DNA Structure And Replication

Question 1

Sequence of DNA that tells a cell how to assemble amino acids into a particular protein

Answer 1

Gene

Question 2

Single building block of DNA

Answer 2

Nucleotide

Question 3

Nucleotide consists of

Answer 3

Deoxyribose
Phosphate group
Nitrogenous bases

Question 4

(2) are_____, which have a two-ring structure

Answer 4

Adenine (A) and guanine (G)

purines

Question 5

(2) are_____, which have a single-ring structure.

Answer 5

Cytosine (C) and thymine (T)

pyrimidines

Question 6

are the information-containing parts of DNA because they form sequences.

Answer 6

bases

Question 7

Nucleotides join into long chains when chemical bonds form between the deoxyribose sugars and the phosphates. This creates a continuous__________

Answer 7

sugar-phosphate backbone

Question 8

The opposing orientation of the two nucleotide chains in a DNA molecule is called_____. It derives from the structure of the sugar-phosphate backbone._______ becomes evident when the carbons of the sugars are assigned numbers to indicate their positions in the molecule

Answer 8

antiparallelism

Question 9

are the informational parts of nucleotides.

Answer 9

DNA bases

Question 10

________of a nucleic acid consists of a 5-carbon sugar, a phosphate group, and an organic, nitrogenous base (G, A, C, or T).

Answer 10

nucleotide

Question 11

These specific purine-pyrimidine couples are called

Answer 11

complementary base pairs

Question 12

Chemical attractions called__________ hold the base pairs together.

They are weak individually, but over the many bases of a DNA molecule impart great strength.

_____hydrogen bonds join A and T, and_____ hydrogen bonds join G and C

Answer 12

hydrogen bonds

Two

three

Question 13

DNA consists of two chains of_______.

Answer 13

nucleotides

Question 14

(a)_______ hold the nitrogenous bases of one strand to the nitrogenous bases of the second strand (dotted lines).

Note that the sugars point in opposite directions—that is, the strands are_____.

Answer 14

Hydrogen bonds

antiparallel

Question 15

The_______ nature of the DNA double helix becomes apparent when the carbons in the sugar are numbered.

Answer 15

antiparallel

Question 16

The double-stranded, helical structure of DNA gives it great strength—____times the strength of single-stranded DNA, C which would not form a helix.

Answer 16

50

Question 17

the DNA coils around proteins called

Answer 17

Histones

Question 18

The bead part is called a_________. It is a little like wrapping a very long, thin piece of thread around your fingers, to keep it from unraveling and tangling.

Answer 18

nucleosome

Question 19

DNA wraps at several levels, until it is compacted into a______.

Specifically, a nucleosome forms around packets of____ histone proteins (a pair of each of four types).

Answer 19

chromosome

eight

Question 20

Altogether, the chromosome substance is called_______, which means “colored material.”

Answer 20

chromatin

Question 21

Chromatin is not just DNA; it is about 30 percent______,
30 percent_______,
30 percent_____, and
10 percent______

Answer 21

histone proteins

DNA binding proteins

DNA

RNA

Question 22

The DNA double helix is______, its strands running in an opposite head-to-toe manner.

Answer 22

antiparallel

Question 23

DNA winds tightly about______, forming______, which in turn wind tighter, forming_______.

Answer 23

histone proteins

nucleosomes

chromatin

Question 24

DNA has _______ replication because each new DNA double helix conserves half of the original

Answer 24

semiconservative

Question 25

some researchers suggested that DNA might replicate in any of three possible ways: ■ ■with one double helix specifying creation of a second double helix, and ■with a double helix shattering into pieces that would join with newly synthesized DNA pieces to form two molecules.

Answer 25

semiconservative conservative dispersive

Question 26

T or F DNA is highly condensed

Answer 26

True!

Question 27

DNA spools around_____ of four types of histone proteins, forming_____.

Answer 27

octets nucleosomes

Question 28

DNA replication occurs during _____ phase of the cell cycle

Answer 28

S phase

Question 29

Enzymes called______ unwind and hold apart replicating DNA, enabling other enzymes to guide the assembly of a new DNA strand.

Answer 29

helicases

Question 30

Human DNA replicates about___ bases per second

Answer 30

50

Question 31

A site where DNA is locally opened, resembling a fork, is called a

Answer 31

replication fork

Question 32

DNA replication begins when a_____ breaks the hydrogen bonds that connect a base pair

Answer 32

helicase

Question 33

hold the two strands apart.

Answer 33

Binding proteins

Question 34

______, then attracts complementary RNA nucleotides to build a short piece of RNA, called an_____, at the start of each segment of DNA to be replicated.

Answer 34

primase RNA primer

Question 35

The RNA primer is required because the major replication enzyme,______, can only add bases to an existing nucleic acid strand. (A______ is an enzyme that builds a polymer, which is a chain of chemical building blocks.)

Answer 35

DNA polymerase (DNAP) polymerase

Question 36

_________attracts DNAP, which brings in DNA nucleotides complementary to the exposed bases on the parental strand; this strand serves as a mold, or template. New bases are added one at a time, starting at the______

Answer 36

RNA primer

Question 37

unwinds parental double helix.

Answer 37

Helicase

Question 38

stabilize separate strands.

Answer 38

Binding proteins

Question 39

adds short primer to template strand.

Answer 39

Primase

Question 40

binds nucleotides to form new strands.

Answer 40

DNA polymerase

Question 41

joins Okazaki fragments and seals other nicks in sugarphosphate backbone.

Answer 41

Ligase

Question 42

________ proofreading activity checks and replaces incorrect bases.

Answer 42

DNA polymerase

Question 43

Continuous strand synthesis continues in a _____ direction.

Answer 43

5′ to 3′

Question 44

Discontinuous synthesis produces Okazaki fragments on the _____template.

Answer 44

5′ to 3′

Question 45

DNAP works directionally, adding new nucleotides to the exposed___′ end of the sugar in the growing strand. Overall, replication proceeds in a ___________ direction, because this is the only chemical configuration in which DNAP can add bases.

Answer 45

3” 5′ to 3′

Question 46

______then seals the sugar-phosphate backbones of the pieces, building the new strand. These pieces, up to 150 nucleotides long, are called_______, after their discoverer

Answer 46

ligase Okazaki fragments

Question 47

also “proofreads” as it goes, excising mismatched bases and inserting correct ones. It also removes the RNA primer and replaces it with the correct DNA bases.

Answer 47

DNA polymerase

Question 48

________, rewinds any sections of the DNA molecule that remain unwound

Answer 48

annealing helicase

Question 49

seal the entire sugar-phosphate backbone. It comes from a Latin word meaning “______.”

Answer 49

ligases to tie

Question 50

T or F DNA replication occurs simultaneously at several points on each chromosome, and the pieces join.

Answer 50

True!

Question 51

At each initiation site,____ directs synthesis of a short RNA primer, which DNA eventually replaces.______ adds complementary bases to the RNA primer.____ joins the sugar-phosphate backbone.

Answer 51

primase DNA polymerase Ligase

Question 52

DNA is highly coiled, and complexed with protein to form_____.

Answer 52

chromatin

Question 53

_______form as hydrogen bonds break between base pairs. ____builds short RNA primers, which DNA sequences eventually replace. Next _______ fills in DNA bases, and ligase seals the sugar-phosphate backbone.

Answer 53

Replication forks Primase DNA polymerase