Transcript heredity section 1

Chapter 11 – Section 1
Heredity
Open your book to page 306
Please take notes on your graphic organizer.
Notes will be on the yellow slides.
Heredity
 Who do you look like? Mom, dad, grandma?
You could have your dad’s eyes and your
mom’s cheekbones.
 As an organism, we are nothing more than a
collection of traits. These traits are passed
down from our parents.
 Heredity – the passing of traits from parent to
offspring.
Genetics
 Genetics has to do with our chromosomes and
the genes that exist on our chromosomes.
 Because you come from two parents (each
provides you with 23 chromosomes for a total of
46), each parent will provide one half of your
genes for any trait. That is called an "allele.“
 So you have two alleles for each gene, one from
each parent.
 Allele – the different forms of a trait that a
gene may have
 Genetics – the study of how traits are
inherited through the interactions of alleles
Gregor Mendel
Father of Genetics
 Gregor Mendel was an Austrian monk who
studied math and science, but became a
gardener in a monastery.
 In 1856, Mendel experimented with pea pod
plants because he was curious about the
connection between the color of a pea flower
and the type of seed that same plant
produced.
 Mendel worked over eight years with pea
plants before he was able to share his results
with other scientists.
 Mendel was the first to trace one trait through
several generations.
 He was the first to use probability to explain
heredity. The use of math in science was not
widely accepted in this time period.
 In 1900, three other scientists solidified Mendel’s
work as they performed their own experiments
and came up with the same conclusion.
 Since then, Mendel is known as the Father of
Genetics
 Each time Mendel performed an experiment in
his garden, he crossed two plants with different
expressions of the trait and found that the new
plants all looked like one of the two parents.
 He started out experimenting with tall and short
pea pod plants.
 Mendel took pollen from tall
plant and hand pollinated this
pollen onto a short plant. He
wanted to know what the
offspring would look like…Tall,
short, or would they be a
medium height.
 The first generation of plants
(the offspring) were tall.
 He performed the experiment
again with the offspring and got
three tall plants and one short
plant.
 Mendel called the “Tall” trait the dominant
allele, because it dominated, or covered
up the “short” trait.
 Mendel called the “short” trait the
recessive allele because the trait seemed
to disappear.
 Dominate traits are always represented
with a capital letter. So a tall plant would
be represented with a capital T.
=T
 Recessive traits are always represented
with a lowercase letter. So a short plant
would be represented with a small t.
=t
 Since Mendel’s death, other scientists
have performed many of Mendel’s
experiments coming up with the same
results.
Let’s Take Some Notes…
Heredity – the passing of traits from parent to
offspring.
You get 23 chromosomes from your mom and
23 from your dad.
Each chromosome contains genes, and on each
gene are two alleles. Alleles contain your
traits.
Let’s Take Some Notes…
Alleles - the different forms of a trait that a gene
may have – they determine the traits you
receive
Mendel – called the Father of Genetics
He worked with pea plants to investigate how
traits were passed from one plant to another

Let’s Take Some Notes…
Dominate Alleles – Covers up and dominates
the other trait (always a capital letter)
Recessive Alleles – the trait that seems to
disappear (always a lower case letter)

Probability
 Probability helps you to predict the
chances of something happening.
 Mendel used probability to make
predictions of his pea plants.
 In order to make accurate predictions,
Mendel used over 30,000 plants over an
eight-year period to gather enough data to
draw a conclusion.
Punnett Squares
 Punnett squares are used to predict what
traits an offspring of two parents may look
like.
 Letters represent the dominant and recessive
alleles. An uppercase letter represents the
dominant allele. A lowercase letter
represents the recessive allele.
Making a Punnett Square
 Each parent will have two
Mom goes on top
T
alleles for each trait.
 The two alleles for your mom
would run across the top of
the square, and dad’s traits
would run along the side.
 Let’s say mom carries two
dominant traits for tall (T)
and dad carries two
recessive traits for short (t).
t
t
T
Mom is top, Dad is down the
side!
 Now we just fill in the
square.
 Follow the white lines
first for the top two
squares, then follow the
green lines to get the two
bottom squares
 Since T is dominate for
being tall, all four
offspring will be tall.
 The dominate T covers
up the recessive t allele.
T
T
Tt
Tt
t
t
Tt
Tt
Let’s practice again..
Mom goes on top
 Mom is dominate for
brown eyes (B)
 Dad is recessive for
blue eyes (b)
 Notice I use the same
letter for the alleles.
The only difference is
one is capital and the
other is lowercase
B
b
b
B
Let’s practice again..
Mom goes on top
 Mom is dominate for red
feathers (A)
 Dad is recessive for
blue feathers (a)
 What will there four
offspring look like?
 What percent chance do
we have that the kids
will have red feathers?
A
a
a
A
A
Let’s practice again…
 Mom carries a dominant




