Unit 1 KA1 Division & Differentiation in Human Cells Flashcards
To be totally cool
What is a somatic cell?
A body cell, uninvolved in the reproduction system
eg, not a germline cell or gamete
What is mitosis?
The process of cell division, when a single mother cell becomes two daughter cells
Each cell would be diploid (46 chromosomes)
How many chromosomes are in a somatic cell?
46
23 pairs of 2 homologous partner chromosomes
What is the sequence of events that takes place in a cell during mitosis?
- Chromosomes replicate and pair up with each’s homologous partner
- Nuclear membrane breaks down
- Chromosomes line up along the equator of the cell
- Spindle fibers pull chromosomes apart (into chromotids) towards the poles
- Nuclear membranes reform
- Cytoplasm divides
- Two daughter cells
What is a germline cell?
A cell that can produce gametes through meiosis
Gametes = sex cells. Meiosis produces haploid cells from diploid cells
Where are germline cells found?
Reproductive organs, overies in females, testes in males
Germline cells are found in the seminiferous tubules in the testes
How do germline cells divide?
- Through mitosis, they produce two daugherd diploid germline cells
- through meiosis, they produce haploid gametes
Haploid = 1 set of chromosomes, Diploid = 2 sets of chromosomes
How many chromosomes are in a germline cell?
46
As they are diploid, they have two sets of chromosomes
How many chromosomes are found in a gamete?
23
Gametes are haploid, so only have one set of chromosomes
What does “Haploid” mean?
A cell with one set of chromosomes
One human chromosome set contains 23 chromosomes
What does “Diploid” mean?
A cell with two sets of chromosomes
Two sets of chromosomes in humans is 23 chromosomes
What is Differentiation?
When an unspecialised cell becomes specialised to carry out a specific function
How does a cell differentiate?
By expressing certain genes that would produce proteins characteristic for that type of cell
What are Stem cells?
Unspecialised cells that can differentiate ibto specialised cells
What are the roles of stem cells?
- Self-renew (Divide to make more of themselves)
- Diffentiate (Turn into other types of cells)
What are the two types of stem cells?
- Tissue Stem cells (Multipotent)
- Embryonic Stem cells (Pluripotent)
Define Multipotent
A stem cell that can differentiate into several types of speialised cells
Define Pluripotent
A stem cell that can differentiate into any type of cell
Where are tissue stem cells found?
In every tissue of a human
Where are embryonic stem cells found?
In a blastocyst, a very early stage of pregnancy, a ball of about 100 cells
Why can embryonic stem cells differentiate into all types of cells (Pluripotent) while tissue stem cells can only differentiate into a few types of cells (multipotent)?
Because in an embryonic stem cell, all genes can be expressed while in a tissue stem cells a lot of the genes have already been switched off so cannot be expressed.
Tissue stem cells can only differentiate into a few cell types
What types can they differentiate into?
The types of cells found in that particular tissue
What therapeutic uses of stem cells are there?
- Corneal Repair
- Regeneration of damaged skin
What research uses for stem cells are there?
- Cell growth
- Differation
- Gene regulation
- Model cells for development of diseases or drug testing
What is the ethical arguments for the use of embryonic stem cells?
- A fertislised egg is not a person
- At less then 14 days, the embryo has no nervous system and thus no feelings
- Abortion is allowed until 20 weeks, so 2 weeks should be fine
- Research into embryonic stem cells could help many people with medical conditions
- Most stem cells are leftovers from IVF and would be destroyed anyway
What are cancer cells?
Cells that divide excessively because they do not respond to regulatory signals
What are the ethical arguments against the use of embryonic stem cells?
- Human life begins with fertisation so the embryo should not be killed
- A fertilised egg has a soul
- Stem cell research is unnatural
These are quite weak arguments im afraid, just out of my textbook :(
What is a tumor?
A mass of abnormal cells
How are secondary tumors formed?
When cells in a tumor fail to attach to each other, they can break apart and be carried through the blood to other tissues and organs when they can settle and form a secondary tumor
