Download DNA Structure and Replication

Unit 7 Lesson 1
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DNA Structure and Replication – Notes – Answer Key
View the presentation. Complete each question below as you read through the information.
Part I What is DNA?
1. DNA stands for Deoxyribonucleic Acid
2. DNA contains all the instructions for all the traits of a living organism.
3. A trait is any characteristic of a living thing. For example (name three traits):
Answers will vary
4. DNA is found in the nucleus of a cell.
5. DNA makes up the chromosomes.
6. Humans have 23 pairs of chromosomes in the nucleus of each cell.
7. A gene is a small segment of DNA.
8. Genes have the instructions for all the traits in an organism.
9. Genes “code” for such traits as eye color, hair type, skin color, height and even diseases.
10. Let’s label! Label 1-5 on
the diagram below:
(word bank: nucleus, cell,
gene, DNA, chromosome)
1 – cell
2 – nucleus
3 – chromosome
4 – DNA
5 - gene
Unit 7 Lesson 1
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11. Several scientists are given credit with the discovery of DNA.
12. James Watson and Francis Crick discovered DNA in 1952.
13. Rosalind Franklin also helped discover DNA.
Part II Structure of DNA
1. DNA resembles a twisted ladder
2. DNA is made up of many nucleotides
3. A nucleotide has three parts: phosphate, sugar (deoxyribose), and base.
One nucleotide:
4. There are 4 bases:
A or Adenine
C or Cytosine
T or Thymine
G or Guanine
5. Phosphates (P) and Sugars (D) make up the sides of the DNA ladder.
6. The bases (A, T, C, G) make up the rungs (steps) of the ladder.
7. Nucleotides will only join in very specific ways. This is similar to a jigsaw puzzle. Only
certain pieces fit together.
8. Adenine (A) only bonds with Thymine (T).
9. Cytosine (C) only bonds with Guanine (G).
Unit 7 Lesson 1
Name ____________________________________________
10. During mitosis and meiosis (remember cell division in Unit 9?) DNA gets copied before a
cell divides.
11. Notice in the picture that the left side of the DNA molecule is identical to the right side.