DNA

Question 1

nucleic acids

Answer 1

• genetic material stored here

- passed from generation to generation via DNA and in some cases RNA (viruses)

Question 2

circular chromosomes

Answer 2

prokaryotes

Question 3

linear chromosomes

Answer 3

eukaryotes

Question 4

plasmids

Answer 4

prokaryotes and sometimes eukaryotes

Question 5

monomer of dna

Answer 5

nucleotide

Question 6

polymer of dna

Answer 6

nucleic acid

Question 7

exons

Answer 7

areas that code for genes

Question 8

introns

Answer 8

areas that don’t code for genes (junk)

Question 9

base pair rules

Answer 9

A binds to T with 2 H bonds

G binds to C with 3 H bonds

Question 10

shape of dna

Answer 10

double helix

Question 11

purines

Answer 11

• 2 carbon rings

- guanine and adenine

Question 12

pyrimidines

Answer 12

• 1 carbon ring

- thymine, cytosine, uracil

Question 13

covalent bonds

Answer 13

between the phosphates and deoxyribose and nitrogenous bases

Question 14

speed of dna replication

Answer 14

• extremely rapid

- in prokaryotes, up to 500 nucleotides added a second

Question 15

accuracy of dna replication

Answer 15

• very accurate

- only about 1 in a billion nucleotides is incorrectly paired

Question 16

origins of replication

Answer 16

• dna replication begins here

- have a specific sequence of nucleotides

Question 17

helicases

Answer 17

unwind the parental double helix and initiate replication

Question 18

replication fork

Answer 18

the shape formed as helicase unwinds dna

Question 19

replication bubble

Answer 19

zones where replication are occurring that you can see

Question 20

single strand binding proteins

Answer 20

keep the separated strands apart and stabilize the unwound dna

Question 21

topoisomerase

Answer 21

prevents the areas above the forks from kinking

Question 22

primase

Answer 22

lays down primer (complementary to dna and about 10 nucleotides long) to start the addition of of new nucleotides

Question 23

dna polymerase

Answer 23

• catalyze synthesis of a new dna strand according to base pairing rules
• new nucleotides align themselves along the templates of the old dna strand and dna polymerase links the nucleotide to the growing strand

Question 24

direction of replication

Answer 24

grow in the 5’ to 3’ direction since new nucleotides are only added to the 3’ end of the the growing strand

Question 25

leading strand

Answer 25

continuous synthesis - grows 5’ to 3’

Question 26

lagging strand

Answer 26

discontinuous synthesis - produced in Okazaki fragments

Question 27

Okazaki fragment

Answer 27

100-2000 nucleotides, synthesized in the 5’ to 3’ direction

Question 28

dna ligase

Answer 28

joins okazaki fragments - forms covalent bonds between the 3’ end of each new fragment to 5’ end of growing chain

Question 29

mistakes in base pairs

Answer 29

= mutation, changes dna -> changes rna-> changes proteins -> changes phenotype -> evolution

Question 30

mismatch repair

Answer 30

• corrects mistakes while new dna is being synthesized
• dna polymerase each newly added nucleotide against its template; if incorrect the enzyme removes and replaces before continuing

Question 31

excision repair

Answer 31

• corrects accidental changes that occur in existing dna

- these changes may result from reactive chemical, radioactivity, x rays, ultraviolet light

Question 32

repair enzymes

Answer 32

• 50 types of dna repair enzymes
• the damaged segment is cut out by one repair enzyme and the remaining gap is filled in by base pairing nucleotides with the undamaged strand, dna polymerase and ligase catalyze the filling in process