Biology (Topic 8) Regulation of Gene Expression NOT COMPLETE

What is a totipotent cell?

stem cell that can divide by mitosis to produce an unlimited number of new cells and can differentiate into any type of body cell as well as extra‑embryonic tissues (e.g., placenta)

What is potency?

The ability of a stem cell to differentiate into more specialized cells

What are the three types of potency?

Totipotency, Pluripotency, Multipotency

What is an embryonic stem cell

Totipotent cell

What is a zygote? What type of cell is it?

Totipotent Diploid cell that forms when a sperm fertilizes an egg

How do totipotent cells become specialised?

They translate one / some parts o there DNA as switching on certain types of genes allows them to develop into specific types of cells, becoming specialized

When cells no longer considered totipotent?

When they become specialized

Why are there not totipotent cells in later stages of development?

They lose their ability to differentiate into cell types

What is a pluripotent stem cell?

Embryonic stem cell that can differentiate into any type of cell in an embryo but are NOT able to differentiate into extra embryonic cells (cells that make placenta)

What is the difference between a pluripotent stem cell and a totipotent stem cell?

Totipotent cells can form all cells including placenta cells

Pluripotent can from all cells BUT NOT placenta cells

How many times can pluripotent stem cells divide and what are they used for?

Unlimited number of times

Used to treat human disorders

What is an Induced pluripotent stem cell (iPS)

Adult somatic cells that are artificially created , they have been genetically reprogramed using transcription factors to be pluripotent

What can Induced pluripotent stem cells differentiate into?

Many different body cells , but not all e.g placenta cells

What is a somatic cell?

Any cell in the body that is not a gamete (sperm or egg) cell

How are Induced pluripotent stem cells genetically reprogramed? What does this result in?

Transcription factors cause specific genes to be expressed, reprograming the cell to behave like an embryonic stem cell

What are two key features that Induced pluripotent cells are capable of?

Self renewal ( dividing infinitely)

Pluripotency (differentiation into any cell type in body)

What is a benefit of using Induced pluripotent cells?

Can be used in research and therapy without ethical concerns

What are multipotent adult stem cells?

Can differentiate into a limited range or type of cell within a specific tissue or organ

What are multipotent stem cells important for?

Tissue maintenance and repair

What is a feature of multipotent stem cells and how can they be used in research?

Used in self renewal

Research into stem cell therapy (introducing adult stem cells into damaged tissue)

What is a unipotent cell?

Adult cells that can only differentiate into their own lineage (they can only differentiate into one specific cell type

What type of cells are most cells in animal bodies?

Uni potent

Where are embryos used in research from?

Donated from patients that have undergone IVF

What are advantages of using Embryonic stem cells

Versatile (adapt to multiple different functions)

Can divide infinitely

Can help develop curative treatments

What is a disadvantage of using embryonic stem cells?

Ethical concerns (embryos have to be destroyed)

Immune rejection risk (foreign antigens)

Tumor cells can form if cell division is not controlled properly

Multipotent adult stem cells can be used in bone marrow transplants, what are other advantages of it?

No ethical concerns : no embryo destruction as harvested from consenting adults

Lower risk of immune rejection (when taken from the same patient)

What are disadvantages of multipotent adult stem cells?

Limited in what they can differentiate into

Harder to isolate and grow

Donated bone marrow can be rejected by the patients immune system

Why are multipotent adult stem cells harder to isolate and grow?

They don’t divide as much as embryonic stem cells

Located deep in tissues

Why can scientists use specific transcription factors to target genes that control pluripotency? (refer to somatic cells)

All somatic cells contain the same genetic material

How do scientists make induced pluripotent stem cells using somatic cells ?

Use transcription factors to target genes that control pluripotency

Switch on genes that control the pluripotency which are usually silenced in differentiated cells

Allowing them to revert to pluripotent cells

What are advantages of induced pluripotent stem cells?

No embryo destruction so fewer ethical issues

Reduced risk of rejection as can be made from patient

What are disadvantages of induced pluripotent stem cells?

High cost and low efficiency ( expensive and only small number of cells treated that become iPS)

Risk of cancer as a result of Ips cells being able to activate genes that control cell division

Reprograming can result in abnormal gene expression , causing iPS to be unpredictable

What is a tissue culture?

When cells are grown artificially separate to parent organism

Why can a clone be made my most plant cells but not animal cells?

many plant cells are totipotent unlike animal cells

What is an explant

small piece of of plant

Describe the method for producing tissue cultures.

Sterilize environment

Cut thin section of plant (explant)

Add to agar

Agar provided nutrients that allow growth

Results: grown plant clone from explant showing that plant cell is totipotent

What is gene expression?

when a gene is activated (turned on) / used to make a product (usually a protein )

What is a transcription factor?

Protein that binds to DNA and regulates gene expression by switching genes on and off

What do transcription factors do?

Activate or repress the transcription of a particular gene

Explain the process of a transcription factor activating or repressing a gene.

TF enter the nucleus from the cytoplasm through nuclear pores

Bind to the promoter region at the start of the gene

This binding allows or prevents the transcription of a gene

TF either assist the binding of RNA polymerase or prevent it from binding

Increasing or decreasing the rate of transcription

What does a transcription factor do to RNA polymerase?

Allow or prevent transcription

Assist the binding of RNA polymerase (to promoter) to stimulate expression

Prevent it from binding to inhibit

What is the promoter region?

Section of DNA upstream of the coding region that is the binding site for proteins that control gene expression (Transcription factors and RNA polymerase)

What does upstream mean?

Section of DNA before the start of the coding region

Where the promoter region is located

What is a steroid hormone?

Small, hydrophobic, lipid based hormone that can diffuse through the cell membrane and through the nuclear pores into the nucleus

What is oestrogen?

Steroid hormone , it stimulates FSH and inhibits LH

Describe the process of oestrogen stimulating transcription.

Oestrogen diffuses through cell surface membrane (as it is lipid soluble) into cytoplasm

Binds to receptors complementary causing receptor to change shape and become activated

Complex diffuses through nuclear pores

Forms a hormone receptor complex

Moves to the DNA and binds to the promoter region

Stimulates transcription

How does the hormone receptor complex stimulate transcription ?

Complex bind to DNA (promotor reigon) and stops or assists RNA polymares from attaching promoter reigon

What is it called when a hormone binds to a receptor?

Hormone receptor complex

What binds to the promoter reigon in the stimulation pathway?

Hormone receptor complex and RNA polymarays

When does the Hormone receptor complex become activated?

When the hormone binds as a result the receptor changes shape