Meiosis is the cell division process that produces gametes, or sex cells, which have half the number of chromosomes as regular body cells. During meiosis, homologous chromosomes pair up and separate, resulting in four gametes with unique combinations of chromosomes from each parent. Non-disjunction during meiosis can result in gametes with an abnormal number of chromosomes, leading to conditions like Down syndrome if fertilization occurs. Prenatal testing allows for the detection of chromosomal abnormalities early in development.

1. 4.2 Meiosis IB Biology I

2. Questions 1) What types of cells do we have in our body? Answer: we have skin cells, neurons, kidney cells, sperm and eggs, etc... 2) How are they formed? Answer: most cells are produced through mitosis. Sex cells (gametes) are produced through meiosis. 3) Why do sex cells need to be produced through different process? Answer: sex cells must have half the number of chromosomes regular body cells (somatic cells) have.

4. What are homologous chromosomes?

5. What is the purpose of meiosis?

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16. Mitosis x Meiosis

17. What is the consequence of non-disjunction?

20. Consequence of non-disjunction

21. Other trisomies... Patau’s Syndrome: chromosome 13 (1:25000 – microcefalia, microftalmia, heart malformation, deafness, blindness, early death) Edward’s Syndrome: chromosome 18 (1:8000 – low ears, neurological problems, hands/feet curved, small chin, malformation of urinary, reproductive and cardiovascular systems, early death) Klinefelter’s Syndrome: extra X (1:1000 – man: gynecomastia, neurological problems, hypogonadism, sterility – sometimes no signs) Turner’s Syndrome: lacking X (1:5000 – woman: low stature, wide neck, low set ears, gonadal dysfunction, sterility, hearing/visual problems, heart disease, neurological problems) XXX (1:1000 – no unusual problems – delayed speech and language skills, learning difficulties, can be sterile) XYY (1:1000 – no phenotype alterations – delayed speech and language skills, learning difficulties)

22. What is the importance of prenatal testing?