diploid

Examples of diploid in the following topics:

• Life Cycles of Sexually Reproducing Organisms

  • In the diploid-dominant life cycle, the multicellular diploid stage is the most obvious life stage, as occurs with most animals, including humans.
  • Fertilization between the gametes forms a diploid zygote.
  • In some plants, such as ferns, both the haploid and diploid plant stages are free-living.
  • The diploid plant is called a sporophyte because it produces haploid spores by meiosis.
  • In animals, sexually-reproducing adults form haploid gametes from diploid germ cells.

• Introduction to Meiosis

  • Meiosis is the nuclear division of diploid cells into haploid cells, which is a necessary step in sexual reproduction.
  • Cells containing two sets of chromosomes are called diploid.
  • Sexual reproduction is the production of haploid cells (gametes) and the fusion (fertilization) of two gametes to form a single, unique diploid cell called a zygote.
  • In most plants and animals, through tens of rounds of mitotic cell division, this diploid cell will develop into an adult organism.
  • However, the starting nucleus is always diploid and the nuclei that result at the end of a meiotic cell division are haploid, so the resulting cells have half the chromosomes as the original.

• Comparing Meiosis and Mitosis

  • They have the same number of sets of chromosomes, one set in the case of haploid cells and two sets in the case of diploid cells.
  • In most plants and all animal species, it is typically diploid cells that undergo mitosis to form new diploid cells.
  • This is half the number of chromosome sets in the original cell, which is diploid.
  • The daughter cells resulting from mitosis are diploid and identical to the parent cell.

• Fertilization

  • The egg and sperm are haploid, which means they each contain one set of chromosomes; upon fertilization, they will combine their genetic material to form a zygote that is diploid, having two sets of chromosomes.
  • The nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.
  • This process ultimately leads to the formation of a diploid cell called a zygote.

• Reproductive Cloning

  • If the egg is fertilized, it is a diploid egg and the individual develops into a female; if the egg is not fertilized, it remains a haploid egg and develops into a male.
  • Sexual reproduction requires two cells; when the haploid egg and sperm cells fuse, a diploid zygote results.
  • If the haploid nucleus of an egg cell is replaced with a diploid nucleus from the cell of any individual of the same species (called a donor), it will become a zygote that is genetically identical to the donor.
  • Somatic cell nuclear transfer is the technique of transferring a diploid nucleus into an enucleated egg.

• Mendel's Law of Segregation

  • Mendel's Law of Segregation states that a diploid organism passes a randomly selected allele for a trait to its offspring, such that the offspring receives one allele from each parent.
  • The law of segregation states that each individual that is a diploid has a pair of alleles (copy) for a particular trait.
  • Each parent passes an allele at random to their offspring resulting in a diploid organism .

• Chromalveolata: Stramenopiles

  • A variety of algal life cycles exists, but the most complex is alternation of generations in which both haploid and diploid stages involve multicellularity.
  • In humans, haploid gametes produced by meiosis (sperm and egg) combine in fertilization to generate a diploid zygote that undergoes many rounds of mitosis to produce a multicellular embryo and then a fetus.
  • In the brown algae genus Laminaria, haploid spores develop into multicellular gametophytes, which produce haploid gametes that combine to produce diploid organisms that then become multicellular organisms with a different structure from the haploid form .
  • As diploid spores, many oomycetes have two oppositely-directed flagella (one hairy and one smooth) for locomotion.
  • Several species of brown algae, such as the Laminaria shown here, have evolved life cycles in which both the haploid (gametophyte) and diploid (sporophyte) forms are multicellular.

• Whole-Genome Duplication

  • Gene loss during diploidization is not completely random, but heavily selected.
  • It has been suggested that many polyploidization events created new species, via a gain of adaptive traits, or by sexual incompatibility with their diploid counterparts.
  • This image shows haploid (single), diploid (double), triploid (triple), and tetraploid (quadruple) sets of chromosomes.

• Seedless Vascular Plants

  • The life cycle of seedless vascular plants is an alternation of generations, where the diploid sporophyte alternates with the haploid gametophyte phase.
  • The diploid sporophyte is the dominant phase of the life cycle , while the gametophyte is an inconspicuous, but still-independent, organism.

• Rhizaria

  • The life-cycle involves an alternation between haploid and diploid phases.
  • The diploid phase is multinucleate, and after meiosis fragments to produce new organisms.