DNA - Exam 2

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What is DNA made up of ?

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Exam 2

203 Terms

1

What is DNA made up of ?

nucleotides

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2

What are the 3 parts to a nucleotide ?

phosphate group (1-3), deoxyribose sugar, nitrogenous base

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3

Which type of base has a double ring structure ?

purines

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4

Which type of base has a single ring structure ?

pyrimidines

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5

What are the 5 nitrogenous bases and which is found in DNA or RNA?

adenine, thymine (DNA), guanine, cytosine, uracil (RNA)

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6

What make deoxygenated-ATP different from THE ATP?

missing OH group on sugar

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7

How many phosphate groups can be attatched to a DNA nucleotide?

1-3

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8

What is the difference in deoxyribose sugar (DNA) and ribose sugar (RNA)?

deoxyribose has H on 2 carbon spot, ribose has OH on 2 carbon spot

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9

Which nitrogenous bases are purines?

adenine and guanine

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10

Which nitrogenous bases are pyrimidines?

thymine, uracil, cytosine

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11

What makes thymine different from uracil?

thymine has methyl group (CH3)

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12

What type of bond links nucleotides?

phosphodiester bonds

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13

Is the linkage of nucleotide (phosphodiester linkage) energetically favorable?

unfavorable because of condensation rxn (covalent bond)

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14

1’ =

nitrogenous base

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15

3’ =

hydroxyl group

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16

5’ =

phosphate group

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17

What is considered the “top” end of DNA and what is always dangling off it?

5’ end; phosphate group always dangling off

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18

What is considered the “bottom” end of DNA and what is the always dangling off it?

3’ end; hydroxyl group always dangling off (OH)

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19

Number such as 5’ and 3’ refer to ?

carbon atoms in sugar ring

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20

What are the two sources of nucleotides?

de novo synthesis and salvage pathway

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21

What is the de novo synthesis?

cutting and pasting from acid or carbohydrate pieces

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22

What and where are nucleotides synthesized?

synthesized by enzymes in cytoplasm and transport to nucleus

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23

What is the salvage pathway?

old nucleotides are fixed up

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24

Which process of making nucleotides is preferred?

salvage pathway (conserves energy)

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25

What happens to nucleotides that cannot be used in salvage pathway?

nucleotide is broken down into uric acid; eliminated

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26

What is leech-nyan syndrome?

X-linked disorder caused by mutation in HGPRT gene (deficiency in HGPRT gene)

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27

What does HGPRT gene do?

makes enzyme needed to recycle purine nucleotides

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28

What happens in the lesch-nyhan syndrome when there is no HGPRT gene?

uric acid is overproduced; causing arthritis, mental disability, hypotonia (weak muscles)

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29

Does a patient of lesch-nyhan have enough DNA?

yes, symptoms are a result of uric acid accumulated in tissues

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30

What causes Alzheimer’s disease?

tau protein hyper-phosphorylation

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31

What do tau protein do to neuronal cells?

stabilize the microtubules (skeletons of neuronal cells)

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32

What does hyperphosphorylation do to tau proteins?

tau drops off and forms tangles, destabilizing the microtubules

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33

Phosphorylated tau also causes ?

chronic traumatic encephalopathy (CTE)

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34

How does phosphorylated tau cause CTE?

repeated blows to head, brain remembers everytime hit

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35

? is important in dephosphorylating proteins

alkaline phosphatase

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36

When there is a phosphatase deficiency, ? occurs

hypophosphatasia, where bones and teeth are not mineralized (soft bones)

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37

When a protein becomes denatured, ? begin to break and unfolds

H bonds

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38

What are the 4 causes of denaturation?

heat, changes in pH, salt concentration, solvent

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39

Denaturation is not always ?, it depends on method and what denaturatued

permanent

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40

What are the two reasons for cooking?

denature bacterial/fungal proteins and break food molecules down to conserve energy

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41

How else can food be denatured besides cooking?

prolonged exposure to acid in lemon, lime, or tequila (usually fish)

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42

Normal pH of vagina is ?

3.8-4.2

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43

How does sperm survive acidic vaginal environment?

sperm contains buffers that protect it from the acidity of vagina

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44

Are A-T bonds stronger, weaker or the same strength as G-C bonds?

G-C bonds are stronger with 3 H-bonds

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45

Why is DNA double stranded?

A-T and C-G pair via H-bonds

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46

DNA is ? as a single strand

unstable

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47

The two strands in DNA are ? meaning ?

antiparallel, running in opposite directions

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48

When calculating percentages of A,T,G, and C in DNA…

A=T and G=C

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49

What is the percentage of uracil in DNA strand?

