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BIO 111 > Chapter 11 > Flashcards

Chapter 11 Flashcards

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Biology 101 flashcards
1
Q

genetic material must be able to..

A
  • contain the information to construct an organisms - a cookbook with ALL the recipes
  • pass from parent to offspring and from cell to cell during cell division (transmission)
  • be accurately copied (replication)
  • account for the known variation between organisms
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2
Q

what is the genetic material?

A

-how is material passed from generation to generation?

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3
Q

what is the genetic material?

A
  • late 1800’s scientist postulated a biochemical basis
  • researchers convinced chromosomes- carry genetic information
  • chromosomes= proteins + nucleotides
  • protein= more complex
  • expected to be the genetic material
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4
Q

Griffiths bacterial transformations

A
  • late 1920’s Frederick griffith work with Streptococcus pneumoniae
  • strains that secrete a capsule look smooth and are fatal in mice
  • strains that do not secrete capsules look rough; not fatal
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5
Q

Griffiths experiment

A
  • injected living type S bacteria into mouse- mouse died. Type S cells are virulent
  • inject living type R bacteria into mouse. Type R cells are benign
  • inject heat-killed S into mouse- benign
  • inject heat-killed S bacteria into mouse and living R bacteria- virulent type S strain in dead mouse’s blood. Living R cells transformed into virulent S cells by a substance from the heat-killed type S cells
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6
Q

Griffiths bacterial transformations results

A
  • genetic material from heat-killed type S bacteria was transferred to living type R bacteria
  • R-bacteria were transformed
  • Griffith did not know the biochemical basis of his “transforming principle”
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7
Q

Griffith’s bacterial transformation; “transforming principle”

A
  • met requirements for genetic material
  • variation- some bacteria make a capsule, some do not
  • the R strain acquired the information to make capsule (a trait)
  • the transformed R cells replicated this information and transmitted it to new cells during cell division to cause an infection
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8
Q

Avery, Macleod and McCarty

A
  • what substance is being transferred from the dead type S bacteria to the live type R?
  • used purification methods to purify different macromolecules (DNA,RNA and proteins)
  • only purified DNA from type S could transform type R bacteria
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9
Q

What happens just before a cell divides?

A

cells exactly double their amount of DNA

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10
Q

Chargaff; DNA position

A
  • he looked at the composition of DNA

- 3 components- a pentose sugar, phosphate group and a nitrogenous base

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11
Q

Chargaffs Rule

A
  • amounts of the 4 bases were not equal
  • however the amount of A=T and amount of G=C
  • Chargaffs Rule
  • double helix counts for this
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12
Q

Structure of DNA

A
  • too small to see through microscope at the time
  • portions of DNA’s structure could be inferred through a technique called X-ray diffraction
  • purified DNA bombarded with X rays
  • takes years to obtain a well made X-ray crystallograph
  • Rosalind Franklin did this
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13
Q

Watson and Crick; DNA structure

A
  • Wilkins gave x-ray graph to Watson and Crick
  • associated the graph to the double helix
  • found ball and stick model consistent with data
  • double helix
  • a purine w/ a pyrimidine
  • correct width of helix
  • fits with Chargaff’s A=T and G=C
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14
Q

5 levels of DNA structure

A
  1. nucleotides
  2. strand
  3. double helix
  4. chromsomes
  5. genome
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15
Q

Nucleotides

A
  • DNA structure

- the building blocks of DNA and RNA

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16
Q

Strand

A
  • DNA structure

- a linear polymer strand of DNA or RNA

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17
Q

double helix

A
  • DNA structure

- the two strands of DNA

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18
Q

chromosomes

A
  • DNA structure

- DNA associated with an array of different proteins into a complex structure

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19
Q

genome

A
  • DNA structure

- the complete complement of genetic material in an organism

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20
Q

nucleotides: DNA

A
  1. Phosphate grouo
  2. Pentose sugar- deoxyribose
  3. Nitrogenous base
    - Purines (A, G)
    - Pyrimidines (C,T)
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21
Q

nucleotides: RNA

A
  1. Phosphate group
  2. Pentose sugar
    - oxyribose
  3. Nitrogenous base
    - Purines (A,G)
    - Pyrimidines (C, U)
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22
Q

Conventional numbering system

A
  • sugar carbons 1’ to 5’
  • base attached to 1’
  • phosphate attached to 5’
23
Q

strand structure

A
  • sugar-phosphate backbone
  • bases on the inside
  • stabilized by H bonding
  • specific base pairing
  • major and minor grooves
24
Q

Chargaff’s rule; strand structure

A
  • A pairs with T via 2 H bonds
  • G pairs with C via 3 H bonds
  • keeps width consistent
  • 10 base pairs per turn
25
Q

Phosphodiester bond

A

-nucleotides covalently bonded via phosphodiester bond- phosphate group links 2 sugars

26
Q

complementary; antiparallel

A
  • 2 DNA strands are complementary
  • 5’- GCGGATTT-3’
  • 3’- CGCCTAAA- 5’

-2 strands are antiparallel
one stand 5’ to 3’ others 3’ to 5’

27
Q
  1. conservative (DNA replication)
A
  • the parental double helix stays together, the new double helix is completely new
28
Q
  1. Dispersive (DNA replication)
A

each daughter double helix is a random mosaic of parental DNA and newly synthesized DNA

29
Q
  1. semiconservative (DNA replication)
A

-each daughter double helix contains one parental strand and one new strand

30
Q

how does DNA replicate?

