Human Genetics

1. Human Genetics

3. Karyotyping: • technique for examining the chromosome make up of an organism • shows chromosomes arranged by size: • homologous pairs • a way of detecting abnormalities • chromosomes paired • Total of 46 chromosomes • Or 23 pair  22 autosomes, somatic cells, body cells & • 1 pair of sex chromosomes XX = female XY = male

4. Chromosome Mapping: Showing the location of particular genes on a chromosome • Identifies traits that are likely to “cross over” together • the closer the traits the more likely the traits will be inherited together.

5. Linkage Groups: • each chromosome carries many genes • genes on the same chromosome = linked group • linked groups tend to be inherited together • crossing over (prophase) can interfere with linkage groups

6. Sex- Linkage: • Genes located on the sex chromosomes • genes found on the x chromosome = x linked • genes found on the y chromosome = y linked • a gene found on either the x or y chromosomes = sex linked

7. STOP!!! CK POINT!! Topic: Intro to Human Genetics Identify the following: What is/are: • Karyotypes • Chromosome mapping • Sex- linked traits

8. Mutations: • any change in the genetic hereditary material of the cell • 2 forms: • inheritable mutations – occur in the sex cells • Chromosomal mutation • Gene mutation • non inheritable mutations – occur in the somatic cells (autosomes, body cells)

9. 2 Types of inheritable mutations: • Chromosomal Mutations And 2. Gene mutations

10. Chromosomal Mutations: • change in the structure of a chromosome • the loss of an entire chromosome or addition of a chromosome • Examples Include: a. Nondisjunction

11. STOP!!! CK POINT!! Topic: Mutations 1 • What is a mutation? • What are the 2 types of inheritable mutations? • Explain how they are different.

12. Chromosome Mutation Cont. A. Nondisjunction: • failure of chromosomes to separate during meiosis • ex. Down syndrome – extra chromosome # 21 • ex. Polyploidy – extra whole sets of chromosomes lethal in humans (3n), often used in agriculture to enhance size of plants causes sterility • Ex .trisomy 18, trisomy 13 • EX. aneuploids – missing chromosome • Sex chromosome aneuploids :

13. Nondisjunction:

14. NondisjunctionDown syndrome(trisomy 21): The result of an extra copy of chromosome 21. Down syndrome affects 1:700 children and severely alters the child's phenotype: • characteristic facial features, short stature; heart defects • susceptibility to respiratory disease, shorter lifespan • prone to developing early Alzheimer's and leukemia • often sexually underdeveloped and sterile

15. Nondisjunction: Patau syndrome (trisomy 13): • serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months.

17. NondisjunctionEdward's syndrome (trisomy 18): • almost every organ system affected Children rarely live more than a few months.

19. Other Examples of Nondisjunction: Sex chromosome aneuploids : Sex chromosome aneuploids • XO = Turners Syndrome • XXY = Klinefelter Syndrome • XXX = Triplo-X Syndrome • XYY =Jacob Syndrome

20. Turners Syndrome: XO individuals are genetically female, however, they do not mature sexually during puberty and are sterile. Short stature and normal intelligence. (98% die before birth)

21. XXY = Klinefelter Syndrome • Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body characteristics. Normal intelligence.

22. XXX = Triplo-X Syndrome • XXX females. 1:1000 live births - healthy and fertile - cannot be distinguished from normal female except by karyotype

23. STOP!!! CK POINT!! Topic: Nondisjunction • What is Nondisjunction? • When does it occur? ( Be Specific) • Identify 3 genetic mutations resulting from nondisjunction. • What is the cause for each?

24. Chromosome mutations (structure): translocation – a section of one chromosome is transferred to a nonhomogulous chromosome addition – a portion of a chromosome is added deletion – a portion of a chromosome is deleted Cri-du-Chat Syndrome (segmental deletion) inversion – order of genes on a chromosome is changed

25. Chromosomal mutation-Deletion: Example - Cri du chat (cry of the cat): A deletion of a small portion of chromosome 5; these children have severe mental retardation, a small head with unusual facial features, and a cry that soundslike a distressed cat.

27. Translocation: • Some human diseases caused by translocations are: • Cancer: several forms of cancer are caused by translocations; this has been described mainly in leukemia • Infertility

28. In summaryChromosomal Mutations: • Chromosomal abnormalities can cause serious mental or physical disabilities, and may lead to the death of the embryo. • Structure of the chromosome has been compromised • The number of chromosomes is incorrect

29. STOP!!! CK POINT!! Topic: Mutations 2 1. Identify 4 structural chromosomal mutations. • How are each of the 4 chromosomes mutated? 3. What is Turners Syndrome?

30. Gene Mutations • Point Mutation – the substitution, addition, or removal of a single nucleotide • substitutions, one nucleotide in a codon is replaced with a different nucleotide, resulting in a new codon. • sickle cell anemia(also called sickle cell disease) is caused by a point mutation that substitutes Adenine for Thymine in a single DNA codon,

31. Gene Mutations Cont. • Frame Shift Mutation -the addition or deletion of a single nucleotide causes the remaining codons to be incorrectly grouped • Addition/removal – a single nucleotide is added or removed • Addition and Deletion Mutations

32. Welcome to Discovery Education Player

33. Mutagenic Agents: • radiation - x-rays, radioactive isotopes, cosmic rays, ultraviolet rays • chemicals – saccharin, nitrates, carcinogens

34. Human Genetic Traits & DisordersX- linked Traits: • traits controlled by the female sex chromosome • symbolized by a character on 1 of the chromosomes • XX’ X’ carries the trait • The female = the carrier • The trait is not visible in the female • Ex. Hemophilia –blood disorder in which blood does not clot properly • Ex. Color blindness – cannot distinguish between red and green

40. X-linked traits cont. • Symbols for constructing a Punnett square (sex-linked trait) • XX normal female • XY normal male • X’X carrier female • X’Y male with hemophilia • http://www.macmed.ttuhsc.edu/Morgan/bleedingdisorders/pages/newpage26.htm

41. Ex. Hemophilia • Hemophiliac male x carrier female • Genotype • Phenotype

42. Hemophilia contin. • Normal male x female carrier • Genotype • Phenotype

43. Multiple Alleles: • 2 or more alleles for a particular trait • alleles are expressed as codominant • ex. Blood types

44. Human Blood Types: • Phenotype Genotype Symbol A AA, AO IaIa, Iai B BB, BO IbIb, Ibi AB AB IaIb O OO ii

45. Blood Types & Punnett Squares; What are the possible outcomes for a heterozygous A blood type crossing with a homozygous B blood type? Genotypes Phenotypes

46. Blood Type Cont. • Construct a punnett square showing a cross b/w a blood type O person with a heterozygous B blood type person • Genotype • Phenotype

47. Polygenic Traits: • traits controlled by 2 or more alleles • expressed as incomplete dominance • ex. Eye color, height, and skin color

48. Genetic Disorders: • Genetic screening or studying karyotyes can show possible genetic disorders • Amniocentesis – karyotyping and analyzing amniotic fluid for fetal cells • Chorionic villisampling – piece of the placenta that is studied for genetic abnormalities • Ex. PKU: a genetic disorder that does not allow the baby to breakdown phenylalanine , can cause severe brain damage • Can be detected and eliminated with special diets