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Biology 1113 > Chapter 16 > Flashcards

Chapter 16 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Frederick Griffith

A

began search for genetic material in 1928

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2
Q

Griffith’s experiment

A

a pathogenic and a harmless strain of bacteria

heat kill pathogenic = harmless

mix with living harmless = living become pathogenic

called this transformation

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3
Q

transformation

A

a change in genotype and phenotype due to assimilation of foreign DNA

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4
Q

Where did evidence for DNA as genetic material come from?

A

Studies of viruses that infect bacteria

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5
Q

bacteriophages

A

viruses that infect bacteria (often simply protein)

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6
Q

Hershey and Chase

A

showed that DNA is the genetic material of a phage known as T2 (not the protein)

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7
Q

Chargaff’s rules

A

The base composition of DNA varies between species

In any species the number of A and T bases are equal and the number of G and C bases are equal.

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8
Q

Wilkins and Franklin

A

X-ray crystallography to study molecular structure

Picture of DNA

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9
Q

Watson and Crick

A

DNA helical with 2 antiparallel strands

2 outer sugar-phosphate backbones (nitrogenous bases inside) [A-T and G-C]

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10
Q

Why does the pairing of pyrimidine and purine make sense?

A

It gives a uniform width to the DNA

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11
Q

semiconservative model of replication

A

when a double helix replicates, each daughter molecule will have one old strand (derived from the parent molecule) and one newly made strand

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12
Q

Competing models of replication at the time of Watson and Crick

A

conservative (old strands rejoin)

dispersive (each strand is mix of old and new)

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13
Q

How did Meselson and Franklin support the semiconservative model?

A

old strands - heavy N
new strands - light N

first replication = hybrid DNA (not conservative)

second replication = 2 light and 2 hybrid (not dispersive)

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14
Q

origin of replication

A

where replication begins (euk may have 100s or 1000s)

2 strands are separated, opening a replication “bubble”

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15
Q

From which direction does replication begin?

A

Both directions

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16
Q

replication fork

A

At the end of each replication bubble: a Y-shaped region where new DNA strands are elongating

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17
Q

helicases

A

enzymes that untwist the double helix at the replication forks

18
Q

single-strand binding proteins

A

bind to and stabilize single-stranded DNA

19
Q

topoisomerase

A

corrects “overwinding” ahead of replication forks by breaking, swiveling, and rejoining DNA strands

20
Q

RNA primer

A

DNA polymerases cannot initiate synthesis of a polynucleotide; they can only add nucleotides to an existing 3’ end

21
Q

primase

A

an enzyme that can start an RNA chain from scratch and adds RNA nucleotides one at a time using the parental DNA as a template, creating short primer (5-10 nucleotides long)

22
Q

DNA polymerases

A

enzyme that catalyze the elongation of new DNA at a replication fork

23
Q

Nucleoside triphosphates

A

“building blocks”

partly cause the reactivity of nucleotides

24
Q

Which direction does a new DNA strand elongate?

A

Only 5’ to 3’

25
Q

leading and lagging strand

A

DNA will synthesize a leading strand moving toward the replication fork and a lagging strand moving away from the replication fork

26
Q

Okazaki fragments

A

synthesize the lagging strand, joined together by DNA ligase

27
Q

What if there are incorrect nucleotides? What is done to prevent/fix that?

A

DNA polymerase proofread new DNA and replace any incorrect nucleotides

28
Q

mismatch repair

A

other enzymes can remove and replace incorrectly paired nucleotides

29
Q

What can change DNA?

A 
harmful exposure (cigarette smoke and X-rays)
spontaneous change (mutations for natural selection)
30
Q

nuclease

A

cuts out and removes damaged stretches of DNA

31
Q

telomeres

A

special nucleotide sequences at the end of euk chromosomal DNA

do not prevent shortening of DNA, but do postpone erosion of genes near the ends of DNA molecules

32
Q

What might the shortening of telomeres be linked to?

A

Aging

33
Q

telomerase

A

catalyzes the lengthening of telomeres in germ cells

34
Q

Why might the shortening of telomeres be helpful?

A

Could prevent cancerous growth by limiting the number of cell divisions

35
Q

nucleoid

A

where the “supercoiled” DNA of bacteria is found

36
Q

chromatin

A

in euk cell, combines DNA precisely with proteins

37
Q

histones

A

proteins responsible for the first level of packing in chromatin

38
Q

heterochromatin

A

highly condensed chromatin even in interphase (difficult to express genetic information coded in these regions)

39
Q

euchromatin

A

loosely packed chromatin

40
Q

Replicating the ends of DNA molecules is not a problem for prokaryotes because…

A

They have circular chromosomes.

Biology 1113 (7 decks)

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