Ch 8 - bio 250

What is a vertical transfer?

Genetic info in parent cell is passed to daughter cell - binary fission

What is a horizontal transfer of DNA?

cell to cell transfer of genetic info without binary fission, genetic information from donor cell and then transferring to a recipient.

What are ways that genetic diversity is generated in eukaryotes?

sexual reproduction, diploid vs haploid cells, and combination of genetic materials between members of a species.

What are ways that genetic diversity is generated in prokaryotes?

binary fission, spontaneous mutations and gene transfers

What is a mutation?

any change in a nucleotide or nucleotide sequence

What is wild type?

normal DNA type sequence for most organisms

What is a genotype?

The collection of genes present on a cell

What is a phenotype?

observable characteristics of a gene

How come phenotypes are traceable back to genotypes

Because of the centra dogma it goes DNA -RNA -Protein -phenotype

What are spontaneous mutations?

naturally occurring mutations in absence of a mutagen

What are the two ways spontaneous mutations occur?

Errors during replication or through transposable elements

What are errors during replication from spontaneous mutations?

DNA polymerase makes a mistake and proofreading doesn’t catch, then the mistake can cause base substitution- adding/subtracting of a nucleotide

What are transposable elements or transposons?

Naturally occurring mobile genetic elements that create insert mutations - can copy segments of DNA and jump to other parts of a gene

What are point mutations?

Change in a single nucleotie

What are forms of base substitution?

Silent mutation, missense mutation, or nonsense mutation

What is a silent mutation?

base change that does not result in a change in the amino acid sequence

What is a missense mutation?

Base change that causes codon to code for a different amino acid

What are the consequences of nonsense mutations?

create a truncated protein - protein that is shorter than normal and usually not functional

What is a nonsense mutation

base change that results in a codon coding for a stop codon

What is a frameshift mutation?

addition or subtraction of 1 or 2 nucleotides

What are contigous nucleotides?

3 bases in a row

What are non contingious nucleotides?

3 bases not in a row

Is the reading frame affected at all in a contigous mutation? If so how?

No, because a codon is either being added or subtracted

Is the reading frame affected at all in a non-contigous mutation? If so how?

yes, it shift between 1st and 3rd addition/deletion and resets back to original reading frame after 3rd mutation

What is a transposon or transposable element?

Mobile genetic elements that move between organisms and withing a single chromosome

What is a knockout mutation?

Insertion mutation, that disrupts coding region of a gene

What type of mutations do transposons form?

Knockout mutations

What are induced mutations?

Mutagen causes the mutations

What are structural analogs?

Base analogs

What is chemical modification of a base?

Many carcinogens chemically modify bases - usually by adding (-CH3) or (-H)

What are intercalating agents?

insert themselves between base pairs

What is an example of an intercalating agent?

Ethidium bromide

What are types of radiation cause induced mutations?

UV radiation and x-rays

How does UV radiation cause mutations?

Creates thymine dimers between bases, which makes it so gene can’t be read properly my polymerase, and can add in base substitutions

How do x-rays cause mutations?

Cause single and double stranded breaks in DNA with cause broken chromosome = death or mutation from faulty repair

What is proofreading by DNA polymerase?

DNA polymerase removes mispaired nucleotide and replaces it with the correct one

What is mismatch repair?

A protein binds to site of mismatch and cuts the unmethylated strand. A short stretch of strand is then degraded and DNA polymerase synthesizes a replacement

What is base excision repair?

Glycolase removes damaged nucleobase. Short strand is degraded and DNA polymerase synthesizes a replacement

What is photoreactivation or light repair

Energy of light is used to break covalent bond between thymine bases, restoring the original molecule. Reaction is catalyzed by photolase enzyme that requires light.

What is nucleotide excision repair or dark repair?

Enzyme removes short stretch of strand with thymine dimer and DNA polymerase synthesizes a replacement.

What is SOS repair?

It fixes mutations causes by x-rays and Gamma rays, usually broken chromosomes

What are the repair mechanisms for an error in nucleotide incorporation?

Proofreading by DNA polymerase or Mismatch repair

What are the repair mechanisms for damaged Nucleobase in DNA?

Base excision repair

What are the defects from spontaneous mutations?

Error in nucleotide incorporation or damaged nucleobase in DNA

What are the defects that are mutagen induced?

Chemical- error in nucleotide incorporation and UV light- thymine dimers

What is the repair mechanism for chemical defects?

Mismatch repair and proofreading by DNA polymerase

What are the repair mechanisms for Thymine dimers?

Photoreactivation, Nucleotice excision repair and SOS repair

What are the two types of Gene transfer in bacteria?

Horizontal and vertical transfer

What is horizontal transfer?

One cell to another

What is vertical transfer?

Parent to daughter cells

What are the mechanisms of horizontal transfer?

DNA mediated transformation, Transduction, and conjucation

What is DNA mediated transformation?

uptake of exogenous DNA

What is required of the recipient cell in DNA mediated transformation

must be competent- natural or artifical

What type of bacteria are usually naturally competent?

Gram positive and gram negative

What is transduction?

Transfer of bacterial DNA using a bacteriophage - During Bacteriophage replication a transducing particle is created and is then used to introduce DNA to another cell

What is generalized transduction?

Any gene can be transferred

What is specialized transduction?

only specific genes can be transferred

What is conjugation?

transfer of DNA from one bacterial cell to another through direct cell to cell contact

Can Conjucation occur in Gram negative and gram positive bacteria.

Yes- but we only know how gram - conjucation works

How does gram - conjucation work?

A donor cell (F+) transgers DNA to a recipient cell (F-) : through the f-pilus or sex pilus on F+ to origin of transfer on F-

How is the F-pilus or sex pilus formed?

Can only form on F+ cells because they contain F Plasmid which created the pilus

What is Hfr conjugation?

Chromosomal DNA is transferred from Donor cell (Hfr) to recipient cell (F-)

What are the characteristics of plasmids?

-Circular double-stranded DNA

-Replicate independently of chromosomal DNA

-Carry a few to several hundred genes

-Non essential

-Transfered through conjugation

How do Plasmids replicate independently of chromosomal DNA?

They have their own origin of replication

What organisms have antibiotic resistance plasmid encoded trait?

Many

What are the plasmid encoded traits we talked about in lecture?

-Antibiotic resistance

-Antibiotic synthesis

-Gas vacuole production

-increased virulence

-Insect toxin synthesis

-Nitrogen fixation

-Oil degredation

-pilus synthesis

-toxin production

-tumor formation in plants

What organism have the plasmid encoded trait antibiotic synthesis?

Streptomyces species

What organism have the plasmid encoded trait gas vacuole production?

Halobacterium species

What organism have the plasmid encoded trait increased virulence

yersinia and shigella species

What organism have the plasmid encoded trait insect toxin synthesis?

Bacillus tharinogiensis

What organism have the plasmid encoded trait nitrogen fixation?

Rhizobium species

What organism have the plasmid encoded trait oil degredation?

Pseudomonas species

What organism have the plasmid encoded trait pilus synthesis?

E-coli, Pseudomonas species

What organism have the plasmid encoded trait toxin production?

Bacillus anthacis

What organism have the plasmid encoded trait tumor formation in plants?

Agrobacterium species

Why are transposons thought about in a clinical setting?

Because it is how antibiotic resistant genes like MRSA are spread

What is the importance of gene transfer from the bacterial perspective?

For genetic variation and adaption to changing environment

What is the importance of gene transfer from the human perspective?

Spread of antibiotic resistance genes and transfer of virulence factors

What is CRISPR?

Defense against bacteriophages- like the immune system of bacteria against bacteriophages.