Meiosis & Mistakes Chapter 10.2.

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Presentation transcript:

Meiosis & Mistakes Chapter 10.2

Meiosis & Genetic Variation Mitosis = identical cells Crossing over in P1 of meiosis allows for genetic variation (different gene arrangements) individuals can be unique

Genetic Recombination Reassortment of chromosomes and genetic information they carry by crossing over or independent segregation Each of the homologous chromosomes has an equal chance of being pulled to one cell versus the other

Mistakes in Meiosis Nondisjunction Failure of homologous chromosomes to separate properly during meiosis one cell will have an extra chromosome and the other cell will be missing a chromosome

Karyotype Chart of chromosome pairs shows unusual numbers of chromosomes in cells Shows if nondisjunction has occurred and chromosome disorders

Normally 46 chromosomes 23 pairs of two All homologous except 23rd pair in males Male: XY Female: XX

Trisomy a gamete with an extra chromosome is fertilized by a normal gamete, the zygote will have an extra chromosome Example: Trisomy 21 (Down Syndrome) Extra chromosome 21 (individual has 47 chromosomes)

Monosomy Individual are missing a chromosome and have a total of 45 chromosomes Most individuals with monosomy do not survive Example: Turner’s syndrome Human females have one X chromosome instead of two

Other Examples: Triploid Occurs when an individual does not separate any of the homologous pairs Gamete has diploid set of chromosomes When fertilized with a normal gamete, the zygote will have three copies of each chromosome

Other Examples: Polyploids more than the usual number of chromosomes (polyploidy) Rare in animals Frequent in plants beneficial