Mitosis And Meiosis Flashcards
(17 cards)
What are the phases of the cell cycle?
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
- G1
- Interphase
- S
- G2
In what phase is there double the amount of DNA?
S-phase
In what phase is there two centrosomes?
G phase
What is the consequence of typical mitosis?
Genetically identical cells
What is the consequence of atypical mitosis?
Genetically not identical cells (in multicellular organisms this causes mosaicism)
What is endomitosis (endoreduplication)?
DNA is duplicated, but during M-phase the nuclear envelope remains intact.
There is no separation of chromatids, or there can be separation of chromatids.
The consequence of endomitosis are giant cells with giant nuclei. There can be polythene (giant) chromosomes or more chromosomes (polyploid cell).
E.g. in salivary glands and liver
What is a polythene cell?
A cell with giant chromosomes. The number of chromosomes is the same, but the amount of DNA increase
What is a polyploid cell?
Polyploid cells have more DNA and an increase in chromosome number
What is the consequence of no cytokinesis?
When there is no cytokinesis, there is no cell division. This creates multinucleated (giant) cells.
E.g. muscle fibers, liver cells, megakaryocyte
Atypical division are usual in what pathological condition?
Tumor cells
What is multipolar division and what is the consequence of a multipolar division?
Bipolar division (normal) is when the centrioles are duplicated. When there is atypical duplication and division of centrosomes, the chromosomes are pulled to more than two poles. This creates abnormal chromosome numbers in the arising cells.
Bipolar (normal)
Tripolar, tetrapolar (abnormal)
What are the mitotic spindle errors that can happen?
Amphitelic: normal
Monotelic: only one microtubule is attached to the centrosome
Synthelic: Microtubules from same pole attach to both centrosomes. This changes the chromosome number, and is called non-disjunction.
Merothelic: a bridge-formation which the check-point machinery cannot detect. Two microtubules from one pole attach to both microtubules, while one microtubule from the other pole also attach to one centrosome.
What is a bridge formation?
When a chromatid is pulled from two poles. The consequence is breakage of the chromosome (structural chromosomal aberration)
What is non-disjunction?
A lack of kinetochor microtubule-attachment to a chromatid. The consequence is an abnormal chromosome number.
What is the result of mitosis and meiosis?
Mitosis - two genetically identical cells (diploid)
Meiosis - four genetically different cells (haploid)
Which phase is the longest in meiosis I?
Prophase, and it can be divided into these phases:
- leptotene
- zygotene
- pachytene
- diplotene
- diakinesis
What are the characteristics of homologous chromosomes in diploid cells?
They are the same shape, size and have the same genes, although the alleles might be different. The origin of the chromosomes are also different (ovum and sperm)
