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Name___________________________________________________Date____________________Period_________4.1 DNA Replication Practice Worksheet

How Does DNA made a copy of itself?

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The double helix of DNA unwinds and each side serves as a pattern to make a new molecule.

Background:

DNA carries the information for making all of the cell's proteins. These proteins implement all of the functions of a living organism and determine the organism's characteristics. When the cell reproduces, it has to pass all of this information on to the daughter cells.

Before a cell can reproduce, it must first replicate, or make a copy of, its DNA. Where DNA replication occurs depends upon whether the cells is a prokaryote or a. DNA replication occurs in the cytoplasm of prokaryotes and in the nucleus of eukaryotes. Regardless of where DNA replication occurs, the basic process is the same.

DNA Replication is a process that must be done exactly. When it is not completed correctly, mutations (mistakes) then result. In order to make sure that everything is replicated correctly, you will want to make sure that you use the proper base pairing rules: A will bond with T only, and G will bond with C only.

Steps in DNA replication are:

1. The enzyme Helicase unzips the DNA molecule by breaking the hydrogen bonds holding the nitrogen bases together.

2. A DNA Polymerase helps complementary nitrogen bases pair on each half of the DNA molecule. Adenine (A) bonds with thymine (T). Guanine (G) bonds with cytosine (C).

3. The result is two identical copies of the DNA molecule. Each new molecule contains one old strand and one new

strand.

REVIEW:

1) DNA is the instructions for making ______________________.

2) Where does replication happen in Prokaryotes? Eukaryotes

3) Are new bases added to the inside or outside of the original strands? (Hint: look at the diagram)

PART A: WATCH AND LEARN!!!

Click on the following link:

Answer the questions below as you watch the tutorial.

YOU MUST CLICK ON ‘THE PLAY BUTTON TO MOVE TO EACH NEW SECTION.

(Section 1 of 8)

1) What is DNA replication?

(Section 2 of 8)

2) Why is DNA replication said to be “semi-conservative”?

(Section 3 of 8)

3) What does the enzyme HELICASE do?

4) The enzyme PRIMASE marks the spot where DNA replication should ________________.

(Section 4 of 8)

5) What is the first step in the DNA replication process? Which protein is involved?

6) What is the place where the two strands of DNA separate called?

7) How do the two strands keep from snapping back together?

(Section 5 of 8)

8) What does it mean that the two DNA stands are “anti-parallel”?

9) The enzyme DNA POLYMERASE attaches new _______________________ to the exposed DNA strand to make a copy of the DNA.

PART B: YOU TRY!!!

Directions:

For each strand of DNA, show the three steps to demonstrate that you could “replicate” the DNA correctly

Example Solution in two parts:

A. Fill in the complementary strand.

Original strand: TCC TG ACCCC GCCGG GATAT CCTTC TACCT CCAAA TGTAT

Complementary strand: AGGAC TGGGG CGGCC CTATA GGAAG ATGGA GGTTT ACATA

B. Split the DNA and fill in the complementary strands to create two complete double helix strands.

T CCTG ACCCC GCCGG GATAT CCTTC TACCT CCAAA TGTAT (original strand)

A GGAC TGGGG CGGCC CTATA GGAAG ATGGA GGTTT ACATA (new strand)

TCCTG ACCCC GCCGG GATAT CCTTC TACCT CCAAA TGTAT (new strand)

AGGAC TGGGG CGGCC CTATA GGAAG ATGGA GGTTT ACATA (original complement)

NOW YOU TRY!

Original DNA molecule:

1. A. Original strand: CCTAT ATCTC TCTAT ATCTC TCATA CTGTG TGTCT CTATA

Complementary strand: GGATA TAGAG AGATA TAGAG AGTAT GACAC ACAGA GATAT

B. Make two new identical molecules of DNA

Replicated DNA molecule:

CCTAT ATCTC TCTAT ATCTC TCATA CTGTG TGTCT CTATA (original strand)

__________________________________________________________________ (new strand)

Replicated DNA molecule:

____________________________________________________________________ (new strand)

GGATA TAGAG AGATA TAGAG AGTAT GACAC ACAGA GATAT (original complement from 1A)

Try it again!

Original DNA molecule:

2. A. Original DNA: CCGGA TTTTA ATTAG CTACT ATCGT ACTAC GTTGG TGCTA

Complementary DNA: _______________________________________________________________________

B. Make two new identical molecules of DNA

CCGGA TTTTA ATTAG CTACT ATCGT ACTAC GTTGG TGCTA (original)

____________________________________________________________________ (new)

____________________________________________________________________ (new)

____________________________________________________________________ (original complement from 2A)

PART C: PUT IT ALL TOGETHER NOW!!!

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8. Why do cells need to make new copies of DNA?

9. Summarize the process of DNA replication.

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OriginalDNA Molecule

NEW DNA

Molecule

NEW DNA

Molecule

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