dnareplication dna replication. before we begin – let’s review take out your dna structure...
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DNADNA ReplicationReplication
Before We Begin – Let’s Review
• Take out your DNA Structure Worksheet– Let’s grade it!!!
1. What is the full name of DNA?
2. What is a gene?
3. Where in the cell are chromosomes located?
4. What two scientists established the structure of DNA?
5. What is the shape of DNA?
6. What are the sides of the DNA ladder made of?
7. What are the “rungs” of the ladder made of?
8. Adenine always binds with _______________________ and _____________________ always binds with Cytosine.
9. Using what you know about nitrogenous base pairing fill in the missing nucleotides:
10.Why is DNA called the “Blueprint of Life?”
A Perfect Copy
• When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.
A Perfect Copy Cont.
1. On a sheet of scrap paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper.
2. Hold the papers side by side, and compare the lines. Do they look the same?
3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same?
4. How could you use the original paper to draw exact copies of the line without tracing it?
5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?
Duplicating DNADuplicating DNA
• During DNA replication:1. The DNA molecule separates into two
strands– Each strand of the double helix of DNA
serves as a template, or model for the new strand
2. Two new complementary strands are produced following the rules of base pairing
The Semi-ConservativeReplication Model
Both Both strands of strands of
original original DNA DNA
serve as serve as templatestemplates
Daughter Daughter chromosomeschromosomes
halfhalf oldold, , half half newnew
DNA Replication
Replication Fork
How Replication Occurs
1.An enzyme
called
helicase unzips
the DNA
2. An enzyme
called
polymerase adds
loose nucleotides
to the growing
strands
Picture It!!!
How Replication Occurs Cont.
3. An enzymecalled ligaseconnects the short strands
together
Replication fork
DNA polymerase
New strand
Original strand
How fast does in happen?
• In each of our cells, the DNA is being
replicated at 50 – 500 nucleotides per second!!!
Let’s put you to the test!
1. The main enzyme involved in linking individual nucleotides into DNA molecules is
a. Transfer RNA
b. Ribose
c. Helicase
d. Polymerase
Let’s put you to the test!
2. The enzyme responsible for “gluing” the new strand of DNA together is:
a. Polymerase
b. Ligase
c. Helicase
d. Dunnocase
Let’s put you to the test!
3. During DNA replication, the DNA molecule separates into ____ strands.
a. Four
b. Three
c. Two
d. One
Let’s put you to the test!
4. The sister chromosomes formed at the end of DNA replication consist of:
a. Half old, half new DNA
b. All new DNA
c. All old DNA
Let’s put you to the test!
5. DNA is replicated at a rate of 50 -500 nucleotides per:
a. Day
b. Hour
c. Minute
d. Second