cell division Flashcards
what are the 3 stages in the interphase?
GAP PHASE 1
SYNTHESIS
GAP PHASE 2
what is the M phase?
Mitosis and cytokinesis
what is the gap phase 1
when the cell grows and new organelles and proteins are made
what is gap phase 2
cell keeps growing and proteins needed for division are made
what is synthesis
cell replicates its dna ready to divide by mitosis
in which stage does the g1 checkpoint occur
in the gap phase 1
in which stage does the g2 checkpoint occur
gap phase 2
what happens in the g1 checkpoint?
cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering the s phase
what happens in the g2 checkpoint?
cell checks whether all the DNA has been replicated without any damage
what occurs in the interphase?
the cells DNA is unravelled and replicated. the organelles are also replicated, ATP content is increased
what occurs in the prophase?
chromosomes condense, centrioles move to the opposite ends of the cell forming a spindle of protein fibres, nuclear envelope breaks down
what occurs in the metaphase?
chromosomes line up along the middle of the cell and become attached to the spindle by their centromere
what occurs in the anaphase?
centromeres divide, separating each pair of sister chromatids. the spindles contract pulling chromatids to the opposite ends of the cell
what occurs in the telophase?
The chromatids reach the opposite poles on the spindle, uncoil and become long and thin, they are now chromosomes. a nuclear envelope forms around each group of chromosomes
what occurs in cytokinesis?
a cleavage furrow forms to divide the cell membrane, cytoplasm divides
usually begins in anaphase and ends in telophase
what is the outcome of mitosis
2 genetically identical daughter cells are formed
define meiosis
production of gametes for sexual reproduction, all cells formed are genetically different to each other
how chromosomes do humans have?
46 chromosomes
what are homologous pairs of chromosomes?
have the same size and the same genes although they can have different version of those genes (alleles)
what happens in meiosis 1, prophase 1?
chromosomes condense
chromosomes arrange themselves in homologous pairs
centrioles move to opposite ends of cell
spindle fibres form
nuclear envelope breaks down
what happens in meiosis 1, metaphase 1?
homologous pairs line up across the centre of the cell and attach to the spindle fibres by their centromeres
what happens in meiosis 1, anaphase 1?
spindles contract separating homologous pairs, one chromosome to each end of cell
what happens in meiosis 1, telophase 1?
nuclear envelope forms, around each group of chromosomes, cytokinesis occurs and 2 haploid daughter cells are produced.
what happens in meiosis 2, anaphase 2?
pairs of sister chromatids are separated, each new daughter cell inherits one chromatid from each chromosome.
4 genetically identical haploid daughter cells are produced. these are the gametes
what are 2 events in meiosis that lead to genetic variation?
crossing over of chromatids
independent assortment of chromosomes
in which stage of meiosis does crossing over of chromatids occur?
meiosis 1, prophase 1
in which stage of meiosis does independent assortment of chromosomes occur?
metaphase 1 and prophase 1
what are stem cells?
unspecialised cells
where in humans are stem cells found?
early embryos and bone marrow
why is it better to have stem cells from early embryos rather than the bone marrow?
as they can develop into any type of cell whereas in adults it can only develop into a limited range of cells
what do cells in the bone marrow differentiate into?
bloods cells, erythrocytes RBC and neutrophils WBC
what do cells in meristems differentiate into?
xylem and phloem
how might stem cells be used to treat Parkinson’s disease?
the disease causes a loss of a type of nerve cell in the brain, these cells release a chemical called dopamine which is needed to control movement, transplanted stem cells may help to regenerate the dopamine producing cells
how does neutrophils structure help them perform their function?
they have flexible shape which allows them to engulf foreign particles
they have many lysosomes in their cytoplasm which contain digestive enzymes to break down engulfed particles
how does erythrocytes structure help them perform their function?
have a biconcave disc shape which gives a large surface area for gas exchange
no nucleus so more room for haemoglobin
how does epithelial cells structure help them perform their function?
ciliated epithelia (AIRWAY) have cilia that beat to move particles away
squamous epithelia (LUNGS) are very thin to allow efficient diffusion of gases.
how does sperm cells structure help them perform their function?
have a flagellum, so they can swim to the egg
lots of mitochondria to provide energy to swim
the acrosome contains digestive enzymes to enable sperm to penetrate the surface of the egg.
how does palisade mesophyll cells structure help them perform their function?
many chloroplasts for photosynthesis, absorb a lot of sunlight
thin walls so co2 can diffuse into the cell
how does root hair cells structure help them perform their function?
large surface area for absorption of mineral ions and water from soil
thin permeable cell wall for entry of water and ions
cytoplasm contains extra mitochondria to provide energy needed for active transport
how does guard cells structure help them perform their function?
thin outer walls and thickened inner walls force them to bend outwards opening the stomata allowing the leaf to exchange gases for photosynthesis
what is a tissue?
a group of cells that are specialised to work together to carry out a particular function, a tissue can contain more than one type of cell
name 2 examples of animal tissues
muscle tissue and cartilage
name 2 types of plant tissues
xylem tissue and phloem tissue
what is an organ?
is a group of different tissues that work together to perform a particular function
what is a example of an organ?
the lungs have squamous epithelial tissues, ciliated epithelia tissue and vascular and elastic connective tissue.
what is an organ system?
organs that work together to make up an organ system, each system has a particular function
what are 2 examples of an organ system?
the respiratory system
the circulatory system
