Cell Reproduction


Cells reproduce by duplicating their cellular contents (including DNA) before undergoing cytoplasmic division to create two new cells

The specifics of this process differ between prokaryotic and eukaryotic cells:


Bacterial Reproduction

Prokaryotic organisms undergo a form of asexual reproduction and cell division known as binary fission

It is not the same as mitosis, there is no condensation of genetic material and no spindle formation

In the process of binary fission:

  • The circular DNA is copied in response to a replication signal
  • The two DNA loops attach to the membrane
  • The membrane elongates and pinches off (cytokinesis) forming two separate cells


The Process of Binary Fission


Animal Reproduction

Animals may grow, replace and repair tissues asexually (via mitosis), but create new organisms via sexual reproduction (meiosis)

Because offspring are the product of two sets of genetic instructions, their cells are diploid (two copies of every chromosome)

Mitosis is used to make new somatic cells which are diploid (2n) and genetically identical

Meiosis is used to make sex cells which are haploid (n) and genetically distinct

These sex cells undergo a process of gametogenesis to become functional gametes

  • In males, the process of spermatogenesis produces four mature spermatids from each germ cell
  • In females, the process of oogenesis produces one mature egg (ovum) from each germ cell


Gametogenesis


When fertilisation of an egg and sperm occurs, the two haploid cells combine to form a diploid zygote which can undergo mitosis

The mitotic division of a zygote will result in a mass of cells that, when differentiated, will form a functioning organism


Overview of Animal Reproduction

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