Human Heredity Chapter 11.1 & 11.3

1. Human Heredity Chapter 11.1 & 11.3

2. RECESSIVE GENETIC DISORDERS • may be passed on to children without “knowing” • both parents are CARRIERS of recessive alleles – Aa x Aa • passed like any recessive trait – offspring must get recessive allele from mother + father – aa Cystic Fibrosis (CF) Albinism Galactosemia Tay Sachs Primordial Dwarfism Phenylketonuria (PKU) Xeroderma Pigmentosum (XP)

3. CYSTIC FIBROSIS (CF) – affects the mucus producing glands, digestive enzymes and sweat glands Cause: • recessive allele that is defective Effects: • excessive mucus production • respiratory system is compromised; high risk of infection • digestive and respiratory system failure • life expectancy 36.8 years Cure/Treatement: • no cure • daily breathing treatments • mucus-thinning drugs • pancreatic enzyme supplements Cystic Fibrosis - http://www.youtube.com/watch?v=PjoE-yzyDNk

4. ALBINISM – partial or total lack of pigment (melanin) in hair, skin and eyes Cause: • recessive allele that is defective Effects : • do not produce normal amounts of melanin • skin susceptible to UV damage • higher risk of skin cancer and eye damage • occurs in humans and other mammals Cure/Treatment: • no cure • protect eyes and skin from sun

5. GALACTOSEMIA – an inability to digest galactose (milk sugar) Cause: • recessive allele that is defective • lack of enzyme that breaks down galactose Effects : • enlarged liver and kidney failure • galactose builds up in the cells and becomes toxic • usually causes no symptoms at birth • if not detected immediately results in liver disease, mental retardation and death  Cure/Treatment: • no cure • children diagnosed early can have a normal, healthy life • treatment is the restriction of galactose and lactose from the diet

6. TAY-SACHS DISEASE – an inability to break down fatty acids: only affects people of Jewish descent Cause: • recessive allele that is defective • lack of enzyme that breaks down fatty substances Effects • inability to break down fatty acids • fatty deposits build up in the brain • brain cells deteriorate • mental capacity is diminished • death by age 5 Cure/Treatment • no cure or treatment

7. Xeroderma Pigmentosum(XP) • recessive genetic disorder • inability to repair damage caused by UV light • in extreme cases, all exposure to sunlight must be forbidden, no matter how small • individuals with the disease are often referred to as Children of the Night • suffer from basal cell carcinomas and other skin malignancies (such as malignant melanoma and squamous cell carcinoma)

8. Primordial Dwarfism • form of dwarfism that results in a smaller body size in all stages of life beginning from before birth • proportionate dwarfism, in which individuals are extremely small for their age, even as a fetus • caused by inheriting a mutant gene from each parent Kenadie - born February 13, 2003 2 lbs 8oz and 11 inches long

9. Phenylketonuria (PKU) • Caused by a mutation in the gene for a liver enzyme called PAH • this enzyme is necessary to metabolize the amino acid phenylalanine Effects of untreated PKU… • children normal at birth but fail to attain early developmental milestones • microcephaly, progressive impairment of mental function seizures, learning disabilities nd other serious medical problems, Cure/Treatment of PKU… • there is no cure • treatment with restricted diet supplemented by amino acids and other nutrients • PKU is commonly included in newborn screenings performed just after birth

10. Dominant Genetic Disorders • onedominant allele (AA or Aa) to inherit the disorder • NO CARRIERS • either you have the disorder or you don’t Huntington’s Disease Achondroplasia Progeria Treacher Collins Marfan Syndrome

11. HUNTINGTON’S DISEASE woman with Huntington’s Disease at age 48 - the genetically programmed degeneration of brain cells Cause: • dominant allele that affects neurological function Effects: • symptoms appear between age 30 - 50 • degeneration of brain cells (neurons) • loss of intellectual faculties • uncontrollable movements • emotional disturbances Cure/Treatment: • none Huntington’s - http://www.youtube.com/watch?v=xguyxdmeUK8

12. ACHONDROPLASIA • a common form of dwarfism Cause: • dominant allele that affects bone growth Effects: • short arms and legs • 75 % of individuals with achondroplasia are born to parents of average size… • this means that most cases of achondroplasia occur “out of the blue” and are the result of a new mutation in the gene Cure/Treatment: • none; normal life expectancy Achondroplasia - http://www.youtube.com/watch?v=d8B-rdUrO9U

