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A&P Lab > Lab 4 > Flashcards

Lab 4 Flashcards

1
Q

Mitosis

A

DEFINE: division of nuc that results in genetically identical daughter cells
FUNCTION: growth, replacement, repair

  • the division of the original parent cell nucleus such that the chromosomal content of the two new daughter cells is identical to that of the parent cell.
  • The division of somatic (body) cells involves nuclear division
  • The original “parent” cell nucleus divides so that the chromosomal content of the two new “daughter” cells is identical to that of the parent cell
  • produces diploid cells 2n (have the full complement of two of each type of chromosome)

Function:
• necessary for human growth and development as it provides a means of forming new cells and it is also necessary for the maintenance of cell populations to replace worn-out, dead or injured cells.

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2
Q

Cytokinesis

A
  • the division of the cytoplasm to form two distinct new daughter cells.
  • cytoplasmic division
  • In animal cells, this cytoplasmic division is accomplished by means of a cleavage furrow, which is a progressive pinching-in of the cell membrane midway in the cell. Actin microfilaments form a contractile ring that ultimately divides the cell in two.
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3
Q

gametes

A
  • Sperm and ova
  • haploid cells, and each cell carries only one copy of each chromosome (23).
  • The original number of chromosomes is only restored after fertilization occurs.
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4
Q

Meiosis

A
  • mechanism used in producing gametes is another type of nuclear division
  • haploid cells n
  • The first division, meiosis I, results in the reduction of the chromosome number. The second nuclear division, meiosis II, is a simple mitotic division
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5
Q

Homologous chromosomes:

A

a pair of chromosomes with one chromosome provided by the female parent (maternal) and the other by the male parent (paternal) that have the identical gene loci (carry genes for the same traits) and identical centromere position.

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6
Q

Diploid number (2n)

A

the characteristic genetic composition of somatic (body) cells, which contain a complete complement of chromosomes (in humans, 46 chromosomes or 23 pairs of homologous chromosomes).

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7
Q

Haploid number (n)

A

the chromosome number characteristic of gametes (sperm and ova), in which only one member of each pair of homologous chromosomes is present (in humans, 23 individual chromosomes).

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8
Q

The two major periods in a cell’s life cycle

A

Interphase - when the cell is not dividing

Cell Division - period of actual dividing

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9
Q

Interphase

A

• total period of time from the formation of a cell until it enters cell division.

• G1 (Gap 1)
> cell grows and performs all its routine metabolic functions, such as duplication of organelles and protein synthesis
> G0 Cells that are destined to never divide again (such as mature nerve (variation of G1)

•S (Synthesis)
> DNA replication (if cell preparing to divide)
> DNA partially uncoils where H-bonds content to N-base pairs
> Old N-base pairs with new N-base and H-bonds reform
> Now there are 2 identical DNA strands. Each duplicated chromosome has two sister chromatids.
> centromere holds the chromatid pair together.
> chromosomes can be distinguished only as a network of dispersed chromatin material (elongated DNA and associated proteins) and not as separate entities.
> Once DNA replication is completed, the cell is committed to undergo mitosis (or meiosis).

•G2 (Gap 2) phases
> the cell prepares for the actual division
> accumulation of energy reserves
> additional growth as well as an
> synthesis of enzymes and other proteins.

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10
Q

Centrosome

A
  • which functions throughout the cell cycle to organize the cell’s microtubules forming the spindle apparatus.
  • The centrosome contains pericentriolar material (complexes composed of tubulin protein)
  • Contain pair of structures known as centrioles
  • During interphase, the single centrosome duplicates forming two centrosomes which remain together near the nucleus
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11
Q

Centrioles

A

• consists of two cylindrical bodies also composed of microtubules, which lie at right angles to each other

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12
Q

Mitosis: Prophase

A
  • chromosomes coil, shorten and become visible
  • mitotic spindle starts to form.
  • An aster extends from each centrosome towards the plasma membrane.
  • Microtubules coming from opposite poles attach to the kinetochore region and are known as kinetochore microtubules
  • Other microtubules just interact with microtubules from the opposite pole of the spindle and are known as nonkinetochore microtubules.
  • END: disappearance of the nuclear membrane and the nucleolus.
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13
Q

Mitosis: Metaphase

A
  • chomos line at at center (equatorial plane or metaphase plate)
  • For each chromosome, the kinetochore region attaches to kinetochore microtubules coming from opposite poles
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14
Q

Mitosis: Anaphase

A
  • centromere of each chromatid pair splits and the chromatids separate. (become daughter chromosome.)
  • The centromere of each pulled towards opposite poles (kinetochore microtubules shorten)
  • cell elongates (nonkinetochore microtubules lengthen.)
  • END: the arrival of the daughter chromosomes at their respective poles.
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15
Q

Mitosis: Telophase

A
  • new nuclear membrane is assembled
  • Nucleoli are reformed
  • chromosomes gradually uncoil and lengthen
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16
Q

Aster

A

A radial array of short microtubules

17
Q

kinetochore

A

Protein complex at the outside of each centromere

18
Q

blastula

A

is an embryological stage in the development of most animals. After an egg has been fertilized (to form a zygote), it begins to divide over and over by mitosis. This type of cell division results in a hollow cluster of cells known as a blastula.

