cell cycle Flashcards
what is G1
growth of cytoplasm and cell membrane. protein synthesis, organelles replicated
what is G0
many cells stop dividing once they have specialised to their roles
what is S phase
DNA replication
what is G2
growth and preparation for mitosis
what is mitosis the division of
nucleus
what is cytokinesis
division of the cytoplasm
what makes stem cells different from normal body cells
they are not specific, have no jobs and have the potential to become any cell (differentiate)
what is the potency of a stem cell
the ability to turn into other cells
where is a totipotent stem cell found
a zygote - fertilised egg cell, and first few cells of the embryo
what can totipotent stem cells differentiate into
any cell type, including the ability to make a complete human
where is a pluripotent stem cell found
cells from an embryo
what can pluripotent stem cell differentiate into
any type of cell, not a whole organism though
where is a multipotent stem cell found
cells from the umbilical cord, bone marrow and other adult body tisses
what can a multipotent stem cell differentiate into
a few different types of cells, such as different types of bone and blood cells
where are chromosomes found in a cell
nucleus
what are chromosomes made of
DNA and histomeproteins
why are chromosomes important
carry DNA and the genetic code
what are the chromosomes in a human nucleus arranged in pairs called
homologous pairs
how many homologous pairs of chromosomes are their in a human
23 pairs or 46 single chromosomes
what is a diploid cell
contains 2 copies of every chromosome in homologous pairs, one is paternal and the other is maternal
what is a haploid cell
contain 1 copy of each chromosome, no homologous pairs and the only haploid cell are the gametes
what are the stages of mitosis
interphase
prophase
metaphase
anaphase
telophase + cytokinesis
what happens in interphase of mitosis
DNA is duplicated, diploid at this stage
what happens in prophase of mitosis
chromosomes become visible, centrioles start to make the spindle, nuclear membrane breaks down
what happens in metaphase of mitosis
the chromosomes move to the equator of the cell. each chromatid is attached at the centromere to the spindle fibres made by the centrioles
what happens during the anaphase of mitosis
centromeres are pulled apart by the spindle fibres, chromatids are pulled to opposite poles of the cell
what happens during telophase of mitosis
the separated chromosomes uncoil, 2 new nuclei start to reform and this stage is followed by cytokinesis
how to work out the mitotic index
number of cells in mitosis/total number of cells
where does meiosis take place
reproductive organs to produce sex cells known as gametes
how many divisions are there is meiosis
2
what happens in interphase of meiosis
DNA is replicating and the chromosomes are not visible
what happens in prophase 1 of meiosis
the chromosomes become visible, made up of two sister chromatids attached at the centre of the centrome, the homologous pairs line up next to each other mixing the DNA - crossing over, at the end of prophase the chromosomes are shorter and the nuclear membrane disintegrates, spindle fibres are then formed and attach to the centromeres.
what happens in metaphase 1 in meiosis
the homologous pairs line up along the equator of the cell, random orientation of the chromosomes occur - line up randomly
what happens in anaphase 1 of meiosis
the homologous pairs begin to separate, each chromosome in a pair migrates to opposite poles, chromosomes still consist of two chromatids held together by their centrosomes - disjunction
what happens in telophase 1 in meiosis
the chromosomes reaches the opposite poles, a nuclear membrane forms around the chromosomes, each cell is a haploid - half the number of normal chromosomes.
what happens in prophase 2 of meiosis
the chromosomes condense and the spindle fibres appear and attach to the centromere, the nuclear membrane breaks down
what happens in metaphase 2 of meiosis
the chromosomes line up at the equator
what happens in anaphase 2 of meiosis
the centromeres splitting and the chromatids are pulled by the spindle fibres towards the opposite poles
what happens in telophase 2 of meiosis
new nuclear membranes reforms, each cell is haploid - half
the net result of meiosis is the production of 4 cells from 1 cell
each cell only containing one set of chromosomes which is half of original
which events in meiosis ensure that siblings end up with different combinations of their parents DNA
prophase 1 - crossing over
metaphase 1 - independent assortment of homologous pairs
