The Cell Cycle Flashcards
What is the cell cycle?
The cell cycle is the process that all body cells in multicellular organisms use to grow and divide.
What is step 1 of the cell cycle?
1) The cell cycle starts when a cell has been
produced by cell division and ends with the
cell dividing to produce two identical cells.
What is step 2 of the cell cycle?
2) The cell cycle consists of a period of cell
growth and DNA replication, called
interphase, and a period of cell division,
called M phase. M phase involves mitosis
(nuclear division) and cytokinesis
(cytoplasmic division).
What is step 3 of the cell cycle?
3) Interphase (cell growth) is subdivided
into three separate growth stages.
These are called G1 , S and G2
What is step 4 of the cell cycle?
4) The cell cycle is regulated by checkpoints.
Checkpoints occur at key points during the
cycle to make sure it’s OK for the process
to continue.
What is the g1 phase
G1 checkpoint The cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S-phase.
What’s S phase
Synthesis phase
SYNTHESIS
cell replicates its DNA, ready to divide by mitosis
DNA replication
Each chromosome becomes two identical copies (chromatids)
Whats the G2 phase
Second growth phase
G2 Checkpoint
The cell checks whether all the DNA has been replicated
without any damage. If it has,the cell can enter mitosis.
Growth of the cell
stores are increased
Duplicates DNA is checker for errors
Why do cells leave the cell cycle 1 differentiation
When a cell becomes specialised to carry a particular function it will leave the cell cycle
Why do cells leave the cell cycle 2
DNA may be damaged
Why do cells leave the cell cycle 3
Cells only dived a limited number of times then become senescent with age the number of these cells in the body increases
Why is mitosis important?
Tissue growth
Tissue repair replacement of damaged or worn out cells
Asexual reproduction
What’s asexual reproduction
Genetically identical offspring from one parent in multicellular organisms
What are chromosomes converted to in DNA replication
Genetically identical DNA molecules known as chromatids
As mitosis begins, the chromosomes are made of two strands joined in the middle by a?
The separate strands are called?
As mitosis begins, the chromosomes are made of two strands joined in the middle by a centromere. The separate strands are called chromatids.
Why are there two strands?
There are two strands because each chromosome has already made an identical copy of itself during interphase. When mitosis is over, the chromatids end up as one-strand chromosomes in the new daughter cells.
Where do spindle fibres attach to move chromatids around the cell
Centromere
What’s mitosis divided into
Prophase
Metaphase
Anaphase
Telophase
What is IPMAT
Interphase Prophase Metaphase Anaphase Telophase
Whats interphase?
Interphase comes before mitosis in the cell cycle. It’s when cells grow and replicate their DNA ready for division.-Interphase —
The cell carries out normal functions,
but also prepares to divide. The cell’s DNA is
unravelled and replicated, to double its genetic
content. The organelles are also replicated so it
has spare ones, and its ATP content is increased
(ATP provides the energy needed for cell division).
What’s prophase
Prophase — The chromosomes condense, getting shorter and fatter. Tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle. The nuclear envelope (the membrane around the nucleus) breaks down and chromosomes lie free in the cytoplasm.
What’s metaphase
Metaphase — The chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere. At the metaphase checkpoint, the cell checks that all the chromosomes are attached to the spindle before mitosis can continue.
What is anaphase
3) Anaphase — The centromeres divide,
separating each pair of sister chromatids.
The spindles contract, pulling chromatids
to opposite ends of the cell, centromere first.
What is telophase
4) Telophase — The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They’re now called chromosomes again. A nuclear envelope forms around each group of chromosomes, so there are now two nuclei.
Cytokinesis definition
Cytokinesis — The cytoplasm divides. In animal cells, a cleavage furrow forms to divide the cell membrane. There are now two daughter cells that are genetically identical to the original cell and to each other. Cytokinesis usually begins in anaphase and ends in telophase. It’s a separate process to mitosis.
Cytokinesis In animal cells
Cleavage furrow forms around the middle of the cell. The cell surface membrane is pulled inwards by the cytoskeleton until it’s close enough to fuse around the middle forming two cells.
Cytokinesis in plant cells.
Plants have a cell wall so it’s not possible for a cleavage furrow to form. Vesicles from the Golgi apparatus begin to assemble in the same place as where the metaphase plate was formed the vesicles fuse with each other dividing the cell into two
How to observe the cell cycle and mitosis by staining chromosomes?
You can stain chromosomes so you can see
them under a microscope. This means you can
watch what happens to them during mitosis —
and it makes high-adrenaline viewing, I can tell
you. These are some plant root cells shown
under a light microscope at different stages of
the cell cycle and mitosis. You need to be able
to recognise, draw and label each stage.
What happens in sexual reproduction?
1) In sexual reproduction two gametes (an egg and a sperm) join together at fertilisation to form
a zygote. The zygote then divides and develops into a new organism.
What is meiosis?
What does it involve?
Cells formed by meiosis are all genetically different because?
2) Meiosis is a type of cell division that happens in the reproductive organs to produce gametes.
3) Meiosis involves a reduction division. Cells that divide by meiosis have the full number of
chromosomes to start with, but the cells that are formed from meiosis have half the number.
Cells with half the normal number of chromosomes are called haploid cells.
4) Cells formed by meiosis are all genetically different because each
new cell ends up with a different combination of chromosomes.
How many gametes does meiosis produce.
Meiosis produces 4 gametes, each is haploid and are all genetically
different