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Biology yr 13 > Control of Gene Expression- BP > Flashcards

Control of Gene Expression- BP Flashcards

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1
Q

What is a stem cell?

A

 a unspecialised/undifferentiated cell
 potential to form different types of cells

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2
Q

How does a stem cell become specialised?

A

 differentiation
 3 changes: cell shape, number of organelles, new content
 occurs by controlling gene expression (some gene are activated, other genes are inhibited)

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3
Q

Stem Cell in Animals/Mammals/Humans?

A
  • embryonic
  • umbilical cord blood stem cells
  • placental stem cells
  • adult stem cells
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4
Q

What are Induced Pluripotent Stem Cells (iPS Cells)?

A
  • turning unipotent body cells into pluripotent cells (like embryonic stem cells)
  • involves activating certain deactivated genes using transcription factors
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5
Q

Stem Cell Therapy in Humans? (2 uses)

A

 use stem cells to produce tissues/organs for transplant
 use stem cells to treat irreversible diseases e.g. heart disease, type 1 diabetes, paralysis (inject stem cells at site of disorder – will differentiate to become local specialised cells e.g. heart muscle cells, beta cells of pancreas, neurones)

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6
Q

what is a totipotent stem cell?

A
  • found in the early embryo
  • can differentiate into any type of cell
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7
Q

what is a pluripotent stem cell?

A
  • found in embryos
  • can differentiate into almost any type of cell
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8
Q

what is a multipotent stem cell?

A
  • found in adults
  • can differentiate into a limited number of specialised cells
  • eg. adult stem cells and umbilical cord blood stem cells
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9
Q

what are unipotent stem cells?

A
  • can only differentiate into a single type of cell
  • derived from multipotent stem cells
  • made in adult tissue
  • eg. cardiomyocytes
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10
Q

Stem Cell in Plants?

A

 In embryo = Zygote/Embryonic Stem Cells
 In adult = Meristem Cells in Stem/Shoot/Root

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11
Q

Uses of Stem Cells from Plants?

A

 traditionally cuttings were taken from plants (stem/shoot/root) and used to grow genetically identical plants – possible due to presence of meristem cells
 tissue culture (micro propagation) = large scale application of cuttings

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12
Q

process of growing genetically identical plants?

A

 take cutting from shoot/stem/root (called explant)
 place explant in nutrient rich medium so meristem cells divide by mitosis
 produces a mass of meristem cells (called callus)
 take each meristem cell and grow in plant growth factor medium to promote differentiation and formation of shoot/root
 transfer plant to soil and greenhouse
 then transfer to field

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13
Q

what is controlling gene expression?

A

 either Activating or Inhibiting a Gene
 activating gene = protein made
 inhibiting gene = protein not made

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14
Q

Example of activating genes? (using oestrogen)

A

 oestrogen can enter a cell by simple diffusion and bind to receptors on the transcriptional factor
 causes transcriptional factor to change shape
 so transcriptional factor can now enter nucleus and bind to promoters on the DNA to activate transcription
= activated genes (protein to be made)

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15
Q

Example of inhibiting genes?

A
  • using siRNA (small interfering RNA)
  • double stranded RNA cut down into small sections
  • made single stranded
  • then attaches to an enzyme
  • siRNA will bind to complementary sections on mRNA
  • the enzyme will cut the mRNA so translation cannot occur
  • gene inhibited (protein not made)
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16
Q

What is Epigenetics?

A

 Heritable changes in gene function without changes to base sequence of DNA
 Changes may due to lifestyle, stress, diet

17
Q

How does Methylation affect the Genome?

A

Increased Methylation :
- adding methyl groups
- this attracts proteins which condense the DNA-Histone Complex
- transcription factors cannot gain access (gene inhibited)

18
Q

What is a Gene Mutation?

A

 a change in the base sequence of DNA
 2 types = substitution and insertion/deletion

19
Q

what is subsitution?

A
  • substitution = replace one base for another, changes one triplet code
  • can be silent (new triplet code codes for same AA), mis-sense (codes for a different AA, so protein shape changes slightly), non-sense (codes for a stop codon, so polypeptide chain not produced)
20
Q

where are stem cells found in plants?

A

meristems

21
Q

what is the epigenome and what does it determine?How?

A

 Chromatin (DNA-Histone Complex) is surrounded by an Epigenome (chemical layer)
 Epigenome can either cause the Chromatin to become more condensed or more loose
 Chromatin becoming more condensed means transcription factors cannot reach the DNA and the gene will be inactivated
 Chromatin becoming more loose means transcription factors can reach the DNA and the gene will be activated
 These changes may be brought about by Acetylation or Methylation

22
Q

Cancer?

A

 caused by mutation of genes that control cell division
 causes of mutation = random or mutagens (chemicals/radiation)
 mutation of proto-oncogene leads to formation of a oncogene = over production of growth factor or receptor proteins permanently active = over stimulation of cell division (uncontrolled cell division)
 mutation of tumour-suppressor gene = loss of protein to inhibit cell division (uncontrolled cell division)

23
Q

Oestrogen and Cancer?

A

Oestrogen leads to activation of genes – high levels of oestrogen can lead to over activation of Proto-Oncogene forming an Oncogene = Cancer (uncontrolled cell division)

24
Q

Oestrogen and Cancer?

A

Oestrogen leads to activation of genes – high levels of oestrogen can lead to over activation of Proto-Oncogene forming an Oncogene = Cancer (uncontrolled cell division)

25
Q

Epigenetics and Cancer?

A

Main Example = increased methylation of tumour suppressor genes leads to inhibition of tumour suppressor genes leading to cancer (uncontrolled cell division)

26
Q

How does Acetylation affect the Genome?

A

Decreased Acetylation:
- removing acetyl groups
- increases positive charges on the Histone
- increases the attraction to the phosphate groups on DNA
- condense the DNA-Histone Complex
- transcription factors cannot gain access (gene inhibited)

Biology yr 13 (19 decks)

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