DNA Discovery Structure Replication

40 questions

1. Describe the two strains of bacteria Griffith used in his experiment with mice.

• S strain (deadly)-produced a protective slime coating that helped it evade the mouse immune system.-caused pneumonia (a deadly lung disease) in mice.

• R strain (harmless)-did not produce a protective slime coating and therefore was easily defeated by the mouse immune system.

2. What happened to the mice when Griffith injected them with the heat-killed S strain?

The mice lived.

The mice died of pneumonia.

+

3. What happened to the mice when Griffith injected them with a mixture of heat-killed S strain and live R strain?

4. A process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria.

a. Transcriptionb. Replicationc. Transformationd. duplication

5. Oswald Avery used ____ to degrade (break down) various molecules taken form heat-killed bacteria.

a. sulfurb. enzymesc. toxinsd. x-rays

6. What types of macromolecules did Avery use enzymes on.

CarbohydratesProteins

LipidsRNADNA

7. What kind of enzyme did Avery use to degrade bacterial proteins?

a. carbohydrasesb. lipasesc. proteasesd. DNAses

Membrane protein

8. How did Avery ensure the validity of the results of his experiment with bacteria and mice?

a. He degraded only one type of molecule at a time. b. He used all the enzymes at the same time.c. He decided not to degrade proteins and DNA.d. He injected a mixture of degraded molecules into

mice at the same time.

9. Bacteriophages are

a. a form of bacteriab. enzymesc. coils of DNAd. viruses

10. What two organisms did Hershey and Chase work with in their study of DNA?

a. Bacteriophages and miceb. E. coli bacteria and micec. Bacteriophages and E. coli bacteriad. Bacteriophages and viruses

Bacteriophages

E. coli bacterium

11. Interpret this micrograph.

Bacteriophages breaking out of a bacterium that has been infected.

BacteriophagesLysed Bacterium

Phages emerging

12. What radioactive element did Hershey and Chase use to “tag” DNA?

32P (phosphorus)

DNA

13. What radioactive element did Hershey and Chase use to “tag” the protein coat?

35S (sulfur)

The amino acid methionine

14. Why can’t Hershey and Chase use to 35S to tag phage DNA?

DNA does not contain sulfur.

15. What results did Hershey and Chase observe?

a. The protein coats were injected into the bacterial cells causing transformation.

b. Protein coats do not contain phosphorus.c. Radioactivity detected inside bacterial cells

came from 32P and not 32S.d. Bacteriophages are good at infecting bacteria.

16. What can be concluded from the Avery and Hershey & Chase experiments?

a. DNA is the transforming molecule.b. Proteins are larger than nucleic acids.c. Enzymes are good at breaking down molecules.d. The S-strain is more deadly than the R-strain.

17. Before DNA could be shown to be the genetic material in cells, scientists had to show that it could

a. tolerate high temperaturesb. carry, make copies of, and transmit informationc. be modified in response to environmental

conditions.d. be broken down into small subunits.

18. A nucleotide does NOT contain a

a. 5-carbon sugar.b. nitrogen basec. proteind. phosphate group

Phosphate group

Sugar (deoxyribose)

Nitrogenous base

19. According to Chargaff’s rule of base pairing, which of the following is true about DNA?

a. A = T, and C = Gb. A = C, and T = Gc. A = G, and T = Cd. A = T = C = G

Erwin Chargaff (1905 – 2002)

A

C

T

G

=

=

Thymine Guanine_____________ Cytosine

20. Name the missing nitrogenous base.

Adenine

21. Use Chargaff’s rule to complete the table below.

Organism % Adenine % Cytosine % Guanine % Thymine

Human 30 30

60100

+ ?

21. Use Chargaff’s rule to complete the table below.

Organism % Adenine % Cytosine % Guanine % Thymine

Human 30 3020 20

60100

+40

22. The bonds that hold the two strands of DNA together come from

a. The attraction of phosphate groups for each other.

b. Strong bonds between nitrogenous bases and the sugar-phosphate backbone.

c. Hydrogen bonds between nitrogenous bases.

d. Carbon-to-carbon bonds in the sugar portion of the nucleotides.

T GA

C

23. What is the term that describes how the two strands in DNA run in opposite directions?

AntiparallelC A T G

T AG C

24. Who took this photo?

Rosalind Franklin

Photo 51

(1920 – 1958)

25. What is this a photo ofand what technique was used to make it?

Photo 51

• The photo shows the structure of DNA

• Rosalind used X-ray diffraction to take the picture

26. List two things this Rosalind Franklin learnedfrom her photo?

• DNA has a double helix shape

• DNA is made of two strands.

• The nitrogenous bases are near the center.

Photo 51

27. Who are these two men and what are they famous for?

• James Watson and Francis Crick.

• They won the Nobel prize for building the first accurate model of DNA.

James Watson(1928 - )

Francis Crick(1916 - 2004 )

28. Name the three parts of the nucleotide shown below?

C

B

A

A. phosphate groupB. sugar (deoxyribose)C. nitrogenous base

29. The process of copying DNA prior to cell division is called

a. cytokinesisb. Interphasec. Base pairingd. replication

30. The diagram below shows the process of DNA

a. replicationb. digestionc. transformationd. transpiration

31. The enzyme that “unzips” DNA during replication is called

a. DNA polymeraseb. carbohydrasec. helicased. replicase

32. The enzyme that “fastens” new nucleotides to the original DNA strand is called.

a. carbohydraseb. DNA polymerasec. helicased. replicase

33. In which direction is the circled DNA polymerase moving?

Right to left

34. From left to right, identify the missing bases.

TG

AC

35. Is the chromosome shown below from a prokaryote or eukaryote? How do you know?

• It is from a prokaryote• The DNA forms a loop or ring like this one

36. The micrograph below shows DNA in fruit flies. What are the “bubbles” (as indicated by the arrows) caused by?

The bubbles are where DNA replication is taking place.

37. Interpret the following sequence of diagrams?

The diagrams demonstrate prokaryote replication, which involves only one replication bubble. Replication

proceeds within the bubble in opposite directions.

Replication bubble

Replication nearly

complete

Two identical

chromosomes result

Replication in two

directions

38. How many replication forks are shown in this micrograph?

There are two forks. One at each end of the bubble.

Replication forks

39. Is this a prokaryotic or eukaryotic chromosome? How can you tell?

• Eukaryotic• The chromosome is rod shaped

instead of circular.

Human chromatids

40. What are the tips of chromosomes called and what enzyme replicates them.

• The tips are called telomeres• The enzyme is telomerase

TelomeresTelomeres