Topic 8 - Totipotent Cells

Question 1

What is a totipotent cells?

Answer 1

Stem cells that can differentiate into any type of cell found in the body and extra-embryonic cells such as those forming the placenta. Found in the early embryo.

Question 2

What is differentiation?

Answer 2

The process by which unspecialised cells become specialised to form specific tissues and organs.

Question 3

What is selective gene expression?

Answer 3

Certain genes are switch on and other are switched off.

Question 4

What are stem cells?

Answer 4

Undifferentiated cells capable of self-renewal: continuously dividing to produce more stem cells. Differentiation: giving rise to specialised cell types.

Question 5

What is a pluripotent stem cells?

Answer 5

Found in the later stages of the embryo and can differentiate into many types of specialised cels, but not extra-embryonic cells.

Question 6

What is a multi-potent stem cells?

Answer 6

Found in adult tissues and a differentiate into a limited range of cell types.

Question 7

What is a unipotent stem cells?

Answer 7

Found in specific tissue and can differentiate into only one type of cell.

Question 8

What are the ethical considerations of using stem cells for treatment?

Answer 8

Embryonic stem cells: using embryos to obtain pluripotent stem cells raises ethical concerns about the destruction of embryos.
Adult stem cells: an alternative that avoids ethical issues but has a limited range of differentiation compared to embryonic stem cells.

Question 9

What treatment can pluripotent stem cells in medicine?

Answer 9

Spinal cord injuries
Heart disease
Type 1 diabetes
Burn treatment
Neurodegenerative diseases

Question 10

What are iPS cells?

Answer 10

Induced pluripotent stem cells.
iPS cells are artificially created pluripotent cells generated from unipotent cells.

Question 11

How are iPS cells produced?

Answer 11

This process involves reprogramming genes to make the unipotent cells behave like pluripotent stem cells.

Question 12

What are the iPS cells?

Answer 12

• Avoids ethical concerns surrounding embryonic stem cells.
• Can be derived from the patient’s own cells, reducing the risk of rejection.

Question 13

What are the stages of producing tissue cultures?

Answer 13

1. Selection of explants: small piece of tissue taken from a parent plant such as a leaf stem or root
2. Sterilisation: the explant using substance like ethanol
3. Placement in growth medium: containing glucose for energy agar minerals and hormones
4. Callus formation

Question 14

What are the advantages of tissue culture?

Answer 14

• rapid multiplication of plants in a short time
• can be carried out all year round, regardless of season
• allows for the production of genetically uniform plants

Question 15

What are the disadvantage of tissue culture?

Answer 15

• requires specialised equipment and skills making it costly
• risk of contamination which can lead to loss of culture
• produced genetically identical plants making them vulnerable to diseases and pests

Question 16

What is meant by Oestrogen as regulating transcription?

Answer 16

Oestrogen regulate transcription factors.

Question 17

What is a transcription factor?

Answer 17

Bind to the specific DNA sequences to initiate or regulate the transcription of genes.

Question 18

What is the process of transcription by oestrogen?

Answer 18

1. Diffusion of oestrogen: oestrogen is lipid soluble, allowing it to freely diffuse through the phospholipid bilayer of a cell membrane.
2. Binding to receptor: once inside the cell oestrogen binds to a specific receptor molecule on a transcription factor in the cytoplasm
3. activation of transcription factor: binding of oestrogen causes a conformational change in the transcription factor. This change enables the transcription factor to bind to DNA.
4. Entry into the nucleus: The activated transcription factor moves into the nucleus via nuclear pores.
5. Stimulation of transcription: Once inside the nucleus, the transcription factor binds to a specific region of DNA at the promoter site.
   This promotes the attachment of RNA polymerase, stimulating the transcription of the gene.
   Oestrogen controls transcription by activating transcription factors.
6. Simulation of transcription:

Question 19

Why is oestrogen regulation important?

