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Bio 130 > Bio 130 ch. 16 study guide > Flashcards

Bio 130 ch. 16 study guide Flashcards

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Biology 101 flashcards
1
Q

What is a karyotype?

A

a photographic representation of the chromosomes from an actively dividing cell. It reveals the number, size, and form of chromosomes found within an actively dividing cell

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2
Q

What are the steps of karyotype?

A
  1. Sample of blood is collected and treated with drugs that stimulate cell division. (chromosomes are readily seen when they are compacted in a dividing cell) Then centrifuged.
  2. The cell pellet is suspended in a hypotonic solution, causing the cell to swell and the chromosomes to spread out from each other.
  3. Centrifuged again to concentrate the cells. The cells are suspended in a fixative, stained, and placed in a slide.
  4. Slide is viewed with a microscope and photographed and arranged electronically on the screen.
  5. For a diploid human cell, 2 complete sets of chromosomes from a single cell constitute a karyotype of that cell.
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3
Q

Banding patterns on chromosomes

A

occur from preferential binding of stains to AT rich vs GC rich DNA seq

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4
Q

What are the different positions of centromere?

A
  1. Metacentric: near the middle
  2. Submetacentric: off center
  3. Acrocentric: near one end
  4. Telocentric: at the end
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5
Q

What are the key phases of Cell Cycle?

A

Interphase (G1, S, G2)

M phase (mitosis + cytokinesis)

  • Divide one cell nucleus into two nuclei
  • Pairs of chromatids are separated and sorted so that each daughter cell receives 46 chromosomes.
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6
Q

What happens during G1 phase?

A
  • commitment to divide
  • accumulate molecular changes that eventually leads to the cell division (envt conditions and signals) -> 46 distinct chromosomes
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7
Q

What happens during S phase?

A
  • each chromosome replicated to form a pair of sister chromatids -> 46 pairs of sister chromatids (total 92 chromatids)
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8
Q

What happens during G2 phase?

A
  • synthesis of necessary proteins for chromosome sorting and cell division + some cell growth
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9
Q

Cyclin

A

protein responsible for advancing a cell through the phases of the cell cycle by binding to a cyclin-dependent kinase

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10
Q

cyclin-dependent kinases (Cdks)

A

A protein kinase that is active only when attached to a particular cyclin. - phosphorylates the proteins needed for the next steps.

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11
Q

What are the 3 checkpoints in the cell cycle?

A
  1. G1 checkpoint
  2. G2 checkpoint
  3. metaphase checkpoint
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12
Q

G1 checkpoint

A
  • restriction point
  • determine if conditions are favorable for cell division and if the DNA is damaged.
  • G1 cyclin is made in response to sufficient nutrients and growth factors.
  • G1 cyclin is degraded after the cell enters the S phase.
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13
Q

G2 checkpoint

A
  • checks for DNA damage, determines if all of the DNA is replicated, and monitors the levels of proteins needed for M phase.
  • Mitotic cyclin is degraded as the cell progresses through mitosis.
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14
Q

Metaphase checkpoint

A

Determines if all chromosomes are attached to the spindle apparatus.

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15
Q

Steps of mitosis?

A
  1. Interphase: Chromosomes have already replicated during interphase.
  2. Prophase: Sister chromatids condense, and the mitotic spindle starts to form. The nuclear envelope begins to dissociate into vesicles. Nucleolus is no longer visible.
  3. Prometaphase: The nuclear envelope has completely dissociated into vesicles, and the mitotic spindle is fully formed. Sister chromatids attach to the spindle via kinetochore microtubules.
  4. Metaphase: Sister chromatids align along the metaphase plate.
  5. Anaphase: Sister chromatids separate, and individual chromosomes move toward the poles as kinetochore microtubules shorten. Polar microtubules lengthen and push the poles against.
  6. Telophase and cytokinesis: chromosomes decondense, and the nuclear envelope re-forms. Cytokinesis separates the mother cell into two daughter cells, and it begins with a cleavage furrow in animal cells.
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16
Q

What are the steps of meiosis?

A

a. G1 phase prior to meiosis

Chromosomes replicate using S phase and then condense at the start of meiosis

b. Meiosis I
Homologous chromosomes separate

c. Meiosis II
Sister chromatids separate

17
Q

What are the steps of meiosis I?