13. Progeria • extremely rare genetic disease wherein symptoms resembling aspects of aging are manifested at an early age • typically live to their mid teens and early twenties • occurs as a result of a dominant, new mutation • rarely inherited Progeria - http://www.youtube.com/watch?v=T8eaD6FdFJw

14. Treacher Collins • rare, congenital disorder characterized by craniofacial deformities • caused by a defective protein called treacle Physical Features Include …. • downward slanting eyes • micrognathia (a small lower jaw) • conductive hearing loss • absent cheekbones • malformed or absent ears. Cure/Treatment… • No cure - only affects physical features • physical features can be made less obvious by plastic surgery Treacher Collins - http://www.youtube.com/watch?v=tYYMRd39wcE

15. Marfan Syndrome • disoder of connective tissue Effects… • unusually tall, long limbs and long, thin fingers • range of expressions - from mild to severe • defects of the heart valves and aorta, lungs, skeleton, hard palate Cure/Treatment…. • no cure • medications to slow progression of disease • new treatments being developed • life expectancy today - similar to that of the average person

16. Codominance and Red Blood Cells Codominance occurs when… • both alleles are dominant • both alleles are fully expressed – NO BLENDING Red Blood Cells (RBCs) can be…. • disc shaped (D) NORMAL – easily flow through blood vessels • crescent shaped (C) ABNORMAL clump and block blood flow DD = all RBC’s normal shaped DC or CD = some RBC’s normal + some abnormal CC = all RBC’s abnormal – causes SICKLE CELL ANEMIA

17. SICKLE CELL ANEMIA • results from misshapen RBC’s Cause: • recessive allele that is defective • both mom and dad are “carriers” Effects: • causes RBCs to be misshapen – “sickle” or “C” or “crecsent” shaped • misshapen RBCs break down prematurely, cannot effectively transport oxygen, are stiff and sticky and block blood flow • pain, organ damage, increased risk of infection Cure/Treatment: • bone marrow transplant – finding matching donor is difficult and procedure has risks – may work for some • regular medical care, pain medicine, fluids, oxygen therapy Sickle Cell Anemia - http://www.youtube.com/watch?v=LlF_8oRs6Bw

18. Videos – Genetic Disorders • Cockayne - http://www.youtube.com/watch?v=6QeXF3d9jY8 • Brittle Bone - http://www.youtube.com/watch?v=6b7cWvMlw8Y • Ectodermal Dysplasia - http://www.youtube.com/watch?v=cAl6ZoQ7Mes • Duchenne MD - http://www.youtube.com/watch?v=CT3CsVoxWs0

19. Tetra-Amelia SyndromeNick Vujicic • rare disorder characterized by the absence of all four limbs LOOK AT YOURSELF http://www.youtube.com/watch?v=Gc4HGQHgeFE

20. PEDIGREE chart which shows the inheritance of a trait from one generation to the next Allows geneticists to trace the transmission of a trait through a family. square = male circle = female colored shape = has trait half colored shape = carrier slash = deceased

21. How many generations are represented?How many males? afflicted males? normal males?How many females? afflicted females? normal females?Any carriers?Sex-linked or autosomal trait?Dominant or recessive trait?Any twins? deceased individuals?

22. Victoria…(born into the British Monarchy in 1819) • 1837 - became Queen of England • 1840 - married her 1st cousin Prince Albert – which was the custom • she was a carrier of HEMOPHILIA • had 9 children and PASSED HEMOPHILIA ON TO SEVERAL OF THEM • ALL OF HER CHILDREN MARRIED INTO THE ROYAL FAMILIES OF EUROPE • HEMOPHILIA BECAME KNOWN AS THE ROYAL DISEASE

24. Princess Alexandrina Victoria… • the granddaughter of Queen Victoria • was born into the British Monarchy in 1872 She was also a CARRIEROF HEMOPHILIA • hemophilia is an X-linked recessive trait • results in an inability to clot the blood

25. Princess Alexandrina Victoria… • married her 2nd cousin, Nicholas Romanov II, Tsar of Russia • they had 5 children … • 4 girls - Olga, Tatiana, Maria, Anastasia • 1 boy - Alexei - heir to the throne - had HEMOPHILIA

26. 1918 - Russian Civil War • Tzar Nicholas II, his wife and their 5 children disappeared

27. 1991 - the remains of Tzar Nicholas, his wife, and 3 of the children were found and exhumed for DNA testing

