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Topic 8 > 8A > Flashcards

8A Flashcards

1
Q

What increases the rate of mutations

A

mutagenic agents

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2
Q

What are the mutations?

A
  • Substitution- base(s) swapped for another
  • Addition - base(s) are added - causing a frame shift
  • Deletion - base(s) are removed - causing a frame shift
  • Duplication - base(s) are repeated - causing a frame shift
  • Inversion- a sequence of bases is reversed
  • Translocation - a sequence of bases is moved from one location to another (can be on the same chromosome or a different chromosome)
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3
Q

What are hereditary mutations?

A

some mutations can cause genetic disorders, if a gamete containing a mutation for a genetic disorder is fertilised, the mutation will be present in the new fetes formed (mutation passed on)

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4
Q

What is a frame shift?

A

the sequence of amino acids in the polypeptide changes, changing the number of bases in the polypeptide, therefore increasing the chance of the triplet code being read in a different way

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5
Q

What a mutagenic agents?

A

things which increase the chance/rate of a mutation occuring

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6
Q

Examples of mutagenic agents

A
  • Acting as a base - chemicals called analogs, can substitute for a base, during DNA Replication, thus changing the base sequence
  • Altering bases - some chemicals can delete or alter bases
  • Changing the structure of DNA - causes problems during DNA Replication
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7
Q

What is acquired mutations?

A

mutations that occur in individual cells after fertilisation

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8
Q

What is cancer?

A

tumour cells which invade and destroy surrounding cells

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9
Q

Name the two types of genes which control cell division

A

Proto-oncogenes and Tumour Suppressor genes

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10
Q

What does the Tumour Suppressor gene do and what would happen if a mutation occurs and the gene is inactive?

A

the Tumour Suppressor Gene slows cell division by producing proteins that stop cells from dividing or causing them to self-destruct
- if a mutation inactivates the gene, the protein isn’t coded for, and the cells will divide uncontrollably, resulting in a tumour

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11
Q

What is it called when a cell is programmed to self-destruct

A

Apoptosis

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12
Q

What does the Proto-oncogene do and what would happen is a mutation occurs and the gene is overactive

A

porto-oncogenes stimulate cell division by producing proteins that make the cell divide
- if a mutation causes the gene to become overactive, more proteins are produced, stimulating the cell to divide uncontrollably, resulting in a tumour.

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13
Q

What is a mutated photo-oncogene called?

A

oncogene

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14
Q

What is a malignant tumour?

A

they are cancerous and more likely to be life-threatening, with whole-body effects (Weight loss, fatigue)

  • They grow rapidly, large in size, with larger nuclei. they become unspecialised, and don’t produce adhesion molecules, so they spread to other regions of the body (Metastasis)
  • They are surrounded by a capsule, which can grow finger-like projections into surrounding tissue and more frequent to reoccur after treatment
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15
Q

What is a benign tumour?

A

They are not cancerous, and are less likely to be life-threatening, with localised effects.

  • Grow slower than malignant tumours, can grow large in size, remain differentiated and produce adhesion molecules so they can stick together - remaining as a tissue.
  • They are surrounded by a capsule of dense tissue to remain as a compact structure. They rarely reoccur after treatment (surgery alone)
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16
Q

Tumour cells are different from normal cells, how?

A
  • They divide more rapidly, with larger nuclei than normal (sometimes more than one nucleus in one cell)
  • They are irregular shaped and don’t produce all the proteins needed to function properly
  • They have different antigens on their surface and don’t respond to grow regulating processes
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17
Q

What is methylation?

A

adding a methyl group onto something

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18
Q

Methylation of DNA

A

it is important as it regulates gene expression - controls whether a gene is transcribed and translated

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19
Q

What is Hypermethylation?

A

when many methyl groups attach, causing the nucleosomes (Histone proteins and DNA) to pack together too closely together so the transcription factors cannot bind to the promotor region to allow DNA Polymerase to bind, stopping the gene being expressed

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20
Q

What is Hypomethylation?

A

when the nucleosomes (Histone proteins and DNA) are packed loosely together, so many promotor regions are accessible for transcription factors, therefore genes are expressed, however this increases the chance of a mutation occurring.

