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MCAT - Biology > Chapter 2 - The Cell Cycle and Mitosis > Flashcards

Chapter 2 - The Cell Cycle and Mitosis Flashcards

1
Q

What are the 5 Stages of Mitosis?

A
  1. G1
  2. S
  3. G2
  4. M
  5. G0
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2
Q

Describe Interphase

A
  • Makes up the first three stages of the cell cycle: G1, S, and G2
  • The longest part of the cell cycle; even actively dividing cells spend roughly 90% of their time in Interphase
  • Cells that do not divide spend all of their time in an offshoot of G1 called G0.
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3
Q

What occurs during the G1 Stage?

A

Known as the Presynthetic Gap. The cell grows and performs normal functions. DNA is examined and repaired. In addition, passage into the S (synthesis) stage is governed by a restriction point; certain criteria must be met before entering S.

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4
Q

What occurs during the S Stage?

A

DNA is replicated so that each daughter cell will have identical copies. After replication, each chromosome consists of two identical chromatids that are bound together at a specialized region known as the centromere.

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5
Q

What occurs during the G2 Stage?

A

Known as the Postsynthetic Gap. The cell passes through another quality control checkpoint: DNA has already been duplicated, and the cell check ensures that there are enough organelles and cytoplasm for 2 daughter cells. This checkpoint ensures that replication proceeds correctly to avoid passing on an error to daughter cells.

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6
Q

What occurs during the M Stage?

A

Consists of Mitosis itself along with Cytokinesis. Mitosis is divided into four stages: Prophase; Metaphase; Anaphase; and Telophase.

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7
Q

What is Cytokinesis?

A

The splitting of the cytoplasm and organelles between the two daughter cells.

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8
Q

What is the main protein in control of the cell cycle?

A

p53 (checkpoint repair)

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9
Q

What are the two molecules responsible for the cell cycle?

A

Cyclins and Cyclin-Dependent Kinases (CDK)

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10
Q

What do transcription factors do?

A

They promote transcription of genes required for the next stage of the cell cycle.

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11
Q

What is the most common mutation found in cancer?

A

Mutation of the gene that produces p53, called TP53. When this gene is mutated the cell cycle doesn’t stop to repair damaged DNA.

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12
Q

What is metastasis?

A

In cancer when the damaged tissues either invade other local tissues or spread the cancer cells distantly throughout the bloodstream or lymphatic system.

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13
Q

Define Mitosis

A

The process by which two identical daughter cells are created from a single cell. Occurs in somatic cells (cells that are uninvolved in sexual reporduction).

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14
Q

What occurs during Prophase?

A

Chromosomes condense and spindles form.

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15
Q

What occurs during Metaphase?

A

The centriole pairs are now at opposite ends of the cell. The kinetichore fibers interact with the fibers of the spindle apparatus to align the chromosomes at the Metaphase Plate.

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16
Q

What occurs during Anaphase?

A

The centromeres split so that each chromatid has its own distinct centromere, thus allowing the sister chromatids to separate. The sister chromatids are pulled toward the opposite poles of the cell by the shortening of the kinetochore fibers.

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17
Q

What occurs during Telophase & Cytokinesis?

A

Telophase is essentially the reverse of Prophase; the spindle apparatus disappears, the nuclear membrane re-forms and the nucleoli reappear. Cytokinesis, which occurs at the end of Telophase, is the separation of the cytoplasm and organelles, giving each daughter cell enough material to survive on its own.

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18
Q

What is the number and ploidy of daughter cells produced via Meiosis?

A

Meiosis I: 2 Haploid daughter cells

Meiosis II: Up to 4 Haploid gametes

19
Q

What is the difference between Homologous Chromosomes and Sister Chromatids?

A

Homologous chromosomes are related chromosomes of opposite parental origin. Sister chromatids are identical copies of the same DNA that are held together at the centromere. After S Phase, a cell contains 92 chromatids, 46 chromosomes and 23 homologous pairs.

20
Q

What occurs during Prophase I?

A

Crossing over during synapsis.

21
Q

What occurs during Metaphase I?

