Chapter 2: DNA - The Genetic Material Flashcards Preview

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Flashcards in Chapter 2: DNA - The Genetic Material Deck (49):

Griffith's Experiment
L> S: virulent strain
L> R: avirulent strain
L> varieties I and II
how can the mutations occur?

L> smooth, shiny colonies
L> rough colonies

- IIS --> R---> IIS
IIIS---> R---> IIIS
L> cannot go between varieties ( i.e. IIS--> IIIS)
AKA they are type specific mutations


Griffith's Experiment
What is the S strain infectious?
L> R strain difference?

- the presence of a polysaccharide coat (capsule) surrounding each cell. Gives them their shiny appearance.
L> lacks the capsule...via mutation stopping it from getting it


Griffith's Experiment Give a run through ! NO PEAKING G.
-Mice + IIR ( R derived from IIS ) = ?
- Mice + living IIIS = ?
- Mice + IIIS (killed via heat) = ?

-Mice + IIR ( R derived from IIS ) = mice lived
- Mice + living IIIS = death ( IIIS could be extracted from blood)
- Mice + IIIS (killed via heat) = mice lived
- Results : bacteria had to be alive and have the coating to be virulent.


Griffith's Experiment Give a run through ! NO PEAKING G. (Part 2)
- mice + (living IIR + heat killed IIIS) = ??
L> issue?
L> conclusion?

- dead mice, living IIIS was found in blood....
L> living IIIS could not be from IIR ( IIR--> IIS)
L>conclusion: IIR had somehow TRANSFORMED into IIIS via interaction with dead IIIS.


Griffith's Experiment Give a run through ! NO PEAKING G.
- Genetic material from the dead IIIS had been added to the ___ in the ___.
- What did Griffith think the unknown agent was? ( transforming principle)

- genetic material, living IIR
- thought a protein was the cause...thought wrong
ALSO agents are important in recombinant dan exp


When you think of Griffith one would think of the discovery of _____?

- genetic material


Avery's experiment:
- what was his study about?

- the transformation of S- type to R-type bacteria to learn what the agent was.


Avery knew the transforming agent had to be one of what four things?

- polysaccharides, proteins, RNA or DNA


Avery's experiment:
- DNA +RNA from IIIS + RNase = ___ + IIR bacteria=???
- DNA + RNA from IIIS bacteria + DNase=___+ RNA IR bacteria = ???

- only DNA remains...
L> added to IIR bacteria
L> = plate growth on medium-> IIIS trasnformants produced
- only RNA remains
L> added to IIR bacteria
L> no IIIS transformants


Avery's experiment:
- results of this showed what?

- DNA not RNA was the transforming nucleic acid agent.


When one thinks of Avery think also of what?

confirmation of genetic material


Hershey and Chase:
L> there was lingering controversy over what?

DNA and protein being the genetic material


Hershey and Chase:
L> they used what to test the controversy in this experiment?

- T2 bacteriophages consisting of only DNA and a protein coat.


Hershey and Chase:
> T2 phage + E.coli and grow in the medium with P32...=?
> T2 Phage + E.coli and grow in the medium with S35=??

- T2 progeny with DNA labeled via P32
- T2 progeny with protein labeled via S35


Hershey and Chase:
> T2 P32 DNA + E.coli --(blend)--> =??
> T2 S35 Protein phage + E.coli---(blend)--> =???
- conclusion?

- phage ghosts outside of cell. (protein)
-radioactivity recovered in host and passed on to phage progeny!
-- radioactivity recovered in phage ghosts and not passed on to the progeny.
L> Protein does not get into the cell and therefore cannot pass on information to other gens therefore DNA is the heredity material...


What is a retrovirus?ex?

- starts off with RNA and uses Reverse transcriptase----> DNA----> RNA
(rna dependent dna poly)


DNA Double Helix:
- consists of two what?

- polynucleotide chains


DNA Double Helix:
- the two strands are antiparallel or parallel?

- antiparallel


DNA Double Helix:
- backbone is made of?

- sugar-phosphate backbone


DNA Double Helix:
- What kind of bonds are between the bases?
L> how many between A and T ?
L> "....." C and G?

