Topic 5 - Continuity Of Cells Flashcards
What is the cell cycle
The formation of new cells involves the production of additional contents before a cell can divide
What are the 3 phases of the cell cycle, and what are they split into
Interphase - G1, S, G2
Mitosis - Prophase, Metaphase, Anaphase, Telophase
Cytokinesis
What is the G1 phase, and what occurs during it
The first gap phase, Synthesis of macromolecules, including proteins and nucleotides, occurs and organelles are produced so that the cell increases in size
What is the S phase, and what occurs during it
DNA synthesis phase, Histones are produced, the DNA and chromatids formed are identical and remain attached until separated during Mitosis
What are Histones
Proteins that bind to and support the DNA with the chromatids
What is the G2 phase, and what occurs during it
The second gap phase, Proteins such as tubulin are synthesised; energy storages are increased; the cell continues to grow in size
What is the function of Tubulin
Tubulin forms the microtubules of the spindle fibres
What is the first phase of Mitosis and what occurs during it
Prophase;
The chromatin condenses to form the chromosomes
The centrioles move towards opposite poles
The spindles begins to form
As each chromosome continues to condense, two chromatids, joined at a centromere, become apparent
What is the second phase of Mitosis and what occurs during it
Metaphase;
The nuclear envelope breaks down
Spindle formation is completed as microtubules extend, forming the fibres
The microtubules of the spindle attach to the centromere of each chromosome
The chromosomes are moved by the microtubules onto the equator of the spindle
What is the third phase of Mitosis and what occurs during it
Anaphase;
The centromeres divide
The spindle fibres pull the centromeres of sister chromatids apart
The sister chromatids move towards opposite poles
What is the fourth phase of Mitosis and what occurs during it
Telophase;
Each chromatid is now a separate chromosome
The two groups of chromosomes reach opposite poles of the new cells
A new nuclear envelope forms around each group
What is the Final phase of the cell cycle and what occurs during it
Cytokinesis - the cytoplasm is separated and the cell divides during cytokinesis to form two daughter cells
What occurs in an Animal cell during cytokinesis
A cleavage furrow forms as protein microfilaments pull the cell surface membrane in along the equator; the furrow deepens and when the membranes fuse the cell is cleaved into two
What occurs in a plant cell during cytokinesis
The Golgi bodies produce vesicles that collect and fuse together to form an equatorial cell plate. The vesicles secret the material of the middle lamellar on each side of which a new cellulose cell wall is laid down
When must a cell only divide
- if sufficient macromolecules and organelles have been assembled so that the cell has grown to an appropriate size
- the DNA is error-free and accurately replicated
- the chromosomes have been positioned correctly during Mitosis
Where are the 3 checkpoints in the cell cycle
Towards the end of G1
Towards the end of G2
During metaphase
What is assessed during the G1 checkpoint
The supply of nutrients and growth factors so that the cell has reached an appropriate size
The DNA is check for damage
What is the G0 phase
The resting phase where cells can remain for days, weeks or years
What is assessed during the G2 checkpoint
It is checked that the DNA has replicated
What is checked during the Metaphase checkpoint
This check establishes whether the chromosomes have correctly attached to the spindle fibres before Anaphase
What is a tumour
A large mass of cells by which a mutation occurs in the cell, then the control mechanisms break down and the cell undergoes repeated, uncontrolled division
What is a benign tumour
A tumour that does not travel to other locations of the body
What is a Malignant tumour
A tumour that continues to grow unchecked and uncontrolled, that are shed and carried around the body by the circulatory system
What are the different processes that may be targeted by anti-cancer drugs
DNA unzipping is inhibited, so that no DNA replication can take place
The synthesis of nucleotides is inhibited
Formation of mitotic spindle is inhibited so the chromatids can separate
What are Genes
The codes for the synthesis of polypeptides and proteins
What are two sets of chromosomes in cells called
Homologous pairs
What is the term Homozygous
If the alleles on the homologous chromosomes are the same
What is the term heterozygous
If the alleles on the homologous chromosomes are different
What is Diploid
Cells contains homologous pairs of chromosomes
Why are Chromatids genetically identical
Because DNA replication produces identical copies
What is Haploid
A cell that contains only one of each type of chromosome
What is a Karyotype
A photomicrograph taken of a cell during nuclear division
What does a human Karyogram contain
23 pairs of chromosomes including a pair of sex chromosomes
What is the difference between Meiosis 1 and Meiosis 2
Meiosis 1 is the separation of homologous chromosomes
Meiosis 2 is the separation of chromatids
What occurs during Prophase 1
As chromosomes condense it becomes apparent that homologous chromosomes have paired and lie alongside each other; each pair is known as a bivalent
The chromatids appear: the chromatids in a bivalent are entwined at points called chiasmata
The chromatids may break at chiasmata and rejoin with a different chromatid
What occurs during Metaphase 1
The bivalents move to the equator of the spindle
Each chromosome of the pair becomes attached to a spindle fibre by its centromere
What occurs during Anaphase 1
Pulling by the spindle fibres causes the homologous chromosomes to move apart towards opposite poles
The homologous chromosomes are separated; each chromosome still consists of two chromatids
What occurs during Telophase 1
Chromosomes reach opposite poles of the cell
A nuclear membrane forms around each separate group of chromosomes; each nuclei contains the haploid number of chromosomes
What is the overall result of Meiosis
The production of 4 haploid daughter cells, each of which is genetically different from the others
What is the significance of Mitosis
The daughter cells possess the same chromosome number as each other and as the parent cell. Mitosis can occur in either diploid or haploid cells
The daughter cells are genetically identical
What is the significance of Meiosis
Meiosis is the type of nuclear division that transforms the diploid condition into the haploid condition
Meiosis produces daughter cells that are genetically different
Why does Crossing-over occur in Meiosis
It occurs as a result of chiasmata formation between the chromatids of the homologous pairs during late Prophase I
