Genetics - Cell Cycle Flashcards
What is the function of cell division?
It allows organisms to grow and develop, to replace dead cells and repair tissue
What is the cell cycle?
The sequence of events a cell goes through in order to duplicate its contents and divide
What does the cell cycle consists of?
Interphase
Mitosis
Cytokinesis
What is interphase?
It involves cellular components being duplicated and being built up
What is the function of interphase?
It prepares the cell for mitosis
What are the three phases of interphase?
G1
S
G2
What occurs during G1?
The cell synthesises new proteins and synthesises new organelles through duplication
This is the first growth stage for the cell
What occurs during S?
DNA replication occurs
What occurs during G2?
The cell synthesis more proteins and duplicates more organelles, in preparation for mitosis
This phase also involves the cell checking for any errors that occurred during the S phase
This is the second growth stage for the cell
What are the four phases of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What occurs during prophase?
The chromosomes condense,
The nuclear membrane disappears
The cell’s microtubules start to disassemble and assemble the spindle fibres
What occurs during metaphase?
The chromosomes line up on the metaphasic plate of the cell
This is an imaginary plane equidistant from the two centrosome poles
The movement is achieved by the assembly and disassembly of the microtubules to form spindle fibres
What occurs during anaphase?
The spindle fibres attached to the kinetochores of the chromosome start to disassemble, pulling the sister chromatids apart to opposite sides of the cell
What occurs during telophase?
The cell forms two daughter nuclei as the chromosomes are fully separated to opposite poles of the cell
The nuclear membrane is reformed around the two nuclei
What occurs during cytokinesis?
The cytoplasm splits and we form two new daughter cells
What is mitosis and cytokinesis collectively termed as?
M phase
What is meiosis?
It is the process of cell division of gametes in the reproductive organs
It results in diploid cells in the ovaries and testes dividing to form haploid egg and sperm cells
How many rounds of cell division occur during meiosis?
Two
How many haploid cells are formed via meiosis?
Four
What are the four phases of meiosis?
Prophase
Metaphase
Anaphase
Telophase
What occurs during meiosis I?
It is a process which is used to separate the homologous chromosomes apart.
What occurs during meiosis II?
It is a process which is used to separate chromosomes apart into chromatids
What occurs during prophase I?
During this step the chromosomes condense, then pair up, gene by gene with their homologous chromosome
What is a tetrad?
It is the structure formed when the homologous chromosomes pair up together during prophase I
What are chiasmata?
The random points at which the the inner non-sister chromatids touch each other when the homologous chromosomes pair up together
At these points, the inner chromatids break and swap section of DNA from after that point
What is the function of chiasmata?
They allow crossing over of genetic information between the homologous chromosomes
This increases variation in gametes and results in recombinant chromosomes
What occurs during metaphase I?
The nuclear membrane breaks down, allowing the homologous chromosome pairs to line up alone the metaphasic plate of the cell
The centrioles also start to create microtubules which extend and attach to the kinetochores of the chromatids
How do chromosomes line up along the metastatic plate of the cell? What does this mean? What is this process called?
They are positioned randomly, irrespective of their parental origin
There is no control over which chromosome of each pair goes to which side of the cell, so there is no maternal set of chromosomes on one side and paternal set on the other
Independent assortment
What is the function of independent assortment?
This results in new combinations of alleles and an increase in variation
What occurs during anaphase I?
The microtubules shorten and pull on the kinetochores so that the homologous chromosomes are pulled to opposite ends of the cell
What occurs during telophase I?
As the chromosomes approach opposite ends of the cell, the cell begins to divide
What occurs during cytokinesis I?
During this step, the gamete mother cell fully separates into two daughter cells
At the end of meiosis one, how many chromosomes and chromatids are found in the daughter cells?
23 chromosomes
46 chromatids
This means the chromosomes consist of two chromatids each
Are cells at the end of meiosis I haploid or diploid?
Haploid
This is due to there being only one copy of the homologous chromosome present in each cell
What occurs during prophase II?
The nuclear membrane of each cell breaks down again
No crossing over occurs as there is only one chromosome now in each cell
What occurs during metaphase II?
The chromosomes line up along the metaphasic plate of the cell but unlike metaphase I the chromosomes line up individually rather than with their homologous chromosome
The centrioles create and extend microtubules so that they can attach to the kinetochores of each sister chromatid
What occurs during anaphase II?
The microtubules shorten and pull on the kinetochores of the chromatids
This results in the chromatids of the chromosomes being pulled to opposite ends of the cell
What occurs during telophase II?
The chromatids (chromosomes) group at each end of the cell and a nuclear membrane form around them
The cell then begins to divide
What occurs during cytokinesis II?
Each cell divides into two, forming a total of four haploid cells
At the end of meiosis two, how many chromosomes and chromatids are found in the daughter cells?
23 chromosomes
23 chromatids
What two processes result in the four haploid cells being genetically different to each other?
Crossing over
Independent assortment