28. HUMAN CHROMOSOMES Human somatic cells contain…. 46 individual chromosomes or 23 chromosome pairs Of these 23 pairs… SEX CHROMOSOMES (1 pair) • determine the sex of an individual AUTOSOMES (22 pairs) • do not determine the sex of an individual

29. KARYOTYPE photomicrograph of the chromosomes in a dividing cell chromosomes are grouped and placed into (23)pairs female - 46 XX male - 46 XY nonhomologous

30. Telomeresprotective caps on ends on chromosomesmade of protein and DNAmay play a role in cancer and aging telomeres are like… aglets on the ends of a shoe string

31. Mutations What is a mutation? a change in the DNA it is interesting that mutations can be helpful, harmful or may have no effect mutations – are a source of genetic variation in LT

32. Mutations What causes a mutation? a mutagen ….anything that can cause a change in the DNA Some mutagens are…. viruses, chemicals, toxins, UV light,…. Mutations can also happen as a result of … DNA being copied incorrectly

33. Types of Mutations SOMATIC cell mutations - affect body (somatic) cells will affect individual, but not offspring GERM cell mutations - affect germ (sex) cells will affect offspring, but not the individual LETHAL mutations will causedeatheither before or shortly after birth

34. Types of Chromosome Mutations Deletion • A piece of a chromosome is LOST Inversion • A piece of a chromosome breaks off, FLIPS OVER + REATTACHES Translocation • A piece of a chromosome breaks off and attaches to ANOTHER chromosome Nondisjunction • Homologues DO NOT SEPARATE PROPERLY DURING CELL DIVISION - results in too many or too few chromosomes

35. loss of a portion of a chromosome

36. Williams Syndrome • caused by spontaneous deletion of genes on chromosome 7 • rare, neurodevelopmental disorder • characterized by, "elfin" facial appearance, low nasal bridge, cheerful demeanor and ease with strangers • developmental delays and cardiovascular problems

37. Inversion – a section of a chromosome breaks off, flips over and reattaches

38. Translocation – a portion of a chromosome detaches and reattaches to a nonhomologous chromosome

39. Let’s Practice – What type of mutation?

40. NONDISJUNCTION - when chromosomes don’t separate properly during CELL DIVISION (CAN OCCUR IN mitosis or meiosis) nondisjunction means “not coming apart”

41. Nondisjunction in Meiosis…can lead to … monosomy (45) – missing a chromosome of a pair (having only 1 chromosome of the pair) trisomy (47) – having an extra chromosome in a pair (having 3 chromosomes in the pair)

42. Conditions resulting from Nondisjunction • Down’s Syndrome • Turner’s Syndrome • Klinefelter’s Syndrome

43. DOWN SYNDROME male or female having an extra chromosome in pair #21 (3 chromosomes instead of 2) - 47 XX or 47 XY

44. Down Syndrome (onosomy) nondisjunction on #21 = Trisomy 21

45. Characteristics of Down Syndrome • almond shaped eyes • flat nose bridge • large tongue • ears are set a bit lower on the head • shorter in stature • simean crease on the palm of the hand • possible congenital heart defects • lat feet, sandal toe (large gap between big toe and the next) • lower IQ • developmental delays

46. Turner Syndrome (Monosomy) • female missing a sex chromosome; 45 XO • nondisjunction on #23; monosomy

47. Klinefelter Syndrome (Trisomy) • male having an extra sex chromosome • 47 XXY or 48 XXXY; nondisjunction on #23; trisomy

48. Jacob’s or XYY Syndrome (Trisomy) • male having an extra Y (sex) chromosome • 47 XYY; nondisjunction on #23; trisomy • clinical phenotype is normal

49. Fetal (genetic)Testing • pre-pregnancy: DNA testing & genetic counseling • post-pregnancy: PKU testing • during pregnancy: • Amniocentesis • Chorionic Villi Sampling (CVS) • Fetal Blood Sampling

50. Amniocentesis - a small amount of amniotic fluid (containing fetal tissues and cells) is extracted from the amniotic sac surrounding the developing fetus - the DNA is examined for genetic abnormalities Chorionic Villi Sampling (CVS) - the removal of a small piece of the placenta (chorionic villi) during early pregnancy to screen for genetic defects – the placenta has the same genetic makeup as the fetus Fetal Blood Sampling (FBS) - the collection of fetal blood from the umbilical cord or fetus – the blood is tested genetic defects or other abnormalities