Download How DNA Works

Name: _________________________ Hr. : __________ Date: ____________Due: __________
Ch. 4, Sec. 2
How DNA Works
1. How much DNA does a single cell in your body hold? ______________________________________
2. What shape does DNA take in a cell that lacks a nucleus?
a. a loose loop
c.
a tight chain
b. a structure d.
d.
a protein
3. What are the structures that strands of DNA are bundled into in a cell with a nucleus called?
a. nucleotides
c.
chromosomes
b. loose loops
d.
tight chains
4.
A string of nucleotides that give the cell information about a certain trait is known as a(n)
______________________.
5. How many chromosomes does a human cell have before division? ______________________.
6. When a cell is ready to divide, how many chromatids make up a chromosome? __________________
7. The _______________ code is read like a book.
8. The alphabet of the code is made of the ______________.
9. Groups of three bases are the codes for specific ______________________.
10. A long string of amino acids forms a(n) ______________________.
11. Instructions for making a protein are given by each ______________________.
12. List two examples of things proteins help determine about you. _______________________________
13. Several forms of RNA or ______________________ help change DNA code into proteins.
14. Because it is so similar to ______________________, RNA can serve as a temporary copy of a
DNA sequence.
15. The “factory” that assembles proteins is known as a(n) ______________________.
16. A mirror-like copy of DNA called ______________________ moves from the nucleus to
the ribosome.
17. Another form of RNA called ______________________ matches amino acids with the bases on
the messenger RNA.
Put the following steps in making a protein in order by putting a number in the space provided: 1 for step 1,
2 for step 2, etc.
_____18. The RNA copy is fed through the ribosome.
_____19. Transfer RNA molecules deliver amino acids to the ribosome.
_____20. Transfer RNA molecules pick up amino acids from the cytoplasm.
_____21. The amino acids are joined to make a protein.
_____22. A mirror-like copy of the gene is made of RNA.
23. Changes in the number, type, or order of bases on a piece of DNA are known as _________________.
Match the correct definition with the correct term. Write the letter in the space provided.
____ 24.
A base pair is added.
____ 25.
A base pair is replaced.
b. insertion
____ 26.
A base pair is removed.
c. deletion
a. substitution
27. Physical or chemical agents known as ______________________ can cause mutations in DNA.
28. List two examples of mutagens. ______________________
29. Sickle cell disease is caused by a(n)
a. substitution mutation.
b. deletion mutation.
______________________
c. insertion mutation.
d. blood vessel mutation.
30. The manipulation of individual genes within organisms by scientists is called
a. mutation.
c. genetic property.
b. drug enhancement.
d. genetic engineering.
31. List two possible uses of genetic engineering.
______________________
______________________
32. Because DNA is unique, DNA ______________________ can identify the unique patterns in an
individual’s DNA and help solve crimes.
33. Only identical twins have truly identical ______________________.
34. A scientifically created organism that has an exact copy of another organism’s genes is a(n)
______________________.
D:\769814539.doc
Mutations
 DNA is made up of nucleotides that each contain a sugar, a phosphate, and a base.
 The four possible bases are adenine, cytosine, thymine, and guanine.
 Remember that adenine and thymine are complementary and form pairs, and
cytosine and guanine are complementary and form pairs.
1.Below is half of a section of DNA that has been split apart and is ready to copy itself. Write the
appropriate letter in the space provided to build the DNA’s new complementary strand.
C
_
G
A
A
C
T
C
A
A
mRNA
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2. Sometimes mistakes happen when the DNA is being copied. These mistakes, or mutations, change the
order of the bases in DNA. There are three kinds of mutations that can occur in
DNA: deletion, insertion, and substitution.
a. Below are two sequences—an original sequence of bases in DNA and the sequence of bases after a
mutation has occurred.
On the original base sequence:
a. Show where the mutation has occurred by circling the appropriate base pair
b. If a mutation has occurred, write what type of mutation it is in the space provided.
Original Sequence
Type of
Mutation
C
G
T
A
T
C
G
C
G
______________
_____
C
G
A
G
______________
_____
T
A
T
A
______________
_____
A
T
T
______________
_____
A
T
A
T
______________
_____
A
T
A
T
______________
_____
T
A
C
G
______________
_____
C
G
______________
_____
T
A
______________
_____
T
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Sequence of
bases after a
mutation has
occurred
C
G
A
______________
_____
______________
_____