The Human Genome Chapter 14. Human Heredity Human chromosomes Karyotype – a picture of chromosomes…
Human Genetics Chapter 14-1, 14-2 Human Heredity.
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Transcript of Human Genetics Chapter 14-1, 14-2 Human Heredity.
Human Genome
• 3 billion base pairs– 6 billion individual bases
• “4 million pages”• Bases (letters) spell out
genes (words) that result in the phenotype (the story)
• Some spell out bad stories (diseases)
• h = hemophilia, a sex-linked disorder
• For each, can you answer…• Is the dad affected?• Is the mom affected?• How many children have the
disease?• How many children are carriers?• How many children are healthy?
(careful!)
PEDIGREES another way to study inheritance
• What do you think the F1 generation (line II) # 2 and #5 offspring represent?
• Can you draw the Punnett Square for the Parent generation? (I)
Pedigrees• Show how traits are passed down through
many generations• Based mostly on phenotypes• Show the actual offspring– Punnett squares show the possible offspring
• Really only works well for single traits– Not polygenic traits
• Only works for inherited traits– Environmental factors play a large role in who we are
Inheriting Diseases
• Just like physical traits, some diseases can be inherited on our chromosomes.
• And, just like physical traits, some are X-linked, some are recessive, some are dominant or codominant.
Genetic Disorder Fact Sheet topicsFragile x syndrome
Gaucher diseaseDuschene Muscular Dystrophy
Marfan syndromeColor blindness
Hurler syndrome
Tay-SachsAlbinism
Cystic FibrosisSickle cell anemia
PKULou Gehrig’s disease
Cri du Chat syndromeHuntington DiseaseTurner’s syndrome
Klinefelter syndromeDown syndromeFanconi anemia
Other Chromosomal Actions
• X-Inactivation if men only need one X chromosome, do women need both X’s? – If not, which one “works”?
• Non-disjunction how gametes can end up with the wrong # of chromosomes in meiosis
X-Chromosome Inactivation
• Men are XY: One X chromosome is enough• Women are XX: The “extra” copy is not needed.
It condenses into a “Barr body.” • Remember, you have trillions of cells. Which X
chromosome that “switches off” can vary in each cell!
Nondisjunction• “Not coming apart”• Homologous
chromosomes fail to separate in meiosis
• Result in Trisomy or Monosomy
• Examples: – Klinefelter syndrome (trisomy
X)– Down syndrome (trisomy 21)– Turners syndrome (X_
monosomy)