1. Sexual and Asexual Reproduction
Reduction-Division
Genetic Recombination

2. Sexual Reproduction
Meiosis

3. Meiosis
The form of cell division by which GAMETES, with HALF the number of CHROMOSOMES, are produced.
DIPLOID (2n)  HAPLOID (n)
Meiosis is SEXUAL reproduction.
TWO divisions (MEIOSIS I and MEIOSIS II).

4. Meiosis Sex cells divide to produce GAMETES (sperm or egg).
Gametes have HALF the # of chromosomes.
Occurs only in GONADS (testes or ovaries).
Male: SPERMATOGENESIS -sperm
Female: OOGENESIS - egg or ova

5. Spermatogenesis n=23 n=23 2n=46 sperm haploid (n) Meiosis II human
sex cell
diploid (2n)
n=23
Meiosis I

6. Oogenesis n=23 n=23 2n=46 Haploid (1n) human egg sex cell
Meiosis II
2n=46
human
sex cell
diploid (2n)
n=23
Meiosis I
Polar Bodies (die)

7. Interphase I Similar to mitosis interphase.
CHROMOSOMES (DNA) replicate in the S phase
Each duplicated chromosome consist of two identical SISTER CHROMATIDS attached at their CENTROMERES.
CENTRIOLE pairs also replicate.

8. Interphase I Nucleus and nucleolus visible. Nucleus chromatin
cell membrane
nucleolus

9. Meiosis I (four phases)
Cell division that reduces the chromosome number by one- half.
Four phases:
a. Prophase I
b. Metaphase I
c. Anaphase I
d. Telophase I
Prophase I

10. Prophase I Longest and most complex phase (90%). Chromosomes condense.
Synapsis occurs - Homologous chromosomes come together to form a tetrad.
Tetrad is two chromosomes or four chromatids (sister and non-sister chromatids).

11. Non-Sister Chromatids-HOMOLOGS
Homologs contain DNA that codes for the same genes , but different versions of those genes
Genes occur at the same locations on each chromosome (called loci)

12. Prophase I - Synapsis
Homologous chromosomes
sister chromatids
Tetrad

13. Homologous Chromosomes
Pair of chromosomes (maternal and paternal) that are similar in shape and size.
Homologous pairs (tetrads) carry GENES controlling the SAME inherited traits.
Each locus (position of a gene) is in the same position on homologues.
Humans have 23 pairs of homologous chromosomes:
a. First 22 pairs of autosomes
b. Last pair of sex chromosomes
LOCI

14. Homologous Chromosomes
eye color
locus
hair color
Paternal
Maternal

15. Crossing Over
Crossing over may occur between non-sister chromatids at sites called chiasmata.
Crossing over: segments of nonsister chromatids break and reattach to the other chromatid.
Chiasmata (chiasma) are where chromosomes touch each other and exchange genes (crossing over.)
Causes Genetic Recombination

16. Genetic Recombination
Tetrad
nonsister chromatids
chiasmata: site of crossing over
variation

19. Sex Chromosomes
XX chromosome - female
XY chromosome - male

20. MEIOSIS I
Meiosis I
Homologs separate

21. Prophase I Nucleus & Nucleolus disappear Spindle forms
Chromosomes coil & Synapsis (pairing) occurs
Tetrads form & Crossing over Occurs
centrioles
spindle fiber
aster
fibers
TETRAD

22. Metaphase I Shortest phase Tetrads align on the equator.
Independent assortment occurs – chromosomes separate randomly causing GENETIC RECOMBINATION

23. Homologs line up at equator or metaphase plate
Metaphase I
Homologs line up at equator or metaphase plate OR

24. Anaphase I Homologous chromosomes separate and move towards the poles.
Sister chromatids remain attached at their centromeres.

25. Anaphase I
Homologs separate

26. Telophase I Each pole now has haploid (1n) set of chromosomes.
Cytokinesis occurs and two haploid daughter cells are formed.

27. Telophase I
cytokinesis

28. Formula: 2n
Example:
2n = 4
then 1n = 2
thus 22 = 4 combinations

29. Sister Chromatids Separate
MEIOSIS II
Sister Chromatids Separate
Meiosis II

30. Meiosis II No Interphase II or very short No DNA Replication
Remember: Meiosis II is similar to mitosis

31. Prophase II Same as Prophase in mitosis Nucleus & nucleolus disappear
Chromosomes condense
Spindle forms

32. Metaphase II Same as Metaphase in mitosis
Chromosomes (not homologs) line up at equator

33. Anaphase II
Same as Anaphase in mitosis
SISTER CHROMATIDS separate

34. 1n Sperm cell fertilizes 1n egg to form 2n zygote
Telophase II
Same as Telophase in mitosis.
Nuclei and Nucleoli reform, spindle disappears
CYTOKINESIS occurs.
Remember: FOUR HAPLOID DAUGHTER cells are produced.
Called GAMETES (eggs and sperm)
1n Sperm cell fertilizes 1n egg to form 2n zygote