A
  1. Prophase I: Homologous chromosomes synapse to form bivalents and crossing over occurs. Chromosomes condense, and the nuclear envelope begins to dissociate into vesicles.
  2. Prometaphase I
  3. Metaphase I: bivalents randomly align along the metaphase plate. Each pair of sister chromatids is attached to one pole.
  4. Anaphase I: Homologous chromosomes separate and pairs of sister chromatids move toward the opposite poles.
  5. Telophase I and cytokinesis: the chromosomes decondense, and the nuclear envelope re-forms. The 2 daughter cells are separated by a cleavage furrow.
18
Q

What are the steps of meiosis II?

A
  1. Prophase II: Sister chromatids condense, and the spindle starts to form. The nuclear envelope begins to dissociate into vesicles.
  2. Prometaphase II: The nuclear envelope completely dissociates into vesicles. Sister chromatids attach to the spindle via kinetochore microtubules.
  3. Metaphase II: Sister chromatids align along the metaphase plate. Each pair of sister chromatids is attached to both poles.
  4. Anaphase II: Sister chromatids separate, and individual chromosomes move toward the poles as kinetochore microtubules shorten. Polar microtubules lengthen and push the poles apart.
  5. Telophase II and cytokinesis: Chromosomes decondense, and the nuclear envelope re-forms. Cleavage furrows separate the 2 cells into 4 cells.
19
Q

What are the two key events during the prophase of meiosis I?

A
  1. synapsis to form the bivalents
  2. Crossing over of the bivalents -> chiasma becomes visible, which is the connection at a crossover site of two chromosomes
20
Q

What is the difference between the end products of mitosis and meiosis?

A

Mitosis produces 2 diploid daughter cells that are genetically identical, while meiosis produces 4 haploid daughter cells that are genetically different. Meiosis reduces the number of sets of chromosomes.

21
Q

What is the difference between mitosis and meiosis?

A
  • DNA replication occurs prior to Mitosis and Meiosis I, but not between meiosis I and II.
  • Synapsis occurs in the prophase of meiosis I to form the bivalents, and crossing over commonly occurs due to this.
  • Pair of sister chromatids is attached to kinetochore microtubules form both poles on mitosis and meiosis II, while it’s attached form just one pole for meiosis I.
  • While the sister chromatids align for mitosis and meiosis II, the bivalents align for meiosis I.
  • Single chromatids, now called chromosomes, move to each pole for mitosis I and meiosis II, but a pair of sister chromatids moves to each pole for meiosis I.
22
Q

What is polyploidy?

A

organism or cell that has three or more sets of chromosomes

(ex: triploid organisms are referred to as 3n and tetraploid is 4n, and they are euploid because they have complete sets of chromosomes.)

23
Q

What is aneuploidy?

A

alternation of the number of a particular chromosome present in an organism or cell, so the total number of chromosomes is not an exact multiple of a set.

24
Q

What is nondisjunction?

A

event in which the chromosomes do not separate properly during cell division.

  • During meiosis I: all haploid cells are aneuploids, resulting in gametes with 4 chromosomes and 2 chromosomes, instead of 3. (two of each n+1 and n-1)
  • During meiosis II: two haploid cells are fine, but the other two will be each n+1 and n-1.
25
Q

How many autosomal and sex chromosomes are in the human cells?

A

Humans have 23 pairs of chromosomes, 46 of all: 44 autosomes and 2 sex chromosomes

26
Q

What are the types of mutations at the chromosomal level?

A
  1. deletion : removes a segment of chromosome
  2. Duplication: doubles a particular region
  3. Inversion: flips a region to the opposite orientation
  4. translocation
  • Simple translocation: moves a segment of 1 chromosome to another chromosome
  • Reciprocal translocation: exchanges places between 2 different chromosomes
27
Q

What are the human diseases due to chromosome abnormality?

A
  • Turner syndrome (XO) can occur when a gamete that is lacking a sex chromosome due to nondisjunction has fused with a gamete carrying an X chromosome.
  • Triple X syndrome (XXX) occurs when a gamete carrying two X chromosomes fuses with a gamete carrying a single X chromosome.
  • Trisomy 21 / Down syndrome: mental impairment, abnormal pattern of palm creases, slanted eyes, flattened face, short stature

Bio 130 (1 decks)

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