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Chapter 4 Genetic Counciling

Chapter 4 Genetic Counciling. Introduction. Often couples would like to know if there are (will be) genetic challenges when they conceive. Other times multiple miscarriages might lead potential parents to be suspect of genetic issues.

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Chapter 4 Genetic Counciling

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  1. Chapter 4 Genetic Counciling

  2. Introduction • Often couples would like to know if there are (will be) genetic challenges when they conceive. • Other times multiple miscarriages might lead potential parents to be suspect of genetic issues. • Genetic counseling may help to provide answers and/or options to these potentially difficult issues.

  3. A chromosomal view:How it’s done. • Two primary methods • are used to visualize • genetic material. • Amniocentesis • Chorionic Villi Sampling • Both methods lead to a • graphic display of • chromosomes known as • a karyotype.

  4. How karyotyping helps. • Karyotyping is useful because it gives us the full picture of the genetic material. • By capturing a cell sample when a cell is in metaphase, the geneticist gains a view of chromosomes when they are condensed and highly compacted during mitosis. • It is particularly good at detecting trisomy 21, the condition which results in Down syndrome.

  5. Lessons from history • Often it becomes necessary to determine the family history through collection of a pedigree. • In a pedigree, males are represented by squares, females by circles, and individuals carrying a genetic disorder by shading.

  6. Fig. 04-02

  7. What’s going on here? REM: Punnett Squares and basic genetics, only recessive offspring of heterzygotes would exhibit a trait.

  8. Unfair odds Chance has no memory! Just becase you’re in the 25%, doesn’t mean you’re safe.

  9. Vindication? Fortunately, it works the other way too, as seen here where affected parents have unaffected offspring.

  10. Other methods of genetic testing Presence of a genetic marker (imperfection) in DNA strands may assist in identifying a genetic disorder. Ex. Huntington’s.

  11. DNA probes are also used to “stick” particular piece of complimentary DNA to single stranded DNA of interest. Usage of fluorescent dyes aids in the detection process.

  12. Methods Compared: Which is Better? Amniocentesis Corionic Villi Fetal Cells 12 weeks 7 weeks 9 weeks miscarriage miscarriage no risk to fetus relatively easy realatively easy more complex 20 d turn around 10 d turnaround ~10 days? detects neural tube detects limb abnor- Tay-Sachs defects malities

  13. Ova screening by laproscopy Preovulatory screening of eggs is relatively new, yet can detect eggs containing genetic disorders. Eggs without those disorders may be used during an in vitro fertilization cycle to ensure a baby free of the disorder.

  14. Testing the egg at an early stage may provide useful • information about the possibility of a genetic disorder. • Informed dicisions may then be made concerning the • pregnancy. • This procedure is carried • out during the early stages • cell development and does • not harm the developing • fetus.

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