Lesson 1 - The cell cycle Flashcards
(22 cards)
meaning mitosis
the process by which a cell divides to produce 2 genetically identical daughter cells
meaning asexual reproduction
the production of genetically identical offspring from a single parent or organism
meaning sexual reproduction
the production of offspring that are genetically different from the parent organisms by the fusion of the 2 gametes
meaning meiosis
a form of cell division in which the chromosome number of the original cell is halved, leading to the formation of the gametes
meaning histones
positively charged proteins involved in the coiling of DNA to form dense chromosomes in cell division
meaning nucleosomes
dense clusters of DNA wound around histones
meaning karyotype
a way of displaying an image of the chromosomes of a cell to show the pairs of autosomes and sex chromosomes
meaning cell cycle
a regulating process of 3 stages: interphase, mitosis and cytokinesis: in which cells divide into 2 genetically identical daughter cells
meaning interphase
the period between active cell divisions when cells increase their size and mass, replicate their DNA and carry out metabolic activities
meaning chromatid
one strand of the replicated chromosome pair that is joined to the other chromatid at the centromere
meaning cyclins
small proteins that build up during interphase and are involved in the control of the cell cycle by their attachment to cyclin-dependent kinases
meaning cyclin-dependent kinases (CDKs)
enzymes involved in the control of the cell cycle by phosphorylating other proteins, activated by attachment to cyclins
why are chromosomes inside cells visible when actively dividing, translucent when not
when the cell starts actively dividing, the chromosomes condense, as they become shorter and denser. Thus, they take up the stains readily
when DNA condenses, how are they packaged efficiently
the DNA winds around the histones to form nucleosomes. These then interact to produce more coiling and supercoiling to form dense chromosome structures
how many chromosomes do human cells possess
46
what are the 5 stages of the cell cycle
- Gap 1
- S
- Gap 2
- Mitosis
- Cytokineses
what happens during Gap 1
The cell assimilates material, grows and develops
what happens during the S stage
the chromosomes replicate and become double stranded chromatids, ready for cell division
what happens during Gap 2
the organelles and other materials needed for cell division are synthesised, and all of the organelles replicate
in multicellular organisms, when does mitosis slow down or stop
once the organism is mature
how is the cell cycle controlled
by a number of chemical signals made in response to different genes. This control is brought a number of checkpoints where the cell cycle moves from one phase to the next
how is the next stage of the cell cycle brought about
control chemicals called cyclins attach to enzymes called CDKs, forming a cycling/CDK complex. This complex phosphorylates other proteins, changing their shape