A
  • the double helix must open
  • strands separate
  • weak H bonds allow this
  • sequence on one strand is a template for the other strand
  • new nucleotides must obey the AT/GC rule
  • the new strand is the “complementary sequence”
  • end up with 2 identical DNA molecules
31
Q

Origin of replication

A
  • starting point
  • opens up to a replication bubble
  • produces 2 replication forks
  • bidirectional replication
  • bacteria have a signal origin
  • eukaryotes have multiple points of origin- speeds up process
32
Q

DNA replication in the cell (in vivo)

A
  • chromosomes are BIG, millions of bases
  • many proteins needed to copy a chromosome
  • copying occurs at many sites
  • or cell will take too long to divide
33
Q

DNA helicase (protein in replication)

A

-binds DNA and travels 5’ to 3’ using ATP to separate strand and move fork forward

34
Q

DNA topoisomerase (protein in replication)

A

relieves additional coiling ahead of replication fork

35
Q

Single-strand binding proteins (replication)

A

keep parental strands open to act as templates

36
Q

DNA polymerase (protein in replication)

A

-synthesizes new DNA strand- requires an RNA primer (short stretch of nucleotides to “grow off” of)

37
Q

DNA polymerase uses dNTPS

A
  • free nucleotides with 3 phosphate groups

- breaking covalent bond to release 2 phosphate groups provides energy to connect adjacent nucleotides

38
Q

DNA polymerase- 2 enzymatic features

A
  1. can’t begin DNA synthesis on a bare template strand
    - DNA primase must make a short RNA primer
    - primer later removed and replaced with DNA
  2. DNA polymerase can only work 5’ to 3’
39
Q

leading strand

A
  • DNA synthesized as one long continuous moelcule
  • DNA primase makes one RNA primer
  • DNA polymerase attaches in 5’ to 3’ direction
40
Q

lagging strand

A

-DNA synthesized 5’ to 3’ as “Okazaki fragments”

41
Q

leading and lagging strands

A
  • DNA polymerase “hopes” back to replicate DNA 5’ to 3’

- DNA ligase fills gaps

42
Q

DNA replication and errors

A
  • error rate about 1/billion bases- really good!
  • approx. 3 errors every time a human cell copies its DNA
  • error rate of nucleotide addition by DNA polymerase about 1/100,000
  • H-bonds between A&T/ G&C more stable than mismatches
43
Q

DNA replication & Errors (mutations)

A
  • DNA polymerase proofreads the sequence as it adds bases

- other DNA repair enzymes remove/fix errors as well

44
Q

Telomeres

A
  • no place for upstream primer, so DNA polymerase cannot copy the tip of the DNA strand with a 3’ end
  • if this replication problem were not solved, linear chromosomes would become progressively shorter
45
Q

Telomerase

A
  • enzyme attaches many copies of DNA repeat sequence to the ends of chromosomes known as telomeres
  • E.g GGGTTA(humans)
  • telomere at 3’ does not have a complementary strand and is called a 3’ overhang
  • complementary strand is embedded in telomerase
  • prevents chromosome shortening
  • provides upstream site for RNA primer
46
Q

Telomeres and aging

A
  • body cells have a predetermined life span
  • skin cell sample grown in a dish will double a finite number of times
  • infants, about 80 times
  • older person, 10to20 times
  • inserting a highly active telomerase gene into cells causes them to continue to divide
47
Q

Werner Syndrome

A
  • telomeres and aging
  • DNA helicase gene mutation
  • leads to lack of DNA repair and shortening of telomeres
  • DNA replication impaired
  • significant premature aging
48
Q

telomeres and cancer

A
  • in 99% of all types of human cancers. telomerase is found at high levels
  • prevents telomere shortening and may play a role in continued growth of cancer cells
  • mechanism is unknown
49
Q

eukaryotic chromosome structure

A
  • typical eukaryotic chromosome may be hundreds of millions of base pairs long
  • length would be 2 meters
  • must fit in cell 10-100um
  • chromosomes composed of chromatin
  • DNA + protein
50
Q

Level 1 of DNA packaging; DNA wrapping

A
  • DNA wrapped around histone protein complexes to form nucleosome
  • “beads on a string”
  • shortens length of DNA moelcule 7-fold
51
Q

Level 2 of DNA packaging; 30nm-fiber

A

current model suggests asymmetric, 3D zigzag of nucleosomes

-shortens length another 7-fold (49-fold..)

52
Q

Level 3 of DNA packaging; Radial loop domains

A

-interaction between 30nm fibers and nuclear matrix

53
Q

3 levels of DNA packaging

A
  • each chromosome located in discrete territory
  • level of compaction of chromosomes not uniform
  • Euchromatin vs. Heterechromatin
54
Q

Cell Division

A

-when cells prepare to divide, chromosomes become even more compacted

BIO 111 (17 decks)

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