1. Meiosis
Biology 2017

2. Homologous Chromosomes
These are chromosomes that carry genes (alleles) for the same traits in the same order. You get one from mom and one from dad. The next slide has a line up of the 22 pairs of homologous chromosomes known as autosomes and the pair of sex chromosomes.

4. Karyotypes
To look at homologous chromosomes, scientists use karyotypes. These are pictures of the pairs of homologous chromosomes lined up, the one from mom is next to the one from dad.

5. Human Female Karyotype

6. Human Male Karyotype

7. Meiosis
Meiosis produces sex cells and reduces the number of chromosomes to one half the amount found in a body cell.
Human body cells have 46 chromosomes so sex cells have 23.
When sperm and egg unite, = 46. This brings the newly formed zygote back to a full complement of chromosomes.

8. Meiosis

9. Crossing Over

10. Meiosis I and Meiosis II

11. Correct Meiosis

12. Meiosis Overview

13. Correct Meiosis

14. Metaphases

15. Correct Meiosis

16. Non-Disjunction
When chromosomes don’t divide evenly in Meiosis I or Meiosis II.

17. Non-disjunction or mistakes in meiosis

18. Down’s Syndrome
A Down’s Syndrome individual has (3) #21 chromosomes instead of 2. This is called a trisomy.
Individuals with Down’s Syndrome have a reduced mental capacity, are short in stature, have fat pads under their eyes that make them resemble people from Mongolia.
At one time people who had Down’s Syndrome where referred to as Mongoloids.

19. Down’s Syndrome Karyotype

20. Individuals with Down’s Syndrome

21. Turner’s Syndrome
A Turner’s Syndrome female has only one X chromosome instead of 2. This is known as a monosomy.
Turner’s Syndrome is only present in females.
They will be short in height, mentally normal, but can’t have children as they are sterile.
They also often have webbed necks and chests that resemble a shield.

22. Turner’s Syndrome

23. Individuals with Turner’s Syndrome

24. Klinefelter’s Syndrome
Klinefelter’s individuals are all male and have at least two X chromosomes instead of 1 along with their Y chromosome.
They have narrow shoulders, wide hips, enlarged breast tissue, extra long arms and are often mentally handicapped. Their genitals are often small, however they can reproduce.

25. Klinefelter’s Syndrome

26. Body shape of Klinefelter’s individual

27. Poly-X Klinefelter’s Syndrome
Males with poly-X Klinefelter syndrome have more than one extra X chromosome, so their symptoms might be more pronounced than in males with KS. In childhood, they may also have seizures, crossed eyes, constipation, and recurrent ear infections. Poly-KS males might also show slight differences in other physical features.
Some common additional symptoms for several poly-X Klinefelter syndromes are listed below.

28. 48,XXYY Tetrasomy
Long legs
Little body hair
Lower IQ, average of 60 to 80 (normal IQ is 90 to 110)
Leg ulcers and other vascular disease symptoms
Extreme shyness, but also sometimes aggression and impulsiveness

29. 48,XXXY (or tetrasomy)
Eyes set further apart
Flat nose bridge
Arm bones connected to each other in an unusual way
Short
Fifth (smallest) fingers curve inward (clinodactyly, pronounced KLAHY-noh-dak-tl-ee)
Lower IQ, average 40 to 60
Immature behavior

30. 49,XXXXY (or pentasomy)
Low IQ, usually between 20 and 60
Small head
Short
Upward-slanted eyes
Heart defects, such as when the chambers do not form properly
High feet arches
Shy, but friendly
Difficulty with changing routines

31. Polyploidy Have more than normal sets of chromosomes
Is rare in animals and results in death
Occurs in plants, creating larger, healthier plants
Examples: Triploid (3 chromosomes/set)
Tetrapoid (4 chromosomes/set)

32. Haploid to Tetraploid

33. Polyploid Plants

34. Polyploidy in Plants
Polyploid organisms have multiple sets of the genome. For example, a strawberry normally has 7 pairs or 14 chromosomes. When a strawberry is polyploid, it can have up to 8 full sets of its genome equaling 56 chromosomes.

35. Effect of Polyploidy in Plants
Increases fruit weight, fruit size, seed size, crop load and flower size
Can be used to create a higher diversity
Increase bloom period
Creates stronger plants

36. Chrysanthemums

37. Beneficial Mistakes

38. How Polyploid Strawberries Are Created

39. Strawberries

40. Polyploid vs. Dipolid