Cell Cycle Flashcards
Why do cells divide?
to grow, heal or reproduce an organism
Explain Daughter and Parent cells
the parent cells are the cells undergoing cell division
the daughter cell is the resulting cells from the cell division
Define Haploid
Cells that contain only one set of chromosomes
Define Diploid
cells that contain two sets of chromosomes
What are some organisms with more than two sets of chromosomes?
plants and fungi
4 sets —> tetraploid
8 sets —> octoploid
Describe Mitosis and the four steps
the process of nuclear replication
(not cell division)
required for any eukaryotic cell prior to cell division
consists of four steps :
Prophase, Metaphase, Anaphase, Telophase
Describe Prophase
the preparation stage for nuclear division
the chromosomes condense out of the nucleoplasm becoming visible under a microscope
Describe the chromosomes during prophase
The chromosomes during prophase consist of two Chromatids joined together
What are Chromatids?
strand of DNA and attached proteins
the nuclear membrane dissolves during prophase, exposing the chromosomes
What is a Centromere?
the point where chromosomes join
Explain how the centrioles work in prophase
Centrioles (two organelles) move to opposite ends of the cytoplasm and act as attachment sites for Spindle Fibres (grappling hooks)
centrioles are only found in animal cells
Where do spindle fibres attach?
Spindle fibres attach to the centromeres of each chromosome pair
(joining point of chromatids)
Describe Metaphase
the second stage of mitosis where chromatids prepare to be separated and divided
chromosomes meet in the center of the cell —> Equator / Equatorial Plane
Describe Anaphase
the third stage of mitosis where genetic information is divided up and sorted to opposite ends
centromeres detach in anaphase, resulting in single chromosomes (separated pairs)
the spindle fibres work w the centrioles to make sure that each end of the cell receives an equal number of chromosomes
they also make sure that each end of the cell contains one of each chromosome
Describe Telophase
the final stage of nuclear division, where new nuclei are formed in preparation for cell division
the separated chromosomes dissolve back into the cytoplasm
nuclear membranes begin to form around the chromosomes at each end of the cell, resulting in new nuclei
When is it clear that Mitosis is complete?
During Telophase, once the nuclei have been reformed
Describe Cytokinesis and when does it occur?
the movement of cytoplasm and organelles
following mitosis, cytoplasm and other organelles divide and move to opposite ends of the cell
part of the M stage
What causes the separation of the newly formed daughter cells?
A Contractile Ring causes the cell membrane to contract and narrow at the centre
once the ring closes completely, it pinches at the centre, resulting in two daughter cells
What is the M phase?
the M phase (cell division) is just one stage of the cell cycle
(m for mitosis)
The M stage occurs after Interphase (G1, S, G2)
contains both cytokinesis and mitosis
Describe Interphase
the three stages between cell division
(inter —> interval between cell division)
G1, S, G2
Describe the G1 phase
the first stage in interphase which stands for 1st growth
the cell grows and performs it’s normal function
longest stage of the cell cycle
Describe S stage
the second stage of interphase, the S stands for synthesis
synthesis in the S stage refers to DNA replication (synthesizing new DNA)
S stage is the cells first preparation for mitosis by doubling the amount of DNA
Describe the amount of DNA in a cell during S stage
the amount of DNA in the cell doubles during S stage, from 46 chromatids to 92 chromatids
still diploid because they are paired through centromeres
92 chromatids, 46 chromosomes
Describe the G2 stage
the final stage of interphase, 2nd growth
stage where the cell grow until it is large enough for cell division
a lot of protein synthesis, specifically the synthesis of spindle fibre proteins
What is at the end of each growth stage?
A checkpoint
Describe the role of G1 Checkpoint Proteins
they ensure that cells have a sufficient size and amount of nutrients
in order to exit G1 cells and begin DNA replication, the cell must receive a signal from outside the cell, which acts as a clearance code
once the g1 checkpoint is cleared, the cell is committed to DNA Replication, no going back
Describe the role of G2 Checkpoint Proteins
they ensure that the cells don’t enter M phase (mitosis) until a DNA damage inspection has been done
this inspection is not perfect and sometimes damaged DNA can get through the G2 checkpoint
the replication of damaged DNA can be dangerous to the cell and organism
What are Somatic cells?
Cells that follow a diploid cell cycle
(2 sets of chromosomes in humans —> 46)
all body cells that aren’t used for reproduction
they are responsible for normal functioning of the individual
Describe Sex Cells, what are they called and how are the reproduced?
haploid cells that involve reproduction
(contain one set of chromosomes —> 23)
also called Gametes
reproduced through the process of Meiosis
Describe Meiosis
similar to mitosis, but contains a second nuclear division
DNA is not replicated prior to the second division of meiosis
The two divisions result in four daughter cells each with a haploid set of chromosomes
Describe Genetic Recombination
prior to the second cell division, the cells undergo genetic recombination
it is the process where sister chromosomes exchange DNA to increase genetic variation
Describe Tumours
cells that grow at an uncontrollable rate
*cell division must be regulated so that cells don’t divide uncontrollably
Describe Benign Tumours
tumours that are located
this means that they don’t infringe upon surrounding tissues or spread throughout the body
Describe Malignant Tumours
Tumours that invade surrounding tissue or spread throughout the body
the common name for malignant tumours is cancer
What is Metastasis?
the spread of malignant cells throughout the body, resulting in tumors
What causes cancer?
Genetic Changes to a cell
these genetic changes result in the changes to the cell cycle, resulting in too much cell division
Describe Oncogenes
A gene that has the potential to make a cell cancerous
oncogenes start as genes responsible for regulating cell division,
these cells have the potential to result in uncontrollable growth and cell division
What are the 4 different factors that can trigger Oncogenes?
- Mutations during DNA Replication
- Mutations due to a Carcinogen (substance that causes cancer)
- Mutation or damage due to Radiation (UV or X-RAY)
- DNA inserted by a Virus (DNA Viruses, like HPV, insert into the DNA)
if they insert into the middle of an oncogenes it results in Cancer
