Cell Division Flashcards
What are the three main causes of tumours?
Oncogenes, mutated tumour suppressor genes and increased oestrogen production
What aspect of the cell do lots of cancer drugs target?
Spindle fibres, as without them working properly, mitosis cannot occur as one of the sister cells would end up with double the required DNA and one would end up with none, resulting in failure in functioning in both of them
What is apoptosis?
Programmed cell death that occurs when mutations are detected to prevent them from spreading
What are the key features of malignant tumours?
- can and do metastasise
- develop their own blood supply
- grow large very rapidly
What are the stages of mitosis?
Interphase - growth and replication of the cell
Prophase - DNA condenses and nuclear envelope disappears, and the centrioles move to opposite poles
Metaphase - spindle fibres attach to centromeres and pulls chromosomes to cell equator
Anaphase - spindle fibres contract, using ATP to pull the chromosomes to opposite sides of the cell
Telophase - cytoplasm and organelles move towards the edges of the cell, and a new nuclear envelope forms
What is a mutation?
Random change to the base sequence of DNA
What form is DNA in when in the nucleus and why?
- Chromatin
- Unravelled, which means that DNA is accessible to transcription and the genetic information can be translated
- DNA organised in this way in all non-dividing cells and during interphase
What does chemotherapy do?
Prevents the synthesis of enzymes required for DNA replication, stopping the cell cycle
What genes cause breast cancer, and why?
BRCA 1 and 2, as they help to make proteins in cells that repair damaged DNA. A mutation would therefore lead to abnormal cell growth, which can cause cancer
What does radiotherapy do?
Damages DNA, forcing the cells to induce apoptosis
What role does increased oestrogen production play in the development of cancer?
- oestrogen activates transcription factors, and subsequently the transcription of genes
- formation of tumours results in even more oestrogen production, attracting white blood cells
How do prokaryotes divide?
Through binary fission - very similar to mitosis, but the DNA cannot condense into chromosomes as it is not associated with histones
What role do mutated tumour suppressor genes play in the development of cancer?
- apoptosis is inhibited and cell division is constantly stimulated
- hypermethylation leads to decreased expression as chromatin is more condensed
What is a germline cell?
Sex cells in any living organism
What role do oncogenes play in the development of cancer?
- mutated versions of proto-oncogenes
- results in cell cycle being permanently switched on, causing excessive cell division
- hypomethylation increases gene expression as chromatin will be less condensed
What form is DNA in during mitosis and why?
- chromosomes
- DNA is packaged into tightly coiled chromosomes, through supercoiling
- enables easy division and transportation, but it cannot b replicated
What is a somatic cell?
Any cell living in an organism that is not a sex cell
What are the key features of benign tumours?
- unable to metastasise
- surrounded by a capsule
- can grow large, but often at a slow rate
How does mitosis occur in plant cells?
Due to the solid cell wall, the cell cannot divide by pinching into the centre, so a cell plate builds up between the two daughter cells instead
What are the stages of the cell cycle? (4)
1) G1 - cell starts to grow and make more cytoplasm and organelles in preparation for mitosis
2) S - DNA synthesis occurs
3) G2 - growth continues
4) M - mitosis occurs and the cell divides
What is mitosis used for?
Repair and replace cells, and grow organisms
How many cases of breast cancer are hereditary?
5-10%
