Download Chapter 8 How Cells Reproduce

Chapter 8
How Cells Reproduce
Macromolecule:
Nucleic Acid
There are two Nucleic Acid Macromolecules
1. DNA =Deoxyribonucleic Acid
“instruction book for the cell”
this cannot leave the nucleus!
2. RNA = Ribonucleic Acid
“reads, copies, and carries it’s version of
the instructions out of the nucleus to the cell to
be used”
DNA
DNA is DOUBLE STRANDED
it has two “sides”
the bases in the middle are connected
with hydrogen bonds
**hydrogen bonds are weak and easily broken*
The TWISTED SHAPE is called a HELIX
DNA is a DOUBLE HELIX shape
Where is DNA found?
• DNA is in the nucleus of every cell in your
body.
• (it is found in every cell of any living thing)
• DNA structure is the same for every living
thing on the planet!
Basic DNA Structure: Double Helix
The bases in DNA are:
Adenine , Thymine, Cytosine, Guanine
They form “base pairs” A-T C-G
This pairing is called Chargraffs Rules
Purine and
pyrimidine bases
Look at the
shape of the
bases --------->>
A, G are 2 circles
Purines
C,T are one circle
Pyrimidines
• This is the actual chemical
structure:
Nucleotides
3 parts:
-Phosphate
-Sugar
-Nitrogenous Base
Nucleotides put
together in long
lines become
nucleic acids.
So what makes a plant different
from a human?
• Nucleotides are the segments of DNA that
include a base.
• The arrangement of these nucleotides and the
bases on them are what determines what
makes things different.
• ALSO, the number of nucleotides can be
different from SPECIES to SPECIES (plant to
human, for instance)
What is a chromosome?
• A chromosome is DNA that is coiled up tightly
into rod shaped structures.
Where are chromosomes in a cell?
• Chromosomes are only found in the nucleus
of a cell when the cell decides to divide into
two cells.
• At all other times, the nucleus contains DNA in
long double helix strands called “chromatin” in
a stage called INTERPHASE
Parts of a chromosome
How do we know so much about
chromosomes?
• Scientists can take pictures of them!
1. Look in the microscope and find a cell that
has started to divide and has coiled the DNA
into chromosomes.
2. Take a picture of that cell.
3. Enlarge the picture so you can see it better.
4. Cut out the chromosomes and lay them out
on paper. Compare them to other cells.
Karyotype = a picture of chromosomes
• It looks like this:
This one has a problem: Down’s
syndrome
Kleinfelter’s Syndrome