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Semester 3 > PP9 > Flashcards

PP9 Flashcards

1
Q

Why do cells divide?

A
  1. Repoduction
  2. growth and developement
  3. tissue renewal
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2
Q

What are the 2 types of cells and associated cell divisions?

A
  1. Somatic cells (all cells in your body except for reproductive cells), divide by mitosis. Results in genetical identical somatic cells with the same number of chromosomes as the original.
  2. Gametes (reproductive cells only ie eggs and sperm), divides by meiosis. Gives games that are genetically similar and have half the number of chrimisine as the original
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3
Q

What are the 3 steps involved in the cell cycle?

A
  • growth of the cell forming cell division
  • copying of the genetic information
  • distribution of copies go genetic information of daughter cells
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4
Q

What are all the steps in the cell cycle?

A

1) Interphase: most of cell’s “life” span (~95%)
a) G1: Growth 1
b) S: DNA Synthesis
c) G2: Growth 2

2) Mitotic phase: (~5%)
a) mitosis
b) cytokinesis

Be careful: It’s easy to get mixed up when answering a test question. The cell cycle is interphase plus mitosis plus cytokinesis. It’s not just mitosis.

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5
Q

How long does the cell cycle last?

A

10-14 hours

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6
Q

What is the G1 phase?

A
  • period of active growth
  • extensive synthesis of new organelles, eventually reaches mature size for type by the time G2 is finished.
  • Many important regulatory proteins are synthesized in this phase
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7
Q

What is S(synthesis) phase?

A
  • Among the many preparations that a cell must make during interphase, one important task is the replication of DNA.
  • During S phase, an exact copy of each chromosome is produced. This has to be faithfully, without errors
  • Occupies about ¼ of the cell cycle.
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8
Q

How many chromosome and chromosomes pairs do humans have?

A

23 different kinds of chromosomes pairs
23 form mom. 23 from dad
Toal of 46 chromosomes.

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9
Q

What is karyotype?

A

Organized profile of a person’s chromosomes; arranged and numbered by size.

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10
Q

What is a homologous chromosome?

A
  • Are a set of one maternal and one paternal chromosomes that pair up with each other inside a cell during meiosis.
  • Homologous pairs of chromosomes are not identical – they are very similar
  • Homologous chromosomes code for the same genes but may have different alleles for that gene.
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11
Q

What is an allele?

A

Allele: any of the alternative versions of a gene that may produce distinguishable differences in an individuals appearance or behaviour.

E.g., two chromosomes may have genes coding for eye color, but one may code for brown eyes, the other for blue.

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12
Q

__ pairs of homologous chromosomes.

__ pair of sex chromosomes.

A

22 pairs of homologous chromosomes.

One pair of sex chromosomes.

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13
Q

What is a ploidy?

A

The number of complete sets of chromosomes in a cell is known as ploidy

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14
Q

haploid vs diploid

A

Cell with one complete set = haploid

Cell with two complete sets = diploid

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15
Q

What happened in DNA replication?

A

The process of duplicating a DNA molecule is called DNA replication (replication, copying)

The two strands of the “parental” duplex separate at the replication fork and serve as template strand for the synthesis of the daughter strand.

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16
Q

What is DNA polymerase? What does it do?

A

DNA polymerase: is the enzyme responsible for making the new “daughter” strand of DNA. DNA is a polymer, so DNA polymerase is the enzyme that makes the polymer, DNA.

DNA polymerase reads the template (parent) strand in the 3’ 5’ direction and synthesizes (makes) the daughter strand in the 5’  3’ direction. Phosphodiester bonds connect the deoxynucleotides. A pairs with T (A=T) and G pairs with C (G  C).

Both original strands are replicated, do when the process is completed, two identical double-stranded DNA molecules (chromosomes) have been produced

17
Q

What does it mean when DNA replication is semiconservative?

A

DNA replication is therefore semiconservative: because after replication, each new DNA duplex will consist of one strand that was originally present in the parental duplex and one newly synthesized “daughter” strand.

18
Q

What are daughter chromosomes?

A

Daughter chromosomes are unreplicated chromosomes that exist as such just after metaphase of mitosis until they are replicated during the S-phase. This term simply implies that replication has not taken place.

19
Q

What are sister chromatids?

A

Copied chromosomes are referred to as sister chromatids. This term is used only when the two former “daughter chromosomes” are connected by a centromere:

  • Both contain the same genetic information.
  • They are physically attached to each other by centromeres.
20
Q

What is a chromosome?\

A

Two genetically identical sister chromatids form a full chromosome

  • In eukaryotic cells, it is a linear piece of DNA
  • Differently numbered chromosomes contain different genes.
  • Chromosomes that have the same number have the same genes but different alleles.
21
Q

Chromatids and daughter chromosomes

A

During S phase of interphase, daughter chromosomes are duplicated. The replicated products are joined together at the centromere and are now called sister chromatids.

