Week 6 (part 1 - ch. 3)

Question 1

Define DNA

Answer 1

A linear polymer of four subunits; the information archive in all organisms.

Question 2

Define double helix

Answer 2

The structure formed by two strands of complementary nucleotides that coil around each other.

Question 3

What are the two major biological functions of DNA?

Answer 3

DNA stores information

DNA transmits genetic information from one generation to the next

Question 4

Defien genetic information

Answer 4

Information carried in DNA, organized in the form of genes

Question 5

Define genes

Answer 5

The unit of heredity; the stretch of DNA that affects one or more traits in an organism, usually through an encoded protein or noncoding RNA

Question 6

Define gene expression

Answer 6

The production of a functional gene product.

Question 7

Define gene regulation

Answer 7

The various ways in which cells control gene expression

Question 8

What causes differences in genes?

Answer 8

the order of the individual sub units (bases) in the DNA

Question 9

Define nucleotides

Answer 9

A constituent of nucleic acids, consisting of a 5-carbon sugar, a nitrogen-containing base, and one or more phosphate groups.

Question 10

What does the elegant shape of the twisting strands rely on?

Answer 10

the structure of the DNA’s subunits aka nucleotides

Question 11

What do nucleotides consist of (3 things)

Answer 11

• a 5 carbon sugar
• a base
• one or more phosphate groups

Question 12

Define sugar

Answer 12

The simplest carbohydrate molecule; also called a saccharide

Question 13

Define base

Answer 13

A nitrogen-containing compound that makes up part of a nucleotide.

Question 14

Define phosphate group

Answer 14

A chemical group consisting of a phosphorus atom bonded to four oxygen atoms.

Question 15

What are the roles of the phosphate group and 5 carbon sugar in the DNA structure?

Answer 15

They form the backbone. Each sugar is linked to the phosphate group of the neighboring nucleotide

Question 16

What is the role of the bases sticking out of the sugar on nucleotides?

Answer 16

They give the nucleotide its chemical identity

Question 17

By convention, which direction are the carbon atoms on the sugar ring in DNA/RNA numbered?

Answer 17

clockwise

Question 18

Define deoxyribose

Answer 18

The sugar in DNA.

Question 19

Where is the base attached on the carbon ring in DNA/RNA?

Answer 19

it is attached to the 1’ carbon

Question 20

Define purine

Answer 20

In nucleic acids, either of the bases adenine and gunanine, which have a double-ring structure

Question 21

Define adenine (A)

Answer 21

A purine base.

Question 22

define Guanine (G)

Answer 22

A purine base.

Question 23

Define pyrimidine

Answer 23

In nucleic acids, any of the bases thymine, cytosine, and uracil, which have a single-ring structure.

Question 24

Define thymine (T)

Answer 24

A pyrimidine base.

Question 25

Define cytosine (C)

Answer 25

A pyrimidine base.

Question 26

Define nucleoside

Answer 26

A molecule consisting of a 5-carbon sugar and a base.

Question 27

a nucleoside with one or more phosphate groups constitutes a _____.

Answer 27

nucleotide

Question 28

Why are nucleoside triphosphates particularly inmportant?

Answer 28

because they are the molecules that are used to form nucleotide polymers: DNA and RNA.

Question 29

What other functions do nucleoside triphosphates do besides make up DNA and RNA?

Answer 29

They are carriers of chemical energy in the form of ATP and GTP

Question 30

Define phosphodiester bond

Answer 30

A bond that forms when a phosphate group in one nucleotide is covalently joined to the sugar unit in another nucleotide.

Question 31

_____ _____ are relatively stable and form the backbone of a DNA strand

Answer 31

Phosophodiester bonds

Question 32

What is the name of the C-O-P-O-C linkage?

Answer 32

Phosophodiester bond

Question 33

What gives DNA strands their polarity?

Answer 33

the phosphodiester linkage

Question 34

Define 5' end

Answer 34

The end of a nucleic acid strand containing a free 5′ phosphate group.

Question 35

Define 3' end

Answer 35

The end of a nucleic acid strand that carries a free 3′ hydroxyl.

Question 36

When a base sequence is stated without specifying the 5′ end, by convention the end at the left is the __ end

Answer 36

5'

Question 37

How would you specify a strand of DNA with the sequence TCGA with the T being nearest the hydroxyl group and the A being nearest the phosphate group?

Answer 37

5′-AGCT-3′ or equivalently 3′-TCGA-5′.

Question 38

How many base pairs are there per complete turn in the the double helix?

Answer 38

10

Question 39

What is the diameter or DNA?

Answer 39

2 nm

Question 40

Define major groove

Answer 40

The larger of two uneven grooves on the outside of a DNA duplex.

Question 41

Define minor groove

Answer 41

The smaller of two unequal grooves on the outside of a DNA duplex.

Question 42

What is the importance of minor and major groove in DNA?

Answer 42

proteins that interact with DNA often recognize a particular sequence of bases by making contact with the bases via the major or minor groove or both.

Question 43

Define antiparallel

Answer 43

Oriented in opposite directions; the strands in a DNA duplex are antiparallel.

