Explain Meiosis and Genetic Diversity - Biology

1. What is a tetrad (bivalent) in meiosis?

   Paired homologous chromosomes with four chromatids total. Forms when homologs pair during prophase I.

2. Which process shuffles whole maternal and paternal chromosomes into gametes: crossing over or independent assortment?

   Independent assortment. Random distribution of intact parental chromosomes.

3. What is the chromosome number change in mitosis from start to finish?

   Chromosome number stays the same. Diploid parent produces diploid daughter cells.

4. What does diploid mean in terms of chromosome sets?

   Two sets of chromosomes ($2n$). Contains chromosomes from both parents in body cells.

5. What is aneuploidy?

   An abnormal number of particular chromosomes. Common result of nondisjunction errors.

6. What is the genetic result of independent assortment?

   New combinations of maternal and paternal chromosomes. Random distribution creates unique chromosome sets.

7. What is the minimum number of genetically distinct gamete types from independent assortment for $n=3$?

   $2^3 = 8$. Each chromosome can orient toward either pole independently.

8. What are sister chromatids?

   Identical copies of one chromosome joined at a centromere. Result from DNA replication before cell division.

9. What is the genetic result of crossing over?

   Recombinant chromatids with new allele combinations. New gene combinations increase genetic variation.

10. What is synapsis in meiosis?

    Pairing of homologous chromosomes during prophase I. Essential for crossing over and genetic recombination.

11. In which division does nondisjunction occur if sister chromatids fail to separate?

    Meiosis II. When sister chromatids stick together improperly.

12. Which type of cell division produces gametes in animals: mitosis or meiosis?

    Meiosis. Only meiosis reduces chromosome number to create sex cells.

13. What is crossing over?

    Exchange of DNA between non-sister chromatids of homologs. Creates new allele combinations on chromosomes.

14. In which meiosis phase does crossing over occur?

    Prophase I. When homologs are paired and can exchange segments.

15. What is polyploidy?

    More than two complete sets of chromosomes (e.g., $3n$). Often results from fertilization errors or nondisjunction.

16. What is mitosis?

    A one-division process producing two genetically identical cells. Maintains chromosome number for growth and tissue repair.

17. What is the genetic similarity of daughter cells after meiosis?

    Genetically different from each other and the parent cell. Crossing over and independent assortment create variation.

18. Identify the immediate product of meiosis I in chromosome form.

    Two haploid cells with duplicated chromosomes. Sister chromatids remain attached after first division.

19. How many daughter cells does one cell produce after mitosis?

    Two daughter cells. One division produces two diploid cells.

20. Choose the word that completes the statement: Meiosis produces cells that are ____.

    Haploid. Meiosis reduces chromosome number by half.

21. In which division does nondisjunction cause gametes with abnormal chromosome number if homologs fail to separate?

    Meiosis I. When whole chromosome pairs fail to separate.

22. Identify the phase when homologous chromosomes separate to opposite poles in meiosis.

    Anaphase I. Whole chromosomes move, not individual chromatids.

23. Which process directly creates recombinant chromosomes: independent assortment or crossing over?

    Crossing over. Physical exchange creates new chromosome combinations.

24. What is nondisjunction?

    Failure of homologs or chromatids to separate properly. Results in gametes with wrong chromosome numbers.

25. Which meiosis division separates sister chromatids: meiosis I or meiosis II?

    Meiosis II. Similar to mitosis, separating duplicated chromosomes.

26. Identify the phase when sister chromatids separate to opposite poles in meiosis.

    Anaphase II. Individual chromatids separate like in mitosis.

27. What is the minimum number of genetically distinct gamete types from independent assortment for $n=10$?

    $2^{10} = 1024$. Ten chromosome pairs create many possible combinations.

28. What are homologous chromosomes?

    A maternal and paternal pair with the same genes. Carry the same genes but may have different alleles.

29. What is meiosis?

    A two-division process producing four haploid gametes. This reduction division creates sex cells for reproduction.

30. What is the main purpose of meiosis II?

    Separate sister chromatids to form haploid cells. The equational division like mitosis.

31. In which meiosis phase does independent assortment occur?

    Metaphase I. When chromosome pairs randomly orient before separation.

32. Which meiosis division separates homologous chromosomes: meiosis I or meiosis II?

    Meiosis I. Reduces chromosome number by half in first division.

33. What is fertilization's main contribution to genetic diversity?

    Random fusion of two genetically unique gametes. Combines genetic material from two different parents.

34. Identify the phase when homologous pairs line up at the cell equator in meiosis.

    Metaphase I. Homologous pairs align rather than single chromosomes.

35. How many daughter cells does one diploid cell produce after meiosis?

    Four haploid daughter cells. Two divisions after one DNA replication cycle.

36. What is the term for cells produced by meiosis in animals?

    Gametes (sperm and eggs). Haploid reproductive cells for sexual reproduction.

37. What is the key difference between metaphase of mitosis and metaphase I of meiosis?

    Mitosis: single chromosomes; meiosis I: homologous pairs. Alignment differs because homologs pair in meiosis.

38. What is the key difference between anaphase of mitosis and anaphase I of meiosis?

    Mitosis: chromatids split; meiosis I: homologs separate. Chromosome separation mechanisms differ between divisions.

39. What is the genetic similarity of daughter cells after mitosis?

    Genetically identical to each other and the parent cell. No genetic recombination occurs during mitosis.

40. How many rounds of DNA replication occur before meiosis I and II?

    One round of DNA replication. DNA copies once but cell divides twice.

41. What is the main purpose of meiosis I?

    Reduce chromosome number by separating homologs. The reductional division creating haploid cells.

42. Which type of cell division is primarily used for growth and repair: mitosis or meiosis?

    Mitosis. Maintains diploid chromosome number for body cell replacement.

43. What is a chiasma (plural chiasmata)?

    The visible site where crossing over occurs. Physical evidence of genetic material exchange.

44. What event must occur before meiosis begins to copy DNA?

    DNA replication in S phase of interphase. Occurs before meiosis I begins, not between divisions.

45. Which process includes two nuclear divisions: mitosis or meiosis?

    Meiosis. Two sequential divisions create four cells.

46. What is the chromosome number change in meiosis from start to finish?

    Diploid to haploid (reduction division). Meiosis halves chromosome number from parent to gamete.

47. What is independent assortment?

    Random orientation of homologous pairs in metaphase I. Each pair aligns independently at the cell center.

48. Choose the word that completes the statement: Mitosis produces cells that are usually ____.

    Diploid (same ploidy as the parent cell). Mitosis maintains the original chromosome number.

49. Identify the immediate product of meiosis II in chromosome form.

    Four haploid cells with unduplicated chromosomes. Sister chromatids separate in the second division.

50. What does haploid mean in terms of chromosome sets?

    One set of chromosomes ($n$). Found in gametes with half the chromosome number.

Study these flashcards