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BI157 > Chapter 16 > Flashcards

Chapter 16 Flashcards

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?

A

bind to unpaired DNA strands to keep them from repairing

19
Q

What is topoisomerase?

A

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

20
Q

What is a primer? (2)

A

Initial nucleotide chain produced during DNA synthesis
Made of RNA

21
Q

What is primase?

A

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

22
Q

What is DNA polymerase? (2)

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)

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?

A

On the free 3’ end of a primer

25
Q

What is a leading strand?

A

end where nucleotides are continuously added

26
Q

What is a lagging strand? (2)

A

end where nucleotide are continuously added away from the replication fork

Synthesized discontinuously, in a series of fragments (Okazaki fragments)

27
Q

How are lagging strands synthesized? (4)

A

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
Q

How is DNA Replicated? (3)

A

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
Q

What is the DNA replication complex?

A

various proteins that participate in DNA replication

30
Q

What happens after nucleotides bond with its template? (2)

A

DNA polymerase proofread each nucleotide

if an incorrect pairing occurs, polymerase removes the nucleotide

31
Q

What is mismatch repair? (2)

A

other enzymes remove and replace incorrectly paired nucleotides

When mismatched nucleotides evade proofreading by a DNA polymerase

32
Q

What is a mutation?

A

permanent changes to DNA

33
Q

What is nuclease? (2)

A

enzymes that cuts out damaged DNA sections

Aka nucleotide excision repair

34
Q

Why does eukaryotic DNA become shorter? (2)

A

it cannot add onto 5’ ends

Results with replications of shorter DNA molecules

35
Q

What are telomeres? (4)

A

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
Q

What is telomerase? (3)

A

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
Q

What are histones? (2)

A

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
Q

What are 10 nm fibers made up of? (2)

A

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
Q

What are 30 nm fibers? (2)

A

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
Q

What are 300 nm fibers? (2)

A

looped domains

30 nm fibers forms loops

41
Q

What are metaphase chromosomes? (2)

A

Looped domains coil and fold

700 nm

42
Q

What are heterochromatin?

A

visible as irregular clumps under a microscope

43
Q

What are euchromatin? (2)

A

less compact chromatin

Used in transcription

BI157 (21 decks)

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