Download HEREDITY - Klahowya Secondary School

HEREDITY
Chapter 4
Why do we look like we do?
1. Describe your understanding of where
genes are located and how they are
passed on to offspring.
2. Explain your understanding of DNA, its
base pairs and how it replicates.
3. Demonstrate your understanding
through various genetic problems.
Opening Tasks
3/4/08
Write down two facts you know about genetics.
3/5/08
Which scientist led us to understanding genetics?
Where are your genes located?
3/6/08
What are dominant and recessive traits?
3/7/08
What are phenotype and genotypes?
3/10/08
We use a _________ __________ to figure out offspring.
Gregor Mendel 1822-1884 Austrian Monk
PRINCIPLES OF HEREDITY
 Mendel’s research
led to our
understanding of
genetics.
• The genetic code
DNA, determines all
our traits inherited
from our parents.
• These traits are passed on by
genes which are located on the
chromatids in the nucleus.
Mendel’s Experiment
 P generation = parents
 F1 generation are the offspring of
the parents (kids)
 F2 generation are the offspring of
the F1 generation
 Trait is a characteristic passed on to
the offspring like height.
 Traits are controlled by the alleles
inherited from the parents
 Alleles are different forms of a gene,
for example the gene for height has
2 alleles – tall and short.
Inheritance Patterns
Genes
Dominant
traits that are strongest
y show up & can hide other traits
Recessive
traits that are weak
they can be hidden by dominant traits
Genotypes
 Show the combination of genes
that are specific for all traits.
Dominant Recessive
traits -capital traits 
letters, TT.
One letter
from each
parent.
symbolized
by lower
case
letters, tt.
Phenotypes
Phenotypes
In each pair
of genes:
show your
physical
 one comes
characteristic: from the
Height
mother
Eye
the other
Hair color
comes from
Skin color.
the father.
Punnett Square
Used to
help solve
genetics
problems
Punnett Squares
 These can be used to show the
probability of specific traits showing
up in the offspring. For Example, sex
of the child

X
X

X

Y
 XX = mother; XY = father genotyoes,
now bring the letter over the box into
the boxes under it.
Practice
 Write mom XX; dad XY
 Now draw a square like the last slide
and place mom’s traits over the top 2
boxes and dad’s traits next to the boxes
on the side.
 Start with mom and the first X, bring it
down & write it into each box it’s over. Do
the same for the second X.
 Repeat this for dad’s traits bringing
each trait across into the boxes it’s next
to.
 Let’s do some others.
Cell division of the sex cells that
form gametes.
Parent cell has 23 pairs
of chromosomes
The chromosomes duplicate
in the first stage
Chromosomes duplicate
giving 46 pairs
Cell divides into 2
cells with half the
number of the
previous cell. Each
has the original
number. 23 pairs
After the final division 4 gamete cells are formed with ½ the number of
chromosomes as the parent. Gametes are the egg cells in females and the
sperm cells in males. Fertilization of the egg and sperm form a zygote.
The father determines
the sex of the child
because he passes on
the Y chromosome.
Remember mom is XX
and dad is XY, therefore
Mom can only pass on
the X.
These traits can be passed
on by mom only. The reason
for this is only the X
chromosome carries traits.
Baldness, colorblindness &
hemophilia are examples of
these traits.
Research a genetic disorder and make a 2 sided
informational brochure on the particular
disorder you’ve chosen. This should include the
following:
 Description of the disorder
 How it is passed on, from mom or dad?
 What are the limitations for the person
affected by the disorder?
 What is the life expectance for this person?
 Include a picture if possible.
Complete the Missing
Children Genetics Mystery.
You will use information
given to you about six
children to try and match
them up with the correct
parents using what you’ve
learned about genetics in
this chapter.
Questions pg.116 #1-4
Questions pg. 120 #1-4
Check Your Knowledge pg. 132 #1-13
Make Connections pg. 133 #1
Face Lab – you need to do this with a partner.
You also need paper and pencil.