19
Q

Genetic variability

A

is introduced in meiosis through the independent assortment of chromosomes and crossing-over

20
Q

Meiosis: Interphase

A
  • specialized cell in the testes or ovaries preparing to enter meiosis
  • G1, S and G2.
  • The centrosome duplicates itself in preparation for cell division.
  • S phase: DNA replicates and each chromosome becomes a pair of sister chromatids held together at the centromere.
21
Q

Meiosis: Prophase I

A

Same:
Nuc envelope breaks down
Chromatin condences
Centriole pairs start migration

Dif:
Chromo finds their buddy (their homo chromo) and then lie side by side
Allows crossing over between non sister chromatids

• the duplicated chromosomes coil, shorten and become visible as individual structures
• the centrosomes (each with a centriole pair) migrate to the opposite poles of the cell
• spindle fibers and astral rays appear
• nucleoli and nuclear membrane disappear
• pairing of homologous chromosomes.
> members of each pair of homo chromo move together and lie side-by-side.
• crossing-over occurs.
• Homo chromo will remain together as a tetrad throughout late prophase I and metaphase I.

22
Q

Meiosis: Metaphase I

A

Same:
Chromo line up
Spindle fibers attach to chromos

Dif:
Stay with homo chromo (in their tetrads)
Kinetocore can only grab the chromo from one side (the other side is protected by their homo chromo)
Independent sorting: the homo chromos can line up with either on either side. Homo chromo get to decide how they line up on metaphase plate

  • homo chromos line up along the metaphase plate of the cell as tetrads. (NOT individual chromosomes).
  • The kinetochore of both chromatids of one chromosome are attached to a kinetochore microtubule from one pole; both chromatids of the other chromosome are attached to a microtubule from the opposite pole.

For example, a hypothetical cell with a chromosome number of 8:
> in mitosis - 8 individual chromosomes line up along the metaphase plate of the cell, two kinetochore microtubules extend to each chromosome,
> in meiosis - 4 homologous pairs of chromosomes (4 tetrads) line up along the metaphase plate of the cell, two kinetochore microtubules extend to each pair of chromosomes.

23
Q

Meiosis: Anaphase I

A

Same:
Kinetochore micro shortenes and pulls chromo appart

Dif:
Homo chromo seperated with sister chromatids together attached at centromere

  • centromeres do not divide and the chromatids do not separate,
  • members of each pair of homologous chromosomes separate and move to opposite poles.
  • one-half of each tetrad is pulled toward a pole of the cell.
  • The chromosome provided by the female parent will move to one pole and the chromosome provided by the male parent will move to the opposite pole.
  • END: arrival of one chromosome from each homologous pair at each pole of the cell. Each of these chromosomes consists of a pair of chromatids held together at the centromere.

For example, a hypothetical cell with a chromosome number of 8:
> at the end of anaphase of mitosis - the centromere splits separating the sister chromatids and 8 chromosomes move to each pole of the cell (each chromosome is a daughter chromosome),
> at the end of anaphase I of meiosis - the members of each homologous pair separate and 4 chromosomes move to each pole of the cell (each chromosome still consists of a pair of chromatids

24
Q

Meiosis: Telophase I

A

Same:
Nuc memb back
Chromo decondences

Dif:
Each daugher cell contains a haploid number of duplicated chromos
New combos on materal and paternal alleles have been generated

  • a nuclear membrane is assembled
  • the nucleoli are reformed and the chromosomes gradually uncoil and lengthen to become a chromatin network.
  • cleavage furrow forms and cytokinesis occurs forming two new daughter cells.

Major Difference:
• the nuclei of the daughter cells have only half as many chromosomes
• each chromosome consists of two sister chromatids

Each of the two new daughter cells contains:
• one member of each homologous pair of chromosomes
• a haploid chromosome number
• chromosomes that consist of two chromatids joined at the centromere.

25
Q

Interkinesis

A
  • The two daughter cells formed may enter a short interphase-like period between the two divisions of a complete meiotic cycle.
  • There is NO further DNA replication and each chromosome is still composed of two sister chromatids.
26
Q

independent assortment

A

The orientation of each homologous pair along the equatorial plane, during metaphase I, is random. Genetic variation is introduced based on how the maternal and paternal chromosomes in each of the 23 pairs align. the homo chromos can line up with either on either side. Homo chromo get to decide how they line up on metaphase plate

27
Q

tetrad

A

Each homo chromo consists of two sister chromatids (4 chromatids in total

28
Q

crossing-over

A
  • the breaking and exchange of genetic material between non sister chromatics in homo chromos
  • occurs in prophase I synapsis
  • breakage and reunion of parts of the maternal and paternal chromatids is a major source of genetic variation. This exchange of genes results in genetic recombination
29
Q

genetic recombination

A

formation of new combinations of genes that accounts for part of the great variation between humans.

30
Q

synapsis

A

Chromo lies side by side with homo pair

the pairing of homologous chromosomes, one from each parent, during early meiosis.

31
Q

how do you know how many chromo?

A

count the # of centromeres

32
Q

3 types of microtubules:

A
  • Kinetochore microtubules: grab onto the kinetochore region of the chromo
  • Non-kinetochore (or polar): Extend from pole to pole but don’t grab on
  • Astral ray: come off the centriole pair stabilize the mitotic spindle (also a microtubule)
33
Q

how many sister chromatids in anaphase?

A

Zero.
In anaphase as soon as they split they become chromosomes so there’s no chromatid. Once theres no duplicated chromasomes theres no sister chromatids

34
Q

what line do the chromosomes line up on in anaphase?

A

equatorial plane or metaphase plate

A&P Lab (11 decks)

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