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(Biology 211) Cellular Biology > Chapter 10 - Cell Reproduction > Flashcards

Chapter 10 - Cell Reproduction Flashcards

1
Q

Sexually reproducing organisms start life as a single cell called…

A

A zygote

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2
Q

Non sexual cells reproduce through what?

A

Cell division

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3
Q

The result of division of a single parent cell to the production of two genetically identical what cells?

A

Daughter cells

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4
Q

All of a cells DNA is called it’s….

A

Genome

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5
Q

The genome of prokaryotes have what characteristics? Where are they found in a prokaryotic cell?

A

They are double stranded DNA molecules in the form of a loop, and found in an area called the nucleoid region

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6
Q

Some prokaryotes have small loops of DNA called…

A

Plasmids

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7
Q

Eukaryotic genomes consist of what shape? What are they called?

A

Linear pieces of DNA called chromosomes

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8
Q

Sex cells are also called

A

Gametes

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9
Q

What is the difference in Number of chromosomes from gametes to somatic cells? For example human cells

A

Gametes have half the number of chromosomes of somatic cells, for example human gametes have 23, somatic has 46

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10
Q

Body cells contain 2 matched or homologous sets of chromosomes while sex cells have just one set of chromosomes, what are these 2 denoted as in genetics?

A

Body cells containing 2 matched or homologous sets of chromosomes are denoted as diploid (2n), while human cells with just one set of chromosomes are haploid (n)

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11
Q

Upon fertilization each gamete contributes one set of chromosomes in a diploid cell which has matched pairs of chromosomes called…

A

Homologous chromosomes

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12
Q

Homologous chromosomes are the same length and have the same genes in exactly the same location called…

A

The locus

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13
Q

What are the functional units of chromosomes and determine specific characteristics by coding for specific proteins?

A

Genes

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14
Q

What are the possible variants of the specific characteristics coded by genes?

A

Traits

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15
Q

A complete gene is made up of how many alleles?

A

2 (1 from each parent)

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16
Q

Alleles can be identical or not, what are they called in each case?

A

Identical (homozygous), different (heterozygous)

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17
Q

What are the only homologous pair of the 23 chromosomes to have genes for different characteristics at the same locus?

A

The X and Y chromosomes

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18
Q

What is at the first level of compaction in chromosomes?

A

The DNA double helix is wrapped around a core of 8 histone proteins along the entire length of the chromosome now called chromatin,

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19
Q

The bead like DNA/histone complexes are called what? How much larger would they be without histones?

A

They are called nucleosomes, they would be 7 times larger without histones

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20
Q

What is the second level of compaction in chromosomes?

A

The nucleosomes and the linker DNA coil into 30nm fibers, shortening the chromosomes by about 50x

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21
Q

What is level 3 of compaction in chromosomes? What is the purpose of this level?

A

A variety of fibrous proteins further condense the chromatin in a non dividing cell, this makes sure no DNA overlaps

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22
Q

If a cell is to divide it enters what phase of interphase?

A

The S-phase where replication of the entire chromosome occurs

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23
Q

Replicated sister chromatids bind together with cohesion proteins, the closest point being where?

A

The centromere

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24
Q

What are the 2 major phases of the cell cycle?

A

Interphase, and the mitotic phase

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25
Q

If cytokinesis does not occur when it needs to what happens?

A

Multiple nuclei is produced

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26
Q

Overall what happens in interphase? What three stages of interphase is there?

A

The cell undergoes growth processes while preparing for cell division. The 3 stages include G1, S, and G2

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27
Q

What happens in G1 phase of interphase?

A

Called the first gap it is where little change is visible in microscope, but much occurs biochemically like chromosomal structure is completed, cell reaches its full size, energy reserves are accumulated and DNA is in its chromatin state

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28
Q

What happens in the S phase of Interphase?

A

DNA synthesis happens here it produces two identical chromatids from each DNA strand, the centrosome is duplicated which will give rise to the mitotic spindle which will move the chromatids and help organize cell division

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29
Q

What happens in the G2 phase of interphase?

A

Now in the second gap, energy stores are replenished, proteins necessary for chromosome manipulation and movement are duplicated, the cytoskeleton is dismantled to provide resources for the mitotic phase

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30
Q

Briefly what does the mitotic phase do? What 2 main phases are there?

A

The duplicates chromosomes (chromatids) are aligned, seperated, and moved into new, identical daughter cells

-2 main phases are karyokinesis and Cytokinesis

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31
Q

What are all the stages in order of karyokinesis?

