DNA

Question 1

what is the shape of a DNA strand

Answer 1

double stranded, antiparallel, double helix

Question 2

is nitrogen hydrophobic or hydrophilic

Answer 2

hydrophobic

Question 3

is phosphate hydrophobic or hydrophilic

Answer 3

hydrophilic

Question 4

what makes the backbone of DNA

Answer 4

sugar + phosphate

Question 5

how many bonds does A form with T

Answer 5

2

Question 6

How many bonds does G form with C

Answer 6

3

Question 7

what is the 5’ end

Answer 7

phosphate group

Question 8

what is the 3’ end

Answer 8

OH group

Question 9

what are the 5 things DNA stability is affected by

Answer 9

Temperature (increase causes denaturation/melting of helix), cations (reduce charge repulsion), base mismatches, length (longer = more stable), proteins (like cations, histones)

Question 10

what is a nucleosome

Answer 10

complex of DNA and histones, loosely packed, site of DNA replication

Question 11

what is DNA like in bacteria

Answer 11

supercoiled and circular

Question 12

where does replication occur

Answer 12

nulceus, mitochondria and chloroplast (not tied to cell division)

Question 13

which phase does replication occur

Answer 13

before the cell divides, S phase

Question 14

what must DNA replication be coordinated with

Answer 14

the cell cycle

Question 15

what does the semiconservative model mean

Answer 15

one new strand and one old strand

Question 16

what is the first step in replication

Answer 16

the helix is unwound at the origin of replication

Question 17

what unwinds the helix and where does it unwind it

Answer 17

helicase, at the replication fork

Question 18

what do single stand binding proteins do when the helix is unwinding

Answer 18

maintain the single strands, keeps them from repairing

Question 19

what prevents the helix from overwinding

Answer 19

topiosomerase

Question 20

what is added to the strands after the helix is unwound

Answer 20

short RNA primers

Question 21

how are RNA primers made

Answer 21

primase

Question 22

what extends/elongates the primers

Answer 22

DNA polymerase 3

Question 23

what direction are nucleotides added

Answer 23

5’—->3’

Question 24

how is the leading strand formed

Answer 24

continuously, 1 primer required

Question 25

how is the lagging strand formed

Answer 25

discontinuously, in a series of segments = Okazaki fragments

Question 26

what happens after the strands are elongated

Answer 26

DNA polymerase 1 removes RNA primer and replaces it with DNA

Question 27

how are okazaki fragments joined

Answer 27

ligase

Question 28

how are errors in the sequence corrected

Answer 28

DNA polymerase proofreads and corrects mispairings

Question 29

what are some examples of DNA mutations

Answer 29

sickle cell anemia, huntingtons disease

Question 30

what is transcription

Answer 30

the synthesis of mRNA using DNA

Question 31

what is translation

Answer 31

synthesis of protein using mRNA

Question 32

where does transcription and translation occur in eukaryotes

Answer 32

nucleus, cytoplasm, ER, golgi

Question 33

where does transcription and translation occur in prokaryotes

Answer 33

cytoplasm

Question 34

what is the function of RNA polymerase

Answer 34

unwinds helix and joins complementary RNA nucleotides to the 3' end of RNA transcript

Question 35

what are the 3 events of transcription

Answer 35

initiation, elongation, termination

Question 36

how is transcription initiated in bacteria

Answer 36

RNA polymerase binds to promoter

Question 37

how is transcription initiated in eukaryotes

Answer 37

RNA polymerase binds to transcription factors that are bound to the promoter

Question 38

what occurs during elongation

Answer 38

polymerase moves downstream, pairing RNA nucleotides with DNA

Question 39

how is transcription terminated in bacteria

Answer 39

proceeds through terminator sequence in the DNA and signals the end of transcription

Question 40

how is transcription terminated in eukaryotes

Answer 40

proceeds through the polyadenylation signal in the pre-mRNA; this is later cleaved off

Question 41

what is a codon

Answer 41

three-nucleotide sequence that specifies a particular amino acid, base unit of the genetic code

Question 42

what are the four features of codons

Answer 42

linear, unambiguous, redundant, universal

Question 43

what is the template strand

Answer 43

the DNA strand that is transcribed

Question 44

what is the coding strand/non-template

Answer 44

same as mRNA, but with T not U

Question 45

what is tRNA

Answer 45

molecule containing anticodon and amino acid

Question 46

what are anticodons

Answer 46

specific sequence of three nucleotides on tRNA; complementary to a codon triplet on mRNA

Question 47

what is rRNA

Answer 47

makes up ribosomes with protein

Question 48

what does ribosomes do in translation

Answer 48

facilitates coupling of tRNA anticodons with mRNA

Question 49

what occurs in initiation

Answer 49

tRNA attaches to small ribosomal subunit to form the pre-initiation complex, the large subunit binds to the small

Question 50

what occurs during the elongation stage

Answer 50

amino acids are added one by one to the preceding amino acid at the C-terminus

Question 51

what does each addition involve

Answer 51

proteins called elongation factors

Question 52

what are the three steps of each addition

Answer 52

codon recognition, peptide bond formation, translocation

Question 53

when does termination occur

Answer 53

when a stop codon in the mRNA reaches the A site of the ribosome

Question 54

what does the A site do in termination

Answer 54

accepts protein called a release factor, this factor causes the addition of a water molecule instead of an amino acid, this reaction releases the polypeptide