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12-1 DNA
__Watson and Crick discovered DNA in 1953.
Video:
Write down 3 things that you remember from the video: What is DNA and How does it Work?
1.____________________________________________________________________________
2. ____________________________________________________________________________
3. ____________________________________________________________________________
DNA stands for: __Deoxyribonucleic Acid______________________________
Very large biomolecule made up of nucleotides
Called the “blueprints of life” because it contains genetic information for the construction
of proteins.
Proteins are essential for life.
DNA floats freely in the cytoplasm of prokaryotic cells like bacteria.
DNA is protected in the nucleus of _eukaryotic cells like “you”.
.
Chromosomes and DNA
A ___gene is a segment of DNA that is passed down from parents to children and confers a trait
to the offspring. Genes are organized and packaged
in
units called “____chromosomes
Each gene encodes for a certain ___protein.
DNA is made of
_____nucleotides______________________________.
Nucleotide is a monomer of nucleic acids made up of 3 parts
-
___Deoxyribose (5 carbon sugar)
-
___phosphate group___________
-
_____Nitrogenous base_________
There are four kinds of Nitrogenous bases in in DNA:
-
__Adenine_(A)__
-
Thymine (T)
-
Guanine (G)
-
Cytosine (C)
DNA Structure –
Made of 2 strands that wrap around each other to form a double helix (looks like a spiral
staircase)
The sides (a.k.a. the backbone) : Alternating Sugar, phosphate, sugar, phosphate
The middle: Nitrogen bases paired together.
Draw and image of DNA structure in the space below, include labels
Base Pair Rule (Chargaff’s Rule)
-
___Adenine
pairs with Thymine______
-
___Cytosine
pairs with Guanine.
Q: DNA is a long molecule made of monomers called
a. nucleotides.
b. purines.
c. pyrimidines.
d. sugars
Q: In DNA, the following base pairs occur:
a. A with C, and G with T.
b. A with T, and C with G.
c. A with G, and C with T.
d. A with T, and C with T.
12–2 Chromosomes and DNA Replication
Replication of DNA
DNA molecules can build an exact copy of itself. This is called replication. (ATP is the energy
source)
Replication is important for reproduction and must occur every time a cell divides.
That way each cell has a complete set of instructions for making proteins.
Steps to DNA Replication
1. In the nucleus, _______hydrogen bonds break between the nitrogen bases of DNA (A, T,
G, C).
2. This causes the DNA to unzip like a zipper.
3. Enzymes in the nucleus called _DNA polymerase directs free floating nucleotides in the
nucleus to attach to each strand following the rules of base pairing.
4. Each strand serves as a template for the new strand.
5. This results in two identical strands of DNA
6. This is called __semi-conservative replication_, producing two copies of DNA that each
_contain one of the original strands.
Q: The first step in DNA replication is
a. producing two new strands.
b. separating the strands.
c. producing DNA polymerase.
d. correctly pairing bases.
Q: The first step in DNA replication is
a. producing two new strands.
b. separating the strands.
c. producing DNA polymerase.
d. correctly pairing bases.
Q: In addition to carrying out the replication of DNA, the enzyme DNA polymerase also
functions to
a.
b.
c.
d.
unzip the DNA molecule.
regulate the time copying occurs in the cell cycle.
“proofread” the new copies to minimize the number of mistakes.
wrap the new strands onto histone proteins.