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How many chromosomes should a “normal” human have? Are females XX or XY?

How many chromosomes should a “normal” human have? Are females XX or XY? How do the words: DNA, gene and chromosomes relate?. 12.2: Chromosomal Disorders. Chromosomal disorders: Errors in the number or structure of a chromosome. Non-disjunction.

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How many chromosomes should a “normal” human have? Are females XX or XY?

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  1. How many chromosomes should a “normal” human have? Are females XX or XY? How do the words: DNA, gene and chromosomes relate?

  2. 12.2: Chromosomal Disorders

  3. Chromosomal disorders: Errors in the number or structure of a chromosome

  4. Non-disjunction Homologous chromosomes or sister chromatids fail to separate during meiosis. Result: Gametes with abnormal # of chromosomes

  5. Non-disjunction

  6. TrisomyHaving 3 of a particular chromosome. Examples Trisomy 21: Down syndrome Trisomy 18: Edwards syndrome - feet with rounded bottom - crossed legs, clenched hands

  7. Trisomies of Sex Chromosomes XXX Female XXY: Klinefelter Male XYY: Male Turner’s Syndrome XO Female 45 Chromosomes

  8. Chromosomal Duplications • Part of a chromosome is repeated. • Vary from fatal to developmental abnormalities. • Often leads to cancer in somatic cells

  9. Chromosomal Deletions • Part of a chromosome is deleted. Ex: Williams Syndrome http://abcnews.go.com/2020/video/williams-syndrome-children-friend-health-disease-hospital-doctors-13817012 Partial deletion of chromosome 7

  10. Chromosome Inversion • Fragment breaks and reverses on the same chromosome. • Not as lethal.

  11. Chromosome Translocation Fragment of one chromosome attaches to ANOTHER, DIFFERENT chromosome. If there is an UNEQUAL swap of segments, results can serious. • List of Chromosome Disorders • http://www.netnet.net/mums/mum_chro.htm

  12. Transposons • Single genes that can move around. • “Jump” from one chromosome to another. • If they insert in the middle of an existing gene, that gene will be disrupted.

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