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Biology 106 Lecture > Chapter 14 > Flashcards

Chapter 14 Flashcards

DNA Structures and Functions

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1
Q

monomers that make up DNA

A

Nucleotide

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2
Q

the 3’ end of one strand faces the 5’ end of the other strand

A

anti-parallel

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3
Q

specific nucleotide sequences where DNA begins to unwind

A

origin of replication

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4
Q

Y-shaped structure formed during initiation of replication

A

replication fork

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5
Q

strand that is synthesized continuously in the 5’-3’ direction, which is synthesized in the direction of the replication fork

A

leading strand

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6
Q

during replication, the strand that is replicated in short fragments and away from the replication fork

A

lagging strand

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7
Q

DNA fragment that is synthesized in short stretches on the lagging strand

A

okazaki fragments

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8
Q

DNA at the end of linear chromosomes

A

telomere

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9
Q

Approximately how many base pairs make up a haploid human genome? How many functional genes does it contain?

A

3 billion base pairs and 20,000-25,000 functional genes are contained in them

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10
Q

What are the building blocks of nucleic acids?

A

nucleotides

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11
Q

What are the three main components of nucleotides? How do the four nucleotides differ? How does DNA differ from RNA?

A

nitrogenous base, pentose sugar (5-Carbon), and phosphate group
They differ based on the nitrogenous base (AGCT)
Sugar

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12
Q

Describe the phosphodiester linkages in nucleic acids. What is the significance of the 5’ to 3’ phosphodiester bond?

A

nucleotides are joined by phosphodiester bonds which are covalent bonds
phospate connects to the hydroxyl of 5’ and one nucleotide of the 3’

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13
Q

How are the nitrogenous bases paired in the double helix? What type of bond holds them together? How many bonds in each pairing?

A

T double bonds with A and C double bonds with G through Hydrogen bonds

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14
Q

What does it mean to say the two strands of DNA in the double helix are “complementary?” What does it mean to say they are “anti-parallel?”

A

The nucleotides pair together and the strands are “opposite:
the strands are flipped 5’ matches with 3’

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15
Q

How do the complementary and anti-parallel characteristics of DNA influence how it replicates?

A

easy to replicate and make a second strand and determines how it is replicated

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16
Q

In DNA replication, the two “old” strands of DNA serve as templates for two new strands. How are the old and new strands paired after replication?

A

semi conservatively
one old strand pairs with a new one

17
Q

In Eukaryotes, the chromatin has two different regions. What are they called? How are the similar? How are they different?

A

Heterochromatin is tightly packaged and the genes are not typically expressed
Euchromatin is less dense and the genes are usually transcribe or read

18
Q

What is the main enzyme involved in DNA replication?

A

DNA polymerase adds nucleotides to the growing chain complementary to the template strand

19
Q

Prokaryotes have how many types of DNA Pol? What are the main function of each

A

3
III is DNA synthesis
II is DNA repair
I is both

20
Q

What is the significance of the origin of replication? How does this site(s) differ from prokaryotes to eukaryotes?

A

where DNA begins to unwind and lets the replication machinery know where to begin
Prokaryotes only have one and eukaryotes have multiple

21
Q

What is the function of the helicase enzyme? How does it accomplish this task?

A

opens/unzips the DNA and forms the replication fork
unzips by breaking hydrogen bonds within the nitrogenous base pairs

22
Q

Where are the replication forks and what takes place in these regions?

A

Where DNA has opened and single-strand binding proteins coat the single strand to prevent it from reattaching

23
Q

How does the cell prevent the DNA from winding back up following the helicase?

A

single-strand binding proteins coat the single strands of DNA

24
Q

What is topoisomerase enzyme? Why is it important? How does it accomplish its task?

A

moves along the DNA molecule ahead of the helix to prevent overwinding of the double helix
causes temporary nicks in the DNA structure and then reseals it

25
Q

In which direction does DNA polymerase add nucleotides to the growing chain? Why can it only operate in this direction?

A

5’-3’ there is no free OH group to form phosphodiester linkages on the 3’ end

26
Q

What is the problem DNA polymerase encounters when trying to start the replication process? How is this problem overcome?

A

the complementary strand has no free OH- group to bind to
RNA Primers

27
Q

Why is RNA primase so important in DNA replication? How does its job differ on the leading vs. lagging strand?

A

provides and OH group to the 3’ end to extend the chain
there are multiple on the lagging strand but only one on the leading

28
Q

What are Okazaki fragments? Why are they made? What are the additional requirements of having to replicate the DNA in this fashion?

A

small fragments of DNA that are used to synthesis the lagging strand
need DNA ligase to glue together

29
Q

What is the function of the sliding clamp?

A

holds the DNA polymerase in place as it adds the nucleotides

30
Q

How is the RNA (primer regions) removed from the new strands of DNA? How are these gaps repaired?

A

exonuclease( DNA Pol I)
deoxyribonucleotides added by DNA polI and the ends are joined together by DNA ligase

31
Q

What is the job of DNA ligase?

A

joins the new DNA pieces to the synthesized strands

32
Q

How many origins of replication are in eukaryotes (humans)?

A

up to 100,000

33
Q

How do the rates of DNA replication compare in prokaryotes vs. eukaryotes? What cellular features account for some of the difference?

A

much slower in eukaryotes because there are more compaction levels and more nucleotides that need to be added

34
Q

What is the significance of having linear forms of DNA rather than circular as in prokaryotes? How have eukaryotic cells overcome this problem? Which cells are vulnerable?

A

there are sections at the end of strands that there is not a place for the primer to be made and the strand cant fully be replicated
create telomere regions
germ cell and adult stem cells

35
Q

What is the name of the enzyme that can extend the ends of the chromosomes?

A

telomerase

Biology 106 Lecture (19 decks)

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