Answer 19

• tissue-specific transcription: allows certain genes to be expressed in specific tissues.
• response to hormonal signals: enables the body to adapt to changed in hormone levels

Question 20

What is genetic expression?

Answer 20

The process where genes are transcribed into RNA and translated into proteins influencing an organisms phenotype.

Question 21

What are the consideration when evaluating data?

Answer 21

Sample size: ensure the data is based on a sufficiently large sample size to be reliable.
Reproducibility: consider whether the experiment has been repeated and if results are consistent.
Control groups: a reliable experiment includes proper controls to validate the results
Confounding variables;es: identify other factors that may influence genetic expression such as temperature or nutrient availability.

Question 22

What are 4 common experimental techniques to evaluate genetic expression?

Answer 22

1. Quantitative PCR: measure the amount of specific mRNA in a sample to infer
2. Western blotting: detects specific proteins to evaluate translation
3. Microarrays: assesses the expression of multiple genes simultaneously
4. RNA-seq: provides comprehensive data on gene expression by sequencing all RNA in a sample

Question 23

what is epigenetics?

Answer 23

The heritable changes in gene function that occur without altering the DNA base sequence. These changes are influenced by by environmental factors such as diet stress, and exposure to toxins which affect how genes are expressed.

Question 24

What is DNA methylation as a mechanism of epigenetic control?

Answer 24

• Methyl groups are added to cytosine bases in DNA
• this process occurs at CpG sites
• methylation makes DNA more tightly packed, preventing transcription factors from binding
• genes become silence

Question 25

What is histone modification as a method of epigenetic control?

Answer 25

- histones are proteins around which DNA is wrapped - acetylation is adding acetyl groups to histones makes DNA less tightly packed allowing transcription, increased acetylation activates genes

Question 26

What is deacetylation?

Answer 26

Removing acetyl groups makes DNA tightly packed preventing transcription .

Question 27

What is non-coding RNA as a mechanism of epigenetic control?

Answer 27

Some non-coding RNA molecules can interfere with gene transcription by finding to DNA or histones influencing gene expression.

Question 28

What are examples of environmental influences on Epigenetics?

Answer 28

Diet: nutrients such as folate can influence DNA methylation patterns Stress: prolonged stress can lead to changes in his stone acetylation Toxins: chemicals like cigarettes can affect epigenetic markets potentially increasing disease risk

Question 29

Give an example of epigenetic and inheritance

Answer 29

Studies have shown that malnourished mothers may pass on changes in gene expression to their children influencing metabolism. However, during gamete formation most epigenetic markers are removed for a process called epigenetic reprogramming those some changes may escape this and be inherited.

Question 30

How can Epigenetics cause cancer?

Answer 30

Abnormal DNA methylation can switch off tumours suppressor genes contributing to cancer development.

Question 31

How can Epigenetics affect autoimmune disorders?

Answer 31

Miss regulation of epigenetic markers can lead to an overreactive immune response.

Question 32

What is a benign tumour?

Answer 32

- Grow slowly and are usually non-invasive. - Can cause mechanical damage by pressing against tissues or blood vessels. - Do not spread to other parts of the body.

Question 33

What is a malignant tumour?

Answer 33

- grow rapidly and are invasive damaging neighbouring tissues - Can spread to other parts of the body via metastasis (through the bloodstream and lymphatic system). - Difficult to treat then benign tumours.

Question 34

What are Proto-oncogenes?

Answer 34

- Stimulate normal cell division by producing proteins that help cells progress through the cell cycle. - When mutated they become oncogenes causing uncontrolled cell division.

Question 35

What is an oncogene?

Answer 35

- formed from mutated Proto-oncogenes - They permanently activate cell surface receptors and code for growth factors that overstimulate cell division.

Question 36

What are tumour suppressor genes?

Answer 36

- normally regulate cell division by slowing it or causing a apoptosis (programmed cell death) when damage is detected. - If these genes are mutated or silenced the cell cycle becomes a regulated leading to tumour formation..