A daughter chromosome is a chromosome that results from the separation of sister chromatids during cell division

22
Q

What is cromatin?

A
  • DNA and protein.
  • Can be loose (euchromatin)
  • Can be more condensed (heterochromatin)
23
Q

What is cromatin?

A
  • DNA and protein.
  • Can be loose (euchromatin)
  • Can be more condensed (heterochromatin)

**During prophase, chromatin condenses like CRAZY into “Chromosomal form”

24
Q

In interphase, what is G2?

A
  • Final stage of interphase and important because it’s during this phase when the cell repairs the newly replicated DNA. Mistakes are not tolerated!
  • 2nd growth phase  cell increase in size slightly
  • Cells begin preparation for the mitotic phase of the cycle, i.e., time to divide and make proteins needed for the process!
  • Centrosomes duplicate
  • Spindle fibers (microtubules) form
25
Q

wHat are the 5 stages of mitosis in order?

A 
prophase
prometaphase
metapahse
anaphase
telophase/cytoikenisis
26
Q

Explain prophase.

A
  • Chromatin condenses into chromosomes
  • Nucleus remains intact (but the nucleolus disintegrates)
  • Centrosomes separate and move around the nucleus.
  • Microtubule fibers extend between the centrosomes forming the mitotic spindle.
27
Q

Do plants have centrosomes?

A

NOPE, only animals

28
Q

Explain prometaphase:

A

Nuclear membrane breaks down
Centrosomes are now positioned at opposite ends of the cell.
Some microtubules attach to the kinetochores (centromere region)

centromere: inside

Motor proteins attach to microtubule tracks coming from the centrioles and the kinetochore/chromosome and move along the track, pulling the chromosome with it.

The microtubules shorten by depolymerization at the end closer to the equator of the cell, i.e., the tubulin dimers forming the microtubules fall away from the end closest to the equator.

29
Q

Explain metaphase.

A
  • Chromosomes become aligned along the cell midline (metaphase plate), also called equator.
  • For each chromosome, the kinetochores of the sister chromatids are attached to microtubules coming from opposite poles.
30
Q

explain anaphase.

A
  • Centromeres break and sister chromatids separate.
  • Chromosomes pulled to opposite ends of the cell, using microtubules as tracks.
  • Cells elongate
  • At the end of anaphase, each pole of the cell has a complete set of chromosomes.
31
Q

explain telophase.

A
  • One copy of each chromosome is present at the opposite ends of the cell.
  • The chromatin fibers starts to loosen and become less coiled.
  • Spindle fibers disappear
  • Nuclear membrane forms around chromosomes.
32
Q

what marks the end of mitosis?

A

Telophase marks the end of mitosis, even if cell division is not entirely complete. The formation of the cleavage furrow is the signal. Actin filaments are pinching the long cell in half.

33
Q

What is cytokinesis?

A
  • When the cytoplasm divides into two new daughter cells.
  • Cell gradually pinches in along the midline forming a cleave furrow
  • 2 new daughter cells are formed with identical genetic information
  • Cells may enter G1 of Interphase and repeat the cycle again! These cells would be blood forming cells, intestinal cells, skin cells, etc.
34
Q

What is the G0 phase?

A
  • Not all cells in your body actively participate in the cell cycle, since not all tissues require rapid replenishing of cells.
  • Many cells pause in the cell cycle somewhere between M phase and S phase for periods ranging from days to more than a year.
  • This period is called G0 phase and is distinguished from G1 phase by the absence of preparations for S phase.
  • Although cells in G0 phase have exited the cell cycle, they are still active in other ways, performing specialized functions
35
Q

Cell division in plants:

A
  • Mitosis in plant cells is similar (but they have no centrioles)
  • Major difference is in cytokinesis:
    Cells can’t pinch in half like in animal cells
    Daughter cells in plants are separated by the cell plate which forms from vesicles from the Golgi. They move to the centre of the dividing cell and form a cell plate.
    The cell membrane will develop on either side of the plate.
36
Q

What is the cell control system?

A
  • Cyclical operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle.
  • At specific times, the cells checks itself to make an assessment if everything is ok.
  • For many mammalian cells, the G1 checkpoint (the “restriction point”) appears to be the most important.
  • If a cell receives a go-ahead signal at the G1 checkpoint then it usually goes through S, G2 and M phases.
  • If it does not, the cell goes to G0
37
Q

How are the checkpoints regulated?

A

These check points are controlled by special regulatory proteins. One of the most important regulatory proteins is called p53, which is classified as a tumor suppressor protein, also called Guardian of the Genome

38
Q

P53 has many mechanisms of anticancer function:

A
  1. It can pause the cell cycle and initiate cell DNA repair mechanisms that spot replication errors and fixes them.
  2. If the DNA cannot be repaired it will induce cell death or apoptosis, which is programmed cell death

Semester 3 (9 decks)

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