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21
Q

Tumour Suppressor genes and Hypermethylation

A

when the Tumour suppressor gene is hypermethylated, the genes are not transcribed, preventing the proteins, which slow cell division, to be made. without these proteins the cell can divide uncontrollably, and can become a tumour

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22
Q

Proto-oncogenes and Hypomethylation

A

when the proto-oncogenes are Hypomethylated, it increases the production of proteins, causing the port-oncogene to act as oncogenes. these proteins stimulate the cells to divide, and with more proteins, the cells divide more rapidly, increasing the risk of becoming a tumour

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23
Q

The role of Oestrogen in breast cancer

A

increased exposure to oestrogen may result in developing breast cancer, although the reasons are unknown, there are some theories

  • it stimulates cells to divide, and when cells are naturally dividing it can increase the chance of a mutation occurring
  • if cells do become cancerous, it can stimulate the cells to divide more rapidly
  • some say it is able to introduce mutations directly to the DNA, increasing the chance of cells becoming cancerous
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24
Q

Risk factors for cancer

A

Genetic factors - some cancers are linked to inherited alleles. if inherited, more likely to get the type of cancer
Environmental factors - exposure to radiation, life-style choices (Smoking, drinking, diet)

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25
Q

Preventing cancer

A

screening your DNA to look for mutations

  • knowing if a mutation is present can help decide any preventative steps (Mastectomy)
  • more sensitive tests can be developed with the known mutation, leading to earlier, more accurate diagnosis’
26
Q

Treating and Curing cancer

A

knowing the mutation can help treat the cancer, but with some mutations require more aggressive treatment than others
- Gene Therapy is also available, where faulty alleles are replaced with healthy alleles (only been used in clinical trials)

27
Q

what are stem cells?

A

Unspecialised cells which can develop into specialised cells.

28
Q

where are stem cells found?

A

all multicellular organisms have stem cells, they are found in the embryo and in some adult tissues (intestines, bone marrow)

29
Q

Totipotent stem cells

A

stem cells which can mature into any type of cells, including the placenta. Only present in mammals in the first few cell divisions

30
Q

Pluripotent stem cells

A

stem cells which can mature into any type of cells, but not the placenta

31
Q

Multipotent stem cells

A

stem cells which can develop into some types of cells

32
Q

Unipotent stem cells

A

stem cells which can only develop into one type of cells

33
Q

Stem cells becoming specialised

A

Due to them only transcribing and translating parts of the DNA. Stem cells contains all possible genes, however only some genes are expressed (Switched on) under certain conditions, while others are not (Switched off)
- when the genes are expressed, they can determine the cell structure and control, specialising them (once specialised, it stays specialised.)

34
Q

What are Cardiomyocytes

A

Heart muscle cells

35
Q

Bone Marrow Transplant

A

bone marrow transplant can be used to replace faulty blood cells - used to treat leukaemia and lymphoma, as well as sickle cell anaemia

36
Q

Stem cell therapies of the future

A
  • Spinal cord injuries
  • Heart disease and damage
  • Bladder conditions
  • Respiratory diseases (Cystic Fibrosis)
  • Organ transplants
37
Q

Sources of Stem Cells - Adult Stem cells

A

Adult stem cells - obtained from the bone marrow (Multipotent) by a simple operation

38
Q

Sources of Stem Cells - Embryonic Stem cells

A

Contained from embryos at an early stage of development - created in a lab (in vitro) for the pluripotent stem cells. Once collected, the rest of the embryo is destroyed.

39
Q

Sources of Stem Cells - Induced pluripotent Stem Cells (iPS cells)

A

Created in a lab, and involves reprogramming specialised adult body cells to become pluripotent. The cells are made to express multiple Transcription Factors that are normally associated with pluripotent stem cells. These Transcription Factorsn cause the Adult cells to express genes that are associated with pluripotent stem cells.
- the transcription factors are introduced to the adult cells by infecting them with a specially modified virus, which contains genes coding for the transcription factors

40
Q

ethical considerations to the source of Embryonic Stem cells

A
  • Some people believe the destruction of an embryo, which could have become a foetus if implanted in the womb, has the right to life.
  • Some people believe that the cells should be taken from an unfertilised egg cell
  • Some people believe only adult stem cells should be used so no embryo is destroyed
41
Q

iPS cell benefits

A
  • can be genetically identical to the patient, so the body wouldn’t reject the new cells/organ etc.
  • no ethical issues regarding embryos as it uses adult stem cells
42
Q