Question 44

What does A pair with?

Answer 44

T

Question 45

What does G pair with?

Answer 45

C

Question 46

What does T pair with?

Answer 46

A

Question 47

What does C pair with?

Answer 47

G

Question 48

Each base pair contains a ____ and a _____

Answer 48

purine | pyrimidine

Question 49

Why does the precise pairing of bases maintain the structure of the double helix?

Answer 49

because pairing two purines would cause the backbones to bulge and pairing two pyrimidines would cause them to narrow

Question 50

Define complementary

Answer 50

Describes the relationship of purine and pyrimidine bases, in which the base A pairs only with T and G pairs only with C

Question 51

Because they form specific pairs, the bases A and T are said to be _____, as are the bases G and C

Answer 51

complementary

Question 52

The specificity of base pairing is brought about by ____ _____ that form between A and T and between G and C

Answer 52

hydrogen bonds

Question 53

How many hydrogen bonds do A and T share?

Answer 53

two

Question 54

How many hydrogen bonds do G and C share?

Answer 54

Three

Question 55

What two things can disrupt hydrogen bonding?

Answer 55

high pH or high temperatures

Question 56

Define base stacking

Answer 56

Stabilizing hydrophobic interactions between bases in the same strand of DNA.

Question 57

What is one of the most important features of DNA structure?

Answer 57

There is no restriction on the sequence of bases along a DNA strand

Question 58

What do the base pairing rules imply?

Answer 58

%A = %T and %G = %C | and that the percentage of purines equals the percentage of pyrimidines

Question 59

Many of the double-stranded DNA molecules in prokaryotic cells are ___ and form _____

Answer 59

circular | supercoils

Question 60

Define supercoils

Answer 60

A coil of coils; a circular molecule of DNA can coil upon itself to form a supercoil.

Question 61

Supercoiling is caused by enzymes called _____ that cleave, partially unwind, and reattach a DNA strand, which puts ____ on the DNA double helix.

Answer 61

topoisomerases | strain

Question 62

Define topoisomerases

Answer 62

Any one of a class of enzymes that regulates the supercoiling of DNA by cleaving one or both strands of the DNA double helix, and later repairing the break.

Question 63

Supercoils relieve the ___ and help to preserve the 10 base pairs per turn in the double helix.

Answer 63

strain

Question 64

n eukaryotic cells, most DNA molecules in the nucleus are _____, and each individual molecule forms one _____

Answer 64

linear | chromosome

Question 65

Define chromosome

Answer 65

In eukaryotes, the physical structure in which DNA in the nucleus is packaged; used more loosely to refer to the DNA in bacterial cells or archaeons.

Question 66

Double-stranded DNA molecules in eukaryotes are usually packaged with proteins called ______, and others, to form a complex of DNA and proteins referred to as ______

Answer 66

histones | chromatin

Question 67

Define chromatin

Answer 67

A complex of DNA, RNA, and proteins that gives chromosomes their structure; chromatin fibers are either 30 nm in diameter or, in a relaxed state, 10 nm.

Question 68

What are the main differences between RNA and DNA

Answer 68

- the sugar in RNA is ribose whereas the sugar in DNA is deoxyribose (which is why RNA is less stable than DNA) - RNA is less stable than DNA - in RNA the base uracil replaces thymine - while the 5′ end of a DNA strand is typically a monophosphate, the 5′ end of an RNA molecule is typically a triphosphate - RNA is usually a shorter strand than DNA - RNA is usually single stranded

Question 69

Why is a deoxyribose called a 2'-deoxyribose?

Answer 69

Because the oxygen is missing of the 2' carbon atom

Question 70

What is the covalent bond which links monomers together?

Answer 70

a phosphodiester bond

Question 71

What is the difference between structural polarity and bond polarity

Answer 71

structural: difference in EN of two ends of a molecule Bond: difference in EN between two atoms bonded together

Question 72

What is the name of the enzyme that forms at the start of transcription? A. RNA polymerase B. DNA polymerase C. DNA gyrase D. RNA helicase

Answer 72

A. RNA polymerase

Question 73

What genetic material is made during the process of transcription? A. mRNA B. tRNA C. rRNA D. All of the above

Answer 73

D. All of the above

Question 74

If the first nucleotide after the promoter on the top DNA strand is changed from G to T, what would the resulting nucleotide be on the mRNA? A. C B. A C. G D. T

Answer 74

B. A

Question 75

If you made a change in the promoter sequence in the DNA, what would happen at the RNA level? A. The RNA polymerase would not be able to recognize and bind the DNA, so no RNA would be made. B. The DNA helicase would not be able to recognize and bind the DNA, so the RNA would not be made. C. The mutation of the DNA would be carrier through to the RNA sequence. D. Nothing, the RNA would be made as usual.

Answer 75

A. The RNA polymerase would not be able to recognize and bind the DNA, so no RNA would be made.

Question 76

If the first nucleotide after the promoter on the bottom DNA strand is changed from C to T, what would the resulting nucleotide be on the mRNA? A. A B. U C. C D. T

Answer 76

A. A