| what is apoptosis | Apoptosis or programmed cell death is the deliberate death of healthy cells
→ natural feature of healthy tissue and cells are preprogramed to die |
| what happens when cell reproduction and cell death is unbalanced | Cell reproduction and death is usually balanced – if there is too much reproduction it can lead to tumours and if there is too much it can lead to neurodegenerative diseases |
| what is the function of apoptosis | Apoptosis is a form of self-defence as well as it killed cells with viruses, old cells, cells with DNA damage, cells of the immune system, and cancerous cells |
| what are three reasons otherwise healthy cells die via apoptosis | → not fully developed cells are killed – in the embryonic brain cells that are not
incorporated into the brain network are killed via apoptosis
→ there are more than needed – it takes energy to keep extra cells alive so excess cells die via apoptosis
→ they have outlived their usefulness – foetuses have webbed toes and fingers and when this feature is no longer needed the cells connecting these extremities die via apoptosis – also when you recover from an illness any leftover immune cells that are not needed anymore die via apoptosis |
| what is syndactyly | Incomplete differentiation of toes or fingers is called syndactyly and is a result of a lack of apoptosis |
| what are the two signals to activate apoptosis | the mitochondrial pathway and the death receptor pathway |
| for what reason is the mitochondrial pathway activated | The mitochondrial pathway is a signal from inside the cell to activate apoptosis and begins when there is serious damage inside the cell (damaged DNA) |
| what are the four steps of cell death via the mitochondrial pathway | → first proteins on the outside of the mitochondria are activated breaking down the mitochondrial membrane
→ this causes an enzyme known as caspase to enter the nucleus and destroy the DNA
→ organelles other than the nucleus and mitochondria are preserved as the cell is broken down into small fragments which are enclosed by a membrane
→ fragments bind to phagocytes which engulf them |
| what is the death receptor pathway | The death receptor pathway is a signal from outside the cell to activate apoptosis – cells have death receptors on their membrane that receive the message to begin apoptosis – process occurs in 5 steps |
| what are the five steps of the death receptor pathway | → message is received, caspases are activated, contact to neighbouring cells is lost, and messages are sent to phagocytes
→ cells shrink and blebs (bumps) form of the outside of the cell
→ caspase enters the nucleus destroying all DNA
→ organelles other than the nucleus and mitochondria are preserved as the cell is broken down into small fragments which are enclosed by a membrane
→ fragments bind to phagocytes which engulf them |
| what are blebs | they are bumps on the outside of the cell which are caused by the onset of apoptosis via the death receptor pathway |
| what is caspase | caspase is an enzyme that destroys DNA and it is used in apoptosis |
| what can too much apoptosis lead to | Too much apoptosis can lead to neurodegenerative diseases such as AD and PD |
| what can too little apoptosis lead to | Too little apoptosis can lead to the formation of cancer and can lead to autoimmune diseases |
| what is necrosis | Is a type of cell death that occurs when cells are damaged by chemical or mechanical trauma |
| what are the main two steps of necrosis | → first the plasma membrane is damaged so it can’t control what enters and exits the cell, chromatin clumps, organelles swell, and the mitochondria has a loosely clumped texture almost resembling tufts of wool
→ cell swells and bursts, spreading intracellular contents over nearby cells causing inflammation |
| what causes necrosis | chemical or mechanical trauma |
| what is chemotherapy | Chemicals that inhibit mitosis and causes apoptosis – also blocks growth promoting signals |
| what are some side effects of chemotherapy | Side effects – also effects cells that divide fast such as hair follicles and cells in the digestive tract |
| what are the two types of chromosomal abnormalities or mutations | numerical or structural |
| define aneuploidy | it is when there is an abnormal number of chromosomes |
| what are the two main types of aneuploidy | monosomy and trisomy |
| what is trisomy | when there is an additional chromosome |
| what is monosomy | when there’s one chromosome missing – usually fatal (turners’ syndrome is one of the only survivable monosomy syndrome) |
| what is mosaicism and how does it usually present physically | when someone has two or more sets of cells that vary genetically – can affect any cell – begins as one or a small group of cells which are affected but then it spreads – can be present in some tissues and now others causing an unsymmetrical appearance |
| what is the difference between chimaerism and mosaicism | they are essentially the same (more then one set of cells - additional cell lines in some cells) however chimaeras involves a larger input of genetically different cells whereas chimaerism usually only starts off with one or two abnormal cells |
| what are the two types of structural abnormalities relating to centromeres | dicentric and acentric |
| what is dicentric | when a chromosome has 2 centromeres |
| what is acentric | when a chromosome doesn't have a centromere |
| what are the four structural changes that can occur as a result of faulty meiosis | deletion, duplication, inversion, and translocation |
| what is a duplication abnormality | duplication is when a segment is repeated |
| what is a deletion abnormality | deletion is the removal of part of a chromosome |
| what is an inversion abnormality | inversion is when a segment of the chromosome is reversed |
| what is a translocation abnormality | translocation is the movement of a segment from one chromosome to a non-homologous one |
| what is Down syndrome and what type of disorder is it | down syndrome is when a person has an extra copy of chromosome 21 – this is a trisomy disorder (trisomy 21) |
| what are the three trisomy syndromes that are compatible with life | down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and patau syndrome (trisomy 13) |
| what is non-disjunction | Occurs when chromosomes don’t separate in meiosis – either meiosis 1 or 2
Causes one gamete has an extra copy of a chromosome and one to have one less chromosome – leads to aneuploidy disorder |
| what is non-disjunction in sex chromosomes | when there is either an extra or a missing sex chromosome |
| what are the 4 syndromes related to the non-disjunction of allosomes | turners syndrome (XO), Klinefelter's syndrome (XXY), trisomy X (XXX) and trisomy Y (XYY) |
| what is turners syndrome | turner’s syndrome is when a person is missing an X chromosome meaning there’s only 45 chromosomes rather than 46 – occurs only in females – most foetuses with turners’ syndrome are spontaneously aborted it if they survive past infancy their prognosis is usually good (will have certain health issues but they can usually be fixed) |
| what is Klinefelter's syndrome | Klinefelter’s syndrome is when males have an additional X chromosome – usually leads to infertility |
| what is Trisomy X | Trisomy X or super female syndrome occurs when there is an extra X chromosome – effects 1 in 1000 females (most feel no side effects – usually some psychological effects) |
| what is trisomy XYY | Trisomy Y or XYY syndrome is when a male displays an addition Y chromosome – very common and very few side effects |
| what is the only form of genetic variation in asexual reproduction | Errors that occur during S phase in regard to DNA replication are passed on to daughter cells
– mutations like these are the only form of genetic variation in asexual reproduction |
| what is one cause of mutations during mitosis | mutagens increase the rate that DNA changes and can negatively affect proto-oncogenes and tumour suppressor genes (genes that control cell cycle)
- the presence of mutagens is one of the main causes of mutations in offspring produced asexually |
| what are mutagens | Mutagens are substances or agents, such as radiation or a virus, that increase the rate that DNA changes
- can negatively affect proto-oncogenes and tumour suppressor genes |
