Question: Explain Variegation in Ivy (ix): mitosis
Mitosis is the process by which the nucleus and cytoplasm in a cell divide and form two identical cells. The division starts when DNA replication already has takes place. DNA contain genetic information vital for proper cell function. Chromosomes, present in the nucleus when mitosis takes place, are complexes of tightly-coiled DNA (loosely bundled DNA are called chromatins). Diploid plants, like Hedera helix, have two versions of each chromosome (homologous chromosomes), one from the seed parent and another from the pollen parent.
The first phase (prophase) is when the chromatins condense together into chromosomes, the nuclear membrane disintegrates and a spindle appears. The second phase (metaphase) is when the chromosomes line up on the equator of the spindle. The stage where the replicated chromosomes split by the threads of the spindle and are pulled apart to the opposite poles is called the third phase (anaphase). During the fourth fase (telophase) a new nuclear membrane forms around the separated chromosomes and a cell plate is formed to divide the two cells (cytokinesis).
If a mutation arises only in one copy of homologous chromosomes and the gene is dominant, like the colour yellow for a leaf, each cell has a dominant gene for yellow and a recessive gene for green chloroplasts resulting in a yellow sport. If mitotic recombination occurred, it's possible the following will happen: one of the cells may be lost, and the surviving cell can lead to an entire layer.
Source: Variegated trees & shrubs, Ronald Houtman, 2004, Timber Press
I tried to create a 'roadmap' of the possible changes which I'll share in my next post.
The first phase (prophase) is when the chromatins condense together into chromosomes, the nuclear membrane disintegrates and a spindle appears. The second phase (metaphase) is when the chromosomes line up on the equator of the spindle. The stage where the replicated chromosomes split by the threads of the spindle and are pulled apart to the opposite poles is called the third phase (anaphase). During the fourth fase (telophase) a new nuclear membrane forms around the separated chromosomes and a cell plate is formed to divide the two cells (cytokinesis).
If a mutation arises only in one copy of homologous chromosomes and the gene is dominant, like the colour yellow for a leaf, each cell has a dominant gene for yellow and a recessive gene for green chloroplasts resulting in a yellow sport. If mitotic recombination occurred, it's possible the following will happen: one of the cells may be lost, and the surviving cell can lead to an entire layer.
Source: Variegated trees & shrubs, Ronald Houtman, 2004, Timber Press
I tried to create a 'roadmap' of the possible changes which I'll share in my next post.
posted by Me, Myself and Ivy at 1:40 PM
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