Unit 4 Pt 1

Question 1

Primase makes a short strand of ______ to initiate DNA replication.

Answer 1

RNA

Question 2

2. The enzyme that copies DNA is called ______.


Answer 2

DNA polymerase

Question 3

___ ____ helps to seal gaps in the DNA strand.

Answer 3

DNA ligase

Question 4

The location where DNA replication begins is called the ______ of replication.

Answer 4

origin

Question 5

Prokaryotes typically have ______ origin(s) of replication, while eukaryotes have ______.

Answer 5

→ one; many

Question 6

The enzyme ______ unwinds the DNA double helix.


Answer 6

helicase

Question 7

Once helicase separates the strands, ______ bind to prevent them from reannealing.


Answer 7

single-stranded binding
proteins (SSBP)

Question 8

The enzyme ______ helps relieve tension and prevent tangling during replication.

Answer 8

topoisomerase

Question 9

DNA polymerase can only add nucleotides to an existing strand, so it requires a short piece of RNA called a(n)

Answer 9

RNA primer

Question 10

DNA polymerase reads DNA from ______ to ______, and builds the new strand from ______ to ______.

Answer 10

3′ to 5′ ; 5′ to 3′

Question 11

The strand that is copied continuously is called the ______ strand.

Answer 11

leading

Question 12

The strand that is copied in fragments is called the ______ strand.

Answer 12

lagging

Question 13

The short fragments formed on the lagging strand are called ______ fragments.

Answer 13

okazaki

Question 14

After RNA primers are removed, ______ fills in the missing nucleotides.

Answer 14

DNA polymerase (a different type)

Question 15

After gaps are filled, ______ seals the DNA backbone.


Answer 15

DNA ligase

Question 16

Prokaryotic DNA is typically ______, while eukaryotic DNA is ______.

Answer 16

circular; linear

Question 17

1. The ends of linear chromosomes are called ______.


Answer 17

telomeres

Question 18

Each time a eukaryotic cell divides, its telomeres get ______.

Answer 18

shorter

Question 19

Prokaryotic replication is faster partly because it proceeds in ______ directions from the origin.


Answer 19

both

Question 20

1. DNA polymerases also act as proofreading enzymes to check for and fix ______.


Answer 20

mistakes or mismatches

Question 21

DNA is a nucleic acid that forms a ______ structure, resembling a twisted ladder.

Answer 21

Double helix

Question 22

DNA’s double helix consists of two ___-____ backbones with _____ _____, like a twisted staircase. This structure is critical for its function and replication.

Answer 22

DNA’s double helix consists of two sugar-phosphate backbones with nucleotide rungs, like a twisted staircase. This structure is critical for its function and replication.

Question 23

The two backbones of DNA are made of alternating ______ and ______ groups.

Answer 23

Deoxyribose, phosphate

Question 24

____ (a sugar) and phosphate groups form the backbone, providing structural support, while ____ connect the strands.

Answer 24

Deoxyribose (a sugar) and phosphate groups form the backbone, providing structural support, while nucleotides connect the strands.

Question 25

The four nitrogenous bases in DNA are adenine, thymine, guanine, and ______.

Answer 25

Cytosine

Question 26

In DNA, adenine always pairs with ______, and guanine always pairs with ______.

Answer 26

Thymine, cytosine

Question 27

Specific base pairing (A-T, G-C) via ____ bonds makes DNA strands _____, crucial for accurate replication.

Answer 27

Specific base pairing (A-T, G-C) via hydrogen bonds makes DNA strands complementary, crucial for accurate replication.

Question 28

DNA strands are ______ because they run in opposite directions, with 5’ and 3’ ends oriented differently.

Answer 28

antiparallel

Question 29

DNA strands are antiparellel: One strand runs 5’ to 3’, the other 3’ to 5’, due to the orientation of ____ (5’) and ____ (3’) groups on deoxyribose sugars.

Answer 29

One strand runs 5’ to 3’, the other 3’ to 5’, due to the orientation of phosphate (5’) and hydroxyl (3’) groups on deoxyribose sugars.

Question 30

The 5’ end of a DNA strand has a free ______ group, while the 3’ end has a free ______ group.

Answer 30

Phosphate, hydroxyl

Question 31

The 5’ carbon has a phosphate, and the 3’ carbon has a hydroxyl (-OH), defining the ____ structure and replication direction.

Answer 31

antiparallel

Question 32

DNA’s primary function is to store instructions for building ______, which determine an organism’s traits and functions.

Answer 32

proteins

Question 33

DNA replication occurs during the ______ phase of interphase to prepare for cell division.

