Topic 4.2

4.2.1 & 4.3.3: Events of Meiosis

Meiosis is a reduction division of a diploid nucleus to form a haploid nucleus. he process includes pairing of homologous chromosomes and crossing over, followed by two divisions where each division includes prophase, metaphase, anaphase, telophase and cytokinesis. The result is four haploid cells, known as gametes.

meiosis link meiosis animation
Definition homologous chromosomes

4.2.2 & 4.2.5: Homologous chromosomes

Homologous chromosomes are the same length, have the same centromere position and staining pattern. They also possess genes for the same character set same loci. In karyotyping, chromosomes are arranged in pairs according to their size and structure, the staining pattern can also be used. Karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities. Placing your mouse pointer on the figure will show a stained chromosome.

Definition homologous chromosomes

4.3.4: Can you explain Non-disjunction and Down Syndrome?

Place mouse pointer on the figure to see how non-disjunction leads to Down Syndrome (Trisomy 21)

Non-disjunction explained
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