A

Homologous pairs (tetrads) align at the metaphase plate, and each pair attaches to a separate spindle fiber by its kinetochore.

22
Q

What occurs during Anaphase I?

A

Homologous pairs separate and are pulled to opposite poles of the cell. This process is called disjunction and it accounts for Mendel’s first law (of segregation).

23
Q

What occurs during Telophase I?

A

A nuclear membrane forms around each new nucleus. Chromatin may or may not decondense; interkinesis occurs to prepare for Meiosis II.

24
Q

What is Interkinesis?

A

A short rest period where chromosomes partially uncoil.

25
Q

What do Meiosis II and Mitosis have in common?

A

Very similar to Mitosis in that sister chromatids - rather than homologues - are separated from each other.

26
Q

What occurs during Prophase II?

A

The nuclear envelope dissolves, nucleioli disappear, the centrioles migrate to opposite poles, and the spindle apparatus begins to form.

27
Q

What occurs during Metaphase II?

A

Chromosomes line up on the metaphase plate.

28
Q

What occurs during Anaphase II?

A

Centromeres divide, separating the chromosomes into sister chromatids. These chromatids are pulled to opposide poles by spindle fibers.

29
Q

What occurs during Telophase II?

A

A nuclear nembrane forms around each new nucleus. Cytokinesis follows and two daughter cells are formed. By completion of Meiosis II, up to four haploid daughter cells are produced per gametocyte.

30
Q

What is the function of Interstitial Cells of Leydig?

A

To secrete testosterone and other male sex hormones (androgens).

31
Q

What is the function of Steroli Cells?

A

To nourish sperm during devel.

32
Q

Which phase of Meiosis are Primary Oocytes arrested in?

A

Prophase I

33
Q

Which phase of Meiosis are Secondary Oocytes arrested in?

A

Metaphase II

34
Q

What is the acrosome? Which organelle forms it?

A

The acrosome contains enzymes that are capable of penetrating the corona radiata and zona pellucida of the ovum, permitting fertilization. It is a modified Golgi Apparatus.

35
Q

Once formed, where does sperm gain motility?

A

The Epididymus. Sperm is stored here until ejaculation

36
Q

What do the bulbourethal glands produce?

A

A clear, viscous fluid that cleans out all remnants of urine and lubricates the urethra during sexual arousal.

37
Q

Describe Spermatogenesis.

A

Four haploid cells are produced from a Spermatogonium. After S Stage, the germ cells are called primary spermatocytes. After Meiosis I, they’re called secondary spermatocytes. After Meiosis II, they’re called spermatids. After maturation, they’re called spermatozoa.

38
Q

Which hormones are key to sexual differentiation in a fetus with XY genotype? Describe the expected phenotype if receptors of these hormones are absent.

A

Androgens, such as testosterone, lead to male sexual differentiation. Absence of androgen receptors (known as androgen insensitivity syndrome) leads to an XY genotype with phenotypically female characteristics.

39
Q

What results from Oogenesis?

A

One haploid ovum and a variable number of polar bodies are formed. *go back to notes for step-by-step process.

40
Q

What are the 4 phases of the Mentrual Cycle?

A
  1. Follicular
  2. Ovulation
  3. Luteal
  4. Menses
41
Q

What occurs during the Follicular Phase?

A

Egg develops, endometrial lining becomes vascularized and glandularized. FSH levels increase; LH levels stay the same; Estrogen levels decrease then increase; and Progesterone levels decrease.

42
Q

What occurs during Ovulation?

A

Egg is released from follicle into peritoneal cavity. FSH levels increase; LH levels increase; Estogen levels increase; and Progesterone levels decrease.

43
Q

What occurs during the Luteal Phase?

A

Corpus luteum produces progesterone to maintain endometrium. FSH levels decrease; LH levels remain the same; Estrogen levels increase; and Progesterone levels increase.

44
Q

What occurs during the Menses Phase?

A

Shedding of endometrial lining. FSH levels decrease; LH levels decrease; Estrogen levels decrease; and Progesterone levels decrease.

MCAT - Biology (12 decks)

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