Question 37

What is the role of the pigeon genetics in cancer?

Answer 37

1. Abnormal methylation: -hyper methylation of tumour suppressed genes can silence these genes leading to cancer. - hypo methylation of oncogenes can activate them causing uncontrolled cell division. 2. Oestrogen and breast cancer: - Increased oestrogen levels in post menopausal women can contribute to breast cancer - Oestrogen bines to transcription factors activating genes that promote cell division and leading to tumour formation

Question 38

What is RNA interference?

Answer 38

A natural process in cells that regulates gene expression by degrading mRNA preventing it from being translated into a protein. This process is mediated by small RNA molecules such as siRNA and microRNA.

Question 39

How does siRNA work?

Answer 39

1. Double stranded RNA is cleared into small interfering RNA by an enzyme called Dicer. 2. One strand of siRNA binds to a protein complex called RISC. 3. The siRNA within the RISC complex bind to complementary sequences on mRNA molecule. This binding forms double-stranded mRNA which is recognised as abnormal by the cell go out, please 4. Enzymes within the RISC complex degrade the double stranded mRNA, this prevents translation effectively the gene

Question 41

How is microRNA formed?

Answer 41

Transcribed as a longer RNA module and then processed into shorter strands by enzymes like Dicer.

Question 42

How does miRNA work?

Answer 42

MiRNA binds to the RISC complex similarly to siRNA however miRNA is not fully complementary to its target mRNA so it often inhibits translation rather than degrading the mRNA.

Question 43

What are the three key differences between siRNA and miRNA?

Answer 43

From double stranded RNA - single-stranded RNA Fully complementary to mRNA - partially complementary to mRNA Degrades target mRNA - inhibits translation

Question 44

What are two applications of RNA interference?

Answer 44

- research: RNAi is used to study gene function by silencing specific genes in model organisms - Therapeutics: RNAi is being developed to treat diseases like cancer and genetic disorders by silencing harmful genes.

Question 45

What are tumours?

Answer 45

Abnormal growth of cells caused by uncontrolled cell division.

Question 46

What are the five differences between benign and malignant tumours?

Answer 46

Slow - rapid Localised, no metastasis - spread via metastasis to other areas. Limited harm - severe harm disrupts vital processes Easier to treat low recurrence - hard high recurrence risk Normal - abnormal poorly differentiated cells.

Question 47

What are three factors contributing to tumour development?

Answer 47

1. Mutations: changes in the DNA base sequence can lead to the activation of oncogenes or inactivation of tumour suppressor genes. Mutations may be caused by exposure to carcinogens such as UV radiation chemicals or viruses. 2. Abnormal methylation.: hyper methylation means to suppress genes are silence preventing them from controlling cell division and Hypo-methylation means proto-oncogenes become overactive promoting excessive cell division 3. Hormones: increased oestrogen levels particularly in breast tissue can activate genes that promote cell cell division increasing the risk of tumour development.

Question 48

What are the four characteristics of tumour development?

Answer 48

- loss of cell cycle control: mutations can disrupt normal cell cycle checkpoints allowing damaged or abnormal cells to divide. - Uncontrolled growth: cells continued, dividing despite signals to stop forming a tumour – Invasion of tissues, malignant tumours invade surrounding tissues and may metastasise. -- resistance toapoptosis cell failed to undergo program death leading to the survival under accumulation

Question 49

How can you prevent tumours?

Answer 49

- avoid exposure to the known carcinogens. - Maintain a healthy lifestyle including a balanced diet and regular exercise. - Regular screenings to detect tumours early.

Question 50

What is the treatment for tumours?

Answer 50

- surgery: on removal of the tumour. - Chemotherapy: targets rapidly dividing cells. - Radiotherapy: uses radiation to kill cancerous cells. - Targeted therapies: inhibit specific molecules involved in tumour growth.