Download Directed Reading B

Name ______________________________ Class___________________Date__________________
Skills Worksheet
Directed Reading B
Section: How DNA Works
Circle the letter of the best answer for each question.
1. How much DNA does a human cell contain?
a. 30,000 m
b. less than 1 m
c. about 2 m
d. more than 10 m
UNRAVELING DNA
2. What is DNA often bundled into?
a. proteins
b. chromosomes
c. bases
d. traits
3. What is a string of nucleotides called?
a. traits
b. loops
c. a cell
d. a gene
4. How many chromosomes does a human cell have before dividing?
a. unlimited
b. 23
c. 46
d. 12
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Genes and DNA
Name ______________________________ Class___________________Date__________________
Directed Reading B continued
GENES AND PROTEINS
Circle the letter of the best answer for each question.
5. What do three bases form?
a. DNA
b. gene
c. chromatin
d. amino acid
6. What does each gene have instructions for making?
a. a protein
b. a cell
c. an amino acid
d. DNA
Proteins and Traits
7. What do proteins act as?
a. organisms
b. bases
c. codes
d. chemical triggers and messengers
Help from RNA
8. What other type of molecule helps make proteins?
a. RAD
b. RNA
c. DNR
d. DTR
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Genes and DNA
Name ______________________________ Class___________________Date__________________
Directed Reading B continued
The Making of a Protein
Read the words in the box. Read the sentences. Fill in each blank with
the word or phrase that best completes the sentence.
ribosome
transfer RNA
messenger RNA
9. A mirrorlike copy of a DNA segment is called
______________________.
10. The RNA copy goes through a protein assembly line called a
______________________.
11. The message is translated by ______________________ and a protein is
made.
CHANGES IN GENES
Mutations
Circle the letter of the best answer for the question.
12. Changes in the bases of DNA are called what?
a. extras
b. roller coasters
c. accidents
d. mutations
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science and Technology
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Genes and DNA
Name ______________________________ Class___________________Date__________________
Directed Reading B continued
Read the words in the box. Read the sentences. Fill in each blank with
the word or phrase that best completes the sentence.
deletion
substitution
insertion
13. When a base is left out, the change is called a(n)
______________________.
14. When an extra base is added, the change is called a(n)
______________________.
15. When the wrong base is used, the change is called a(n)
______________________.
Do Mutations Matter?
Circle the letter of the best answer for each question.
16. Which of these does not result from mutation?
a. an improvement
b. a harmful change
c. cell repair
d. no change
How Do Mutations Happen?
17. What is one way mutations happen?
a. because of ribosomes
b. because DNA wears out
c. because of random errors
d. because of sugars
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Genes and DNA
Name ______________________________ Class___________________Date__________________
Directed Reading B continued
Circle the letter of the best answer for each question.
18. What are agents that might damage DNA called?
a. ribosomes
b. mutagens
c. generations
d. regulations
AN EXAMPLE OF SUBSTITUTION
19. What can a mutation produce?
a. a bad sunburn
b. transfer RNA
c. the wrong protein
d. cigarette smoke
20. What is caused by of a substitution mutation?
a. blue eyes
b. sickle cell disease
c. height
d. red hair
USES OF GENETIC KNOWLEDGE
Genetic Engineering
21. What is it called when scientists change an organism’s genes?
a. DNA fingerprinting
b. genetic engineering
c. genetics
d. transfer RNA
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science and Technology
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Genes and DNA
Name ______________________________ Class___________________Date__________________
Directed Reading B continued
Circle the letter of the best answer for each question.
22. What happened when scientists added a firefly gene to a plant?
a. The firefly glowed.
b. The plant died.
c. The plant glowed.
d. The plant vanished.
Genetic Identification
23. How are the unique patterns in DNA identified?
a. DNA fingerprinting
b. genetic engineering
c. genetics
d. transfer RNA
24. What is an organism that has an exact copy of another’s DNA called?
a. a twin
b. a brother or sister
c. a clone
d. a child
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science and Technology
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Genes and DNA