Notes: DNA · Watch this animation of DNA Replication: dna replication bozeman science - Bing video...
Transcript of Notes: DNA · Watch this animation of DNA Replication: dna replication bozeman science - Bing video...
Notes:
DNA
I. What is DNA?• DNA (deoxyribonucleic acid) is a type of
molecule found in the nucleus of all cells
that contains instructions for the cell and
determines the traits of the organism.
• Important: All the somatic (body) cells in
an organism have the same exact DNA.
• Do you think every cell uses every gene?
_____No.
But, the code is identical in every
cell of your body because all of
these cells divided by mitosis from
the same cell (the first cell formed
by your mom’s sperm and your
dad’s egg).
II. How was DNA discovered?
• Rosalind Franklin
did experiments with
X-rays to determine
the structure of DNA.
• Watson and Crick
then completed the
model of the DNA
molecule.
II. How was DNA discovered?
• We now know that
DNA has a “double
helix” structure (like a
windy stair case).
II. How was DNA discovered?
Watson and
Crick:
III. What is the structure of DNA?
DNA is made of building
blocks called nucleotides.
Each nucleotide has 3 parts:
Phosphate group
Deoxyribose (sugar)
Nitrogenous base
Draw a nucleotide:
Deoxyribose
sugar
Which part of the nucleotide contains the genetic
instructions? The phosphate, the sugar, or the
nitrogenous base?
_______________________________The nitrogenous base (A, T, G, or C) –the order
of these determines the traits of the organism
Put these in order from smallest to largest:
Gene, nucleotide, chromosome
Nucleotide Gene Chromosome
Nucleotide: a small
piece of DNA
Gene: a small piece of
the chromosome
Chromosome:
an entire
strand of DNA
How do you know which bases
go with which?
• There are 4 base pairs in DNA
– Adenine
– Thymine
– Guanine
– Cytosine
Complimentary Bases
• Only certain bases can “pair up” along two
strands of DNA.
AT
GC“All Together, Go Cowboys”
• The two strands are called complimentary.
DNA Structure
• Each strand of DNA
has a 5’ end and a 3’
end. (This has to do
with the arrangement
of the molecules)
• The two strands are
called antiparallel
because the two
strands are facing
opposite directions.
Practice: Write the complimentary
strand:
5’ TTGCATTCA 3’
_________________3’ AACGTAAGT 5’
Question: If 20 % of a chromosome is made
up of guanine, what percent of the nitrogenous
bases are cytosine? ___________
Why? ___________________________
________________________________
20%
Because every C is paired with a
G. The same is true for A and T
How does DNA get replicated (copied)?
• Each time a cell divides by mitosis, the DNA in that cell must be replicated (copied).
• This insures that both daughter cells have a complete set of genetic material.
DNA
• Step 1: The DNA is unzipped at the base pairs by a protein called helicase.
• Step 2: Each nucleotide on the parent strands are paired with a new complimentary nucleotide. (A-T, G-C)
• Step 3: Nucleotides are bonded together by a protein called polymerase.
• Step 4: Two DNA molecules are formed - each with a parental strand and a new strand.
How does DNA get replicated (copied)?
• This process is
called
semiconservative
because the new
strand is ½ old
DNA and ½ new
DNA.
What does semiconservative mean?
Watch this animation of DNA Replication:
dna replication bozeman science - Bing video
Write this song down to help you remember the parts of
DNA: (to the tune of row row - row your boat)
We love DNA
Made of nucleotides
Sugar, phosphate, and a base
Going down the sides