DNA – What Is It?

Write down everything you know about DNA on the back of the notetaking worksheet

What is it?

D = DeoxyriboN = nucleicA = AcidDeoxyribonucleic Acid

Length of Cell Cycle:

Length of cell cycle depends on the type of cell.

Liver cell takes 22 hours to divide, some cells, like nerve cells, stay in interphase for years.

(liver cell)

DNA Replication

Ensures that each daughter cell has genetic information to carry out its activities.

DNA carries all the cells instructions.

DNA is passed from parent cell to daughter cells.

Structure of DNA

DNA molecule looks like a twisted ladder

The molecule is known as a “double helix”

Sides of molecule are made of sugar (deoxyribose) and phosphate

Rung of molecule is made of nitrogen base pairs

DNA Structure Continued

Rung of molecule is made of nitrogen bases

Names of bases: (A) adenine (T) thymine (G) guanine (C) cytosine

DNA Structure Continued

One unit made up of a phosphate, sugar and nitrogen base is called a Nucleotide.

Nucleotide = base + sugar + phosphate

Replication Process

Replication starts by the molecule unwinding and separating.

They separate between the nitrogen pairs (on the rungs)

Free floating nitrogen bases pair up with bases on each half of the DNA molecule.

A always pairs with T G always pairs with C The order will exactly

match the parent DNA molecule

Answer the following questions on a sheet of paper.

1. What does the length of the cell cycle depend on?

2. What does DNA stand for?

3. Name 2 reasons DNA replication is so important.

4. Describe what a DNA molecule looks like.

5. What is another name for a DNA molecule?

6. What are the sides of the DNA molecule composed of?

7. What are the “rungs” of the DNA molecule composed of?

8. What are the names of the “rungs” of a DNA molecule?

9. What is a nucleotide and what are they made of?

10. Draw a picture of a DNA molecule and label each part.

11. List the steps of DNA replication.

12. Describe which base pairs always pair up together during replication.