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-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.