P020A Developmental Disabilities

1. P020ADevelopmental Disabilities Mrs. Elizabeth Keele Lecture 2

2. Course Content #7 • Describe the 2 types of mental retardation that are determined at the time of conception: • Chromosomal abnormalities • Gene determined disorders

3. Cells - • Humans are made up of cells

4. Cells • Cell • Nucleus • Chromatin • Chromosomes

5. What is a chromosome? • Thread like structures • Inside nucleus of each cell

6. What is a chromosome? • Thread like structures • Composed of • Protein • Deoxyribonucleic acid (DNA) • Makes up your genes

7. Somatic Cells / Diploid cells Sex Cells / Haploid Cells Only have 23 chromosomes Sole representative sperm / eggs called gametes • 23 Pairs of Chromosomes • Diploid cells contain two complete sets (2n) of chromosomes • Total • 46 • 1 - Maternal • 1 - Paternal

8. Karyotype

9. 2 types of cells: Somatic cells Sex cells Divide through meiosis • Divide through mitosis

10. Course Content #9 • Differentiate between meiosis & mitosis and describe the stages of meiosis and mitosis

11. Cell division Mitosis Meiosis Reduction division Divides 2 times Results 4- daughter cells Haploid cells (1/2 # chromosomes) • Equal cell division • Cell duplicates • Divides one time • Result • 2 - Daughter cell • Identical to mother cell

12. Mitosis • Interphase • Preparatory • Centrioles doubles

13. Mitosis • Prophase • Chromosomes double

14. Mitosis • Prometaphase • Nucleus dissolves • Polar centrioles • Microtubules attach

15. Mitosis • Metaphase • Chromosome align

16. Mitosis • Anaphase • Chromosomes separate

17. Mitosis • Telophase • Cell division begins

18. Mitosis • Cytokinesis • Two daughter cells • Identical

19. http://www.youtube.com/watch?v=cvlpmmvB_m4 • http://www.youtube.com/watch?v=zGVBAHAsjJM

20. Cell division Mitosis Meiosis Reduction division 2 divisions Results 4- daughter cells Haploid cells (1/2 # chromosomes) • Equal cell division • Cell duplicates • Divides once • Result • 2 - Daughter cell • Identical to mother cell

21. Meiosis • http://www.youtube.com/watch?v=D1_-mQS_FZ0 • http://www.youtube.com/watch?v=zGVBAHAsjJM

22. Meiosis • Sexual reproduction • Form Haploids • Gamete • Sperm & eggs • Reduce the number of Chromosomes

24. Meiosis does two things. • One diploid cells produces four haploid cells.

25. Why do we need meiosis? • Reduce # chromosome • ½

26. 2nd purpose of meiosis • Genetic diversity • Accomplished through • independent assortment • crossing-over

27. The Stages of Meiosis: • aka: Reduction Division

28. Meiosis I : Separates Homologous Chromosomes • Interphase • Each of the chromosomes replicate

29. Prophase I • Chromosome match up with their homologous pair • Fasten together (synapsis) • tetrad • Crossing over can occur. • exchange of segments

30. Metaphase I • The chromosomes line up at the equator attached by their centromeres to spindle fibers from centrioles. • Still in homologous pairs

31. Anaphase I • spindle move chromosomes toward the poles

32. Telophase I • End 1st division • cytoplasm divides • two daughter cells.

33. Meiosis II : 2nd division • Proceeds similar to mitosis • THERE IS NO INTERPHASE II !

34. Prophase II • Spindle • Move toward equator

35. Metaphase II • The chromosomes are positioned on the metaphase plate in a mitosis-like fashion

36. Anaphase II • Centromeres separate • Move toward opposite poles • individual chromosomes

37. Telophase II and Cytokinesis • Nuclei form at opposite poles of the cell and cytokinesis occurs • After completion of cytokinesis there are four daughter cells • All are haploid (n)

38. One Way Meiosis Makes Lots of Different Sex Cells (Gametes) – Independent Assortment Independent assortment produces 2n distinct gametes, where n = the number of unique chromosomes. In humans, n = 23 and 223 = 6,000,0000. That’s a lot of diversity by this mechanism alone.

39. Meiosis – division error Chromosome pair

40. Meiosis error - fertilization • Often occurs with the 21stpair • Trisomic zygote • Downs Syndrome

41. Course Content #14 • Explain how the presence or absence of a Y chromosome determines the sex of an individual.

42. 23 chromosomes • 22 • Autosomes • Same male to female • Same loci • Same function • 1 • Sex chromosome

43. What is a chromosome? • In cell nucleus • DNA thread coiled around proteins • Histones • Chromosome constriction point • Centromere

44. How many chromosomes do people have? • 23 pairs • total of 46. • 22 autosomes • look the same in both males and females. • 1 pair sex chromosomes • #23 • differ between males and females. • Females • XX • Males • one X and one Y

45. Can changes in the number of chromosomes affect health and development? • Normally • 23 pairs of chromosomes • Total 46 chromosomes in each cell • Change the # of chromosomes  problems with • growth, • development, • function of the body’s systems.

46. Chromosomal Abnormalities Numerical Abnormalities: • Missing a chromosome from a pair • monosomy • Two chromosomes • trisomy

47. Chromosomal AbnormalitiesStructural Abnormalities: • Deletions: • A portion of the chromosome is missing or deleted. • Duplications: • A portion of the chromosome is duplicated • Translocations: • A portion of one chromosome is transferred to another • Inversions: • A portion of the chromosome has broken off

48. Trisomy • Extra chromosome • Down syndrome • three copies of chromosome 21 • total of 47 chromosomes per cell

49. Monosomy • Monosomy • loss of one chromosome in cells, • Turner syndrome is a condition • Female • only one copy of the X chromosome • total =45 chromosomes

50. Course Content #10 • Explain the process by which humans inherit 23 chromosomes from each parent to create a total compliment of 46 chromosomes (23 pairs).