0%

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50

Complementary base pairing forms what shape?

double helix

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51

The major grooves are ? and the minor grooves are ? in a double helix structure

major=wider, minor=narrow

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52

DNA is ? and the distance between sugar phosphates differ

asymmetrical

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53

What is the double helix structure most similar to?

staircase, proteins able to grip nitrogenous bases easier

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54

How many bases are in each turn?

10.4

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55

What is an ester bond?

C-O

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56

Where do most protein contact interactions occur?

major groove

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57

How many H-bonds does it take to stabilize G-C pair?

3 bonds

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58

How many H-bond does it take to stablize A-T pair?

2 bonds

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59

What does A-T pair having only 2 H-bonds allow for more easily?

easier to seperate 2 bonds for transcription and replication

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60

Which direction are nucleotide sequences are read?

5’ to 3’ (left to right)

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61

The 5’ end is always ?

top left

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62

The 3’ end is always ?

bottom right

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63

What types of cells have NO cell wall?

animal and fungal cells

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64

Where is DNA kept in a eukaryotic cell?

mitochondria (most DNA HERE) and nucleus

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65

What is DNA packaged as?

chromosomes (linear)

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66

What is a karyotype?

organized profile of all chromosomes

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67

What are the 3 structure needed to make a chromosome in any eukaryotic organisms?

telomere, replication origin, centromere

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68

What is a replication origin?

w/o this cannot pass on from mother to daughter cell, usually several

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69

What is a centromere?

where mitotic spindle attaches, usually 1

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70

What is a telomere?

caps at the ends of chromosomes, usually 2

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71

Are eukaryotic chromosomes haploid or diploid?

diploid (2 copies of each)

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72

What are homologous chromosomes?

same length, bonding pattern, gene order, but sequence of DNA is not identical

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73

Which human chromsomes are not (always) homologous?

X and Y (sex chromosomes)

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74

What are human chromosomes of males?

XY (Y is smaller)

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75

What are the human chromosomes of females?

XX

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76

What does the SRY gene do in the Y chromosome?

stimulate testes development and testerone production

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77

What humans’ sex during the first stages of development?

female

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78

What is swyer syndrome?

XY individuals who have defects in their testosterone production, have uterus, vagina, no ovaries

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79

What are the 3 possible defects of testosterone production?

SRY gene damaged; has SRY gene, but not producing testosterone; produce testosterone, but cannot recept it

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80

How can individuals with swyer syndrome become pregnant?

hormone therapy or donor embryo implantation

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81

What is the zygote that they believed Foekje Dillema had and what did divide into?

XXY and divided into a mosaic of XX and YY cells

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82

What is a mosaic?

when a person has more than 1 genotype

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83

What is XXY ?

Kleinfelter’s condition, usually in men that have feminized features, smaller size, more body fat (inital 47 chromosomes)

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84

What does intersex mean?

having characteristics of human male and female phenotypes

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85

What is the average length of DNA in the human cell?

2 meters

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86

What is the average diameter of DNA?

10 µmeters

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87

DNA cannot be ? or ? when condensing into nucleus

broken or tangled

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88

What are the 3 parts of chromatin?

DNA, histones, nonhistone binding protein

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89

Is there more DNA or protein in the chromosome?

protein (2x much)

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90

What is the difference between the nucleosome and chromatin?

chromatin includes non-histone proteins

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91

What are the 2 parts of a nucleosome?

DNA and histone

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92

Nucleosomes are sometimes called?

beads on a string

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93

How many times does DNA wrap around cylindrical shaped histone?

1.7

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94

How many proteins are in 1 histone and how many of each?

8 proteins (octamers), 2 of H2A, H2B, H3, H4

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95

Why do histone “tails” (N-terminal ends) stick out?

targets for modification and interactions with other proteins

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96

What are three important things to notice about histone protein structure?

forms cylindrical shape, histones stick out, DNA wraps tightly around histones

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97

Do you think DNA binds to the histone by covalent or noncovalent bonds and why?

noncovalent bonds (weak), must be unwrapped all the time for replication and transcription

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98

Why do you think a large percentage of histone amino acids are positively charged?

DNA is very negatively charged; helps anchor DNA to histone

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99

What are the advantages of G-C bonds on the TOP of histone?

3 bonds more stable

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100

What are the advantages of A-T bonds at the BOTTOM of histone?

2 A-T bonds easier to push together

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