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A2 Biology - Unit 5 > Unit 3.5.7 - Gene Expression > Flashcards

Unit 3.5.7 - Gene Expression Flashcards

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1
Q

Where do specialised cells originally come from?

A

Stem cells

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2
Q

What are stem cells?

A

Unspecialised cells that can develop into other types of cells.

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3
Q

What is meant by stem cells are self renewal?

A

They are capable of dividing to produce more stem cells.

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4
Q

Name two places you would find stem cells in multi cellular organisms?

A

In the embryo and in some adult tissue like bone marrow.

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5
Q

What are totipotent stem cells?

A

Stem cells that can mature into any other type of cell.

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6
Q

What are multipotent stem cells?

A

Stem cells that can develop into a few types of cells.

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7
Q

How do stem cells become specialised generally?

A

They only transcribe and translate part of their DNA because certain genes are turned off.

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8
Q

During transcription and translation how do stem cells become specialised in three steps?

A
  1. Genes that are expressed get transcribed into mRNA which is then translated into proteins.
  2. These proteins modify the cell and determine the cell structure and control cell processes.
  3. These changes caused by these proteins causes the cell to become specialised.
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9
Q

Once the stem cells become specialised why does it stay specialised?

A

The changes are hard to reverse.

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10
Q

Where are stem cells found in mature plants?

A

In the meristems.

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11
Q

Where are the meristems?

A

Areas where the plant is still growing like in the root and shoots.

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12
Q

Are plants stem cells multipotent or totipotent?

A

Totipotent

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13
Q

What type of cloning is tissue culture?

A

Invitro

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14
Q

What is tissue culture?

A

Growing a plant tissue artificially.

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15
Q

Describe in four steps how you carry out tissue cultures?

A
  1. A single totipotent stem cell is taken from the meristem.
  2. The cell is placed in some growth medium that contains nutrients and growth factors.
  3. The plant’s stem will grow and divide into a mess of unspecialised cells.
  4. If the conditions are suitable the cells will mature into specialised cells.
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16
Q

What two diseases to stem cell therapies currently exist for?

A

Diseases affecting the blood and the immune system.

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17
Q

How can bone marrow transplant be used to treat diseases of the blood in two steps?

A
  1. Bone marrow transplants replaces the faulty bone marrow in patients with abnormal blood cells.
  2. The stem cells used divide and specialise to produce healthy blood cells.
18
Q

Why can stem cells be used to replace damaged tissues?

A

They can divide into specialised cell types and replace damaged tissues.

19
Q

What are the two potential sources for stem cells?

A

Adult stem cells and embryonic stem cells.

20
Q

Are adult stem cells or embryonic stem cells more flexible and why?

A

Embryonic stem cells because they are totipotent.

21
Q

How are embryonic stem cells collected?

A

Embryos are grown in a lab using IVF, once the embryos are 4 - 5 days old stems cells are removed and the rest of the embryo is destroyed.

22
Q

What are three reasons for using embryonic stem cells?

A
  1. stem cells can be obtained from unfertilised embryos so the embryo wouldn’t survive past a few days.
  2. They are totipotent.
  3. Using them for treating diseases could save lives or improve a person’s quality of life.
23
Q

What are two reasons against using embryonic stem cells?

A
  1. There are adult stem cells so why use them.

2. Results in the destruction of an embryo which could have grown into a human being.

24
Q

Even though all the cells in an organism carry the same gene why do the structure and function of the cells vary?

A

Not all the genes in the cell are expressed.

25
Q

What is the transcription of genes controlled by?

A

Transcription factors.

26
Q

How do transcription factors bind to the promoters?

A

They move from the cytoplasm to the nucleus, bind to specific DNA sites called promoters near the target gene and they control expression there.

27
Q

How do transcription factors control expression?

A

They control the rate of transcription.

28
Q

What are two broad types of transcription factors?

A

activators and repressors.

29
Q

How do activators change the rate of transcription?

A

They increase it by helping RNA polymerase to bind.

30
Q

How do repressors change the rate of transcription?

A

Decrease the rate of transcription by stopping RNA polymerase from binding.

31
Q

Name one common molecule that binds to a transcription factor in the body.

A

Oestrogen

32
Q

How does oestrogen affect transcription in 3 steps?

A
  1. It binds to transcription factors called oestrogen receptors forming an oestrogen - oestrogen receptor complex
  2. The complex moves from the cytoplasm into the nucleus where it binds to specific DNA sites near the target gene where it acts as an activator or repressor
  3. Whether the complex acts as a activator or repressor depends on the cell and the target gene
33
Q

Why do the levels of oestrogen affect the rate of transcription?

A

It can form complexes with transcription factors which act as repressors or activators

34
Q

What type of RNA can also affect gene expression?

A

siRNA

35
Q

What does siRNA stand for?

A

Small interfering RNA

36
Q

What does siena look like?

A

Short molecules of double stranded RNA that is complementary to the specific target genes and the mRNA thats formed from it

37
Q

What does siRNA interfere with to affect gene expression?

A

Transcription and translation

38
Q

What is the mechanism called that siRNA affects translation through?

A

RNA interference

39
Q

What are the three steps in RNA interference?

A
  1. In the cytoplasm siRNA and associated proteins bind to the target mRNA
  2. The proteins cut up the mRNA into sections so it can no longer be translated
  3. So the siRNA prevents the expression of the specific gene as its proteins can no longer be made during translation
40
Q

How does siRNA have the potential for treating genetic disorders?

A

By stopping a known harmful gene from being expressed

A2 Biology - Unit 5 (8 decks)

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