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CMMB > Cells Part 2 > Flashcards

Cells Part 2 Flashcards

1
Q

What are the 2 states of chromatin?

A

Open (euchromatin) and closed (heterochromatin)

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2
Q

What is general chromatin closure associated with?

A

Differentiation; more differentiation = more closure

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3
Q

What does the histone code do?

A

Helps to organize chromatin and regulate gene expression

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4
Q

What does each nucleosome consist of?

A

2 of each: H2A, H2B, H3 and H4; and a flexible amino tail (NH2-terminus) that sticks out past the DNA and 1.8 turns of DNA

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5
Q

What makes up the histone code?

A

Histone modifications

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6
Q

Define Differentiation

A

The process by which cells specialize into different cell types

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7
Q

Where are modifications to the histone code made?

A

At the flexible amino terminus of the histones

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8
Q

What is phosphorylation of an amino acid commonly associated with?

A

Signalling pathways that activate proteins

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9
Q

What 2 amino acids are methylated?

A

Arginine and lysine

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10
Q

What amino acid is commonly acetylated?

A

Lysine

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11
Q

What do non-histone proteins use modified residues for?

A

Docking sites

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12
Q

What determines the properties of chromatin?

A

Non-histone proteins

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13
Q

What is the purpose of the modified residues in the histone code?

A

Determines the interaction of the histone tails with DNA, other proteins, or other histone tails to determine the chromatin structure

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14
Q

True or false, RNA cannot silence chromatin

A

False, non-coding RNA can silence chromatin by encouraging the modification of the histone tails

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15
Q

What are the 2 types of structures that are able to be methylated? Is it reversible?

A

DNA on the 5-carbon position of a cytosine residue, and histones can be mono or di methylated on an arginine or lysine residue; this is reversible

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16
Q

What enzyme acetylates histones?

A

Histone acetyl transferase (HATs)

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17
Q

What enzyme deacetylates histones?

A

Histone deacetylase (HDACs)

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18
Q

True or false, acetylation always opens chromatin and methylation always closes chromatin.

A

False, this is just what happens in general

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19
Q

What enzyme is responsible for methylating histones?

A

Histone methyl transferase

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20
Q

What are HDACs, HMTs, and HATs classified as?

A

Chromatin remodelers

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21
Q

What does open chromatin allow room for?

A

Transcriptional machinery

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22
Q

What happens when H3K9 is methylated?

A

Recruits heterochromatin protein-1 (HP1) and results in further compaction

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23
Q

What allows heterochromatin protein-1 (HP1) to bind to methylated histones?

A

Contains a chromodomain which binds methylated histones

24
Q

What type of RNA encourages the closing of the X chromosome? Is it coded from coding or non-coding RNA

A

Xist RNA, turned on in compacted chromosomes. It is coded from non-coding RNA

25
Q

Is the histone code able to be reprogrammed?

A

Yes

26
Q

What is one of the things that can reprogram the histone code?

A

The micro environment that the cell is placed in

27
Q

Does reprogramming occur in tumour cells?

A

Yes, they reprogram themselves and surrounding cells to aid in their survival

28
Q

What is the difference between therapeutic and reproductive cloning?

A

In therapeutic cloning the embryo is destroyed for therapeutic purposes and reproductive cloning creates a baby.

29
Q

What is the similarity between therapeutic and reproductive cloning?

A

In each case there is an embryo created

30
Q

How is each tissue type repaired and maintained?

A

Each tissue likely has a tissue specific stem cell for repair and maintanence

31
Q

During development, what structures are totipotent? Why is it considered totipotent?

A

Only the embryo/zygote is totipotent. It is totipotent because it produces both the embryo and the extra embryonic tissues (has the potential to become a full organism) (global DNA)

32
Q

During development, what structures are considered pluripotent? Why are they considered pluripotent?

A

Embryonic stem cells. Considered pluripotent because they cannot generate a full organism (they cannot generate the extra embryonic tissues) but can generate a number of different tissue types (global DNA repression)

33
Q

During development, what structures are considered multi-potent? Why are they considered multi-potent?

A

Adult tissue specific stem cells. Considered multi-potent because they can only create cells of a certain tissue type. (Repression of lineage-specific genes)

34
Q

List the important steps of reproductive cloning:

A
  1. Enucleate egg cell
  2. Collect donor nucleus from tissue cells
  3. Fuse egg with donor nucleus and shock with electricity to activate it
  4. Implant in female
  5. Reprogramming of the chromatin occurs
35
Q

How is the differentiated donor nucleus in a reproductive cloning experiment reprogrammed?

A

The egg has built in reprogramming machinery that turns on developmental genes and turns off differentiates genes

36
Q

What is therapeutic cloning used for?

A

Used to produce cloned organs to prevent rejection

37
Q

What is done to produce cloned organs as opposed to a full organism?

A

The embryonic stem cells are removed from the blastocyst and grown in a cell culture with a micro environment that will allow the cell to differentiate into the desired cell types

38
Q

What are the 4 cell types that can be made using therapeutic cloning?

A

Blood cells, liver cells, muscle cells, and nerve cells.

39
Q

Define self-renewal

A

The production of cells with similar capacity to proliferate and differentiate (production of more cells of the same type)

40
Q

Define commitment

A

The production of cells committed to differentiate

41
Q

What is the difference between a committed cell and a stem cell in terms of proliferation?

A

Stem cells have a low rate of proliferation where as a committed progenitor cell divides a lot and can produce a large number of cells.

42
Q

Define unipotent

A

Completely differentiated cell types. (Promoter hypermethylation, depression of lineage genes)

43
Q

How can differentiated cells be reprogrammed to a less differentiated cell?

A

Histone code must be changed (it’s an up hill battle)

44
Q

Why does the egg need to reprogram the chromatin?

A

Sperm and eggs are highly specialized differentiated cells and the egg needs to turn sperm and egg specific genes off and open tissue coding genes.

45
Q

True or false, sperm chromatin does not contain histones

A

True

46
Q

What does sperm chromatin contain that is different from other cell types? Why?

A

Sperm contain profanities instead of histones because it makes reprogramming go faster

47
Q

When does the reprogramming of their sperm and egg cells occur?

A

After fertilization

48
Q

What is the problem with cloning?

A

Differentiated nuclei contain histones instead of protamines so reprogramming takes longer. Success of the cloning is species dependent as the shorter the length of the reprogramming window the harder it is to create a successful clone

49
Q

Define plasticity

A

The ability of a partially differentiated adult stem cell to change its genetic program and differentiate into cells of another tissue.

50
Q

How is plasticity accomplished?

A

Exposure to a different micro environment

51
Q

What’s another word for plasticity?

A

Trans-differentiation

52
Q

How does the environment reprogram a cell?

A

We don’t know

53
Q

Why is plasticity useful?

A

It happens naturally for natural repair of tissues

54
Q

True or false, differentiation is restrictive.

A

False, differentiation is not very restrictive, trans-differentiation occurs within and across developmental cell types in a blastocyst

55
Q

True or false, there are many genes required to turn a differentiated cell into a stem cell

A

False, there are only a few key genes that are required.

56
Q

What are the 6 things that cellular interactions are required for?

A

Intercellular communication, survival, tissue strength, organ function, immune system function, and embryonic development

CMMB (5 decks)

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