2.6 Foundations in biology Flashcards
Define cytokinesis.
cytoplasmic division following nuclear division, resulting in two new daughter cells.
Define interphase.
Phase of the cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phase.
Define mitosis.
Type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell.
What happens during mitosis overall?
Cell division.
What happens between each M phase during mitosis?
Interphase.
Where are the checkpoints in mitosis?
The two main checkpoints, the G1/S checkpoint, also called the restriction point, and the G2/M checkpoint.
There are other checkpoints, for example, there is one half way through mitosis and one in early G1.
What is the purpose of checkpoints during mitosis?
- To prevent uncontrolled division that would lead to tumors (cancer).
- To detect and repair damage to the DNA (for example damages caused to UV light).
- The cell cycle can not be reversed.
- The DNA is only duplicated once during each cell cycle.
What is the Hayflick constant?
Cells should normally only undergo a certain number of cycles or divisions. The number is about 50 and is known as the Hayflick constant.
What are the stages of the cell cycle starting the mitosis?
- M phase
- G0 (gap 0) phase
- G1 (gap 1) phase -also called the growth phase
- S (synthesis) phase of interphase]
- G2 (gap2) phase of interphase
What occur in the cell during M phase of mitosis?
- Cell growth stops.
- Nuclear division (mitosis) consisting of stages: prophase, metaphase, anaphase, telophase.
- Cytokinesis
What occur in the cell during G0 phase of mitosis?
- Cells may undergo apoptosis, differentiation or senescence.
- Some types of cells remain in this phase for a long time or indefinitely.
What is apoptosis?
Apoptosis- programmed cell cycle
What occur in the cell during G1 phase of mitosis?
- cell grows and increases in size.
- Transcription of genes to make RNA occurs.
- Organelles duplicate.
- Biosynthesis. e.g. protein synthesis, including making enzymes needed for DNA replication in the S phase.
- The p53 (tumor suppressor) gene helps control this phase.
What occur in the cell during S phase of mitosis?
- Once the cell has entered this phases, it is committed to completing the cell cycle.
- DNA replicates.
- When all the chromosomes have been duplicated, each one consists of a pair of identical sister chromatids.
- This phase is rapid, and because the exposed DNA base pairs are more susceptible to mutagenetic agents, this reduces the chances of spontaneous mutations happening.
What occur in the cell during G2 phase of mitosis?
Cell grows.
What is M phase?
- A checkpoint hat chemical triggers condensation of chromatin.
- Halfway through the cycle, the metaphase checkpoint ensures that the cycle is ready to complete mitosis.
What is G0 phase?
- A resting phase triggered during early G1 at the restriction point, by a checkpoint chemical.
- Some cells,e.g epithelial cells lining the gut, do not have this phase.
What is G1 phase?
- A G1 checkpoint controls mechanism ensures that the cell is ready to enter the S phase and begin DNA synthesis.
What is S phase?
Because the chromosomes are unwound and the DNA id diffuse, every molecule of DNA is replicated.
Housekeeping genes- those which are active in all types of cells, are duplicated first. Genes that are normally inactive in specific types of cells are replicated last.
What is G2 phase?
Special chemicals ensuring that the cells is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and formation of the spindle.
What does prophase look like in mitosis?
What does Metaphase look like in mitosis?
What does anaphase look like in mitosis?
What does prophase look like in mitosis?
What acronym is used to remember the stages of mitosis?
PMAT
What us a chromotid?
One of two identical halves of a replicated chromosome.
Define mitosis.
A type of nuclear division that maintains the chromosome number; in each new daughter cell contains the same genetic information as the parent cell. They’re genetically identical and is a product of asexual reproduction.
What is the significance of mitosis in the life cycle?
- Asexual reproduction-e.g. strawberries forming new plantlets at the end of runners and protoctists dividing to form new individuals.
- Growth- all multicellular organisms by producing more cells that are genetically identical to each other which occurs by mitosis.
- Tissue repair
What has happened during the synthesis that must have occurred before prophase?
The chromosomes have replicated.
What happens during prophase in mitoisis?
- Nuclear envelope breaks down
- Centriole divides and these two new daughter centrioles move to opposite poles of the cell.
- Tubulin (cytoskeleton protein) threads from a spindle between these new centrioles.
What happens during metaphase in mitosis?
- Pairs of chromatids attach to the spindle threads at the equator region of the cell.
- The chromosomes attach by there centromeres.
What happens during anaphase in mitosis?
- The centromere of each pair of chromatids splits.
- Motor proteins, walking along the tubulin threads, pull each sister chromatid of a pair, in opposite directions, towards opposite poles.
- Because these centromere goes first, the chromatid, now called chromosomes, assume a V shape.
What happens during telophase in mitosis?
- The separated chromosomes reach the poles.
- A new nuclear envelope forms around each set of chromosomes.
- The cell now has two nuclei each genetically identical to each other and to the parent cell which they arose.
What happens after mitosis?
Cytokinesis- once mitosis is complete, the cell splits in two, so that each new cell contains a nucleus.
What happens during cytokinesis in animal cells?
The plasma membrane folds inwards and ‘nips in’ the cytoplasm.
What happens during cytokinesis in plants cells?
An end plate forms where the equator of the spindle was, and new plasma membrane and cellulose cell-wall material are laid down on either side along this end plate.
Define differentiation.
Process by which stem cells become specialised into different types of cell.
What are epithelial cells? And where are they found? Give some examples?
Cells that are lining tissue. They’re found on the inside and the outside of your body. e.g. makes up the walls of the alveoli and capillaries; and line your intestines.
What is an erythrocyte?
Red blood cell.
What is a neutrophil?
Type of white blood cell that is phagocytic (can ingest microbes and small particles).
What is a stem cell?
Unspecialised cell able to express all of its genes and divide by mitosis.
What is a zygote?
Multicelluar organisms start life as a undifferentiated cell, called a zygote.
How does a zygote form?
A zygote results when an ovum (egg cell) is fertilized by a spermatozoon and the two haploid nuclei fuse to give a cell with a diploid nucleus.
Are zygotes specialised?
No. It is a stem cell. All the genes in its genome are able to be expressed.
What happens to a zygote after several mitotic divisions?
After several mitotic divisions, an embryo forms, containing many undifferentiated embryonic cells.
What happens as an embryo continues to develop after it is no longer a zygote?
The embryonic cells differentiate as certain genes are switched off and other genes may be expressed more so that:
- The proportions of different organelles differ from those of other cells.
- The shape of the cell changes.
- Some of the contents of the cell changes.
Also to this differentiation, each cell type is specialised for a particular function.