dna replication

Question 1

why is dna used as a template

Answer 1

since dna is double stranded, each strand can be used as a template to make the other strand through the process of base pairing. the two strands are complementary.

Question 2

why is dna replication important.

Answer 2

so when cell divides into two identical daughter cells, each contains complete set of dna. this is also important for growing organisms, repair and replacement of cells.

Question 3

why is dna replication called semi-conservative?

Answer 3

because each new strand of dna contains one strand strand of the original dna, so its called that. each parental strand acts as a template for a new complementary strand.

Question 4

helicase

Answer 4

unwinds the two coiled strands of dna, and it breaks the hydrogen bonds between the base pairs on the two parental strands of dna.
(step 1: separation)

Question 5

replication fork

Answer 5

the point where the parental strands of dna are separated.
(step 1: separation)

Question 6

single stranded dna binding proteins (ssb)

Answer 6

attach to the separated strands, keeping them apart and preventing them from coiling. (step 1: separation)

Question 7

RNA primase

Answer 7

adds short length of rna primar so that polymerase knows where to start. (step 2: elongation)

Question 8

polymerase

Answer 8

binds to the dna molecule and matches each expose nucleotide with its complemetary base pair. (step 2: elongation)

Question 9

DNA polymerase limitations

Answer 9

1) can only build dna strand in one direction
2) needs enzyme called primase to make an rna primer as a starting point.
3) the rna primer is eventually removed and the is filed in by polymerase 1.

Question 10

what direction does polymerase synthesis new complementary dna strands in the…

Answer 10

5’ to 3’ direction

Question 11

different strands

Answer 11

leading strand: one new strand is continuously replicated.
lagging strand: okazaki fragments, other new strand is replicated in small segments.

Question 12

dna ligase enzymes

Answer 12

will link the sugar-phosphate backbone between the okazaki fragments into one long strand. (step 3: termination)

Question 13

nucleases enzymes

Answer 13

proofread the copied dna strands to check for errors. (step 3: termination)

Question 14

replication bubbles

Answer 14

since dna molecules (chromosomes) are so long, replication occurs simultaneously at many points along chromosome which is called replication bubbles until two complete and identical double stranded chromosomes are produced. (step 3: termination)

Question 15

what are replication strands called

Answer 15

called sister chromatids, which are joined together at the centromere

Question 16

mistakes during replication

Answer 16

1. a change in the nucleotide sequence at one location called a mutation may have serious effects on the cell
2. dna can be damaged by a variety of environmental factors and agents like hazardous chemicals, ultraviolet radiation, etc which cause uncomplimentary nitrogen bases to become paired.

Question 17

what prevents damage for replication??

Answer 17

damage is prevented by nucleus and dna polymerase that runds along the strands of dna looking for mismatched pairs. once a damaged section is detected, another enzyme snips the error from the chain and replaces it with the correct nucleotide sequence