Cell Cycle, Mitosis and Meiosis Flashcards
List the stages of the cell cycle in order and outline what happens at each stage. (F)
- interphase
- mitotic phase
Outline what happens at interphase. (F)
- DNA is replicated
- protein synthesis
- mitochondria and chloroplasts divide
Outline what happens at mitosis. (F)
- nuclear division
- cell division
List the 3 stages of interphase in order. (F)
- G1
- S
- G2
Describe what happens at G1. (F)
- protein synthesis
- organelle replication
- cell increases in size
Describe what happens at S. (F)
- DNA is replicated
Describe what happens at G2. (F)
- cell continues to grow in size
- energy stores increased
- duplicated DNA checked for errors
List the 2 stages of the mitotic phase and outline what happens at each stage.
- mitosis
- cytokinesis
Outline what happens at mitosis.
- nuclear division
Outline what happens at cytokinesis.
- cytoplasm divides, producing two cells
Describe the significance of G0 as a phase that cells enter when they leave the cell cycle.
Allows for:
- differentiation and cell specialisation
- removal of damaged cells
Outline the role of checkpoints to control the cell cycle. (F)
- monitor and verify that the processes at each phase has been accurately completed
- prevents progression of damaged cells
Where does the G1 checkpoint occur?
- end of G1 phase
- before S phase
What is checked at the G1 checkpoint?
- cell size
- nutrients
- growth factors
- DNA damage
Where does the metaphase checkpoint occur?
- metaphase
- (where chromosomes are attached to spindles and are aligned)
What is checked at the G2 checkpoint?
- cell size
- DNA replication
- DNA damage
What is checked at the metaphase checkpoint?
- chromosome attachment to spindle
Outline the link between cell-cycle regulation and cancer. (S+C)
- cancer is caused by uncontrolled division of cells
- tumours are result of damage or spontaneous mutation of genes that encode proteins involved in regulating cell cycle i.e. checkpoint proteins
Define the term “mitosis”. (F)
Nuclear division stage in the mitotic phase of the cell cycle.
Define the term “chromosome”. (F)
Structure of condensed and coiled DNA in the form of chromatin. Chromosomes become visible under the light microscope when cells are preparing to divide.
Define the term “chromatid”.(F)
A single copy of DNA.
Define the term “sister chromatids”. (F)
Two identical copies of DNA (a chromosome) held together by a centromere.
Define the term “centromere”. (F)
Region at which two chromatics are held together.
Define the term “centrioles”. (F)
Component of the cytoskeleton of most eukaryotic cells, composed of microtubules.
Define the term “spindle fibres”. (F)
A network of microtubules that form the mitotic/meiotic spindle for chromosome segregation in cell division.
Define the term “homologous pairs”. (F)
Matching pair of chromosomes, one inherited from each parent.
List the stages of mitosis in order. (F)
- prophase
- metaphase
- anaphase
- telophase
Describe what happens at prophase in mitosis. (F)
- chromatin condenses to form chromosomes that are visible under a light microscope
- spindle fibres form
- centrioles migrate to opposite poles of the cell
- nuclear envelope disappears
Describe what happens at prophase in mitosis. (F)
- chromatin condenses to form chromosomes that are visible under a light microscope
- spindle fibres form
- centrioles migrate to opposite poles of the cell
- nuclear envelope disappears
- nucleolus disappears
Describe what happens at anaphase in mitosis. (F)
- centromeres divide
- chromatids pulled to opposite poles by shortening spindle fibres
- V shape formed from being dragged through cytosol
Describe what happens at telophase in mitosis. (F)
- chromatids have reached poles and are called chromosomes
- nuclear envelope reforms
- chromosomes uncoil
- nucleolus formed
- cytokinesis begins
Explain the role of the centrioles and spindle fibres in mitosis.
- centrioles aid in spindle formation
- spindle fibres are responsible for segregation and separation of chromatids
Explain the role of the centrioles in mitosis.
Aid in spindle formation
Explain the role of the spindle fibres in mitosis.
- form metaphase plate
- segregation and separation of chromatids
Describe the process of cytokinesis in animal cells.. (F)
- cleavage furrow forms in middle of cell
- plasma membrane pulled inwards by cytoskeleton until it can fuse in the middle
Describe the process of cytokinesis in animal cells. (F)
- cell walls so no cleavage furrow
- vesicles from Golgi apparatus assemble where metaphase plate was
- vesicles fuse with each other and cell surface membrane
- new sections of cell wall form along new sections of membrane
Describe the relative quantity of DNA in a dividing cell, using x as the initial quantity.
- x at beginning
- 2x at S, during DNA replication
- x at cytokinesis, when 2 daughter cells are formed
Calculate the mitotic index of a sample of dividing cells.
(number of cells in mitosis / total number of cells) x 100
Calculate how many cells have been produced during mitosis from one cell given the number of cell cycles that have taken place. (F)
x = number of cell cycles
cells produced = 2^x
Explain how to calculate the length of time each stage in the cell cycle takes given a sample of cells undergoing mitotic cell division and the total duration of the cell cycle.
(sample of cells in stage / total number of cells) x total duration of cell cycle
Describe the purpose of mitotic cell division. (F)
To produce genetically identical daughter cells.
List 4 roles of mitotic cell division. (F)
- growth of tissues
- replacement of tissues
- repair of tissues
- asexual reproduction
Define the term “diploid”. (F)
Normal chromosome number: two chromosomes of each type – one inherited from each parent.
Define the term “haploid”. (F)
Half the normal chromosome number; one chromosome of each type.
Define the term “gamete”. (F)
Haploid sex cells produced by meiosis in organisms that reproduce sexually.
Define the term “zygote”. (F)
The initial diploid cell formed when two gametes are joined by means of sexual reproduction. Earliest stage of embryonic development.
