The mitotic cell cycle Flashcards
Chromatids
- 1 of 2 identical parts of a chromosome
- held together by a centromere
- formed during interphase by the replication of a DNA strand
Centromere
region of the chromosome to which the microtubules of the spindle attach during cell division
Kinetochores
a protein structure found at the centromere of a chromatid to which microtubules attach during cell division
Telomere
protective sequence of nucleotides found at the ends of the chromosomes
Function of telomeres
- needed for successful cell division
- permit continued replication
- prevent loss of genes
Cell Cycle
- G1 phase
- S phase
- G2 phase
- Mitosis
- Cytokinesis
Cell cycle definition
sequence of events taking place from one cell division until the next
Interphase phases
- G1 phase
- S phase
- G2 phase
Interphase
- longest phase
- normal cell functions
- cell grows to its normal size
- time spent between cell divisions
G1 phase
- cells make RNA, enzymes & other proteins needed for growth
- at the end, cell becomes committed to dividing or not
S phase
- DNA replication so that each chromosome consists of 2 identical chromatids
G2 phase
- cell continues to grow
- new DNA is checked & any errors are repaired
- preparations are made to start cell division
Mitosis
nuclear division that produces 2 genetically identical daughter cells
Roles of mitosis
- maintains genetic stability
- ensures cells retain function
- maintains chromosome number
Functions of mitosis
- growth
- cell replacement
- repair of tissues
- asexual reproduction
- immune response
Stages of mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
- centrosomes migrate to opposite poles of mitotic spindle
- chromatin starts to condense
- nuclear envelope & nucleolus begin to disappear
Metaphase
- centrosomes are at poles of the cell and organise the production of spindle microtubules
- chromosomes line up across equator of spindle
- each chromosome splits at centromere
- chromosomes start to be pulled apart by microtubules
Anaphase
- chromatids move to opposite poles, centromeres are first pulled by microtubules
- spindle fibres contract and chromosomes are pulled to the opposite ends
Telophase
- nuclear envelope and nuceolus start reforming
- nucleus divides
- chromosomes are at poles of cell
Cytokinesis
division of cytoplasm
Cytokinesis in plant cells
- cell plate forms across equator of cell ; cellulose, cell wall laid down
- cytoplasm is hence divided into 2
Cytokinesis in animal cells
- contractile ring forms, pushing the equator of cell inwards, forming a cleavage furrow
- cleavage furrow deepens as active filaments in the ring contract
- cell eventually splits into 2
Differences in plant & animal cell mitosis
- plant cells don’t have any visible centriole
- in plant cells, daughter cells get separated by cell plate, there is no cleavage furrow
Centrosome
- an organelle found in animal cells that acts as the MTOC for construction of the spindle
- present at the poles of cell
Centrioles
- act as MTOCs
- assemble/form spindle fibres during prophase
- contraction of spindle fibres during anaphase separates sister chromatids
Stem cell
a relatively unspecialised cell that retains the ability to divide an unlimited amount of times and has the potential to become a specialised cell
Potency
extent of the power of a stem cell to produce different cell types
Stem cell therapy
introduction of new adult stem cells into damaged tissue to treat a disease or injury
Totipotent
stem cells that can produce any type of cell
Pluripotent
stem cells that form all the cells that will lead to the development of the embryo and later the adult
Multipotent
stem cells that are only able to produce a few types of cells
Cancer
a result of uncontrolled mitosis, due to a mutation ; cancerous cells divide repeatedly and form a tumour
Benign
a tumour that will not spread, safe, and will break down after some time
Malignant
tumours that spread throughout the body, invading & destroying tissues, causing cancer
Metastasis
cells that break off and spread through the blood and lymphatic system to other parts of the body to form secondary growths
Risk of metastasis
most dangerous characteristic of cancer because it can be very hard to find the secondary growths and remove them
Carcinogen
a substance or environmental factor that can cause cancer
Mutation
a random change in the base sequence of DNA or in the number of chromosomes
Cellular changes that occur in the development of cancer
- mutation occurs in gene responsible for cell division ; formation of oncogene
- causes uncontrolled cell division
- coordination of cell cycle is lost
- loss of function and lack of specialisation occurs
- a tumour is formed, an irregular mass of cells showing an abnormal change in shape