A

Prophase, prometaphase, metaphase, anaphase, telophase and cytokinesis

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32
Q

What happens in the prophase? Be specific

A

-nuclear envelope starts to dissociate and membranous organelles fragment and disperse towards the periphery of the cell

-centrosomes move to opposite poles

-microtubules start to form the mitotic spindle between the centrosomes

-sister chromatids coil more tightly coiled with the help of condensing proteins and become visible in a light microscope

33
Q

What happens in the prometaphase? Be specific

A

-each sister chromatid develops a protein structure called a kinetochore at the centromeres region, the kinetochore proteins attach and bind to the mitotic spindles

-centrosome proteins extend and attach to the kinetochores

-sister chromatids are arranged so as to face opposite poles of the cell

-polar microtubules reach only halfway and contribute to cell elongation

-astral microtubules extend only short distances from the centrosomes and aid in spindle orientation and mitosis regulation

34
Q

What happens in the metaphase? Be specific

A

-all the chromosomes (chromatids) are aligned on a plane called the metaphase plate

-sister chromatids are tightly attached to each other by cohesion proteins and are maximally condensed

35
Q

What happens in the anaphase? Be specific

A

-cohesion proteins degrade

-sister chromatids seperate at their centromere

-each chromatid is now called a single chromosome and are quickly pulled towards the centrosomes by the microtubules

-cell becomes elongated

36
Q

What happens in telophase? Be specific

A

-chromosomes reach their opposite poles and begins to decondense to take the form of chromatin

-the mitotic spindle depolarizes into tubulin monomers

-the nuclear envelope forms around the chromosomes

37
Q

What happens in cytokinesis?

A

It is the seperatiom of the cytoplasmic components into the daughter cells

-remember when it does not occur cells become multinucleated

38
Q

When does animal cytokinesis start? And what happens?

A

In late anaphase,
a contractile ring forms just inside the plasma membrane at the former site of the metaphase plate where actin filaments form and pull the equators of the cell inward forming a fissure called a cleavage furrow which deepens as the actin ring contracts eventually cleaving the cell into 2

39
Q

What happens in plant cytokinesis?

A

A new cell wall must form between the daughter cells during telophase, Golgi vesicles are transported on microtubules to form a phragmoplast at the metaphase plate, the vesicles fuse and coalesce from the center towards the exiting cell walls, this structure is called a cell plate and enlarged until it fuses with the cell walls, glucose then is used by enzymes to build the new cell wall between the membranes of the cell plate

40
Q

What do cells do in there G0 phase?

A

Nothing, they are not actively preparing to divide and are inactive

(Some cells are temporarily here due to environmental factors or lack of GF)

(Some cells are even permanently in G0)

41
Q

What are all the cell cycle lengths in human cells? And most typical examples?

A

It can be a few hours in embryonic development, 2-5 days seen in epithelial cells, or an entire lifetime spent in G0 seen in cortical neurons and cardiac muscle fibers

42
Q

Fruit fly cell cycles complete in how much time? What is it due to?

A

About 8 minutes due to the formation of multinucleated zygotes

43
Q

List some ways the cell cycle can be inhibited or initiated

A

-death of nearby cells can either initiate or inhibit cell division

-crowding can inhibit it

-when cells are too large their surface to volume ratio becomes too small initiating cell division

-growth promoting hormones (ex. HGH in high amounts triggers a lot of cell division resulting in gigantism, in low amounts it results in dwarfism)

44
Q

What are the three main internal checkpoints that prevent a compromised cell from continuing to divide?

A

They are called cell cycle checkpoints and the 3 are

1) G1 checkpoint
2) G2 checkpoint
3) M checkpoint

45
Q

What does the G1 checkpoint asses?

A

-If all conditions necessary for cell division are favorable, (the cell is irreversibly committed to division past this checkpoint)

-growth factors play an important role in carrying the cell past this checkpoint, also both internal factors like adequate reserves and cel size

-DNA damage is assessed

(if all conditions are met the cell can proceed past this checkpoint)

46
Q

If conditions are not met at the G1 checkpoint what happens?

A

Problems may be remedied or the cell may pass into G0 and wait for conditions to improve

47
Q

What is assessed in the G2 checkpoint?

A

-cell size and protein reserves

-all the chromosomes must be replicated, and the DNA must not be damaged (if damaged, DNA repair mechanisms may be attempted)

48
Q

What is added in the M checkpoint?
When does this checkpoint occur

A

This occurs at the end of metaphase

-sister chromatids must be correctly attached to the spindle, since anaphase is an irreversible step the cycle will not proceed formally until the kinetochores of each pair of sister chromatids are attached to at least 2 spindle fibers arising from opposite poles

Often called the spindle checkpoint

49
Q

What are the 2 types of regulator molecules of the cell cycle?

A

Positive or negative regulators

50
Q

In brief terms what are cyclins and cyclin-dependent kinases (Cdk)?

A

They are positive regulators of the cell cycle, they control the progress of the cell through the checkpoints

51
Q

What are the 4 types of cyclins?

A

Cyclin D, E, A, and B

52
Q

What happens to the cyclins when the cel moves onto the next phase?

A

They are degraded by cytoplasmic enzymes

53
Q

Where and when does each Cyclin progress the cell cycle?

A

-Cyclin D and E move the cell last G1 and into the S phase,

-Cyclin A moves the cell past the G2 checkpoint

-Cyclin B moved the cell past the M phase

54
Q

What must happen in order for cyclins to function?

