete dominance, the dominant allele does
not cover up the expression of the recessive allele.
Why do we look like our parents?
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Aa
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Punnett Squares
• A diagram that is used to predict the
genotype and phenotype of the
offspring based on the genotype of the
parents.
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It’s a probability
problem!
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p
P
Pp
Pp
p
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Pp
½ purple pea plants; ½ white pea plants
Punnett Squares
1. What is the probability that this couple will
have a child with brown eyes?
2. What is the probability that
this couple will have 3
children with brown eyes?
Bb
Bb
BB=
Bb=
bb=
More Punnett Squares
There are 10 guinea pigs in a litter. Five of the guinea pigs have long hair, and five
have short hair. Long hair is dominant and short hair is recessive. What are the
genotypes of the parents?
Genotype
for long hair:
Genotype
for short hair:
Applications of math in genetics
Selective breeding—The selection of
certain seeds or animals for
reproduction so that the next
generation has the same desirable
traits.