- hydrogen
L> two bonds
L> triple bonds


DNA Double Helix:
- Why is it ideal for denaturation of DNA to occur in areas rich in A and T?

- because the bonds between A and T are much weaker in comparison to the strong triple hydrogen bonds of C and G


DNA Double Helix:
- Bases per turn?



DNA Double Helix:
- Major Groove?
- Minor Groove?

- proteins/factors can come in and interact with the DNA to control it's expression or synthesis... but it does not interrupt binding of bases. ( easier on major groove bc the backbone isn't in the way)


Three types of DNA?

1. A-DNA
2. B-DNA
3. Z-DNA



- it's right handed
- 10.9 bases per turn
- 2.2nm
- short and wide
- dehydrated (extracted DNA)


B-DNA characteristics!

- right handed
- 10 bases per turn
- 2 nm
- long and thin
- in solution ( within cell?)


Z-DNA characteristics!

- left handed
- 12 bases per turn
- 1.8 nm
- long and thin
- unknown location


B-DNA is a ____ that aids in certain cell processes, such as recombination!

- conformation


Z-DNA ___ have been found in cells.

- binging proteins


Prokaryote Chromosomes:
- structures DNA can take?

- double stranded, single, circular or supercoiled


Prokaryote Chromosomes:
L> They tend to have a main area of genetic material and then about _ or more smaller chromosomes.

- 1
L> they can replicate autonomously of the main one.....may be or not be essential to the cells life


Prokaryote Chromosomes:
L> Plasmid?

- autonomously replicating small chromosomes to essential to the life of the cell


Prokaryote Chromosomes:
- Nucleoid?

- chromosomes arranged in a dense clump in a region of the cell ( bacteria and archaea)
L> no membrane separating it from the rest of the cell


Prokaryote Chromosomes:
- Supercoiled??
L> knick?

- genetic material is twisted in space about its own axis
L> when a break occurs in a strand of the backbone....of a supercoiled circular DNA molecule...via tension from supercoiling... DNA spontaneously untwists and produces a relaxed DNA circular.


Can supercoiling occur in linear chromosomes?

- yes
- occurs at localized regions and the ends behave as if they are fixed.


Types of supercoiling:
- positive
- negative

- one more turn to make
- one less turn to make


Prokaryote Chromosomes:
- Topoisomerase?

- enzyme that controls the amount and type of DNA supercoiling found in all organisms! can make one or two cuts in dan to take out tangling ...


Prokaryote Chromosomes:
- Topoisomerase (DNA gyrase?)...eases what?

- eases tension in the genome if this is absent the organism dies.


Eukaryotic Chromosomes :
- Chromatin?

- combination of DNA and protein..packages DNA into smaller volumes.


Eukaryotic Chromosomes :

- proteins that package and order DNA
-most abundant protein in chromatin
- 5 types


Eukaryotic Chromosomes :
DNA loop?

- access for replication...attach to nuclear lamina keeping it in place while other things occur.



- haploid DNA content in our cells


C-value paradox?

- if an organism has a high c value it does not mean it is more complex..


Chargaff's Rules?(list em)

1. Purine bases = 50% if all DNA nucleotides in an organism
2. Pyrimidines bases = 50% of all DNA nucleotides in an organism
3. Adenine nucleotides= thymine nucleotides
4. Guanine nucleotides = cytosine nucleotides


Details of Chromatin?
Two main kinds?

1. Euchromatin
2. Heterochromatin


Details of Chromatin?
1. Euchromatin ?

1. parts of genome in its active cycle...
L> genes that are actively transcribed
- house keeping genes
L> not packed as densely, generally lacking repetitive sequences


Details of Chromatin?
2. Heterochromatin?
L> types? (2)

- generally transcriptionally inactive...
L> Constitutive
L> Facultative


Details of Chromatin?
2. Heterochromatin
L> Constitutive

- same position on homologous chromosomes
L>centromeres and telomeres condensed , highly repetitive and inactive transcription


Details of Chromatin?
2. Heterochromatin
L> Facultative?

L> more variable depending on cell type or its stage....specialized proteins
L> not always transcribed ex seminal vesicles