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AP Biology A and D > Molecular Basis of the Gene > Flashcards

Molecular Basis of the Gene Flashcards

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1
Q

Transformation

A

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

Think: Griffith and Avery

Griffith did not know in 1928 what the transforming factor was made of!

Avery and team figured it out.

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2
Q

phage

A

Virus that attacks bacteria

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3
Q

Chargaff’s rules

A

DNA base composition varies between species

For each species. the % of A and T are roughly equal

The % of G and C bases are roughly equal.

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4
Q

photo 51

A

Confirmed DNA is a helix

2 strands (not 3)

uniform width (eliminating Watson’s idea that A could pair with A)

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5
Q

Antiparallel

A

subunits run in opposite directions

5’ to 3’ paired to a strand that is running 3’ to 5’

The 5’ end has a phosphate group, the 3’ a -OH

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6
Q

semiconservative model of replication

A

Proposed by Watson and Crick, proven by Meselson and Stahl.

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7
Q

origins of replication

A

sites where DNA replication begins

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8
Q

Replication fork

A

Y shaped region where the parental strands are being unwound by helicase (shown in yello)

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9
Q

single-strand binding proteins

A

bind to unpaired DNA strands to keep them from re-pairing

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10
Q

topoisomerase or gyrase

A

The untwisting of the DNA causes strain ahead of the fork.

Topoisomerase relieves the strain.

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11
Q

primer

A

short stretch of RNA (5 to 10 nucleotides long)

Made by primase.

The primer is shown in green.

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12
Q

DNA polymerase

A

catalyze the synthesis of new DNA by adding nucleotides to the 3’ end of the preexisting chain.

There are several polymerases in E.Coli but 2 you need to know.

DNA polymerase I and DNA polymerase III

There are 11 in eukaryotes!

DNA polymerase can add 500 nucleotides per second in prokaryotes and 50 per second in human cells.

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13
Q

dATP or dGTP, etc

A

a sugar, base, and three phosphates.

2 phosphates are released when a nucleotide is added.

exergonic reaction/helps drive polymerization

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14
Q

leading strand vs. lagging strand

A

leading: one primer, made continuously by DNA pol III
lagging: many primers, made discontinuously, series of segments called Okasaki fragments.

Fragments are 1000-2000 nucleotides in E. coli and 100-200 nucleotides in Eukaryotes

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15
Q

ligase

A

enzymes the joins the sugar-phosphate backbones of the Okasaki Fragments

We’ll see it again in figure 13.21 and 13.25

Anytime repairs must be made, ligase is used!

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16
Q

mismatch repair/change in base repair

A

Even though DNA polymerase is a great proofreader (there is one error per 10 billion nucleotides) it does happen.

Other enzymes remove (nuclease) and replace incorrectly paired nucleotides.

Ligase seals the backbone together.

One mismatch is associated with a form of colon cancer.

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17
Q

telomeres

A

As a result of many rounds of replication, DNA molecules get shorter.

telomeres protect the ends of DNA-contain no genes.

A buffer zone of repeated TTAGGG to protect genes.

Postpone erosion of genes

The telomerase enzyme lengthens telomeres but is not active in most human cells.

The shortening of telomeres is proposed to play a role in aging.

Short Video: https://www.youtube.com/watch?v=U0fRAr-ZHCo

https://www.healthline.com/health/telomeres#telomere-lengthening

18
Q

purine

A

2 ring nitrogenous base

Includes A and G

19
Q

pyrimidine

A

one ring nitrogenous base

includes cytosine, thymine and uracil

20
Q

hydrogen bonds

A

hold DNA together

3 for G and C

2 for A and T

21
Q

covalent bond

A

holds:

sugar to phosphate

sugar to nitrogenous base

22
Q

semiconservative replication

A

one old strand and one new strand.

Meselson-Stahl

23
Q

replication fork

A

Y shaped region where the parental strands are being unwound

24
Q

primer

A

short strand of RNA made by primase

5-10 nucleotides long

uses parental strand

25
Q

DNA polymerase

A

There are two you need to know:

I removes primer and replaces RNA with DNA

III adds a DNA nucleotide to the RNA primer and then keeps going until the end of the DNA strand

50/second in human cells

26
Q

leading vs. lagging strand

A

Leading:DNA polymerase continuously adds nucleotides to the new strand as fork progresses.

Lagging: discontinuous, moving away from the fork, series of segments called Okasaki fragments

27
Q

DNA ligase

A

The enzyme that glues the fragments into a continuous step.

Can glue a plasmid together or when a repair is made to the DNA

28
Q

nuclease

A

DNA cutting enzyme.

Removes damaged DNA

29
Q

telomeres and fertility

A

no genes

end of chromosomes

repetitions of TTAGGG

a buffer zone that protects genes

postpone erosion of genes

30
Q

telomerase

A

an enzyme that elongates telomeres

active in germ cells, not somatic cells

may be overacitve in cancer cells

31
Q

histone

A

100 amino acids

first level DNA packing

Four types of histones

32
Q

nucleosome

A

DNA wound twice around a protein core of 8 histones

33
Q

30-nm fiber

A

interaction between histone tails of one nucleosome and the linear DNA and nucleosomes on either side

Found in interphase

34
Q

heterochromatin

A

10 nm, 30 nm and looped

not accessible to transcription (genes are not expressed or are off)

35
Q

genetic engineering

A

direct manipulation of genes for practical purposes

agriculture

criminal law

medical research

36
Q

plasmid

A

a circular molecule of DNA

37
Q

recombinant DNA

A

a molecule of DNA containing two different sources often different species

38
Q

restriction enzymes

A

cut up DNA at a specific site, called a restriction site

39
Q

sticky ends vs. blunt ends

A

unpaired bases

40
Q

PCR

A

polymerase chain reaction

This technique can make billions of copies of a specific target DNA

41
Q

CRISPR Cas 9

A

bacterial protein that helps defend bacteriophage infections.

Cas9 works with guide RNA (homing device)

Cas9 cuts specific DNA.

Triggers DNA repair or the DNA can be knocked out

42
Q

gene drive

A

altering genes in an insect (example) so that it can’t transmit disease

engineering the new allele so that it is much more highly favored for inheritance

reproduction drives the new allele through the population

AP Biology A and D (7 decks)

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