Exam1 - Ch. 8-11, 1-3

Question 1

central dogma of molecular biology

Answer 1

describes the flow of genetic information from DNA to RNA to proteins

• DNA replication
• transcription
• translation

Question 2

what is the substance of inheritance?

Answer 2

traits (phenotypes) are passed on from generation to generation

Question 3

1868

Answer 3

Johann Friedrich Miescher
isolated the nucleus
determined the large amount of a substance that is high in phosphorous and is slightly acidic
this material contained both DNA and proteins

Question 4

1887

Answer 4

Albrecht Kossel

DNA is composed of 4 nitrogenous bases: adenine, cytosine, guanine, and thymine (ACGT)

Question 5

1919

Answer 5

Phoebus Aaron Theodore Levene
nucleic acids are composed of “nucleotides”
each nucleotide has a base, a sugar (ribose or deoxyribose) and a phosphate group

Question 6

1955

Answer 6

Erwin Chargaff finds that DNA contains equimolar amounts of A&T and C&G

Question 7

if DNA molecules 40% G, what % is A?

Answer 7

G=C
A=T
G+C = 80%
A+T = 20% / 2 = 10%
A=10%

Question 8

1929

Answer 8

Fred Griffith

discovered “killing property” (phenotype) can be transferred into harmless strain - “bacterial transformation”

Question 9

transformation

Answer 9

harmless R cells are transformed into deadly S cells when mixed with heat-inactivated S debris
no living S-cells required for R to S transformation

Question 10

1944

Answer 10

Oswald Avery et al.
DNA is the genetic material sufficient to do transformation
candidate substances: protein, RNA, DNA
protein-destroying enzyme (protease)
RNA-destroying enzyme (RNase)
-both have an effects on S to R transformation
-proteins and RNA are not the genetic material
DNA-destroying enzyme (DNase)
»destroys transformation ability of S-debris R to S (harmless to killer)

Question 11

nucleotides (deoxyribonucleotides)

Answer 11

2’ - deoxyribose (a five-carbon sugar)
phosphoric acid
one of four nitrogen-containing bases denoted A, T, G, and C

Question 12

Chargaff Parity Rule

Answer 12

%A = %T and
%G = %C

Question 13

H Bonding

Answer 13

A=T 2 hydrogen bonds

G=C 3 hydrogen bonds

Question 14

sugar-phosphate backbone of polynucleotide strands

Answer 14

deoxyribose sugars alternating with phosphate groups

Question 15

phosphate links

Answer 15

5’ and 3’ carbon of adjacent sugars

Question 16

covalent chemical bonds

Answer 16

phosphodiester bond

Question 17

antiparallel

Answer 17

2 polynucleotide strands run in opposite directions

Question 18

Watson and Crick

Answer 18

structure of DNA (double helix)
paired bases on single plane (planar)
ribose rings not planar
major/minor grooves

Question 19

major groove

Answer 19

1 helical turn
10 basepairs (bp) =
34 Angstrom =
3.4 nanometer

Question 20

3D DNA structure (Watson and Crick)

Answer 20

2 polynucleotide chains twisted around one another as right-handed helix
“right-handed double helix” : clockwise turns away from observer (backbone)
strands connected via hydrogen bonds between stacked bp
paired bases planar, parallel to one another, perpendicular to the long axis of the double helix

Question 21

Rosalind Franklin

Answer 21

X-ray
diffraction pattern
used to determine 3D structure of DNA

Question 22

DNA form (2 of 3)
B form

Answer 22

most common under physiological conditions

typical right handed helix

Question 23

DNA form (1 of 3)
A form

Answer 23

short and fat
exists when less water is present
uncommon in most physiological conditions

Question 24

DNA form (3 of 3)

Answer 24

left handed DNA

can occur in cells undergoing active transcription and in regions of DNA that have alternating C-G nucleotides

Question 25

Watson-Crick model of DNA replication

Answer 25

Each DNA strand template for synthesis of new strand
hydrogen bonds between DNA bases break > strand separation
template (parental) strand determines sequence of bases in new strand (daughter) = complementary strand preserves genetic information

Question 26

how is DNA packaged into chromosomes

Answer 26

via a special coiling around itself that only depends on DNA (“negative supercoiling”)
plus association with various proteins that help packaging the DNA

Question 27

human genome

Answer 27

6 billion base pairs (2meters in length)

typical nucleus about 5 microns in diameter

Question 28

advantages of supercoiling

Answer 28

separation of strands during replication/transcription is faster and requires less energy
can be packed into smaller space

Question 29

topoisomerases

Answer 29

enzyme breaks DNA strands passes one end through it then repairs

Question 30

positive supercoil

Answer 30

overrotate

Question 31

negative supercoil

Answer 31

underrotate

Question 32

1st step in central dogma

Answer 32

replication

Question 33

semiconservative replication

Answer 33

each of the original nucleotide strands remains intact (conserved)
the original DNA molecule is half (semi) conserved during replication

Question 34

1958

Answer 34

Meselson and Stahl

parental strands serve as templates for new strands

Question 35

characteristics of replication

Answer 35

semiconservative replication can take place in several ways
-circular (bacteria)
-linear (most eukaryote)
-replicons (units of replication)
-replication origin (OR; start site)
-replication bubble (unwinding of the double helix)
-replication fork (point where the nucleotide strands separate from the DNA helix)
replication bubble moves away from replication fork

Question 36

requirements of replication

Answer 36

template of ssDNA
raw materials (substrates) to be assembled into a new nucleotide strand
enzymes/proteins that "read" the template and assemble the substrates into  DNA molecule

Question 37

dNTPs

Answer 37

deoxyribose sugar + a base (nucleoside)n + 3 phosphates

Question 38

how are new nucleotides added?

Answer 38

dNTPs
building blocks (substrates) of new DNA molecules
added to the 3’-hydroxyl (OH) group of the growing nucleotide strand

Question 39

how is circular DNA replicated?

Answer 39

E. coli
DNA synthesis is often bidirectional, but can be unidirectional
replication starts from a single origin of replication, producing a theta structure
as parental strands separate and new strands are being synthesized, a replication fork forms