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The Human Body > Lecture 15: Meiosis > Flashcards

Lecture 15: Meiosis Flashcards

1
Q

What is the only haploid cell in humans called?

A

gametes

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2
Q

How many chromosomes does a haploid cell have?

A

23

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3
Q

Why do haploid cells only have 23 chromosomes?

A

Because they will have 46 once they combine with another cell, to allow them to combine.

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4
Q

In Meiosis I, are there haploid cells?

A

Yes, but with duplicated chromosomes.

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5
Q

In Meiosis II, are there diploid cells?

A

No, there are haploid cells with unduplicated chromosomes.

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6
Q

How many phases are there in Meiosis? (I or II) Name them.

A
  • There are four phases in each meiosis

- Prophase I & II, Metaphase I & II, Anaphase I & II, Telophase and Cytokinesis I & II

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7
Q

What is the Chiasmata?

A

The part of the chromosome that is crossing over.

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8
Q

In what phase of Meiosis does crossover occur?

A

Prophase I

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9
Q

What happens in Metaphase I?

A

The chromosomes form a metaphase plate and microtubules attach to the kinetochore in the centromere of a chromosome.

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10
Q

What happens in Anaphase I?

A

Each pair of homologous chromosomes separate, sister chromatids remain attached.

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11
Q

What happens in Telophase & Cytokinesis I?

A

A cleavage furrow forms and two haploid cells are created. Sister chromatids are still in tact.

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12
Q

What is the difference between Meiosis I & II?

A

At the end of Meiosis II, the sister chromatid are separated, and the result is 4 haploid daughter cells containing unduplicated chromosomes. At then end of Meiosis I, the result is the sister chromatids are still in tact, and there are 2 haploid cells with duplicated chromosomes.

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13
Q

What is a tetrad?

A

When homologous sister chromatids group together.

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14
Q

What is the action of crossing over called?

A

Synapsis.

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15
Q

What happens during synapsis?

A

DNA is exchanged between the two homologous chromosomes at the chiasma.

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16
Q

What does the process of synapsis create?

A

They create infinite genetic possibilities.

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17
Q

What are the differences between Mitosis and Meiosis?

A

After the chromosome duplication, the results are different.
-Mitosis: end with duplicated chromosomes.
-Meiosis: ends with homologous chromosome pairs.
After Anaphase & Telophase,
-Mitosis: daughter cells have 2n
-Meiosis I: haploid have 1n with duplicated chromosomes.
-Meiosis II: haploid 1n with unduplicated chromosomes.

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18
Q

How many cell divisions are there in Meiosis?

A

2

19
Q

Does the synapsis of homologous chromosomes happen in Mitosis?

A

No, it happens in Prophase I in Meiosis I.

20
Q

What is the number of daughter cells in genetic composition in Mitosis & Meiosis?

A
  • Mitosis: 2 daughter cells (diploid) and are genetically identical to the parent cell
  • Meiosis: 4 haploid cells, containing half as many chromosomes as the parent cells, and genetically different from each other and the parent cells.
21
Q

What role does Meiosis play in the animal body?

A

it produces gametes and reduces the number of chromosomes by half and introduces genetic variability.

22
Q

What role does Mitosis play in the animal body?

A

They enable multicellular adults to arise from the zygote. They produce cells for growth, repair, and in some species, sexual reproduction.

23
Q

What are sex differences in Meiosis?

A
  • Girls: result is one oocyte and three polar bodies.

- Boys: result is four sperm cells.

24
Q

When does spermatogenesis begin?

A

Puberty and continues indefinitely

25
Q

When does oogenesis begin?

A

During fetal development but pauses at Prophase I, and it resumes each menstrual cycle but does not actually finish, only happens when egg is fertilized.

26
Q

Where does spermatogenesis perform Mitosis?

A

Spermatogonia

27
Q

What are the cells called during different phases of Meiosis in spermatogenesis?

A

Before meiosis: Primary spermatocyte.
After meiosis I: Secondary spermatocyte.
After meiosis II: Spermatids.

28
Q

What needs to occur in order for a spermatozoa to be complete?

A

the spermatid needs to grow a tail to become a spermatozoa.

29
Q

Where does the maturation of the spermatozoa occur?

A

In the seminiferous tubules.

30
Q

How many types of cells support spermatogenesis and name them.

A
  • Two types
  • Leydig (Interstitial) cells
  • Sertoli cells
31
Q

Where are the Leydig cells located and what do they do?

A

Located between seminiferous tubules and they produce a large amount of testosterone which stimulates spermatogenesis.

32
Q

Where are the Sertoli cells located and what do they do?

A

Located in the seminiferous tubules and they support growing spermatocyte, and help accumulate testosterone in the seminiferous tubules, removes unnecessary waste, and produce certain hormones to feed back to the brain about spermatogenesis.

33
Q

Where is spermatozoa stored?

A

In the epididymis.

34
Q

What pathway does spermatozoa go through to leave the body?

A

Start at the epididymis. When ejaculation occurs, they leave through the vas deferens, which merges into the urethra.

35
Q

How many glands contribute to the production of semen? name them.

A

Seminal vesicle, prostate gland and bulbourethral (Cowper’s) gland

36
Q

Which gland produces 60% of the fluid in semen?

A

Seminal vesicle

37
Q

What is the purpose of the liquid in the seminal vesicles?

A

To help counter the destructive environment of the vagina, with fructose as fuel for the spermatozoa.

38
Q

What does the prostate gland produce and what is its purpose?

A

A fluid to help sperm survive the vagina, and also makes semen less thick to be able to swim more freely.

39
Q

What does the Cowper’s Gland produce and what is its purpose?

A

A clear fluid prior to ejaculation to neutralize urine in the urethra.

40
Q

Is the spermatogenesis random?

A

No, the hypothalamus produces GnRH, which travels to the pituitary gland and activates it.

41
Q

What does the pituitary gland produce?

A

it produces FSH and LH which travels in the blood to the testes.

42
Q

What does LH cause?

A

it allows Leydig cells to produce testosterone.

43
Q

What does FSH cause?

A

causes Sertoli cells to clump testosterone together and to produce inhibin.

44
Q

List the general process of hormonal help in spermatogenesis.

A
  • Hypothalamus -> GnRH -> pituitary gland -> FSH and LH -> blood
  • LH -> Leydig cells -> testosterone
  • FSH -> Sertoli cells -> clumped testosterone and inhibin
  • Inhibin and testosterone -> brain -> reduce production of GnRH

The Human Body (9 decks)

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