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Biology > 8.2 - Gene expression and cancer > Flashcards

8.2 - Gene expression and cancer Flashcards

1
Q

What is a totipotent cell and why are they specialised?

A
  • can divide and produce any type of body cell
  • only occur for a limited time in early mammalian embryos
  • zygote
    specialised: only translate part of their DNA during development
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2
Q

What is a pluripotent cell?

A
  • can differentiate into any cell found in embryo but not extra-embryonic (placental) cells
  • can divide in unlimited numbers
  • can be used in treating human disorders
  • found in embryos
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3
Q

What is a unipotent cell?

A
  • adult cells that can only differentiate into their own lineage
  • found in mature mammals
  • most cells in animal bodies are unipotent
    e.g cardiomyocytes
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4
Q

What is a multipotent cell?

A
  • can divide to form a limited number of different cell types
  • found in mature mammals
  • divide in unlimited numbers
  • bone marrow cell/adult stem cell
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5
Q

How can induced pluripotent stem cells (iPS cells) be produced?

A
  • from adult somatic cells (unipotent)
  • using appropriate protein transcription factors
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6
Q

Describe how oestrogen initiates transcription

A
  • binds to receptors in cell membrane
  • switches on genes for cell growth
  • transcription factors enters nucleus via nuclear pore + combines with DNA, stimulating transcription
    (increased oestrogen can cause cancer)
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7
Q

Define epigenetics

A

heritable changes in gene function, without changes in DNA base sequence

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8
Q

What is methylation?

A
  • CH3 attaches to cytosine (sometimes adenine)
  • if promoter region methylated, transcription factor cannot bind so transcription prevented (mutation)
  • so gene not expressed as DNA wound up
  • so protein not produced that prevents cell division = no control of mitosis
  • increased methylation = decreased gene expression
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9
Q

What is acetylation?

A
  • COCH3 group added to lysine (a.a.) found within histones
  • reduces attraction of - charged DNA backbone to histone
  • DNA less condensed so transcription machinery can access DNA
  • increased acetylation = increased gene expression
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10
Q

Define epigenome

A

chemical groups on DNA molecule that cause it to wind/unwind in response to environmental factors e.g age, stress, pollution
BUT DNA base sequence unchanged

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11
Q

How is a stem cell produced

A
  • zygote + blastocyst (very early embryo)
  • embryonic stem cells removed from inner cell mass removed
  • grown in culture in lab (fluid w/ nutrients) to grow more cells
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12
Q

How are iPS cells produced?

A
  • body cell genetically reprogrammed by adding certain genes
  • iPS cell formed (behaves like embryonic stem cell)
  • culture of iPS cells grown in lab
  • differentiate into all possible specialised cell types
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13
Q

How do iPS cells behave like pluripotent stem cells?

A
  • transcription factors present in pluripotent cells isolated
  • used to make adult specialised cells express ‘switched off’ genes
  • infected with modified virus making its DNA make transcription factors
    (allows cell to behave as pluripotent)
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14
Q

Examples of stem cell therapies

A
  • spinal cord injuries
  • heart disease
  • organ transplants
  • bladder conditions
  • respiratory diseases (donated windpipes)
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15
Q

4 mechanisms that control gene expression

A
  • transcriptional regulation
  • post transcriptional regulation
  • translational regulation
  • post-translational regulation
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16
Q

How can transcription of a particular gene be controlled?

A
  • all transcription factors must combine and form Transcription Initiation Complex (TIC)
  • specific TIC controls transcription of particular gene
17
Q

What are transcription factors?

A
  • regulatory proteins which can cross cell and nuclear membranes
  • lipid-soluble
  • can be activators/repressors
  • a protein complex with different subunits
  • DNA binding domains specific to base sequence in promoter region of complementary gene
18
Q

How do inhibitory transcription factors work?

A
  • bind to and neutralise stimulatory transcription factor subunit
  • OR bind to TIC and prevent it becoming complete and active
19
Q

1st mechanism

A
  • water soluble hormones act by 2nd messengers e.g insulin
  • lipid soluble hormones act directly e.g oestrogen
20
Q

RNA interference (RNAi)

A
  • occurs in cytoplasm
  • post-transcriptional
21
Q

Describe process of RNA interference

A
  • double stranded RNA (dsRNA) hydrolysed into siRNA
  • siRNA binds to protein complexes in cytoplasm which use energy from ATP to separate 2 siRNA strands, exposing nucleotide bases
  • single-stranded siRNA binds to target mRNA via complementary base pairing
  • mRNA cut into fragments by another enzyme
  • mRNA can’t be translated = no protein production
  • fragments broken down into RNA nucleotides by enzymes
22
Q

What does micro RNA (miRNA) do? (type of RNAi)

A

targets multiple mRNA molecules

23
Q

Describe main characteristics of benign tumours

A
  • slow growth
  • very large growth but can’t spread
  • compresses tissues, preventing blood flow and nerve impulses
24
Q

Why does mitosis not happen all the time?

A

cell cycle controlled

25
Q

Describe main characteristics of malignant tumours

A
  • fast growth
  • spread through blood/lymph (metastasis) and invade surrounding tissues
  • cancerous; ‘steal’ nutrients from healthy cell, causing surrounding cell death
26
Q

Define tumour

A

abnormal mass of cells

27
Q

Define apoptosis

A

cells self-destruct to ensure they don’t divide

28
Q

Features of tumour suppressor genes

A
  • slow cell division
  • stimulate apoptosis
    (loss of these allows cancer)
29
Q

Features of proto-oncogenes

A
  • stimulate cell division
  • inhibit differentiation
  • halt cell death
  • mutated version: oncogenes (cancerous, can be 1 or more)
30
Q

What do oncogenes do?

A
  • increase cell’s continual growth and division
  • decrease differentiation
  • decrease apoptosis
31
Q

Describe the process of hypermethylation

A
  • tumour suppressor genes inactivated
  • decreased transcription
  • increased cell division and tumour formation
    e.g BRCA1 gene (breast cancer)
32
Q

Describe the process of hypomethylation

A
  • occurs in oncogenes, activating them
  • forming tumour
33
Q

Why might an individual who inherits increased risk of developing cancer not have it?

A
  • often born w/ 1 defective copy of tumour suppressor gene
  • 2 defective copies lead to cancer
  • unless 2nd copy mutates, person has a functional copy of the gene
34
Q

Define promoter region

A

DNA section upstream from coding region that is protein binding site for gene expression
e.g RNA polymerase during transcription

Biology (40 decks)

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