Answer 33

S phase

Question 34

DNA replication is ______ because each new DNA molecule contains one original strand and one new strand.

Answer 34

Semiconservative

Question 35

The original double helix splits, and each strand templates a new complementary strand, preserving half the original DNA.

Answer 35

Semiconservative replication

Question 36

Step 1 of Replication: The enzyme ______ unwinds and splits the DNA double helix at the origin of replication, creating a replication fork.

Answer 36

helicase

Question 37

Step 1 of Replication: _____ unzips the DNA, separating base pairs (A-T, G-C) to expose templates for replication.

Answer 37

helicase

Question 38

Step 2:1 of Replication: ______ proteins bind to separated DNA strands to prevent them from re-annealing during replication.

Answer 38

Single-stranded binding proteins (SSBPs)

Question 39

Step 2:1 of Replication: ____ stabilize single strands, ensuring they remain accessible for replication enzymes.

Answer 39

Single-stranded binding proteins (SSBPs)

Question 40

Step 2:2 of Replication: The enzyme ______ relieves tension ahead of the replication fork to prevent DNA tangling during unwinding.

Answer 40

Topoisomerase

Question 41

Step 2:2 of Replication: _____ reduces twisting stress caused by helicase, keeping DNA stable and untangled.

Answer 41

Topoisomerase

Question 42

Step 3 of Replication: ______ synthesizes makes a short strand of RNA primers to provide a starting point for DNA polymerase during replication. Explanation: DNA polymerase cannot initiate synthesis alone; ____ adds RNA primers as a foundation.

Answer 42

Primase

Question 43

Step 4 of Replication: ______ copies DNA by adding nucleotides in the 5’ to 3’ direction and removes RNA primers.

Answer 43

DNA polymerase

Question 44

Step 4 of Replication: ________ reads the template (3’ to 5’) and builds the new strand (5’ to 3’), also replacing primers with DNA.

Answer 44

DNA polymerase

Question 45

Step 5 0r 6 of Replication: The enzyme ______ seals gaps in the new DNA strand, especially where RNA primers were removed.

Answer 45

DNA ligase

Question 46

Step 5 or 6 of Replication: _____ joins DNA segments, seals the gaps, ensuring a continuous backbone, particularly between Okazaki fragments.

Answer 46

DNA ligase

Question 47

Step 4 of Replication -Elongation: The ______ strand is copied continuously in the 5’ to 3’ direction, following helicase. : Its orientation allows ____ ______to synthesize it smoothly in one piece as the replication fork opens.

Answer 47

Leading strand DNA polymerase

Question 48

Step 4 of Replication -Elongation: The ______ strand is copied discontinuously in short chunks called Okazaki fragments due to its 3’ to 5’ orientation. :___ _____ works backward in segments, requiring multiple RNA primers and ligase to connect fragments.

Answer 48

lagging DNA polymerase

Question 49

Short DNA segments on the lagging strand, synthesized between RNA primers, are called ______ fragments.

Answer 49

Okazaki fragments

Question 50

These fragments are joined by ligase to form a continuous lagging strand after primer removal.

Answer 50

Okazaki fragments

Question 51

Eukaryotic DNA is ______ and has multiple origins of replication, unlike prokaryotic DNA, which is circular.

Answer 51

linear

Question 52

Linear DNA has ends (______) that shorten per replication, while circular DNA replicates bidirectionally from one origin.

Answer 52

Linear DNA has ends (telomeres) that shorten per replication, while circular DNA replicates bidirectionally from one origin.

Question 53

The ends of eukaryotic chromosomes, called ______, shorten with each replication and may contribute to aging.

Answer 53

Telomeres

Question 54

_____ protect chromosome ends but lose segments over time, potentially affecting cell longevity.

Answer 54

Telomeres

Question 55

Prokaryotic DNA replication is faster because it is ______ from a single origin, unlike eukaryotic replication.

Answer 55

bidirectional

Question 56

Two helicases move in opposite directions from one origin, speeding up _____ replication compared to _____ unidirectional replication.

Answer 56

Two helicases move in opposite directions from one origin, speeding up prokaryotic replication compared to eukaryotic unidirectional replication.

Question 57

After replication, ______ repair corrects mismatched bases, such as a G-T pair instead of G-C. ____ _____ identifies and replaces incorrect bases to maintain genetic accuracy.

Answer 57

DNA polymerase

Question 58

______ repair removes and replaces large damaged DNA segments caused by chemicals or radiation (Excision Repair). _____ excises damaged regions and fills them with correct nucleotides to restore the sequence.

Answer 58

DNA polymerase