Topic 1 - The cell cycle Flashcards
what is mitosis
the process by which a cell divides to produce 2 genetically identical daughter cells
what is meiosis
a form of cell division in which the chromosome number of the original cell is halved, leading to the formation of the gametes
what is asexual reproduction
the production of genetically identical offspring from a single parent ot organism
what is sexual reproduction
the production of offspring that are genetically different from the parent organisms by the fusing of 2 gametes
what are histones
positively charged proteins involved in the coiling of DNA to form dense chromosomes in cell division
what are nucleosomes
dense clusters of DNA wound around histones
what is a karyotype
a way of displaying an image of the chromosomes of a cell to show the pairs of autosomes and sex hormones
what is the cell cycle
a regulated process of 3 stages (interphase, mitosis, cytokinesis) in which cells divide into 2 genetically identical daughter cells
what is interphase
the period between active cell division when cells increase in size and mass, replicate their DNA and carry out normal metabolic activities
what is a chromatid
one strand of the replicated chromosome pair that is joined to the other chromatid at the centromere
what are cyclins
small proteins that build up during interphase and are involved in the control of the cell cycle by their attachment to cycle-dependent kinases
what are Cyclin-dependent kinases (CDKs)
enzymes involved in the control of the cell cycle by phosphorylating other proteins, activated by attachment to cyclins
what is DNA made up of
a mass of coiled threads of DNA and proteins
when the cell is not actively dividing, what colour are the chromosomes
translucent
when the cell is actively dividing, why do the chromosomes take up the stain
the chromosomes condense by becoming shorter and denser
how is a chromosome coiled up efficiently
the DNA winds around the histones to form a nucleosome. These then interact to produce more coiling and supercoiling to form dense chromosome structures
how many chromosomes do humans have
46
how many pairs of chromosomes do humans have
23
when does G1 (gap 1) happen in the cell cycle
the time between, the end of the previous round of mitotic cell division and the start of chromosome duplication
what happens in G1 (gap 1)
- the cell increases in size as it produces necessary components for mitotic cell division
- All of the organelles duplicate
- The cell carries out normal metabolic cell division
- the cell checks for sufficient nutrition & energy reserves, proper growth and absence of DNA damage
what happens in S
- Each chromosome is copied to form two identical sister chromatids held together by a centromere
- Histones are synthesized and incorporated into newly formed DNA
- The centrosome is also duplicated
what happens in G2 (gap 2)
- tubulin is produced for the synthesis of spindle fibres
- any errors in the replicated DNA are corrected to prevent mutations
- The cell checks that the DNA has been replicated, it is undamaged, and if the cell is large enough
what happens during M (mitosis) in the cell cycle
the cells are actively dividing
what happens during C (cytokinesis) in the cell cycle
the new cells seperate
when does the cell cycle slow down or stop in multicellular organisms
when the organism is mature
what is the cell cycle controlled by
a number of chemical signals made in response to different genes
how are the chemicals that control the cell cycle controlled
proteins called cyclins build up and attach to enzymes called CDKs. The cyclin/CDK complex formed phosphorylates other proteins, changing their shape and bringing about the nexts stage in the cell cycle
