3B Cell Cycle, Fertilisation Flashcards
cell cycle
a regulated process of three stages (interphase, mitosis and cytokinesis) in which cells divide into two genetically identical daughter cells
interphase
the period between active cell divisions when cells increase their size and mass, replicate their DNA and carry out normal metabolic activities
mitosis
the process by which a cell divides to produce tow genetically identical daughter cells
meiosis
a form of cell division in which the chromosome number of the original cell is halved, leading to the formation of the gametes
asexual reproduction
the production of genetically identical offspring form a single parent or organism
histones
positively charged proteins involved in the coiling of DNA to form dense chromosomes in cell division
nucleosomes
dense clusters of DNA wound around histones
karyotype
a way of displaying an image of the chromosomes of a cell to show the pairs of autosomes and sex chromosomes
chromatid
one strand of the replicated chromosome pair that is joined to the other chromatid at the centromere
cyclins
small proteins that build up during interphase and are involved in the control of the cell cycle by phosphorylating other proteins, activated by attachment to cyclins
cyclin - dependent kinases CDKs
enzymes involved in the control of the cell cycle by phosphorylating other proteins, activated by attachment to cyclins
prophase
- the first stage of active cell division
- the chromosomes are coiled up and consist of two daughter chromatids joined by the centromere
- the nucleolus breaks down
metaphase
- the second stage of active cell division
- a spindle of overlapping protein microtubules forms
- the chromatids line up on the metaphase plate
centromere
the region where a pair of chromatids are joined and which attaches to a single strand of the spindle structure at metaphase
telophase
- fourth stage of active cell division
- a nuclear membrane forms around the two sets of chromosomes
- the chromosome
clones
genetically identical individuals resulting from asexual reproduction in a single parent
mitotic index
the ratio between the number of cells in a tissue sample that are in mitosis and the total number of cells in the sample
diploid (2n)
a cell with a nucleus containing two full sets of chromosomes
haploid (n)
a cell with a nucleus containing one complete set of chromosomes
zygote
the cell formed when two haploid gametes fuse at fertilisation
gonads
the sex organs in animals
ovaries
the female sex organs in both animals and plants; they produce the female gametes called ovules in plants and ova in animals
pollen
the spore which contains the haploid male gametes of plants
testes
the male sex organs in animals that produce the male gametes
- sperm
spermatozoa (sperm)
the haploid male gametes in animals
ova
the haploid female gametes in animals (singular = ovum)
microspores
the result of meiosis in plants that develop into the spore (pollen) containing the male gametes
microspores
the result of meiosis in plants that develop into the spore (pollen) containing the male gametes
megaspores
the result of meiosis in plants that develop into the female gametes, ovules
homologous pairs
matching pairs of chromosomes in an individual which both carry the same genes, although they may have different alleles
crossing over (recombination)
the process by which large multi-enzyme complexes cut and re-join parts of the maternal and paternal chromatids at the end of prophase I, introducing genetic variation
chiasmata
the points where the chromatids break during recombination
mutation
a permanent change in the DNA of an organism
independent assortment (random assortment)
the process by which the chromosomes derived from the male and female parent are distributed into the gametes at random
independent assortment (random assortment)
the process by which the chromosomes derived from the male and female parent are distributed into the gametes at random
gametogenesis
the formation of the gametes by meiosis in the sex organs
oocyte
a cell in an ovary which may form an ovum if it undergoes meiotic division
acrosome
the region at the head of the sperm that contains enzymes to break down the protective layers around the ovum
zona pellucida
a layer of protective jelly around the unfertilised ovum
sporophyte generation
the diploid generation in plants that produces spores by meiosis
gametophyte generation
the haploid generation in plants that gives rise to the gametes by mitosis
gametophyte generation
the haploid generation in plants that gives rise to the gametes by mitosis
sporophyte
the diploid main body of the plant
microgametes
the male gametes produced in plants, the pollen grains
tube nucleus
the male nucleus that will control the production of the pollen tube in fertilisation
tube nucleus
the male nucleus that will control the production of the pollen tube in fertilisation
generative nucleus
the male nucleus that will fuse with the female nucleus
pollen tube
a tube that grows out of a pollen grain down the style, into the ovary and through the micropyle of the ovule to carry the generative nucleus (which divides to form two male nuclei) to the ovule
pollen tube
a tube that grows out of a pollen grain down the style, into the ovary and through the micropyle of the ovule to carry the generative nucleus (which divides to form two male nuclei) to the ovule
placenta (plant)
the pad of special tissue that attaches the plant ovule to the ovary wall
megagamete
the female gamete, the egg cell, in plants
ovules
the haploid female gametes in plants
anthers
male sex organs in plants that produce the male gametes contained in the pollen
polyploidy
a cell or an organism with more than two sets of chromosomes
fertilisation
the fusing of the haploid nuclei from two gametes to forma diploid zygote in sexual reproduciton
metaphase plate (equator)
the region of the spindle in the middle of the cell along which the chromatids line up
anaphase
- third stage of active cell division
- the centromeres split so chromatids become new chromosomes; they are moved to the opposite poles of the cell, centromere first, by contractions of the microtubules of the spindle
sexual reproduction
the production of offspring that are genetically different from the parent organism or organisms by the fusing of two sex cells
cytokinesis
the final stage of the cell cycle before the cell enters interphase again - division of the cytoplasm at the end of mitosis to form tow independent, genetically identical cells
