1 / 24

Chapter 12

Chapter 12. Chromosomes and Human Inheritance. Human Chromosomes. Diploid = 46, Haploid = 23 Sex chromosomes different than others Not homologous pairs Female = two X chromosomes (XX) Male = one X & one Y chromosome (XY) Autosomes —non-sex chromosomes, same in both genders. karyotyping.

dena
Download Presentation

Chapter 12

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 12 Chromosomes and Human Inheritance

  2. Human Chromosomes • Diploid = 46, Haploid = 23 • Sex chromosomes different than others • Not homologous pairs • Female = two X chromosomes (XX) • Male = one X & one Y chromosome (XY) • Autosomes—non-sex chromosomes, same in both genders

  3. karyotyping • Culture cells, stimulate mitosis, stop division at metaphase • Hypotonic solution swells cells, separates them & chromosomes • Take picture, cut & paste

  4. Autosomal inheritance • Autosomal Dominant • Allele expressed in heterozygotes • AA or Aa show dominant phenotype

  5. Autosomal dominant • Achondroplasia • Embryonic cartilage in skeleton doesn’t develop properly • “Dwarf”, average 4’ tall • Huntington’s Disease • Nervous system deteriorates • Symptoms often not seen until after 30 • Die in 40s or 50s

  6. Autosomal inheritance • Autosomal Recessive • Recessive phenotype only shown with homozygous recessive • Heterozygous is “carrier”

  7. Autosomal recessive • Albinism • Lack of normal amounts of melanin (pigment) in body • Cystic fibrosis • Thick mucus in lungs & digestive tract • Breathing & digestion difficult • Most common lethal genetic disorder among caucasians

  8. Sex determination • Humans • XX = Female • XY = Male

  9. Sex determination • Fetal development • 7 weeks, “uncommitted” • Y chromosome present  male sex organs • Y chromosome absent  female sex organs

  10. Sex determination • Different species have different systems • X-Y • XX = Female, XY = Male • X-O • XX = Female, X = Male • Z-W • ZW = Female, ZZ = Male • Haplo-Diploid • 2n = Female, n = Male

  11. X-Linked inheritance • Non-sexual gene “linked” to a sex chromosome (X) • NOT present on Y chromosome • Recessive & dominant alleles • XR, Xr, Y • XRXR, XRXr, XRY = dominant phenotype • XrXr, XrY = recessive phenotype

  12. X-linked inheritance XB = Bald, recessive trait X, Y = Non-bald, dominant trait XB Y XB Y X X XB X X Y XBXB= bald woman XXB = carrier woman XX = normal woman XBY = bald man XY = normal man XB X

  13. X-Linked inheritance • Baldness • Red-Green Color Blindness • Hemophilia A • Lack of certain clotting factors • Blood cannot clot, bleed uncontrollably

  14. Chromosome structure • Changes in physical structure of chromosome • Cause genetic disorders or abnormalities • Rare • Duplication • Deletion • Inversion • Translocation

  15. duplication • DNA sequences are repeated 2 or more times • Unequal crossing-over • Broken piece of chromosome attaches to homologous chromosome • Huntington’s Disease • Affects coordination & movement • Affects mental abilities, personality

  16. deletion • DNA sequence deleted • Unequal crossing-over • Chemical damage • Most cause serious disorders or death • Cri du chat syndrome • Severe developmental & neurological problems • Unusual cry of infant (“cry of the cat”) • Unusual physical appearance

  17. inversion • DNA sequence reverses • No loss of DNA or chromosome part • No problem for carrier if non-crucial gene • Some may not know until children have problem • Chromosome 9 • No health problems for parent • May increase risk of miscarriage

  18. translocation • Broken part of one chromosome attaches to another • Usually reciprocal (both exchange broken parts) • Often cause reduced fertility • Severe problems rare • Can include several cancers

  19. Chromosome number • Aneuploidy—one more one less chromosome than normal • Usually fatal for humans • Most miscarriages • Nondisjunction—one or more pairs do not separate during meiosis • Polyploidy—cells with 3 or more copies of one or more chromosomes • Trisomic—cells with 2n+1 of one chromosome, 2n of all others

  20. nondisjunction

  21. Down syndrome • Only trisomy that reaches adulthood • Extra copy of chromosome 21 • Mostly through nondisjunction at meiosis • Abonormal mental, heart, and skeletal development

  22. Sex chromosome abnormalities • Turner syndrome • Nondisjunction of sex chromosomes • Only one X, noted as “XO” • 98% of embryos miscarry • Adults very short, but well proportioned • Sterile, limited sex hormones • Klinefelter syndrome • 2/3 Nondisjunction of sex chromosomes • XXY • Mostly normal, some learning disabilities • Lower testosterone, higher estrogen • “Feminized” male characteristics

  23. Human genetic developments • Phenotype treatments • Phenylketonuria (PKU)—lack of enzyme, can’t convert certain amino acid, brain function problems • Restrict intake, can lead normal life • Genetic screening • Detect alleles that can cause disorders • Prenatal diagnosis • Amniocentesis—collect fluid from around fetus • Cells in fluid from fetus, can analyze for disorders

More Related