GENETICS EXAM 3
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bacteria and viruses are diploid or haploid?
auxotroph vs prototroph
- phototrophs are organisms that can synthesize all the compounds needed for growth. (can be grown on minimal medium)
- auxotrophs cannot synthesize one or more of the necessary compounds for growth
3 ways bacteria transfer genetic information...
conjugation between F+x F- results in what types of exconjugants?
- F+x F- results in two F+ cells
- process: pilus, one strand of plasmid moves across, DNA complement synthesized on both single strands, cells separate
how does F+ cell become Hfr cell?
F factor is integrated into the bacterial chromosome
Hfr x F- results in what types of exconjugants?
- Hfr x F- results in an Hfr cell and an F- cell with extra genes
- process: bacterial chromosome integrates F factor and becomes Hfr, Hfr able to conjugate with F- cell and transfer some genes, F factor does not transfer
what is an F' cell?
when the F factor that had been integrated into the Hfr chromosome excises it brings a few genes along with it
F' x F- what types of exconjugants?
- F' and a merozygote (also F')
- process: F factor of Hfr cell excises from chromosome bringing a few genes along, now considered F', when crossed with F-, the F factor along with the excised genes are transferred and the recipient cell now may have two copies of those genes, a merozygote considered partially diploid
F factor plasmids vs R plasmids
- F factor plasmids confer fertility; genes for sex pilus
- R plasmids have resistance transfer factor (RTF) that codes for plasmid transfer AND r-determinants that confer resistance to antibiotics
Viral DNA that integrates into the bacterial chromosome is called a ______
viral DNA that can be integrated in to the host DNA or replicated in the bacterial cytoplasm
to serve as genetic material a molecule must be able to satisfy these 4 criteria:
- store information
- express information
- allow variation by mutation
central dogma of molecular genetics
- transcription: three types of RNA are synthesized from DNA
- mRNA - messenger
- rRNA - ribosomal
- tRNA - transfer
- translation: mRNA synthesizes proteins
- DNA-->transcription[m/r/t RNA]-->ribosome-->translation-->protein
- 1927 - rats - avirulent strains could be transformed to virulence
- some "transforming principle" exists
- Rough was avirulent
- Smooth was virulent
- Heat-kill Smooth, avirulent
- combine with Rough
- "transforming principle" was DNA
- treated cells with different enzymes to selectively remove protein, RNA, or DNA -- only when DNA was removed did transformation not occur
Hershey and Chase experiments
- - DNA, not protein, genetic material
- used E. coli and bacteriophage
- using radioisotopes 32P and 35S
- 32P w/ phosphate backbone of DNA
- 35S w/ sulfur of protein bodies of bacteriophage
retroviruses - unusual replication
- RNA serves as template for synthesis of complementary DNA by the RNA-dependent DNA polymerase, reverse transcriptase
- This DNA can be incorporated into the host-cell genome.
- When transcribed copies of original retroviral RNA chromosomes also produced
DNA is a nucleic acid
nucleotides are the building blocks of DNA.
Nucleotides consist of ...(3)
- nitrogenous base
- pentose sugar
- phosphate group
two kinds of nitrogenous bases and types of each na d
- Purines: Adenine and Guanine; double ring structure
- Pyrimidines: Thymine (or Uracil) and Cytosine; single ring structure
2' C difference between deoxyribose and ribose
- Ribose = OH
- Deoxyribose = H
what type of bond links nucleotides?
specifically where does this bond exist?
phosphodiester bond between the phosphate group at the C-5' and the OH group at the C-3' position
Watson and Crick year
space between base pairs
length of one complete turn
minor groove and major groove
right or left handed
- 2 nm
- .34 nm
- ten base pairs = 3.4 nm
- 1.2 nm and 2.2 nm
- right handed
number of hydrogen bonds between base pairs
DNA replication is semiconservative experiment...
who, when, how
- Meselson and Stahl
- Used 15N-labeled E. coli in a medium containing 14N
- -- in prokaryotes
- long stretches of short repeating sequences at the ends of linear chromosomes
- preserve integrity and stability of chromosomes
- active in germ cells -- NOT eukaryotic somatic cells
chromosomes -- viral vs bacterial vs eukaryotic
- viral -- DNA or RNA, single or double stranded, circular or linear
- bacterial -- DNA, circular, double stranded, few proteins
- eukaryotic -- DNA, linear, double stranded, many proteins
levels of DNA packaging
2nm DNA --> 11nm nucleosome --> 30nm solenoid --> looped domains --> 300nm chromatin fibers --> 700nm chromatid --> 1400nm chromosome
highly repetitive, short repeated sequences found in heterochromatic centromeric regions of chromosomes
- Variable Number Tandem Repeats
- Short Tandem Repeats
Short Interspersed ElementsLong Interspersed Elementsdispersed throughout genomeThey are retrotransposons that are generated via an RNA intermediate
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