Ch 8

Question 1

What did the experiments of Griffith and Avery show?

Answer 1

The transformation experiments of Griffith and Avery showed that DNA carried genetic information.

Question 2

What did Hershey and chase use to identify DNA as the genetic material?

Answer 2

Alfred Hershey and Martha Chase used the bactriophage T2 and radioactive labels to identify DNA as the genetic material.

Question 3

What is a DNA molecule made of?

Answer 3

The DNA molecule is a long chain of nucleotides.

Question 4

What is each nucleotide made of?

Answer 4

Each nucleotide is made of a phosphate group, the 5-carbon sugar deoxyribose, and one of the four different nitrogen bases.

Question 5

What are the double helix?

Answer 5

The two strands of the double helix are complementary.

Question 6

What forms bonds with each other? Why?

Answer 6

Purines can form hydrogen bonds only with pyrimidines. Adenine can bond to thymine. Cytosine bonds with guanine.
Only those can bond with each other because they have opposite charge and the same amount of bonding sites.

Question 7

What happens during replication?

Answer 7

During replication, enzymes unwind and separate the double helix, and complementary bases are added to the exposed strands. Each new double helix consists of one old DNA strand linked to one new DNA strand.

Question 8

What are coding regions of DNA called?

Answer 8

Coding regions of DNA are called exons. Noncoding regions are called introns.
Many eukaroytic genes are interpreted by segments of DNA that do not code for proteins

Question 9

What did McClintock discover?

Answer 9

Barbara McClintock’s work involved the study of repeating genes called transposons, which can jump to new locations on a chromosome.

Question 10

How can transposons affect genes?

Answer 10

Jumping genes can cause mutations.

Question 11

What do certain genes protect?

Answer 11

It has been discovered that certain genes protect living things from damaging mutations. Such a gene is p53, which suppresses the development of cancerous tumors.

Question 12

DNA or Protein is hereditary material?

Answer 12

It was thought that it was protein as it is more complex than DNA (20 different building blocks instead of only 4)

Question 13

Vaccine

Answer 13

substance prepared from weakened or killed microorganism introduced to the body to produce immunity. Immune system responds to pathogen marker protein - which it will “remember” and defend against, if it ever shows up again.

Question 14

Describe Griffith’s experiment with S. Pneumonia bacteria

Answer 14

S colony - deadly due to polysaccharide capsule and grows in smooth edged colonies
R colony – harmless because no capsule and grows in rough edged colonies
S colony – kills mice because mouse immune systems can’t fight it due to its protective polysaccharide capsule
Procedure:
1. R bacteria – doesn’t kill, without a capsule, it is easily defeated by immune system of mouse
2. S bacteria kills
3. Heat-killed S - does not kill
4. Heat-killed S + R – kills AND R has capsule (transformed)

Question 15

Describe Oswald Avery’s experiment

Answer 15

They know there is protein in Heat-killed S stuff and DNA in it (prior knowledge). Uses protein destroying enzymes and DNA destroying enzymes on two separate batches of heat-killed S before mixing with R. Transformation still happened with protein destroying enzyme batch but not with DNA destroyed. Concludes activity responsible for transformation not affected by protein destroying enzyme but is affected by DNA destroying
Experimental Group# 1
- Adds protein destroying enzyme to one batch of heat-killed-S
- Then adds some R
- The injects the mouse and the mouse dies AND the R inside it now has a capsule - has undergone transformation with instructions (from intact DNA)
Experimental Group# 2
- Adds DNA destroying enzyme to one batch of heat-killed-S
- Then adds some R
- The injects the mouse and the mouse lives AND the R has not undergone transformation - has no capsule (DNA instructions were destroyed)

Question 16

Chase and Hershey

Answer 16

They know that viruses are made of protein and DNA (prior knowledge). They grew two batches of bacteriophages (viruses that infect bacteria); one in radioactive phosphorus and one in sulfur, to detect whether DNA (has phosphorus in its phosphate group) or protein (has sulfur in it) is the informational material the viruses would be injected into the bacteria.
Experimental Group# 1
- Lets bacteriophages grown in radioactive phosphorus infect (inject their genetic material) bacteria.
- Shakes the viruses off bacteria with a blender
- Further separates the bacteria from viruses by centrifuging
- Bacteria is now radioactive indicating the radioactive DNA was injected
Experimental Group# 2
- Lets bacteriophages grown in radioactive sulfur infect (inject their genetic material) bacteria.
- Shakes the viruses off bacteria with a blender
- Further separates the bacteria from viruses by centrifuging
- Bacteria is NOT radioactive indicating the radioactive protein was NOT injected

Question 17

Watson and Crick used what three pieces of prior knowledge to come up with the structure of DNA

Answer 17

1 - Base-pairing rules of Erwin Chargaff who observed:
• amount of Adenine always equals Thymine
• amount of Guanine always equals Cytosine
No matter what organism the 1 to 1 ratio between A and T ….and G and C is always the same
# 2 - Maurice Wilkins & Rosalind Franklin’s X-Ray photo suggested DNA is in a helical shape
# 3 Their own knowledge of chemical bonding (such as - adenine has two hydrogen bonding sites, as does thymine)

Question 18

Purines

Answer 18

Adenine and guanine

Double ring carbon and nitrogen

Question 19

Pyrimidines

Answer 19

Thymine and cytosine

Single ring

Question 20

Why is the AT/CG pairing complementary?

Answer 20

This arrangement is complimentary allowing for precise duplication when DNA strands split; each separate strands serves as a template for building new molecules

Question 21

Replication

Answer 21

Synthesizing new molecule at replication fork

Question 22

Helicase

Answer 22

Enzyme that split helix into two strands

Question 23

DNA polymerase

Answer 23

Enzyme that moves along strands adding appropriate (complimentary) nucleotides AND proof-reads to correct any mistakes.
DNA replication takes place at many locations along molecule to speed up the process

Question 24

The physical features (form) of DNA molecule allow for specific ability (function):

Answer 24

1. The weak hydrogen bonds of the rungs of the ladder between nitrogenous bases allows them to be broken easily for replication and transcription (to make mRNA to make protein)
2. The complementary pairing of nucleotides allows on singled sided stand to serve as a template to construct the matching side
3. The strong covalent bonds keep the sequence of nucleotides from breaking or changing easily (mutating)
4. The consistent 1 ring nitrogenous base hydrogen bonded to a two ring nitrogen base to form the rungs of the ladder keep equal distance between the sides and allow for helixing (twisting) to make it more compact… and even 3D spacing in the twist, for easy transcription of genes.

Question 25

Econ’s interspersed with introns may offer genetic flexibility for evolution because:

Answer 25

1. Econ’s can be shuffled to make slightly different proteins
2. When exons are added into a non-coding region of an intron they will not cause a problem (mess a coding sequence up)

Question 26

Multigene families

Answer 26

Many versions of a gene