Unit 8

Question 1

Define Transformation.

Answer 1

a process where some bacteria take up foreign genetic material (naked DNA) from the environment

Question 2

Define Bacteriophage.

Answer 2

a kind of virus that infects bacteria, composed of DNA/RNA cores and a protein coat

Question 3

Define Nucleotide.

Answer 3

a compound made of a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base
4 types of nitrogenous bases: Adenine, Thymine, Guanine, Cytosine

Question 4

Define Base Pairing.

Answer 4

the principle that states that adenine and thymine pair together, and cytosine and guanine pair together in DNA strands

Question 5

Define Histones.

Answer 5

proteins

Question 6

Define Nucleosomes.

Answer 6

a DNA-histone complex which makes bead-like structure (unit of chromatin)

Question 7

Define Chromatin.

Answer 7

made of nucleosomes (DNA coiled around protein) packed together in eukaryotes to make the chromosome

Question 8

Define Supercoils.

Answer 8

a thick rope-like structure created by nucleosome coils

Question 9

Define Replication.

Answer 9

the copying process in which a cell duplicates its DNA before dividing, ensuring each resulting cell has a complete set of DNA molecules

Question 10

Define DNA Polymerase.

Answer 10

the principal enzyme involved in DNA replication

Question 11

What are Purines?

Answer 11

Adenine and Guanine

Question 12

What are Pyrimidines?

Answer 12

Cytosine and Thymine

Question 13

Define Leading Strand Properties.

Answer 13

• RNA Primase makes primer, which creates a starting point.
• DNA polymerase continuously adds nucleotides from that point forward towards the replication fork
• 5’-3’ direction

Question 14

Define Lagging Strand Properties.

Answer 14

• RNA Primase makes primer, DNA polymerase starts working backwards on the strand (away from replication fork).
• The strands are synthesized in short bursts, called Okazaki fragments.
• Another kind of DNA polymerase has to go back and replace RNA primers.
• DNA ligase comes around and joins the bases together.
• 3’-5’ direction

Question 15

Explain Griffiths’ Experiment.

Answer 15

• Frederick Griffith wanted to learn how bacteria produce pneumonia. He tested two strains on mice, and both grew well, but only one caused pneumonia.

Conclusions:
- A chemical substance from one cell is chemically transforming another cell. (Something from the dead, boiled, lethal bacteria changed the harmless bacteria)

Question 16

Explain Averys’ Experiment.

Answer 16

• Repeated Griffith’s experiment, using enzymes that destroyed proteins, lipids, carbs, and RNA, but transformation still happened. When they finally did it with DNA, transformation stopped happening.
• Conclusions:
  1. Avery and other scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.
  2. DNA is the transforming factor.

Question 17

Explain Hershey-Chases’ Experiment.

Answer 17

• Alfred Hershey and Martha Chase studied viruses, and found that whatever the bacteriophage was injecting inside the bacteria was the genetic material. Thus, they coated the virus’ DNA in phosphorus-32 (radioactive isotope) and the protein in sulfur-35 (radioactive isotope).
• Conclusions:
  1. They found phosphorus-32 inside the bacteria and concluded that the genetic material of the bacteriophage was DNA, not protein.
  2. Genes are made up of DNA.

Question 18

Explain Chargaffs’ Rules.

Answer 18

• Erwin Chargaff found that cytosine and guanine percentages were equal in DNA samples, just as adenine and thymine balanced each other out in the same way.
• Conclusions:
  C and G come in the same amounts.
  A and T come in the same amounts.
  C + G is NOT equal to A+ T

Question 19

Explain Rosalind Franklins’ Experiment.

Answer 19

• Used x-ray diffraction, stretching DNA fibers to make the strands parallel and aiming x-ray beams at the sample. She recorded the scattering pattern and made the famous photo 51.
• The x-shape in the picture indicated 2 strands in the structure and nitrogenous bases begin towards the center.

Question 20

Explain Watson and Cricks’ Experiment.

Answer 20

Watson saw Rosalind Franklin’s photo 51 and within a few weeks, he and Crick made a 3D model with 2 strands in a double helix which was published in a one-page paper.