cell division Flashcards
The cell cycle has three phases what are they
interphase, mitosis(nuclear division), cell division (cytokinesis)
what happens during interphase
During Interphase the cell increases in mass and size and carries out its normal cellular functions (eg. synthesising proteins and replicating its DNA ready for mitosis)
what are the 3 phases of interphase
G1 phase, S-phase, G2 phase
what happens during G1
Cell grows and receives a signal to divide,
what happens during S-phase
Synthesis of new DNA, DNA replicate in nucleus( resulting in each chromosome consisting of 2 identical sister chromatids)
what happens during G2 phase
Further cell growth
Error checking of newly synthesised DNA
in mitosis the movement from one phase to another is triggered by chemical signals is called what
cyclins
what occurs after interphrase
nuclear division- mitosis- referred to as the m phase, cell growth stops
what happens after mitosis
cytokenisis- cell split into 2 identical individual cells
how is DNA stored
DNA is stored as chromosomes
what are chromosmes
thread like structure which constist of DNA tightly coiled around proteins called histone proteins.
how much chrosomes do the human haves
46 chromosmes- 23 pairs
what is a homologous pair
a chromosome inherited from paternal and one chromosome inherited from maternal
what is a chromotid
a half of a chromosome- sister chromotid
what is a chromotid in a chromosome held together by
a centomere
what are diploid cells
a complete double set of a chromosome
what are haploids
a single set of chromosomes
what is cancer
uncontrollable cell division- mitosis
what does cancer lead to
tumours- irregular mass of cells
how do cancer start
when changes occur in the genes that control cell division
what are the 2 types of cancer
benign and malignant
what are benign tumours
they do not spread from their original site- don’t cause cancer- often in a capsule
what are malignant tumours
cancer that burst from its capsule and spread to rest of body destroying and invading other tissues- spread from site of origin
how does malignant tumours spread
via the bloodstream or lymphatic system
what does malignant tumours interfere with
normal function of the organ.
what is metastasis
spreading of cancer- malignant
how do most cancer treatment stop cancer
they control the rate of mitosis.
what do most people who have cancer posses.
the p53 gene.
what is mitosis
when the nucleus divides- type of cell division which produces 2 identical daughter cells.
what does mitosis do
increase the number of cells during growth
does the daughter cells have the same exact DNA as the parent cell
yes
what are 3 importances of mitosis
growth, repair and for asexual reproduction
how many stages does mitosis have and what are they
4- prophase, metaphase, anaphase,telophase
what happens during prophase
chromosomes condense and become thicker and are now visible under a microscope. Centrioles seperate and move to opposite poles of cell. Each centriole forms spindle fibres. Chromotin condenses into chromosomes and the nucleolus disappears- chromosomes free in cytoplasm.
what are centrioles
bundles of proteins
what is metaphase
longest phase of mitosis- there is no longer a nucleus- chromosomes line up along the equator of the cell-Each chromosome attaches to the spindle by their centromere and chromotid.
what is anaphase
The centromeres divide to separate each pair of sister chromatids. -The spindle fibres contract and shorten to pull the chromatids to opposite poles of the cell. -Each chromatid is pulled by its centromere.
what happens in telophase
The chromatids reach the opposite poles of the cell where they uncoil to become long and thin chromosomes again. -A nuclear envelope forms around each set of chromosomes to form two nuclei and the nucleolus starts to reform.
what type of cells don’t divide
specialised cells once they differentiate from stem cells.
why can’t neurones divide
they lack centrioles- cannot divide- also division would lead to loss of memories and connection.
why can’t red blood cells divide
they lack a nucleus and other organelles need for division to maximise haemoglobin. They must be continually produced from stem cells.
how many chromotids may a chromosome have
1 or 2 depending on the cell cycle.
what type of cells are involved in meoisis
gamete cells- sexula reproduction
how many nuclear divisions does it have and what are they called
2- meiosis 1 and meiosis 2
what is the significance of meiosis
it increases variation by combing the genetic variation of 2 organisms by a process of random fertlisation
