1 / 79

Pedigree Analysis and Inheritance Patterns in Human Traits

This chapter explores the analysis of pedigrees and the inheritance patterns of human traits, including dominant and recessive traits, sex-linked traits, and autosomal traits. It also discusses the risk of diseases and the importance of genetic counseling and prenatal testing.

wcummings
Télécharger la présentation

Pedigree Analysis and Inheritance Patterns in Human Traits

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 6 Matters of Sex

  2. QSR #2 • 1. A trait that is __________________, will be found mostly in males while ___________________ traits will be spread out evenly between males and females. • 2. _________________ are the tips of the chromosomes – only about 5% of the entire chromosome. • 3. The blood-clotting disorder, __________________, is a ____________ trait since its found mostly in males. • 4. The nucleus of a cell in a female, during interphase, has one dark-staining X chromosome called a _____________________________.

  3. MendelianInheritance of Human Traits • Family trees • Pedigree • a graphic representation of genetic inheritance thru a family. • Looks similar to a family tree • Uses symbols • Male • Female • Children • relationships

  4. Pedigrees • Family history of traits recorded over generations • Can tell if the trait is dominant • Recessive • Sex-linked • Autosomal • Circles –females • Squares –males • Marriage horizontal lines • Vertical lines children

  5. Analyzing Pedigrees • Sex-linked vs autosomal • Only seen in males ---sex linked • Both sexes equally---autosomal • Dominant vs recessive • Trait is dominant then every infected individual’s parent will have the disease • Recessive—parents are normal children are infected

  6. Risk of Diseases • Use pedigrees • Genetic counseling • Prenatal testing • Amniocentesis/chorionic villi sampling to determine karyotypes

  7. ON THE FOLLOWING SLIDE, BE SURE TO LABEL: • 1. Dominant or Recessive • 2. Sex-linked or Autosomal

  8. ON THE FOLLOWING SLIDES, BE SURE TO LABEL: • 1. Dominant or Recessive • 2. Sex-linked or Autosomal • 3. Tell the genotype of each person

  9. Practice constructing a pedigree: • Ben and Jan are married with 4 boys. Ben has dimples as does his 2 oldest boys. Jan’s parents do not have dimples. Their youngest son married a female with dimples and together they have 2 daughters and a son – all of who have dimples 

  10. QSR#3Questions for Trait A pedigree(use the letter B/b) 1.  Does a dominant or recessive allele produce the trait?  Explain. 2.  Is it autosomal or sex-linked?  Explain. 3.  What are the genotypes of all the individuals in the pedigree?  (Write them on the pedigree.) 4.  What is the genotype of individual IV-2?  Explain. 5.  What is the genotype of individual IV-6?  Explain. 6.  What is the genotype of individual I-1?  Explain

  11. InhertitanceSymptoms

  12. Recessive Autosomal Heredity • Offspring must have 2 traits before the disorder will show up – must be passed down from both parents • If the parents’ do not show signs of the disorder, they are considered to be CARRIERS • This is why blood relatives should not have children together – no incest!!!! Consanguinity: “shared blood”—family members may share certain traits or disorders

  13. Recessive Autosomal Heredity • 1. males and females are equally affected • 2. Affected males and females can transmit the gene, unless it causes death before reproductive age • 3. The trait can SKIP generations • 4. Parents of an affected child are heterozygous or carriers

  14. CANCER

  15. Recessive Heredity • Ex: Tay-Sachs—problem with chromosome 15 • Recessive disorder of the central nervous system • An enzyme that breaks down lipid produced and stored under tissues is not made and this lipid accumulates in the cells • Survival rate: 4-5 years • Occurs in many Jews

  16. Infants with Tay-Sachs disease appear to develop normally for the first few months of life. Then, as nerve cells become distended with fatty material, a relentless deterioration of mental and physical abilities occurs. The child becomes blind, deaf, and unable to swallow. Muscles begin to atrophy and paralysis sets in. A much rarer form of the disorder which occurs in patients in their twenties and early thirties is characterized by unsteadiness of gait and progressive neurological deterioration. Patients with Tay-Sachs have a "cherry-red" spot in the back of their eyes. The condition is caused by insufficient activity of an enzyme called hexosaminidase A that catalyzes the biodegradation of acidic fatty materials known as gangliosides.