trait for curly hair (C) AND
a recessive trait for straight
hair (c).
Dad carries two recessive
traits for straight hair (c).
What will their offspring
look like?
What percentage will have
curly hair?
What percentage will have
straight hair?
Mom goes on top
C
c
c
c
 Mom is recessive for




brown fur (b)
Dad is dominant for gray
fur (B)
Notice Dad is on top of
the square.
It doesn’t really matter
which parent goes on
top and which goes on
the side. It will work out
the same.
For this class, we will
always put the mother
on top
Dad is on top
Genotype
 The two letter code for each
T
T
t
Tt
Tt
t
Tt
Tt
offspring is called a
genotype.
 For example, Tt is the
genotype for all four
offspring.
This is a
genotype
Phenotype
 The description for each two
T
T
t
Tt
Tt
t
Tt
Tt
letter code for each offspring
is called a phenotype.
 For example, if I were to
describe each offspring I
would say that all of the
offspring will be tall.
 Describing an offspring as
being tall is stating its
phenotype.
Let’s put it together!
Mom goes on top
 Mom carries two
recessive alleles for
blonde hair (b).
 Dad carries a dominate
allele for black hair (B)
and a recessive allele
for blonde hair (b).
 What percentage of
their offspring will have
blonde hair?
 What percentage of
their offspring will have
black hair?
b
B
b
b
 There is a 50% chance
the babies will have
blonde hair and a 50%
chance the babies will
have black hair.
Mom goes on top
b
b
B
Bb
Bb
b
b b
b b
 What are the possible
genotypes?
Bb, bb
 What are the possible
phenotypes?
Black hair, blonde hair
Let’s Take Some Notes…
 Punnett Squares
 Punnett squares are used to predict
what traits an offspring of two parents may
look like.
 Letters represent the dominant and
recessive alleles. An uppercase letter
represents the dominate allele. A
lowercase letter represents the recessive
allele.

Let’s Take Some Notes…
 The letters form a code of the genotype,
or the genetic makeup of an organism.
 Phenotype – the way an organism looks
and behaves as a result of its phenotype
(the way an organism looks)

Homozygous
 When the two letter code (the genotype) is
the same, we say that the pair is
homozygous.
 “Homo” means the same
 Examples – BB, bb
 It doesn’t matter if the code is two
dominant alleles (BB) or two recessive
alleles (bb) as long as they are the same.
Purebred
 A purebred is the same thing as a
homozygous pair.
 For example – if you have a black lab and
you breed the dog with another black lab, the
dog would be a purebred because both
parents have the same alleles.
Heterozygous
 When the two letter code (the genotype) is
different, we say that the pair is
heterozygous.
 “Hetero” means different
 Examples – Bb
Hybrid
 A hybrid is the same thing as a heterozygous
pair.
 For example – if you have a poodle and
breed it with a golden retriever, the dog would
be a mix of the two. The alleles from each
parent are different.
Hybrid
 You may have heard of hybrid cars.
 These cars run on both gasoline AND a
battery.
 They are called hybrids because they run
on both.
 One could assume that an all gasoline car
could be called a purebred (this is a joke
of course!)
Let’s Take Some Notes…
Homozygous – an organism that has two alleles
that are the same (BB or bb)
Heterozygous – an organism that has two different
alleles for a trait (Bb)
Hybrids – when an organism receives different
alleles from each parent (Example - Bb)
Purebred - An organism that always produces the
same traits generation after generation. (Example –
BB or bb)