Benefits to Stem cell therapy

A
  • they could save many lives - people waiting for organs can use their own stem cells to make another organ which won’t be rejected
  • improve the quality of life- replace damaged cells in the eyes of blind people
43
Q

The role of Transcription factors

A

some transcription factors, called activators, stimulate/increase the rate of transcription by helping RNA Polymerase to bind to the start of a target gene and activate transcription.
some transcription factors, called repressors, inhibit the transcription of a gene, once bound to a target gene they stop RNA Polymerase from binding, stopping transcription

44
Q

That is the region called before a gene

A

the promotor region

45
Q

The role of oestrogen in Transcription

A

Oestrogen can bind to a Transcription factor, called an oestrogen receptor, forming a oestrogen-oestrogen receptor complex, where it can bind to specific DNA sites (Promotor region) and act as a activator of transcription

46
Q

What is RNAi

A

a small, double stranded RNA molecule which stop mRNA from target genes from being translated into proteins.

47
Q

The role of siRNA

A
  • Once the mRNA has left the nucleus, double stranded siRNA associates with several proteins and unwinds. one of the single stranded siRNA is selected.
  • the single stranded siRNA binds to the target mRNA as they have complementary base sequences.
  • the proteins associated with the siRNA cut the mRNA into fragments, so it can no longer be translated.
48
Q

miRNA

A

miRNA is similar to siRNA, and occurs in plants. but in mammals, miRNA is usually fully complementary to the base sequence of the mRNA, so it is less specific - targeting more than one mRNA molecule
- miRNA exits as a long, folded double strand, and carries out the same process as siRNA. however, instead of cutting and destroying the fragments, it blocks the translation of the mRNA, and then is either stored or destroyed.

49
Q

How does Epigenetic control work?

A

it can determine whether a gene is switched on or off, and works through the attachment and removal of chemical groups (known as epigenetic tags) These tags don’t alter the DNA sequence however alter how easy it is for an enzyme and other proteins needed for transcription and translation

50
Q

Can you inherit Epigenetic changes

A

most epigenetic marks/tags are removed between generations, but some escape the removal process and are passed onto offspring. This means that the offspring can be affected by environmental changes that affected their parents/grandparents

51
Q

Transcription Factors and inhibiting gene expression

A

when a gene is not being expressed, the site on the transcription factor that binds to the promoter region may be blocked by an inhibiter, preventing the gene being expressed.

52
Q

Oestrogen and gene transcription

A

Oestrogen can diffuse into the cytoplasm of the cell (lipid soluble - can pass through the phospholipid bilayer)

  • it combines with a site on a receptor molecule of the transcription factor, changing the shape of the receptor and releasing the inhibitor from the transcription factor
  • transcription factor can now enter the nucleus through a nuclear pore and bind to the promotor region
53
Q

What is Chromatin?

A

a complex of DNA and histone proteins

54
Q

What determines the shape of the DNA-Histone complex?

A

chemicals called tags, which are also called the Epigenome.

55
Q

When chromatin is loosely packed and is more accessible to transcription factors for them to bind to promoter regions for a gene to be expressed, what is it called?

A

Euchromatin

56
Q

When chromatin is tightly packed and there is less acetylation of the histone proteins, what is it called?

A

Heterochromatin

57
Q

What is Acetylation?

A

Histone proteins become acetylated in a reaction with Acetyl CoA. it donates its Acetyl group, making it more negatively charged, repelling the DNA (which is negatively charged) thus, the chromatin is loosely packed, so transcription factors can easily bind to the promotor region

58
Q

Decreased Acetylation

A

Less Acetyl groups from Acetyl CoA, therefore the histone proteins are more positively charged, so the DNA is more attracted to the histone proteins, so the chromatin is more tightly packed, preventing Transcription factors from binding to the promotor region and expressing genes.

59
Q

Methylation of DNA

A

when a Methyl group is added to the DNA (base Cytosine - CpG) it induces deacetylation, therefore the chromatin is more densely packed, preventing the binding of transcription factors, thus, silencing genes

60
Q

What can highly methylated regions, inactivating genes cause?

A

the early development of cancer, as some genes which repair damaged cells can be switched off, so there are more mutations from the decreased repair of damaged sequences

61
Q

Treating disease with epigenetic therapy

A
  • Inhibiting enzymes involved with either histone acetylation or DNA Methylation
  • drugs which can prevent genes being switched off to treat a disease, by increasing acetylation, so the gene is expressed.

Topic 8 (2 decks)

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