MEIOSIS ESSAY
Describe the structural suitability of a chromosome and different events in meiosis1Structural suitability of chromosome
❖ It must contain of two chromatids
❖ That are joined by a centromere
❖ It must be in X-shape
❖ It must be able to overlap at point called chiasmata
Stages of meiosis 1
❖ Interphase
❖ Chromosomes coil up
❖ DNA Replication takes place
❖ Prophase 1
❖ Homologous chromosome pair up and crossing over occurs
❖ Nuclear membrane disintegrates and centrioles move to
opposite poles
❖ Metaphase 1
❖ Microtubules form Spindle fibers which attaches to centromere
❖ Pair of homologous chromosome align at the equator of a cell
❖ Anaphase 1
❖ Spindle fibers shortens pulling paired homologous chromosome to opposite poles
❖ Paired homologous chromosomes become separated so that each pole have one chromosome
❖ Telophase 1
❖ Nuclear membrane integrates around chromosomes at opposite poles.
❖ The cell undergoes cytokinesis to form two haploid daughter cells
MEIOSIS AND DOWN SYNDROME
Describe how meiosis contribute to genetic variation and how abnormal meiosis leaf to down syndrome and polyploidy. Also describe advantages of polyploidy in agriculture.Meiosis
❖ Crossing over occurs during prophase1
❖ Homologous chromosome pair up
❖ Each chromosome has two chromatids
❖ Chromatids overlap
❖ At point called chiasma
❖ To exchange genetic material
❖ Between non-sister chromatids
❖ Each gamete will have mixture of genes from both parents
❖ Which brings about variation
❖ Random arrangement of chromosomes at equator
❖ Each pair of homologous chromosomes
❖ May line up either way on spindle
❖ Independently of each other
❖ Genetics will form differing mix of parental chromosomes.
Down syndrome
❖ In meiosis1 chromosome pair 21 fails to separate
❖ In meiosis2 chromatics of chromosome 21 fails to separate
❖ Referred to as Non-disjunction
❖ One gamete will have extra copy of chromosome 21
❖ If this gamete fuses with normal gamete
❖ The resulting zygote will 47 chromosomes
❖ Leading to down syndrome.
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