A

They must be bonded to a Cyclin dependent kinase and this complex must be phosphorylated, the phosphorylated Cdk/cyclin complex in turn phosphorylates the specific proteins that move the cell through the checkpoint. The cell MUST have the full suite Cdks and Cdk/cyclin complexes to proceed through the checkpoints

55
Q

What are the 3 well understood negative regulators of the cell cycle? (These stop the cell cycle)

A

Retinoblastoma protein (Rb), p53, and p21

56
Q

What are retinoblastoma proteins?

A

They are tumor-suppressor proteins

57
Q

Where were the 3 negative regulators discovered and at what point in the cell cycle do they primarily function at?

A

They were discovered in cancerous cells and function primarily at the G1 checkpoint

58
Q

What is and How does p53 function?

A

-is a multi-functional protein that acts when there is DNA damage to cells preparing for passage into the G1 checkpoint

-p53 halts the cell cycle if DNA damage is detected and recruits other proteins to repair the damage

59
Q

If damage cannot be repaired by p53 what happens?

A

It directs cell apoptosis (cell suicide)

60
Q

What does p21 do?

A

It enforces the halt in the cycle directed by p53 by binding to and inhibiting the action of the Cdk/Cyclin complexes

61
Q

Cells under stress accumulate more levels of what inhibitor molecules?

A

P53, and p21

62
Q

Retinoblastoma protein monitors what?

A

Cell size and other regulator proteins

63
Q

When is retinoblastoma protein referred to as active? What does it do?

A

When it is unphosphorylated and binds to transcription factors like E2F blocking them from producing the proteins necessary for G1/S transition

64
Q

When is retinoblastoma protein considered inactive?

A

When the cell size increases retinoblastoma protein is slowly phosphorylated until it releases E2F, then it is considered in an inactive state

65
Q

Once E2F is released from retinoblastoma protein what can it do?

A

It can now turn on genes that produces the transition proteins

66
Q

What must happen to both positive and negative regulators at the end of each checkpoint?

A

All positive regulators must be turned on and negative to be turned off

67
Q

Cancer does occur despite the redundancy of the cell cycle, it is extremely critical when associated with what phase?

A

In the S phase during replication

68
Q

Replication errors are called…

A

Mutations

69
Q

When mistakes go uncorrected in the cell cycle what often happens?

A

The cell cycle speeds up as the control and repair mechanisms decrease

70
Q

When uncontrolled growth outpaces normal growth in an area what can result?

A

A tumor

71
Q

Genes that code for positive cell cycle regulators are called what? What are they called when they become mutated and cancerous?

A

Proto-oncogenes, when mutated they are called oncogenes

72
Q

Cdk genes are considered oncogenes, so if they are not paired with their proper cyclin what might happen to the cell?

A

It could push through its cell cycle and sighted cells may have increased activity of positive regulators accumulating even more mutations

73
Q

What do tumor suppressor genes do?

A

Code for negative regulator proteins that when activated can prevent the cel from undergoing uncontrolled division

74
Q

What are the best understood tumor suppressor genes? What do they do to help with the uncontrolled division in a cell cycle?

A

Retinoblastoma proteins, p53, p21 which function by putting up a roadblock to cell cycle progression until certain events are completed

75
Q

A cell with a faulty p53 gene may fail to do what? If this happens what would the process be like? (Be as detailed as you can)

A

Detect errors present in genomic DNA. The faulty p53 gene would not be able to signal for necessary DNA repair enzymes to be made, this DNA going uncorrected would prevent apoptosis from being triggered and the cell would become cancerous. The loss of p53 function may also prevent p21 production resulting in the loss of effective blocks on Cdk activation and the cell would proceed directly from G1 to S phase

-the daughter cells will carry this mutated p53 gene and further mutations could accumulate resulting in more tumor growth

76
Q

How do bacteria divide?

A

Via binary fission

77
Q

What is different about binary fission overall from eukaryotic cell division?

A

It is a much faster and easier process, there are also no histone proteins present in bacteria, however there are cohesion and condensing proteins involved

78
Q

What is the whole process of binary fission? (Be specific)

A

The bacterial chromosome is attached to the plasma membrane at about the midpoint of the cell

-replication of the DNA is bidirectional moving away from the origin on both strands simultaneously, each new strand is pulled, seperated as the cell elongates

-after chromosomes have cleared the midpoint of the cell the cytoplasm begins to seperate, and a protein called filament temperature-sensitive mutant Z (FtsZ) directs the formation of the partition between the nucleoids

-formation of the FtsZ ring triggers the accumulation of other proteins that work to build the new plasma membrane and cell wall

-a septum is formed between the daughter nucleoids, and gradually extends from the periphery to the center of the cell, once the new cell walls are formed and in place the daughter cells seperate

79
Q

What is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule

A

Alleles

(Biology 211) Cellular Biology (12 decks)

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