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-disjunctionHomologous chromosomes or sister
chromatids fail to separate during meiosis.
Result: Gametes with abnormal # of chromosomes
Non-disjunction
Trisomy Having 3 of a particular chromosome.
Examples
Trisomy 21: Down syndrome
Trisomy 18: Edwards syndrome
- feet with rounded bottom
- crossed legs, clenched hands
Trisomies of Sex Chromosomes
XXX Female
XXY: Klinefelter Male
XYY: Male
Turner’s Syndrome
XO Female
45 Chromosomes
Chromosomal Duplications Part of a chromosome is repeated. Vary from fatal to developmental abnormalities. Often leads to cancer in somatic cells
Chromosomal Deletions Part of a chromosome is deleted.
Ex: Williams Syndromehttp://abcnews.go.com/2020/video/williams-syndrome-children-friend-health-disease-hospital-doctors-13817012
Partial deletion of chromosome 7
Chromosome InversionFragment breaks and reverses on the same chromosome.Not as lethal.
Chromosome Translocation
• List of Chromosome Disorders• http://www.netnet.net/mums/mum_chro.htm
Fragment of one chromosome attaches to ANOTHER, DIFFERENT chromosome.
If there is an UNEQUAL swap of segments, results can serious.
TransposonsSingle 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.