Topic 11: Cell Growth And Differentiation Flashcards
How is a zygote formed?
- for fertilisation to occur, a sperm must penetrate the various layers that surround the egg and then enter the cytoplasm of the egg cell.
- the haploid sperm nucleus then fuses with the haploid egg nucleus to creat a single diploid cell known as a zygote.
- the DNA of the chromosomes of the zygote, half from the mother and half from the father creates a new genome that contains all the genetic information needed to form a unique human being
What is a human embryo?
The entity that is produced by the first mitosis division of the zygote produced after completion of fertilisation of the egg by sperm, and this stage continues to the eighth week of fertilisation.
What is a blastocyst?
By the fifth day or embryonic development the embryo is no longer a solid mass of cells but consists of hollow fluid file structure called a blastocyst, with an inner mass of cells surrounded by an outer layer of cells. The inner cell mass of the blastocyst will form the tissues of the embryo, while the cells of the outer layer will become the embryonic contribution to the placenta.
What is gastrulation?
The complex cell migration that reorganise the inner cell mass of the embryo blastocyst into a three layered structure.
What are the germ layers?
The cell migrations and the reorganisation produce three distinct layers of cells known as the primary germ layers which are composed of stem cell that can give rise to or differentiate into various specialised cells.
When does and embryo become a foetus?
Nine weeks after fertilisation is regarded as the point at which the feral stage of development is reached, determined by the presence of all major body organs.
What are stem cells?
Undifferentiated or unspecialised cells that have the ability to differentiate into organ or tissue specific cells with specialised functions such a muscle cells, skins cells etc.
What are the two types of stem cells found in mammals?
EMBYRONIC STEM CELLS- isolated from inner cell mass of blastocysts
ADULT STEM CELLS- found in various tissues
Define totipotent
Have the potential to give rise to all dell types
Found in fertilisation egg
Define pluripotent
Cells of primary germ layers can differentiate into many cell types found in inner cell mass of embryonic blastocyst.
Define multipotent stem cells
Can differentiate into closely related family of cells
Blood stem cells could become red or white blood cells or platelets.
Define oligopotent
Can differentiate into w few cells
Adult somatic lymphoid or myeloid stem cells
Define unipotent
Can produce cells only of their own type but they a termed stem cells because they can self renew
Adult somatic muscle stem cells
Define cell based therapy
The use of stem cells to replace lost or damaged cells with the scope of treating or preventing a disease or condition
Define therapeutic cloning
Involves the creation o fan embryo through the technique of somatic nuclear transfer for the purpose of obtaining stem cells from that embryo which can be used to treat a patient with degenerative disease
What are ethical issues related to stem cells?
- creating an embryo for the purpose of obtaining stem cells will lead to the death of an embryo
- many donated eggs are required for this procedure. There is some concern that women might be coerced into providing eggs or be financially exploited if eggs can be purchased
Define congenital malformation
Abnormalities arising cure antenatal development
What factors cause abnormalities?
Genetic defects
Single gene defects, chromosomal defects
Environmental factors
What is a single gene Defect?
Usually inherited and most commonly appearing in newborn of unaffected parents who are heterozygous carriers of the allele involved. Caused by mutation of the gametes in fertilisation
Dwarfism, cystic fibrosis
What is chromosomal abnormality?
Presence of an extra copy of a chromosome (trisomy), results from disruption of the normal cell cycle
Down syndrome, Edwards syndrome, partial syndrome
How is the cell cycle regulated to prevent mutations?
-checkpoints such as g1 ensure DNA replication is error free, if it needs to be repaired the process of the cell cycle is delayed.
-proteins cycling ensure chromosomes are attached to the correct spindle fibres so that an equal distribution of chromosomes to daughter cells occurs
-normal cells display so called contact inhibition which means they will stop dividing if they overgrow adjacent cells
-chemical signals convey information to cells about when to divide faster and when to slow down or stop
—> oncogene, continue dividing
Tumour suppressor genes, stop dividing
Define apoptosis
If cells are chromosomally abnormal or damaged, they receive a signal to self destruct in a process known as programmed cell death
What is cancer?
A disease in which cells divide in an uncontrolled manner, forming an abnormal mass of cells. It results from the loss of control in the cell cycle
What causes cancer?
Carrying certain genes in your genome can increase risk of developing cancer
Environmental factors such as mutagens Uv radiation Carcinogenic chemicals in cigarettes Viruses Diet
