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BI157 > Chapter 16 > Flashcards

Chapter 16 Flashcards

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1
Q

What is transformation?

A

a change in genotype and phenotype due to the assimilation of external DNA by a cell

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2
Q

What is a virus, and how does it infect?

A

DNA enclosed by a protective coat

In order to infect, it must take over a cell’s metabolic machinery

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3
Q

What is the heriditary material?

A

Nucleic acid

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4
Q

How do nitrogenous base amounts differ? (2)

A

Different species have different concentrations of specific nitrogenous bases

example- human nucleotide has 30.4% adenine, while sea urchins have 32.8%

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5
Q

What is Chargaff’s rule? (3)

A

The base composition of DNA varies between species

For each species, the percentage of A and T bases are roughly equal, and the percentages of G and C

bases are roughly equal

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6
Q

What is a double helix?

A

Presence of two strands

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7
Q

What is antiparallel? (2)

A

subunits run in opposite directions

The sugar-phosphate backbones of DNA run antiparallel

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8
Q

Why don’t bases pair like-like? (2)

A

because purines (adenine and guanine) are twice is wide as pyrimidines

The opposite pairs can also bond due to hydrogen bond placement

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9
Q

What is the basic model of DNA replication? (3)

A

The parental model has two complementary strands of DNA

The two strands separate. Each parental strand serves as a template for a new, complementary strand

Nucleotides complementary to the parental strands connect to form the sugar phosphate backbones of the new daughter strands

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10
Q

What is the semiconservative model? (2)

A

DNA replication model where the parent strand is used to make a new strand

Correct model

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11
Q

What is the conservative model of replication?

A

DNA replication where the parent strands somehow come back together after the process

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12
Q

What is the dispersive model?

A

all four strands of DNA following replication have a mixture of old and new DNA

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13
Q

What is the origins of replication? (2)

A

a site where the replication of chromosomes begin

Contain a specific sequence of nucleotides

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14
Q

How do bacteria replicate chromosomes? (2)

A

A bubble separates the circular DNA strands

Replication of DNA proceeds in both directions until the molecule is copied

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15
Q

How do eukaryotic chromosomes replicate? (2)

A

Multiple origins of replication
Proceeds from the 5’ to 3’ direction

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16
Q

What is the replication fork? (2)

A

end of a replication bubble

Y-shaped region where the parental strands of DNA are being unwound

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17
Q

What is a helicase?

A

enzymes that untwist the double helix at the replication forks

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18
Q

What is a single-strand binding proteins?

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A

bind to unpaired DNA strands to keep them from repairing

19
Q

What is topoisomerase?

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A

relieves strain of double helix by breaking, swiveling, and rejoining DNA strands

20
Q

What is a primer? (2)

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A

Initial nucleotide chain produced during DNA synthesis
Made of RNA

21
Q

What is primase?

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A

Synthesizes a primer by starting a complementary RNA chain from a single RNA nucleotide

22
Q

What is DNA polymerase? (2)

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A

catalyze synthesis of new DNA by adding nucleotides to a preexisting chain

Requires a primer and a DNA template strand

23
Q

What is dATP? (3)

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A

Nucleotide added consists of a sugar attached to three phosphate groups

Two phosphate groups are lost as each monomer joins the growing end

Releases pyrophosphate

24
Q

What direction does DNA polymerase add nucleotides?

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A

On the free 3’ end of a primer

25
What is a leading strand?
end where nucleotides are continuously added
26
What is a lagging strand? (2)
end where nucleotide are continuously added away from the replication fork Synthesized discontinuously, in a series of fragments (Okazaki fragments)
27
How are lagging strands synthesized? (4)
Each fragment is primed separately DNA pol 3 forms an okazaki fragment DNA pol 1 replaces the RNA nucleotides of the adjacent primer with DNA nulceotides DNA ligase form s a bond between the new DNA and the DNA of adjacent Okazaki fragment
28
How is DNA Replicated? (3)
Helicase unwinds the parental double helix Molecules of single-strand binding protein stabilize the unwound template strand Leading strand is synthesized continuously in the 5’ to 3’ direction by DNA pol 3
29
What is the DNA replication complex?
various proteins that participate in DNA replication
30
What happens after nucleotides bond with its template? (2)
DNA polymerase proofread each nucleotide if an incorrect pairing occurs, polymerase removes the nucleotide
31
What is mismatch repair? (2)
other enzymes remove and replace incorrectly paired nucleotides When mismatched nucleotides evade proofreading by a DNA polymerase
32
What is a mutation?
permanent changes to DNA
33
What is nuclease? (2)
enzymes that cuts out damaged DNA sections Aka nucleotide excision repair
34
Why does eukaryotic DNA become shorter? (2)
it cannot add onto 5’ ends Results with replications of shorter DNA molecules
35
What are telomeres? (4)
nucleotide sequences that prevent genes from eroding away Consists of multiple repetitions of one short nucleotide sequence Prevents the staggered end of the daughter molecule from activating the cell’s system for monitoring DNA damage Acts as a buffer zone against gene shortening
36
What is telomerase? (3)
catalyzes the lengthening of telomeres Not active in human somatic cells Active in cancerous cells, preventing cell division from shortening telomeres, prolonging cell division
37
What are histones? (2)
responsible for the first level of DNA packing in chromatin ⅕ of this is positively charged, binding to the negative phosphate backbone of DNA
38
What are 10 nm fibers made up of? (2)
Nucleosome- beadlike structures making up unfolded chromatin DNA wound twice around a protein core of 8 histones Two of H2A, H2B, H3, H4 Linker DNA- the “string” between nucleosome
39
What are 30 nm fibers? (2)
Interaction between histone tails of one nucleosome and the linker DNA and nucleosomes on either side H1 histone interacts, causing the 10 nm fiber to coil and fold to form a chromatin fiber
40
What are 300 nm fibers? (2)
looped domains 30 nm fibers forms loops
41
What are metaphase chromosomes? (2)
Looped domains coil and fold 700 nm
42
What are heterochromatin?
visible as irregular clumps under a microscope
43
What are euchromatin? (2)
less compact chromatin Used in transcription

BI157 (21 decks)

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