TOPIC 4: GENETICS

1. TOPIC 4: GENETICS

2. 4.1: Chromosomes, genes, alleles and mutations

3. 4.1.1 Eukaryotic chromosome STATE: Eukaryotic chromosomes are made of DNA and proteins

4. 4.1.2: Gene Define gene: A heritable factor that controls a specific characteristic. It is a section of DNA that codes for making one or more polypeptides.

5. 4.1.2: Allele Define allele: One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the same gene.

6. 4.1.2: Genome Define genome: The whole of the genetic information of an organism

7. 4.1.3: Gene Mutation Define mutation: A change in the base sequence of a gene

8. 4.1.4:Sickle cell anaemia

9. CCU GUG GAG amino proline VALINE glutamic acid acids

11. 4.1.4:

12. 4.1.4

13. Explain the causes of sickle-cell anemia. [8] M11/4/BIOLO/HP2/ENG/TZ2/XX caused by gene mutation; (sickle-cell anemia) due to a base substitution (mutation); changes the code on the DNA; which leads to a change in transcription / change in mRNA; DNA changes from CTC to CAC/GAG to GTG / mRNA changes from GAG to GUG;  (accept DNA changes from CTT to CAT/GAA to GTA / mRNA changes from GAA to GUA) which (in turn) leads to a change in translation / change in polypeptide chain/ protein; (the tRNA) adds the wrong amino acid to the polypeptide chain; glutamic acid replaced by valine; produces abnormal hemoglobin; causing abnormal red blood cell/erythrocyte shape / sickle shape; which lowers the ability to transport oxygen; sickle-cell allele is codominant; homozygote/HbS HbS have sickle cell anemia/is lethal / heterozygote/HbS HbA has the sickle trait/is carrier (and is more resistant to malaria);

14. Explain the cause of sickle cell anemia and why it has been selected through natural selection. [8] M08/4/BIOLO/SP2/ENG/TZ1/XX+

15. Explain the effect of base substitution mutation in sickle cell anemia. [3] N07/4/BIOLO/HP2/ENG/TZ0/XX+

17. One homologous pair of chromosomes in their non-duplicated form

18. Two homologous pairs of chromosomes. Chromosomes are shown in their duplicated form.

19. DNA Replication

20. Define: Homologous chromosomes: matching pairs of chromosomes

21. 4.2: Meiosis STATE: Meiosis is a reduction division of a diploid nucleus to form haploid nuclei Diploid: # of chromosomes in a body (somatic) cell (2n) Haploid: # of chromosomes in a sex cell (n)

22. Prophase I of Meiosis I • Homologous chromosomes pair up forming a synapsis and crossing over occurs • Nuclear membrane breaks down • Chromosomes condense and supercoil • Spindle microtubules develop from the centrioles.

23. Metaphase I of Meiosis I Microtubules attach to chromosomes. Homologous chromosomes are “pushed and pulled” by microtubles to the equator of the cell.

24. Anaphase I of Meiosis I Homologous chromosomes separate and are pulled to opposite poles. Chromosomes are still in their duplicated form. Cytokinesis occurs

25. Telophase I of Meiosis I Chromosomes arrive at the poles Chromosomes number is reduced by half. Chromosomes uncoil New nuclear membrane reforms. Microtubules break down

26. Prophase II of Meiosis II Nuclear membrane breaks down Chromosomes supercoil Centrioles move to the poles and spindle microtubules develop

27. Metaphase II of Meiosis II Spindle microtubules attach to chromosomes and move chromosomes to the equator of the cell

28. Anaphase II of Meiosis II Sisiter chromatids separate (and are now are called chromosomes) are pulled towards opposite poles

29. Telophase II of Meiosis II Chromosomes uncoil Nuclear membrane reforms Cytokinesis

30. Meiosis: Type of nuclear division in which one parent diploid nucleus divides into four daughter haploid nuclei, each genetically different to each other.

31. DNA replication in the S-phase of interphase

33. Homologous chromosomes separate in meiosis I

34. Sister chromatids separate in meiosis II

35. a A

36. A a A a

37. A a Aa AA A Aa aa a

38. 4.2.1: Meiosis

39. 4.2.2: Homologous Chromosomes

40. 4.2.3: Process of Meiosis

41. 4.2.3: Crossing over

42. 4.2.3: Stages of Meiosis

43. 4.2.4: Non-disjunction

44. Fertilization following Meiosis II error: Trisomy 21: Down syndrome What should happen

45. Non-disjunction http://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20II.htm http://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20I.htm

46. 4.2.5: Karyotyping STATE: In karyotyping, chromosomes are arranged in pairs according to their size and structure

47. Normal Male

48. Normal Female

49. Chromosomes in their duplicate form

50. Gorilla Karyotype