cell cycle Flashcards
What is meiosis
Process in which sex cells, gametes, are made in reproductive organs
Involves the reduction division of a diploid germline cell into 4 genetically distinct haploid nuclei
Prophase 1
Chromosomes condense
Nuclear membrane dissolves
Homologous chromosomes form bivalents, sister chromatids
Crossing over occurs
Metaphase 1
Spindle fibres from opposing centrosomes connect to bivalents at the centromeres and align them all along the middle of the cell
Independent assortment
Anaphase 1
Spindle fibres contract
Homologous chromosomes move to opposite poles of the cell
Crossing over occurs creating genetic varitation
Telophase 1
Chromosomes decondenses and assemble at each pole, nuclear membrane may reform, cell divides( via cytokinesis) to form 2 haploid daughter cells
Prophase 2
Chromosomes remain in pair up and recondense
Nuclear envelope breaks down again
Spindle fibres reform
Centrioles move to opposite poles of the cell
Metaphase 2
Sister chromatids are aligned on the equator of the cell by the spindle fibres
Anaphase 2
Centromere divides
Sister chromatids are separated
Spindle fibres contract
Chromatids, now called chromosomes move to the poles of the cells
Telophase 2
Chromosomes uncoil and de condense.
Spindle fibres break down
Nuclear envelopes reform
Cell undergoes cytokines
Cytokines - meiosis
Cytoplasm and surface membrane divide
Creating 4 independent haploid daughter cells
Importance of cell cycle
Growth of tissue
Replacement of damaged cells
Repair of body tissue
Asexual reproduction- fungi
2 stages of cell cycle
Interphase: growth phase 1, synthesis , growth phases 2
M phase: mitosis, cytokines
Growth phase 1
Synthesis of proteins
Organelles replicate
Cell increases in size
Synthesis phase
Replication of each chromosomes in the nucleus
Growth phases 2
Cell continues to grow in size
Duplicated DNA is checked for errors
Energy stores are increased
Growth phase zero
Phase where the cell leaves the cell cycle ( resting)
If dna is damaged
Or is no longer able to divide
Problems if DNA is not checked
Mutation in DNA sequence
Daughter cells will not receive identical genetic information
Proteins not made or do not function properly
Prophase , mitosis
Chromosomes condense and thicken , becoming visible
Sister chromatids join at the centromere
2 centrioles migrate to opposite poles of the cell
Spindle fibres attach to specific areas on the centromeres and stat to move the sister chromatids to the equator of the cell
Nuclear envelope disappears
Metaphase mitosis
Pairs of chromatids are moved by the spindle fibres to align at the metaphase plate
Anaphase , mitosis
Centromeres holding the pairs of chromatids in each chromosome divide
Chromatids separate
Spindle contracts (fibres shorten)
Each chromatid is pulled by their centromere to opposite poles of the cell
Telophase mitosis
Chromatids have reach opposite poles of the cell, they uncoil
Chromsomes assemble at each pole
Nuclear envelope reforms and encloses around the chromosomes at each pole
Cytokines, mitosis
cleavage furrow ( animals ) , cell plate ( plants ) forms Results in 2 genetically identical daughter cells being formed
G1 checkpoint
End of growth phase one, and before synthesis
Checks that chemicals needed for replication are present
Checks for damage to DNA before entering synthesis phase
Cell size
Nutrients
Growth factors
G2 checkpoint
Cell size
DNA replication
DNA damage
How do fungus cells divide
Budding
Features found in mature plant cells that are not found in unspecialised cells
Nucleus cytoplasm cell wall
What features of the DNA molecules is changed due to mutation
Sequence of bases
Possible effects of mutation
shorter due to deflection/ stop codon
Longer due to duplication
What is meant by a homologous pair of Chromosomes
1 maternal one paternal Carry the same genes as their parents Carry different alleles Similar length Centromere in the same position Pair up in meiosis to form a bivalent
Interphase
DNA is replicated and checked for errors
Protien synthesis occurs
Mitochondria grow and divide, increasing in number
Chloroplast grow and divide in plant + algae
Normal metabolic processes of cells occur
Significance of meiosis
Formation of sex cells, gametes
Creates genetic variation
How does meiosis create genetic variation
Independent assortment of homologous chromosomes - metaphase 1
Crossing over of sister chromatids - anaphase 1
Independent assortment- metphase 2
Significance of meiosis
Formation of sex cells, gametes
Creates genetic variation
How does meiosis create genetic variation
Crossing over- part of each homologous chromosome switches (at points called chiasmata) as the are moved through the liquid cytoplasm, they entangle. This also causes mutation
Independent assortment- orientation and positions of homologous chromosomes is random along the metaphase plate
How to measure rate of mitosis
Dissect samples from different parts of plant then stain and view under light microscope and record how many cells are undergoing mitosis.
The parts with more mitosis have a faster rate of growth
M checkpoint
Checks sister chromatids are attached to spindle fibres
