Cell continuity Flashcards
cell continuity
existing cells divide and produce new cells
genome
all the genetic material in an organism
where is most of the DNA in the cell found
in the nucleus
how is DNA organised
into structures called chromosomes
Chromosomes
thread like structures in the nucleus
what are chromosomes composed of
DNA and protein
carry thousands of genes
in a non-dividing cell, describe the chromosomes
uncoiled and form a tangled mass called chromatin
when a cell is dividing, describe the chromosomes
they contract and thicken
haploid cell
has one set of chromosomes
– one of each type of chromosomes
diploid cell
has two sets of chromosmes
– two of each type of chromosme
n represents
haploid cell
2n represents
diploid cell
what describes the sequence of events in a dividing cell
the cell cycle
interphase
the non-dividing cell
what happens to the cell during interphase
it grows and increases in size
what do cells make during interphase
proteins, lipids
what happens to during organelles interphase
they are replicated
- mitochondria
- chloroplasts
- ribosomes
what happens to the DNA during interphase 2
it uncoils
it makes a copy of itself
what hold the identical chromosomes together
a centromere
what happens to the nucleus during division
it divides (mitosis)
what happens to the cytoplasm during division
it divides (cellular division)
all body cells in organisms of the same species have
the same number of chromosmes
during growth and cell multiplication, what must be kept constant
the number of chromosomes per cell must be kept constant
what does mitosis produce
2 identical daughter cells
explain how the 2 daughter cells are identical
the same number and same type of chromosomes
what cells can divide by mitosis
haploid and diploid cells
4 stages of mitosis in order
prophase, metaphase, anaphase and telophase
when does interphase occur
between miotic divisions
describe chromosomes during interphase
uncoiled and not visible
3 things that happen during interphase
DNA replicates
molecules are synthesised
organelles are replicated
DNA replicating
an identical copy of each chromosome is made
what has happened by the end of interphase? 3
the chromosomes will have duplicated and begin to become visble
spindle fibres will be forming
the nuclear membrane will be breaking down
describe the chromosomes during prophase
they become shorter and visible as threads
each chromosome has replicated to make two identical chromosomes joined at the centromere
spindle during prophase
the spindle forms
nucleus during prophase
nuclear membrane breams down
chromosome during metaphase
chromosmes line up on the equator of the cell
centomeres during metaphase
centromeres are attached to spindle fibres frome each side of the cell
3 steps of anaphase
centromeres split
spindle fibres contract
identical chromosomes separate and are pulled to opposite poles of the cell
3 steps of telophase
chromosomes uncoil and begin to revert to chromatin
nuclear membranes form
nuclei are formed
what is cytoplasm divided by in an animal cell
a cleavage furrow forming along the equator
cell is pinched in two
what do separates the cytoplasm in a plant cell
divided by a cell plate forming across the middle of the cell
cell membranes and cell walls are formed on each side of the plate
2 results of mitosis
2 identical daughter cells
chromosome number is kept constant (have the same number as the parent)
genetic information in daughter cells in mitosis
identical genetic material and information passes into each new cell
role of mitosis in unicellular organisms
reproduction
3 roles of mitosis in multicellular organisms
growth
replacement of cells
repair of tissues
location of mitosis in plants
root tips, shoot tips, meristems, buds
location of mitosis in animals
skin (epithelium), bone marrow
what does meisois mean?
reduction divison
2 results of meiosis
a diploid nucleus divides by meiosis to form 4 daughter cells with half the number of chromosomes present inthe parent cells
the daughter cells are genetically different
what are gametes
haploid cells that can fuse (sex cells)
what are special about the gamete nuclei
they have half the number of chromosomes present in the parent nuclei
what does meiosis produce
haploid gametes
2 roles of meiosis
sexual reproduction
genetic variation
what happens to genes during meiosis
genes are separated producing ddifferent arrangements every time
how does meiosis produce genetic variation
daughter cells are always different
2 locations of meiosis in animals
testis//ovary
2 locations o meiosis in plants
anther//ovule
2 characteristics of mitosis that are different meiosis
number of chromosomes stays constant
daughter cells are identical
2 characteristics of meiosis that are different mitosis
number of chromosomes is halved
daughter cells are different
definition of cancer
a group of disorders of the body in which cells lose the normal control of mitosis
benign tumours
do not move and invade
malignant tumours
spread and can be life threataning
metastisis
the spread of cancer
mutations
can change normal cells into cancer cells
what is cancer caused by?
mutagens
5 mutagens
radiation chemicals cigarette smoke asbestos some viruses