  17. Recessive Heredity • Ex: Phenylketonuria (PKU) • Recessive disorder that results from the absence of an enzyme that converts one amino acid, phenylalanine to a different amino acid tyrosine • Affects the CNS • Common among Nordic or Swedish people

  18. PKU • Normal at first • Then the baby begins to drink milk which has high amounts of phenylalanine • Mental retardation occurs • Special diets until brain is fully developed • Chromosome 12

  19. Dominant Heredity • One gene from either parent and the child is affected • Tongue rolling • Hapsburg lip • Free earlobes • Hitchhiker’s thumb • Almond shaped eyes • Thick lips • Hair in the middle section of your fingers

  20. Dominant Heredity • Ex: Huntington’s Disease • Lethal genetic disorder— AUTOSOMAL DOMINANT • Breakdown of certain areas of the brain • No treatment • Onset is between 30 and 50 • +++++++++++++++++++++++++++++++++++

  21. Sex-LinkeD Recessive • Found on the X chromosome • Females: XX – 2 copies • Males: XY – 1 copy • Ex: colorblindness: Females XcXc • Males XcY • Others: hemophilia and male-pattern baldness

  22. Sex-Linked Dominant • Ex: Rett Syndrome • This type is rarely found in males because many types are fatal or cause them to die before the reproductive age • EX: Fragile X Syndrome

  23. Rett Syndrome Brain disorder – causes the “forgetting” of things previously learned -- very similar symptoms to Autism --only found in female – WHY?

  24. Fragile X syndrome Missing piece of X chromosome Mental retardation, large ears, elongated face ***************************************

  25. QSR #6 • 1. Explain why DOMINANT, x-linked disorders are more commonly found in females. • 2. __________________ is a disorder with chromosome 15 that prevents the body from producing an enzyme needed to break down lipids around nerves of the CNS. • 3.___________________ means “shared blood” and is shown by the symbols:____________________-

  26. Incomplete dominance • Homozygous Red Snap Dragons x Homozygous White Snap Dragons • Pink Snap Dragon • RR x R’R’ • Neither allele is completely dominant over the other one • R—protein to make red pigment • R’—makes no pigment • Pinkish color • Does have segregation of alleles • What happens in the F2 generation?

  27. When Heredity Follows Different Rules • Mendelian Genetics • Simple---dominant or recessive alleles • NOT ALWAYS THIS SIMPLE!!!!!!

  28. Codominance • Both phenotypes appears • Chickens • Black-feathered and white-feathered birds both homozygous • BB x WW • Produces a chicken with black and white feathers—checkered • ++++++++++++++++++++++++++++

  29. Practice problems --

  30. QSR #8 • 1. If both parents carry the recessive allele that causes cystic fibrosis (autosomal recessive trait), whats the % chance that their child will have it? • 2. PKU is a recessive disorder that results from the absence of an enzyme that turns _________________ into tyrosine. • 3. Tay-sachs occurs mainly in ____________.

  31. Sex determination (how bout we review a little :O…) • Autosomes • Chromosomes that are not involved with determining sex • 1-22 pairs • Sex chromosomes • X and y chromosomes that determine the sex of individuals

  32. Sex-linked traits • Traits that are found on the x and y chromsomes • X and y are not homologous • Found by Thomas Hunt Morgan • Used flies and noticed that the male had white eyes; crossed red x white and got red; did not get the 3:1 ratio because only males had white eyes

  33. Sex-linked traits • Color blindness • Male pattern baldness • hemophilia

  34. Multiple Alleles • Traits that are controlled by 2 or more alleles • Pigeon feathers • Ash-red • Wild type blue feathers • Chocolate feather • Blood types – A and B are codominant, O is recessive.

  35. Polygenic Inheritance • Is the inheritance pattern of a trait that is controlled by two or more genes • Genes maybe on the same chromosome or on different chromosomes • When a trait is produced by main gene interactions • Ex: Skin color: • Dominant genes A,B,&C – control dark pigmentation • Recessive genes a,b,&c – has lowest amount of pigmentation • EX: AaBbCc would be what skin color?________________ • ++++++++++++++++++++++++++++++++++++++

More Related