Section 10-1



Section 10-1

VOCABULARY REVIEW

1. A virulent strain of a bacterium is one that causes

disease.

2. Transformation is the transfer of genetic material

from one cell to another cell or from one organism

to another organism.

3. A bacteriophage is a virus that infects bacteria.

MULTIPLE CHOICE

1. a 2. c 3. d 4. a 5. b

SHORT ANSWER

1. to show that live R cells are not virulent

2. to show that live S cells are virulent and can kill a

mouse

3. to show that heat-killed S cells do not cause disease

4. to show that something in the heat-killed S culture

was acting on the live R cells to kill the mouse;

experiment 3 showed that it was not the killed S

cells themselves that killed the mouse.

5. The slippery capsule prevents the cells of the

defense system from capturing and destroying

the bacterial cells.

STRUCTURES AND FUNCTIONS

1. Experiment 2

2. Experiment 1

Section 10-2

VOCABULARY REVIEW

1. A purine is a nitrogenous base with two rings of

carbon and nitrogen atoms. Examples may include

adenine or guanine.

2. A pyrimidine is a nitrogenous base with one ring

of carbon and nitrogen atoms. Examples may

include cytosine or thymine.

3. A complementary base-pair is a pair of nitrogenous

bases connected to each other by hydrogen

bonds. Examples may include adenine-thymine

and cytosine-guanine.

4. A nitrogenous base is a base in DNA containing

nitrogen and carbon.

MULTIPLE CHOICE

1. c 2. d 3. a 4. b 5. b

SHORT ANSWER

1. The three parts are a deoxyribose sugar, a phosphate

group, and a nitrogenous base. The phosphate

group and the base are connected to different parts

of the sugar.

2. Since guanine and cytosine are complementary,

another 15% of the nucleotides must contain

cytosine. The remaining 70% of the nucleotides

(100%–30%) must contain adenine and thymine in

equal proportions (35% each), since they are complementary

to each other.

3. Complementary base pairing is important because

the hydrogen bonds between the bases hold the

two strands of DNA together and because it serves

as a way for DNA to replicate.

4. The X-ray diffraction photographs showed that the

shape of the DNA molecule was a double helix.

STRUCTURES AND FUNCTIONS

a, deoxyribose; b, guanine; c, adenine;

d, phosphate group

Section 10-3

VOCABULARY REVIEW

1. A replication fork is a Y-shaped region that results

when the two strands of DNA separate during

replication.

2. A helicase is an enzyme that separates the strands

of DNA during replication.

3. Semi-conservative replication produces a new

DNA molecule with one original strand and one

new strand.

MULTIPLE CHOICE

1. b 2. a 3. b 4. d 5. c

SHORT ANSWER

1. Replication occurs simultaneously at many origins

along the DNA.

2. Producing exact copies ensures that when a cell

divides, the offspring cells will receive the same

genetic information as the parent cell.

3. Cancer can result when errors occur in the replication

of DNA in genes that control how a cell

divides. A mass of cancerous cells called a tumor

can result.

4. The hydrogen bonds break easily, making it easier

for the two strands in the molecule to separate

during replication. The strong covalent bonds

ensure that the sequence of nucleotides remains

fixed in each strand.

STRUCTURES AND FUNCTIONS

Part a: helicase enzymes separate DNA strands;

Part b: DNA polymerase enzymes add complementary

nucleotides to each original strand of DNA and covalent

bonds form between adjacent nucleotides;

Part c: DNA polymerases finish replicating DNA and

fall off, two DNA molecules identical to original DNA

molecule have formed.

Section 10-4

VOCABULARY REVIEW

1. A codon is a sequence of three mRNA nucleotides

that codes for a specific amino acid or a start or

stop signal.

2. Translation is the process of assembling polypeptides

from information encoded in mRNA.

3. An anticodon is a sequence of three tRNA

nucleotides that pairs with a specific codon.

MULTIPLE CHOICE

1. a 2. d 3. b 4. b 5. b

SHORT ANSWER

1. The anticodons are UAC, GUA, CGU, and UCA.

(The last three nucleotides in the mRNA sequence

are a stop codon, which has no anticodon.) The

polypeptide will initially contain four amino acids.

2. The tRNA that pairs with the start codon on

mRNA carries methionine.

3. RNA contains ribose; DNA contains deoxyribose.

RNA usually contains uracil in place of thymine.

RNA is single stranded; DNA is double stranded.

4. All of the codons from the deletion point to the

end of the transcript would be shifted by one

nucleotide, so the sequence of amino acids specified

from that point on would be different.

Translation would terminate prematurely if the

shift resulted in a new stop codon before the end

of the transcript.

Back Print

9

Copyright © by Holt, Rinehart and Winston. All rights reserved.

Modern Biology Study Guide Answer Key

STRUCTURES AND FUNCTIONS

a, polypeptide or protein; b, peptide bond;

c, amino acid; d, tRNA; e, anticodon; f, codon; g, mRNA

or transcript; h, ribosome

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download