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Chapter 11 Inheritance & Heredity

Chapter 11 Inheritance & Heredity. When is a recessive trait expressed?. When an individual is homozygous recessive for that particular trait When someone is heterozygous for a trait, they are considered a… carrier. Recessive Genetic Disorders:. 1 . Cystic Fibrosis -1 in 3500

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Chapter 11 Inheritance & Heredity

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  1. Chapter 11 Inheritance & Heredity

  2. When is a recessive trait expressed? • When an individual is homozygous recessive for that particular trait When someone is heterozygous for a trait, they are considered a…carrier

  3. Recessive Genetic Disorders: • 1. Cystic Fibrosis -1 in 3500 -the gene that codes for a specific protein is defective -produces excess mucus -digestive/respiratory problems

  4. Albinism: -1 in 17,000 -genes do not produce normal amounts of melanin pigment -skin UV susceptible -lack of color in skin/hair/eyes http://www.knowlton-family.co.uk/Albinism/Photo.htm

  5. Galactosemia: -1 in 50,000 -absence of gene that codes for enzyme that breaks down galactose -mental disabilities -liver/kidney problems

  6. Tay-Sachs Disease -1 in 2500 -absence of enzyme that breaks down fatty substances -mental disabilities/build up in brain -lipids build up in central nervous system -death usually by age 5

  7. If a disorder is considered to be a dominant genetic disorder, how many affected alleles do you have? • 1 or 2

  8. Dominant Genetic Disorders: • Huntington’s Disease -1 in 10,000 -gene affecting neurological function is defective -onset usually in the 40’s -ability to move deteriorates

  9. 2. Achondroplasia -1 in 25,000 -gene that affects bone growth is abnormal -short arms/legs -large head

  10. What is a pedigree? • A diagram that traces the inheritance of a particular trait through several generations • May or May not show carriers…be careful! • If someone is a carrier, their genotype must be heterozygous Common symbols: see board

  11. 11.2 Complex Patterns Mendelian Inheritance: follows typical dominant/recessive rules Non-Mendelian Inheritance: does NOT follow typical rules

  12. Types of Non-Mendelian Inheritance • When traits are inherited in this pattern, the phenotype is intermediate between the two homozygotes. What is this pattern called? Incomplete Dominance Example: Red x white = pink

  13. Incomplete Dominance

  14. What is codominance? :results in both phenotypes being expressed Example: black x white = black/white spotted

  15. Codominance

  16. How is sickle-cell anemia passed? Heterozygous: lead normal life; may have a FEW symptoms Homozygous for trait: have full-blown sickle cell…health issues result because the blood does not transport adequate oxygen. How are sickle-cell anemia & malaria related to each other? Those that are heterozygous for the sickle-cell trait have a HIGHER resistance to malaria

  17. What are ‘traits controlled by more than 2 alleles’ called? • Multiple alleles • Explain how blood types are passed on: • ABO blood groups: • IA = type A • IB = type B • i = type O • IA & IB are codominant/ i is recessive

  18. Multiple Alleles

  19. What is epistasis? The effect where one allele hides behind the effects of another allele. Example: Dog fur *E determines dark pigment ee will have no pigment *B determines how dark EEbb or Eebb = chocolate brown eebb, eeBb, eeBB = yellow coat

  20. How is it determined if something is going to be male or female? XX vs. XY What is an autosome? 1st 22 pairs of chromosomes -another name for body cells What are Barr bodies? -located in nucleus -inactivated chromosomes

  21. D. What are sex-linked traits? :traits controlled by genes located on sex chromosomes (23rd pair)

  22. What gender can get a X-linked trait? Males AND Females. -males are more likely because they only need one affected X to get it, instead of females, which need 2 What gender can get a Y-linked trait? Only males…females do not have Y Red-green color blindness & hemophilia are bothX-linked

  23. What is ‘the inheritance pattern of a trait that is controlled by two or more genes’? Polygenic Inheritance Name a human trait that is passed through polygenic inheritance: skin color, hair color, height

  24. Polygenic Inheritance

  25. Give at least 5 examples of external environmental influences: • Sunlight • Temperature • Diet • Exercise • Water

  26. 11.3 What is a karyotype? A micrograph that shows the pairs of homologous chromosomes -arranged in decreasing size

  27. How many pairs are in a karyotype? 23 pairs How many of those pairs are autosomes? 22 How many of those pairs are sex chromosomes? 1

  28. What is nondisjunction? Condition where sister chromatids fail to separate properly

  29. What do you call it when you have one of a particular type of chromosome? monosomyWhat do you call it when you have three chromosomes of one kind? trisomyDown Syndrome is an example of nondisjunction. What is the scientific name for the most common form down syndrome?Trisomy 21

  30. Trisomy 21 (Down Syndrome)

  31. Turner’s Syndrome -XO -female with only one X -can cause infertility, masculinity symptoms, etc. Kleinfelter’s Syndrome -XXY or XXXY, etc. -male with too many X’s -Can cause infertily, feminine symptoms Other disorders…

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