35. Telophase II

36. Fertilization The fusion of a sperm and egg to form a zygote.
A zygote is a FERTILIZED EGG
n=23
egg
sperm
n=23
2n=46
zygote

37. Question:
In terms of Independent Assortment -how many different combinations of sperm could a human male produce?

38. Answer Formula: 2n Human chromosomes: 2n = 46 n = 23
223 = ~8 million combinations

39. Meiosis video
Mitosis vs Meiosis

40. Variation Also known as GENETIC RECOMBINATION
Important to population as the raw material for NATURAL SELECTION.
All organisms are NOT alike
Strongest “most fit” survive to reproduce & pass on traits

41. Question:
What are the 3 sources of genetic recombination or variation?

42. Answer: CROSSING OVER (prophase I)
INDEPENDENT ASSORTMENT (metaphase I)
RANDOM FERTILIZATION

43. Question:
A cell containing 20 chromosomes (diploid) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes?

44. Answer:
10 chromosomes (haploid or 1n)

45. Karyotype
An organized picture of the chromosomes of a human arranged in pairs by size from largest to smallest.
Pairs 1-22 called AUTOSOMES
Last pair are SEX CHROMOSOMES
Male - XY

46. Karyotype
Female - XX

48. Karyotype
Down Syndrome – Trisomy 21
Female - XX

49. Question:
A cell containing 40 chromatids at the beginning of meiosis would, at its completion, produce cells containing how many chromosomes?

50. Answer:
10 chromosomes

51. Meiosis: Males vs. Females
Females only produce One egg cell (not four like a male)
Must conserve the cytoplasm (resources) for the early development of the zygote
Only one of the two cells produced at the end of Meiosis I will Move on due to Unequal division of the cytoplasm
Only one of the remaining two survive during Meiosis II for same reason

54. Male Reproduction Terms
Anatomy:
Testis (external): Circular Shaped, primary organ of sperm production
Penis (external): Copulatory (intercourse) organ, also used to urinate
Epididymis (adjacent to testicle): site of sperm storage
Urethra (internal): Tube of urination and sperm ejaculation
Prostate (internal): At junction of both vas deferens, adds nutrition to semen
Seminephrous Tubules (inside testicle): Site of sperm production (meiosis)
Vas Deferens : Tube connecting testicle (epididymis) to urethra

56. hormones Luteinizing hormone (LH) Follicle Stimulating Hormone (FSH)
Testosterone

57. Female Reproduction Terms
Anatomy:
Cervix (internal): Portal between vagina and uterus/closed during pregnancy
Vagina (internal): Organ of copulation
Urethra (internal): Connects bladder to external
Ovary (internal): Site of egg production (meiosis)
Uterus (internal): Site of pregnancy, fetus is nourished by blood supply
Fallopian Tube (internal): Site of fertilization, connects the ovary to the uterus
Labia (external): tissue folds of female genetalia
Clitoris (external): analogous to male penis
Vulva (external): both labia and clitoris combined

59. FSH= Stimulate the follicle to develop (the egg develops in ovary)
LH= Causes ovulation (release of egg from ovary)
Progesterone = “promote-gestation (pregnancy)
Estrogen = promotes “estrus” (“heat in animals)

60. Reproductive/Development Terms
Fertilization union of sperm and egg
Zygote Diploid result of sperm + egg
Blastula Early stage resulting from mitosis
Embryo weeks 1-8 in human development
Fetus resembles adult form of human, after 8 weeks to parturition
Dilation of Cervix beginning of opening of birth canal
Parturition act of giving birth

63. Binary fission Budding Self Propagation
Asexual Reproduction
Binary fission
Budding
Self Propagation

64. Asexual Reproduction
Involves the production of offspring from just one parent.
Offspring have identical genetic material as parent.

65. Binary Fission Simplest form of asexual reproduction
Cell just splits in two
Common among prokaryotes.

66. Spores Single spore will develop into an adult
Common among molds and fungi

67. Budding
Cell nucleus and sytoplasm divide into two cells of unequal size.
Yeast

68. Vegetative propagation
Plants which produce organisms that are initially attached to the parent plant.
Strawberries send out runners.
Take root
Develop new plant

69. Regeneration
Ability to develop lost body parts or to form new individuals from a single fragment.
Starfish
Salamanders
Plants

70. Asexual Reproduction