HEREDITY
Why do we look like we do?
Learning Targets
 Describe how evolution lead to the diversity of species on





earth today.
Explain the function of chromosomes, where they are
located and what information they carry.
Explain the process of mitosis and why the offspring of
sexual reproduction have more diverse characteristics that
asexual reproduction.
Understand that genes are passed on independently of each
other trait.
Be able to predict the outcome of genetic crosses .
Explain why genetic variation is important to survival of a
species.
Read pgs. 110 – 117; Ch.6 Friday 4/23
Vocabulary Definitions of key terms pgs. 110
Questions pg. 115
Read pgs. 118-123
Questions pg. 123
Questions pg. 130
Read pg. 131-137 & 144 - 155
Activities
Class survey
Punnett Squares
Corn toss
Dragon activity
Opening Tasks
4/5/10
How do the nitrogen bases pair up to code for protein.
4/6/10
What is your definition of genetics?
4/7/10
Which scientist led us to understanding genetics?
Where are your genes located?
4/8/10
What are dominant and recessive traits?
4/9/10
What are phenotype and genotypes?
April 6, 2010
 ?? of the day
 How do the nitrogen bases pair up to code
for protein?
 Go over DNA/Genes Worksheet
 Read Pages 110-117
 Vocabulary due Thursday, key terms page 110
 Pre – activity worksheet
 Begin Notes
April 7, 2010
 ?? Of the day:
 Which scientist led us to understanding
genetics?
 Where are your genes located?
 Go over Video Worksheet
 Notes/Review on DNA
 Start that genetics!!
DNA Replication
 Ensures each daughter cell will have an exact copy of the
genetic material it needs to carry out its activities.
 Reminder: DNA (and RNA) is made up of nucleic acids –
long organic molecules made of – C, O, H, N, and
phosphorus
 Replication of DNA takes place during Interphase
DNA Replication (cont.)
 DNA is made of a sugar molecule called deoxyribose, a
phosphate, and nitrogen bases in the shape of a ladder or
spiral staircase.
– Deoxyribose and phosphate make up the outside supports (or the
sides of the ladder)
– Nitrogen bases make up the rungs of the ladder
• The same bases always pair, A-T and C-G and in a specific order
determining protein formation.
• Adenine - Thymine
• Guanine - Cytosine
The Structure of DNA
DNA Replication Process
 Replication begins when the two sides unwind and
separate (like unzipping a zipper)
 The DNA separate between the paired bases
 Nitrogen bases floating in the nucleus pair up with the
bases on each half of the DNA molecule to make two
new identical strands.
DNA Replication
DNA Replication (in action)
www.geneticalpha.com/what%20we%20do/default.html
PRINCIPLES HEREDITY
OF
 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 = grandparents
 F1 generation are the offspring of the grandparents
(your parents)
 F2 generation are the offspring of the F1
generation (you)
 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.
Genes
Dominant
traits that are strongest
they show up & can hide other traits
Recessive
traits that are weak
they can be hidden by dominant traits
Inheritance Patterns Continued
 Genotypes show the
combination of genes
that are specific for all
traits.
 Dominant traits are
symbolized by capital
letters, TT. One letter
from each parent.
 Recessive traits are
symbolized by lower
case letters, tt.
 Phenotypes show your
physical
characteristics like
height, eye, hair color
& skin color.
 In each pair of
genes, one comes
from the mother and
the other comes from
the father.
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.