Mistakes Meiosis.notebook
February 17, 2014
Mistakes in Meiosis
Nondisjuntion ­ failure of chromosomes to separate properly
Feb 15­7:39 AM
Leads to conditions like….
1. Trisomy ­ extra chromosomes
Ex: trisomy 21 ­ individual has three chromosome # 21’s in their body cells = Down’s syndrome
How many total chromosomes would this individual have in their body cells? _47_____
Feb 15­7:44 AM
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Mistakes Meiosis.notebook
February 17, 2014
2. Monosomy ­ missing a chromosome
Example: Turner Syndrome ­ human female with one X sex chromosome instead of XX
(XX = Female XY = Male)
Turners Female = X_
The other X is missing
Feb 15­7:46 AM
3. Polyploid ­ homologous chromosomes do not separate at all. Rare in animals, common in plants.
Ex: The extra sets of chromosomes in plants makes larger fruit and flowers and healthier plants ­ great economic value!
Metaphase of meiosis 1
XX
XX
XX
XX
None
Feb 15­7:47 AM
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Mistakes Meiosis.notebook
February 17, 2014
Feb 15­7:55 AM
Question: Which would be worse…a chromosomal mistake in the gamete (sex cell) or a mistake in a somatic (body cell) cell?
Definitely a gamete because it controls the whole organism's genetics and not just an individual body part. Feb 15­8:00 AM
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Mistakes Meiosis.notebook
February 17, 2014
Karyotyping
Picture of chromosomes arranged in •
homologous pairs. Starts from largest to smallest.
•
Sex chromosomes shown last
•
Feb 15­8:01 AM
Sex chromosomes ­ One pair per person
XX­ female XY = male
Autosomes ­ humans have 22 pairs of
homologous non­sex chromosomes
Feb 15­8:02 AM
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Mistakes Meiosis.notebook
February 17, 2014
Karyotopes Showing Nondisjuntion
Feb 15­8:04 AM
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