Chapter 12- DNA

Question 0

(Frederick Griffith-1928) method of experimenting

Answer 0

Isolated harmless r-strain and harmful s-strain
S-smooth colonies of bacteria- caused pneumonia

R- rough colonies of bacteria- harmless

Question 1

Frederick Griffith-1928

Answer 1

Studied how bacteria makes people sick

Question 2

Harmless r-strain + mouse (Frederick Griffith-1928)

Answer 2

Living mouse

Question 3

Harmful s-strain + mouse (Frederick Griffith-1928)

Answer 3

Dead mouse

Question 4

Heat-killed S-strain + mouse (Frederick Griffith-1928)

Answer 4

Living mouse

Question 5

Heat-killed s-strain + r-strain (Frederick Griffith-1928)

Answer 5

Dead mouse

Something transferred from the dead S to the R – the genes = “transformation”

Question 6

Oswald Avery- 1944

Answer 6

Studied what transferred in griffith’s experiment

Question 7

(Oswald Avery- 1944) method of experimenting

Answer 7

He denatured (destroyed) different things (carbs, proteins, lipids, RNA) in the bacteria using enzymes

Destroyed one cellular component at a time and examined whether transformation still occurred

Question 8

(Oswald Avery- 1944) transformation factor

Answer 8

Only denaturing DNA stopped transformation = DNA was transforming factor

Question 9

Alfred Hershey and Martha Chase- 1952

Answer 9

Studied bacteriophages (viruses that infect bacteria) by radioactively tagging a virus as verification of Griffith and Avery’s conclusions

Question 10

(Alfred Hershey and Martha Chase- 1952) methods of experimenting

Answer 10

Radioactively tagged protein coat and DNA of the virus
Coat: sulfur-35
DNA: phosphorous-32

Question 11

(Alfred Hershey and Martha Chase- 1952) conclusions

Answer 11

The infected bacteria had P-32; so it was DNA that transferred

Question 12

Role of DNA

Answer 12

Storing information
Copying information
Transmitting information

Question 13

Components of DNA

Answer 13

made up of a string of nucleotides that are held by covalent bonds

Question 14

DNA nucleotides

Answer 14

Has 3 parts:
5- carbon sugar (deoxyribose)
Phosphate group
Nitrogenous base (either adenine, thymine, guanine, or cytosine)

Question 15

(Finding the structure of DNA) Erwin chargaff’s rule

Answer 15

Percent of adenine is almost equal to percent of thymine

Percent of guanine is almost equal to percent of cytosine

Question 16

(Finding the structure of DNA) Rosalind Franklin- 1953

Answer 16

Photographed DNA

DNA = dots in rounded x shape

Question 17

(Finding the structure of DNA) Watson and crick- 1953 (thieves)

Answer 17

Couldn’t create DNA model that fit all roles
Watson saw franklin’s DNA photo
Modeled the double helix structure

Question 18

Structure of DNA

Answer 18

Two strands
Double helix (twisted ladder)
Antiparallel strands
[A and T] or [G and C] are held together by weak hydrogen bonds (weak bonds= separate easily for copying)
A-T and G-C = base pairing (explains chargaff’s rule)
Each strand can create its complementary strand

Question 19

Craig venter and Francis Collins- 2000

Answer 19

Analyzed complete human genome

Question 20

DNA replication

Answer 20

Before a cell divides it copies its DNA in a process called replication and ensures that each daughter cell has the same DNA

Question 21

DNA replication process

Answer 21

DNA molecule separates, creating replication forks (100s of R.Fs in eukaryotic cells, only 1 R.F in prokaryotic cells because replication occurs in both directions)

Question 22

DNA replication process part 2

Answer 22

New bases are added by DNA polymerase:

• base pairing (a-t and g-c)
• creates the complementary strand

Question 23

Result of DNA replication

Answer 23

2 DNA molecules identical to each other & the original
Each new semi-conservative (conserving one original strand) DNA molecule has:
- one original strand
-one new strand

Question 24

(Role of enzymes in DNA replication) DNA polymerase

Answer 24

Synthesizes new DNA (reads original strand and attaches new nucleotides)
Copies
Only works in 5’ to 3’ direction and so when it has to work in 3’ to 5’ direction it does it backwards and 3 at a time which results in Okazaki fragments (small chunks of DNA that are copied but not yet linked together)
Checks sequence for accuracy

Question 25

(Role of enzymes in DNA replication) DNA helicase

Answer 25

Unzips DNA (breaks the hydrogen bonds)

Question 26

(Role of enzymes in DNA replication) DNA ligase

Answer 26

Connects Okazaki fragments

Question 27

(Role of enzymes in DNA replication) telomerase

Answer 27

Adds telomeres- tips of chromosomes, short repeat DNA segments
Extremely difficult to copy
Protects important sequences of DNA
DNA is safe after repeated replications

Question 28

(Replication in living cells) during mitosis and meiosis all new cells

Answer 28

Attach regulatory proteins to start s- phase
Replicate their DNA
Check DNA replication for accuracy
Attach new telomeres if needed
Create new daughter cells
Mitosis ends- 1 original strand & 1 new strand
Meiosis ends - either 1 original strand OR 1 new strand

Question 29

Eukaryotic DNA replication

Answer 29

Spaghetti or x DNA in nucleus
Replication starts at hundreds of locations
Proceeds in both directions
Loose until condensed in prophase

Question 30

Prokaryotic DNA replication

Answer 30

Circular DNA found in cytoplasm
Starts at a single point
Proceeds in 2 directions