Human Heredity 11.3 Human Chromosomes Humans have 46 chromosomes Occurs in 23 pairs 22 pairs are...
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Transcript of Human Heredity 11.3 Human Chromosomes Humans have 46 chromosomes Occurs in 23 pairs 22 pairs are...
![Page 1: Human Heredity 11.3 Human Chromosomes Humans have 46 chromosomes Occurs in 23 pairs 22 pairs are autosomes 2 of the 46 are sex-determining chromosomes.](https://reader036.fdocuments.in/reader036/viewer/2022062517/56649ee95503460f94bfa5da/html5/thumbnails/1.jpg)
Human Heredity
11.3
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Human Chromosomes
Humans have 46 chromosomesOccurs in 23 pairs 22 pairs are autosomes2 of the 46 are sex-determining chromosomes (X and Y)XX=Female, XY=MalePicture of chromosomes=karyotypekaryotypeDoctors use to determine sex of baby and genetic abnormalities
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Karyotype Studies
Karyotype—micrograph in which the pairs of homologous chromosomes are arranged in decreasing size.
Images of chromosomes stained during metaphase
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SAMPLE KARYOTYPE
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Nondisjunction
Cell division during which sister chromatids fail to separate properly
Example: Down syndrome – person has an extra copy of chromosome 21
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Pedigree
Chart that shows relationships within families often used to trace lineage of a disease/disorderCircle=FemaleSquare=MaleShaded=Affected__ marriageI children
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Human Genes
Autosomal Recessive Disorders-caused by 2 recessive alleles present (ex: PKU, Tay Sach’s, CF)
Autosomal Dominant Disorders-only one allele present causes affliction (ex: dwarfism, Huntington’s Disease)
Codominant Alleles-Sickle Cell
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Recessive Disorders
A.Cystic fibrosis: Homozygous recessives (cc) have cystic fibrosis - body cannot make needed chloride channel, high concentrations of extracellular chloride causes mucous to build up, infections, pneumonia. Diet, antibiotics and treatment can extend life to 25 years or more.B.Tay-Sachs: Enzyme that breaks down brain lipids is non-functional in homozygous recessives (tt). Buildup of lipids causes death by age 2-3
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Dominant Disorders*Achondroplasia (dwarfism): AA =
Homozygous dominant is lethal - fatal (spontaneous abortion of fetus). Aa = dwarfism. aa = no dwarfism. 99.96% of all people in the world are homozygous recessive (aa)
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Dominant Disorders
B. Polydactyly (extra fingers or toes): PP or Pp = extra digits, aa = 5 digits. 98% of all people in the world are homozygous recessive (pp)
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Co Dominant Alleles
ss= sickle cell anemia (misshapen Sickle Cell: many believe sickle cell anemia co evolved with malariacells lead to death)SS= normal red cells, healthySs= not enough sickle cells to kill and resistant to malaria! (body destroys the sickle cells and the parasite)