Lesson 3: Asexual Reproduction

Advantages of asexual reproduction

• No mate needed

• no specialized systems/organs needed

• invariable heredity generation after generation are identica

Disadvantages of asexcual reproduction

• if the environment changes, it may not be able to adapt

• if individuals are affected the whole population will suffer

Interphase

• Cell spends most of its time in this phase

• cell is actively taking in nutrients, excreting waste, and producing enegery and proteins

• DNA strands are duplicated when cell is triggered to divide

G₁

DNA strands are contained in nucelus, and the DNA becomes chromatin (46 chromosomes)

S

chromosomes are repkicated to form sister chromatids (2 DNA strands) helf together by a centromere (92 strands, 46 chromosomes)

G₂

cell checks for any errors in the duplicated chromosomes and makes changes

Prophase

• strands of DNA condense into X’s

• nucleus and nuclear membrane dissolve and all other cell functions stop

• centrioles move to opposite sides of the cell and make spindle fibres

Metaphase

The double chromosomes move towards the centre line of the cell in a single row

Anaphase

• spidnle fibres shrink and pull centromeres apart

• seperates double chromosomes into single strands (daughter chromosomes)

• Pulled to the poles at the end of anaphase, and chromosomes group around centrioles

  (2 groups of 46 single chromosomes)

Telophase

• Final phase of cell division

• parent cell has 2 regions of DNA at oppositve ends

• Chromosomes are back to being thin

• 2 distinct nuclei form

Cytokenesis

• FInal stage, cytoplasm pinches in along a line between the 2 nuclei

• Each cell has 46 chromosomes (n)

Animal cells in cytokenesis

daughter cells are completely seperate

Plant cells in cytokenesis

plate forms between daugter cells, still attached