Reproduction - Asexual Reproduction

Lecture #12

Reproduction

• definition: the biological process of producing new individuals

• two types:

  • asexual

  • sexual 

asexual and sexual reproduction

what are the two forms of reproduction?

asexual reproduction

• definition: the production of offspring that does not involve fertilization 

  • offspring are genetically identical (clones) of their mother

• Pros: faster, safer, and energetically “cheaper”

• Cons: lower genetic diversity

• the only true means of reproduction among prokaryotes (occasionally found in eukaryotes)

the production of offspring that does not involve fertilization

what is the definition of asexual reproduction?

female

• definition: the sex that creates eggs

Genetic diversity

• definition: the variation within the genome of a species

  • number of different alleles for every gene in the populations collective DNA

• it enables evolution

Binary Fission

• the type of asexual reproduction that prokaryotes do to reproduce 

Horizontal Gene Transfer

• Definition: the movement of genetic material between genetically unrelated individuals 

  • adding genes to the individual libraries of prokaryotes

• prokaryotes employ this to counteract the lack of genetic diversity that comes with Binary Fission

• 3 types of this:

  • transformation

  • conjunction

  • transduction

• very different inheritance patterns than species practicing sexual reproduction

  • individual bacterial within the same species are highly variable

    • ex) two cells of E. coli can differ by as much as 30% of their genome (more than all the genetic diversity across all vertebrates)

transformation, conjunction, transduction

what are the 3 types of horizontal gene transfer? 

Horizontal Gene Transfer - Transformation

• Definition: Taking stray DNA from the environment and incorporating it into your genome

• possible bc when a unicellular organism dies:

  • its membranes collapse and its DNA is released into the environment

• Loose DNA is absorbed by other cells

  • this DNA does not have to come from the same species

Tardigrades (water bears)

• eukaryotes that perform horizontal gene transfer - transformation

• animals, distantly related to arthropods

• as much as 17.5% of its DNA are from completely unrelated organisms (plants, fungi, bacteria etc.)

  • outside versions of genes completely replace the tardigrade version

• How?: they can desiccate and enter a type of resting stage

  • Genome with partially break apart during this phase

  • Incorporate environmental DNA when they rehydrate and reconnect their genome

Horizontal Gene Transfer - Conjugation 

• Definition: two living cells intentionally share plasmid DNA through a connective structure known as a pilus 

• as close as prokaryotes get to sexual reproduction (still not quite the same thing)

Horizontal Gene Transfer - Transduction

• Definition: DNA transfer mediated by viral infection

• steps:

  • 1) a virus infects a prokaryotic cell

  • 2) during infection, the cell is killed and some of the viral particles incorporate the DNA of their host into their own

  • 3) Virus with host DNA infect new cell, but does not kill it

    • passing on DNA of old host to the new cell

1) a virus infects a prokaryotic cell, 2) during infection, the cell is killed and some of the viral particles incorporate the DNA of their host into their own, 3) Virus with host DNA infect new cell, but does not kill it

what are the steps to Horizontal Gene Transfer - Transduction? 

For gene therapy, stem cells can be altered or corrected in a lab to become cells to fight disease

Why is Horizontal Gene Transfer - Transduction a tool for medicine?