Download Genetics and Heredity

Genetics and
Heredity
A. Heredity
 The passing of traits from parent to offspring.
A. Heredity
1) Genes on
chromosomes control
the traits that show up
in an organism.
2) The different forms of
a trait that a gene may
have are alleles
(corresponding pairs
of genes located on the
chromosomes).
A. Heredity
3) During meiosis a
pair of
chromosomes
separates and the
alleles move into
separate cells.
4) Each chromosome
now contains one
gene for each trait.
A. Heredity
5) The study of how
traits are
inherited is called
genetics.
B. Gregor Mendel
1) Known as the
father of genetics
– Austrian monk
– Studied mathematics
and science
– Began experimenting
with garden peas in
1856
_ The patterns he
observed became
known as Mendel’s
Laws of Heredity
B. Gregor Mendel
2) Mendel was the first
to use the
mathematics of
probability to
explain heredity
and to trace one
trait for several
generations.
C. Hybrid
 A hybrid receives different
genetic information for a
trait from each parent.
– Dominant allele- covers
up or dominates the
other trait.
– Recessive allele- trait
that seems to disappear.
D. Probability
Probability helps
you predict the
chance that
something will
happen.
E. Punnett Square
A Punnett square can
help you predict what
an offspring will look
like.
– Uppercase letters stand
for dominant alleles.
(Dominant alleles are
“in control”.)
– Lowercase letters stand
for recessive alleles.
F. Genotype
 The genetic makeup of an organism
(internal)
– Homozygous- an organism with two alleles for
one trait that are the same (Ex. Written TT, or tt)
*Mendel would have called it purebred*
– Heterozygous- an organism with two alleles for
one trait that are different (ex. Written Tt)
*Mendel would have called it hybrid*
G. Phenotype
The way an organism looks or behaves as
a result of its genotype (physical)
Punnett Practice
This animated Punnett square shows a cross
between a homozygous brown-eyed father
(BB) and a homozygous blue-eyed mother
(bb).
All of the children
will be
heterozygous for
Brown eyes (Bb).
Punnett Practice
The orange bird has two
dominant A genes.
• We put two A s along the top
of the square.
The blue bird has two recessive
a genes.
• We put two a s down along
the left side of the square.
All the offspring have the genes Aa.
They will all have orange feathers, but will carry a recessive gene for
blue feathers.
This is called the F1 generation.
Punnett Practice
Now suppose that two individuals from the F1
generation become parents.
• The baby birds (offspring) are called the F2
generation.
• You can see how their genes work out.-The offspring are coded in the squares.
• One bird will be orange with two AA genes.
• Two birds will be orange with genes coded
Aa.
• One bird will be blue and will have two
recessive aa genes.
Individual nests of birds may not turn out exactly like this, but if there are
many baby birds, they will work out genetically with the ratios 1:2:1.