Define the term “meiosis”. (F)
Form of ell division where the nucleus divides twice (meiosis I and meiosis II) resulting in a halving of the chromosome number and producing four haploid cells from one diploid cell.
Define the term “reduction division”. (F)
Cell division resulting in the production of haploid cells from a diploid cell; meiosis.
Explain the role of meiosis in life cycles.
- produces sex cells with half the number of chromosomes
- zygotes will be diploid
- chromosome number of an organism doesn’t double with each round of reproduction
State 2 ways in which meiosis produces variation. (F)
- crossing over
- independent assortment of chromosomes
Suggest the importance of the creation of different allele combinations in populations.
- increases genetic biodiversity
- decreased risk of disease wiping population out
- allows for adaptation
Define the term “homologous chromosomes”. (F)
Matching pair of chromosomes, one inherited from each parent.
Define the term “bivalent”. (F)
The name for two homologous chromosomes that have paired up in prophase I of meiosis.
Define the term “crossing over”. (F)
The exchange of DNA between chromatids of homologous chromosomes.
Define the term “random independent assortment”. (F)
The fact that which daughter cell a chromosome ends up in after Meiosis I or a chromatid ends up in after Meisosis II is random and independent of the fate of chromosomes from other homologous pairs.
State the stages of meiosis in order.
- prophase I
- metaphase I
- anaphase I
- telophase I
- prophase II
- metaphase II
- anaphase II
- telophase II
Outline what occurs in meiosis I. (F)
- reduction division
- pairs of homologous chromosomes are separated
- haploid cells
Outline what occurs in meiosis II. (F)
- similar to mitosis
- separation of chromatids
- four haploid daughter cells
Describe what happens at prophase I of meiosis. (F)
- chromosomes condense
- nuclear envelope disappears
- nucleolus disappears
- spindle formation begins
- homologous chromosomes pair up to form bivalents
- crossing over occurs when sister chromatids of homologous chromosomes entangle
Describe what happens at metaphase I of meiosis. (F)
- homologous pairs of chromosomes assemble on metaphase plate
- homologous pair orientation on metaphase plate is random and independent of other homologous pairs
Describe what happens at anaphase I of meiosis. (F)
- homologous chromosomes are separated and pulled to opposite poles
- chromatids remain joined together
- sections of DNA on non-sister chromatids break off and rejoin following crossing over
- recombinant chromatids formed and sister chromatids are no longer identical
Describe what happens at telophase I of meiosis. (F)
- chromosomes assemble at each pole
- nuclear membrane reforms
- chromosomes uncoil
- cell undergoes cytokinesis and divides into two cells
- haploid cells formed
Describe what happens at prophase II of meiosis. (F)
- chromosomes condense and become visible
- nuclear envelope breaks down
- spindle formation begins
Describe what happens at metaphase II of meiosis. (F)
- individual chromosomes assemble on metaphase plate
- independent assortment of chromosomes
Describe what happens at anaphase II of meiosis. (F)
- chromatids are pulled to opposite poles after division of centromeres
Describe what happens at telophase II of meiosis. (F)
- chromatids assemble at poles
- chromosomes uncoil to form chromatin
- nuclear envelope reforms
- nucleolus becomes visible
- cytokinesis forms 4 haploid daughter cells
Describe the process of crossing over and explain how it produces genetic variation. (F)
- chromatids of homologous chromosomes twist around each other and cross many times
- at metaphase I, break at chiasmata to exchange equal sections of DNA
- sister chromatids on a single chromosomes are no longer genetically identical
Describe the process of random independent assortment and explain how it produces genetic variation. (F)
- in meiosis I, chromosomes can line up in different ways before homologous chromosomes separate
- in meiosis II, chromatids can line up in different ways before chromosomes separate
- independent of orientation of other homologous chromosomes/chromatids
- each daughter cell has a different combination of alleles
Explain (given the chromosome number of the species) how to calculate the total number of possible genetically different gametes that could be produced through independent assortment only.
x = number of chromosomes
total number = x^2
Compare meiosis I and meiosis II.
- both produce haploid chromosomes
- meiosis I separates homologous chromosomes, whereas meiosis II separates chromosomes
- meiosis I forms two daughter cells whereas meiosis II forms four daughter cells
- random independent assortment occurs at metaphase
Compare meiosis I and meiosis II.
- both produce haploid cells
- meiosis I separates homologous chromosomes, whereas meiosis II separates chromosomes
- meiosis I forms two daughter cells whereas meiosis II forms four daughter cells
- random independent assortment occurs at metaphase
State the similarities between meiosis I and meiosis II.
- both produce haploid cells
- random independent assortment occurs at metaphase
State the similarities between meiosis I and mitosis.
- both produce two daughter cells
- similar anaphase and telophase
State the similarities between meiosis II and mitosis.
- separation of chromatids at metaphase
- similar prophase and anaphase
State the differences between meiosis I and meiosis II.
- MI separates homologous chromosomes, whereas MII separates chromosomes
- MI forms two daughter cells whereas MII forms four daughter cells
State the differences between meiosis I and mitosis.
- MI produces haploid cells whereas M produces diploid cells
- MI separates homologous chromosomes at metaphase whereas M separates chromosomes
- MI has crossing over occurring at prophase
State the differences between meiosis II and mitosis.
- MII produces four daughter cells whereas M produces two daughter cells
- MII produces haploid cells whereas M produces diploid cells
Compare mitosis and meiosis. (F)
- Mi produces genetically identical cells; Me produces genetically variation
- Mi produces two daughter cells; Me produces 4 daughter cells
- Mi produces diploid cells; Me produces haploid cells
- Mi is used in growth, repair and replacement of tissues as well as asexual reproduction; Me is used in sexual reproduction
