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DNA. DNA. Chromosomes, Eukarotic. Chromosomes, Bacterial. Note: Closed, Circular, Singular, and Haploid. Gene. E. coli = 5 million bp Phage T4 = 170,000 bp. Gene. Alleles. Big Difference between many Eucaryotes and most Bacteria: Bacteria, as Haploids, Express all of their Alleles.

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DNA

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DNA


DNA


Chromosomes, Eukarotic


Chromosomes, Bacterial

Note: Closed, Circular, Singular, and Haploid


Gene

E. coli = 5 million bp

Phage T4 = 170,000 bp


Gene


Alleles

Big Difference between many Eucaryotes and most Bacteria:

Bacteria, as Haploids, Express all of their Alleles

Alleles simply are different Nucleotide Sequences found at the same Location on Different Chromosomes

Usually the differences are quite subtle, e.g., one or two nucleotides different


Mutations

New Alleles arise via Mutation

The new Allelles may or may not be Functionally Different


GAAGCGTT GAAACGTT

CTTCGCAA CTTCGCAA

GAAGCGTT GAAACGTT

CTTCGCAA CTTTGCAA

Mutations


Auxotroph & Prototroph

Prototrophic: microbes that live on a minimal growth medium + inorganic salts + energy source.

Auxotrophic: mutant microbes must be supplied with certain additional nutrients to grow.


Auxotroph & Prototroph

Neurospora crassa

Wt are

ad+

leu +

Auxotrophs are:

ad

leu

ad+

leu+

ad+/leu+

Control


  • Prototrophic: Only dividing cells in minimal media

  • Auxotrophs

Prototrophs are killed

Unaffected by penicillin because then are not dividing

Killed by penicillin Addition

Selecting for Auxotrophs

  • Plate the auxotrophs on plates with various supplements to test for phenotypes

Wash cells, remove penicillin and grow auxotrophs!


Filtration Selection for Auxotrophs


Selection for Prototroph Revertants


Transcription

Certain viruses have genes consisting of single-stranded RNA

These viruses can be either plus-stranded or minus-stranded

Plus-stranded RNA can serve as mRNA

Minus-stranded RNA serve as templates for the synthesis of mRNA


Transcription


Link to Next Presentation


Acknowledgements

www.uta.edu/biology/mcallister/ 5312/download/14_Mutation.ppt

homepage.smc.edu/bober_mary/Bio%2022/ gene%20mut%20web1.ppt


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