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Block Two Cell Bio > DNA > Flashcards

DNA Flashcards

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Biology 101 flashcards
1
Q

Transforming principle

A

2 strains streptococcus pneumonaie; S strain virulent encapsulated; R stain avirulent, unencapsulated; showed live R with heat killed S virulent and encapsulated concluding dead S could transform part of R

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2
Q

DNA As Hereditary Material experiments

A

Transforming principle, DNA is transforming, blender experiment

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3
Q

DNA is transforming

A

fractioned various components of S strain bacteria found that DNA not protein was transforming

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4
Q

Blender experiment

A

worked with bacteriophage composed of DNA and protein; radioactively labled DNA and protein; infected bacteria with radioactive phage and used blender to separate phage coat from infected cells; found only DNA entered bacteria and was in progeny; conclusively shoed DNA as hereditary material

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5
Q

Nucleotide

A

consists of sugar (for DNA deoxyribose), nitrogenous base (purine or pyrimidine), and a phosphate group

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6
Q

Purines

A

adenine and guanine

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7
Q

Pyrimadines

A

Thymine and cytosine

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8
Q

DNA

A

polymer of nucleotides with phosphodiester linkages

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9
Q

Double helix

A

two complementary strands held together by hydrogen bonds; strands are antiparallel; has sugar phosphate backbone running along sides of helix bases are in the center

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10
Q

Principles of base pairing

A

%A=%T; %G=%C; A with T C with G

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11
Q

Genetic information carried in

A

sequence of bases

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12
Q

Directionality of DNA

A

5’ -> 3’ for one strand 3’ ->5’ for its complement

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13
Q

Compacting of DNA with reference to human genome

A

human genome contains about 3 billion base pairs which have to fit in DNA nucleus which is accomplished by 10,000 fold compaction

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14
Q

Chromatin

A

DNA complex with proteins

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15
Q

Heterochromatin

A

highly condensed, typically devoid of genes, associated with low gene expression; 2 types facultative heterochromatin and constitutive heterochromatin

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16
Q

facultative heterochromatin

A

heterochromatic in some cells euchromatic in others

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17
Q

constitutive heterochromatin

A

always heterochromatic

18
Q

euchromatin

A

less condensed associated with transcriptionally active genes

19
Q

Most basic level of packaging

A

nucleosome; consists of 200 bp DNA and 2 molecules of each histone H2A, H2B, H3, H4 creating a bead on a string structure

20
Q

packaging after nucleosome

A

nucleosomes further packaged into 30nm fiber through histone interaction and participation of histone H1

21
Q

Levels of packaging

A

Nucleosome -> 30nm fiber -> 30nm fibers organized into looped domains -> condensed DNA in mitotic chromosomes; net result is each DNA molecules packaged into mitotic chromosome 10,000 fold shorter than its extended length

22
Q

Genome components

A

unique sequence, repetitive sequence

23
Q

Genes

A

unique sequence; regions of DNA that control discrete hereditary characteristics; usually corresponding to a single protein or RNA; can consist of introns, exons, and various regulatory sequences

24
Q

exons

A

include all protein coding sequences (segment of eukaryotic gene that is transcribed into RNA and dictates that amino acid sequence of part of a protein)

25
Q

intron

A

noncoding sequence within eukaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing to produce mRNA

26
Q

Repetitive sequences

A
  1. Retroviral-like elements
  2. Non-Retroviral (non-LTR) retrotransposons
  3. DNA transposons
  4. Simple sequence repeats
27
Q

Retroviral-like elements

A

A form of retrotransposon (mobile DNA elements that move through an RNA intermediate) Have long terminal repeats (LTR) similar to retroviruses

28
Q

non-retroviral (non LTR) transposons

A

many are transcriptionally acitve; often mutated or truncated; only a small subset are able to transpose;
LINE- Long interspersed nuclear elements eg L1 element aprox 7kb
SINE- short interspersed nuclear elements; eg Alu element aprox 100-500bp

29
Q

DNA transposons

A

mobile DNA elements; no RNA intermediate

30
Q

simple sequence repeate

A

Satalites: repeats of 20-200bp units; totaling 100kb-1Mb; eg Alpha satellite at centromere
Mini-satalites: repeats of 10-100 bp units; totaling 1kb-20kb; eg telomeric DNA repeats
Micro-satalites: repeats of 1-6bp units; usually totaling < 150bp eg CA repeat

31
Q

DNA replication is semiconservative

A

each new DNA molecule contains 1 parents strand and 1 newly synthesized strand; shown in experiment where e

  1. grew bacteria in medium with heavy nitrogen
  2. transfered to medium with light nitrogen
  3. isolated newly replicated DNA and measured the density
  4. Results consistent with semiconservative model of DNA replication
32
Q

DNA replication originates

A

originates at replication origins; proceeds in both directions (bidirectional); replication must initiate from a primer

33
Q

DNA synthesis direction

A

occurs 5’ ->3’ meaning antiparallel strands are replicated in opposite directions

34
Q

Leading strand

A

grows in direction of unwinding, produces one continuous new strand

35
Q

Lagging strand

A

grows in opposite direction of unwinding ; as more template DNA is exposed more fragments are initiated;; produces small discontinuous segments of DNA (Okazaki fragments); these are ligated together to form a continuous strand

36
Q

DNA replication factors

A

DNA polymerase, DNA helicase, single stranded DNA binding proteins, Primase, DNA ligase, Teleomerase

37
Q

DNA polymerase

A

Catalyzes addition of new nucleotides at 3’ end of growing chain; multiple distance DNA polymerases mediate specialized functions in higher eukaryotes

38
Q

DNA helicase

A

unwinds DNA in front of the replication fork to prevent tangling of strands

39
Q

Single- stranded DNA binding proteins

A

Binds unwound single stranded DNA and prevents it from reanealing

40
Q

Primase

A

DNA dependent RNA-primase generates a a short piece of RNA that base pairs with template DNA and serves as primer for DNA synthesis; will be removed and replaced with DNA

41
Q

DNA ligase

A

Seals any gaps to produce continuous DNA strand (particularly gaps between Okazaki fragments)

42
Q

Telomerase

A

Assists in replication of chromosome ends (telomers) where lagging strand synthesis is problematic

Block Two Cell Bio (9 decks)

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