Genetic variation in bacteria is due to.....
Mutations! Most frequently arise due to mistakes made during DNA replication and repair.
Bacterial mating - pass F plasmid from F+ male to F- female through sex pilus.
Conjugation = conjugal visit, f plasmid = fuckin
Passed between bacteria, infrequently integrates into host chromosome
Can carry genes for antibiotic resistance
Bacteria are lysed and DNA fragmented - taken up by other bacteria and can be inserted into genome
Bacterial homologous recombination
2 homologous, ds DNA sequences are lined up, nick is made allowing one strand to invade and anneal to complementary strand. The displaced strand is nicked and anneals to the other homologue at which point the ends are ligated to complete formation of the cross-strand exchange
Plasmids integrate into chromosome via short regions of homology
Infection by bacteriophage whose genome can be integrated into the host bacterial's.
When the viral DNA is excised, it can take some bacterial DNA with it. These are then packaged into new bacteriophages which go on to infect more bacteria.
Relatively short DNA sequence that has the capacity to move from place to place within the genome of organisms by a process called transposition
Contribute to genetic diversity by:
1. Disrupting genes where they land
2. Altering expression of neighbor genes
3. Facilitating rearrangement of bac chromosome through homologous recombination
4. Hopping into plasmids or bacteriophages
5. Amplifying copies of antibiotic resistance
At meiosis, maternal and paternal chromosome pairs segregate independently from each other during meiosis.
Eukaryotic homologous recombination
Induced during meiosis after DNA replication. Homologues pair with help of cohesins
Avg of 3 crossovers per chromosome per meiosis
Retrotransposons in Humans
Small mobile DNA elements in humans - (ex LINE 1, SINEs, Alu elements)
Contribute to human genetic diversity
1. Disrupt gene fxn by inserting w/in exon of gene (ex. insertion in Factor VIII gene for hemophilia)
2. Affect expression of genes
3. Create sites for illegitimate homologous recombination (unequal crossovers)
Describe the creation of gene families by unequal crossovers
Transposon insertions that flank a gene can lead to mis-alignment and ultimately lead to "unequal crossing"
Can lead to exon amplification or duplication
Extreme example - dystrophin, probably arose from exon amplification
The movement of whole genes by the transposition of flanking transposable elements
Describe the role of retroviruses and genetic instability
Virus integrates genome into host DNA, can have the following impact on host DNA
1. Disrupts gene function by inserting into exon
2. Since viral promoters can be very active, insertion can inappropriately turn on neighboring genes
3. Upon packaging of new virus, neighboring genes can be incorporated into viral genome and passed on
The average person inherits _____ loss of function alleles. And on average, every person is heterozygous for ________ varients known to caused inherited disorders.