Module 2 Section: 6 - Cell division Flashcards
What are the 3 phases of interphase?
2 phases of mitosis and explain what happens?
Interphase:
- growth phase 1
- synthesis
- growth phase 2
Mitotic phase:
- mitosis= nucleus divides
- cytokinesis= cytoplasm divides & 2 daughter cells produced
What is G0? Why might a cell enter G0?
The resting phase, in which the cell leaves the cycle temporarily or permanently
When a cell is specialized it no longer needs to divide, hence entering G0
Which cells DON’T divide?
DNA damaged cells and senescent cells
What happens at each checkpoint of the cell cycle? (3)
G1 checkpoint checks for:
cell size, nutrients, growth factors, DNA damage
G2 checkpoint checks for:
cell size, DNA replication, DNA error
Spindle assembly checkpoint checks for:
all chromosomes attached to spindles and being aligned
What happens at G1 phase?
- proteins synthesised
- organelles replicated
- cell enlarges
What happens at synthesis phase?
- DNA replicated
What happens at G2 phase?
- energy stores are increased
- DNA checked for errors
- cell enlarges
what are the uses of mitosis
-growth
-repair
-asexual reproduction
-Production of new stem cells
what are the 4 division stages of mitosis in order
-prophase
-metaphase
-anaphase
-telophase
what happens in prophase
-chromosomes condense and become visible
-nuclear envelope breaks down
-nucleolus disappears
-centrioles move to opposite poles and release spindle fibres
what are the parts of the chromosomes called and where are they in the chromosome
- the separate strands are called chromatids
-the middle part that joins the strands together is called the centromere
what happens in metaphase
-chromosomes line up on the metaphase plate (equator)
-spindle fibres attach to centromere
what happens during the anaphase
-centromeres divide separating each pair of sister chromatids
-spindle fibres contract pulling the chromatids to opposite poles
what happens during telophase
-chromosomes begin to grow and become longer and thinner
-spindle fibres begin to disintegrate
-nucleus reforms
-cytoplasm splits(cytokinesis)
what does meiosis produce
gametes
what are all the stages of mitosis and in order
-prophase I
-Metaphase I
-Anaphase I
-Telophase I
-Prophase II
-Metaphase II
-Anaphase II
-Telophase II
what happens in Prophase I
-Chromosomes condense and become visible as sister chromatids
-nuclear envelope breaks down
-nucleolus disintegrates
-Homologous Chromosomes pair up and crossing over occurs
-Centrioles migrate to opposite poles and start to make spindle fibres
what are homologous chromosomes
are pairs of chromosomes that have the same genes but possibly different versions (called alleles) of those genes.
what is crossing over
where homologous chromosomes (the ones from your mother and father) swap some of their genetic material. This creates new combinations of genes.
What happens during crossing over in meiosis?
During crossing over, homologous chromosomes (chromosomes from both parents) line up next to each other in prophase I of meiosis. They exchange genetic material by swapping sections of their chromatids. This creates new combinations of genes, leading to genetic variation in offspring.
what happens in meta phase I
-Homologous Chromosomes align at the metaphase plate
-Independent assortment occurs
-spindle fibres attach to sister chromatid centromere
what is independent assortment
how chromosomes are randomly distributed to gametes
what is the process of independent assortment (answer from marksheet)
-(homologous
chromosomes) line up,
across the centre of the cell
on the equator / on the
metaphase plate
- maternal or paternal
chromosomes / either one
of the homologous pair,
can end up, facing either
pole / in either (daughter) cell
what is a sister chromatid
two identical copies of a single chromosome formed during DNA replication
what is the Chiasmata
point where crossing over occurs
what occurs in anaphase I
Spindle fibre contract and Homologous Chromosomes separate and move to opposite sides of the cell
What happens in Telophase I
-nuclear envelope reforms
-spindle fibres breakdown
-cytokinesis
What happens in Prophase II
-nuclear envelope breaks down
-Chromosomes condense and become visible
-Centrioles move to opposite poles and release spindle fibres
what happens in metaphase II
-Chromosomes line up on the metaphase plate
-Spindle fibres attach to the centromeres
what happens in anaphase II
-Spindle fibres attach back to centromere causing the centromere to divide and chromatids to go to each pole
what happens in telophase II
-Chromosomes start to grow and become longer and thinner
-spindle fibres begin to disintegrate
-Cytoplasm reforms
what 2 events in meiosis lead to genetic variation
-crossing over and Independent assortment
what are senescent cells
cells that have stopped dividing and have reached a stage of permanent growth but don’t die
what is a stem cell
undifferentiated cells which have the potential to differentiate into a range of specialised cell types
what do stem cells in bone marrow differentiate into
blood cells
What do stem cells in the meristem differentiate into
xylem and phloem
How could stem cells cure Alzheimer’s
as with Alzheimer’s nerve cells in the brain die causing memory loss, researchers are hoping to use stem cells to regrow healthy nerves
How could stem cells cure Parkinson’s
as people with Parkinson’s suffer from tremors they cannot control and the disease causes the loss of a particular type of nerve cell that releases dopamine and stem cells could help regenerate dopamine-producing cells
what is the structure and function of neutrophils
f: a type of white blood cell that defends the body against disease
s: flexible shape to engulf foreign particles, many lysosomes to break down engulfed particles
what is the structure and function of erythrocytes
f: red blood cells that carry oxygen in the blood
s: biconcave disc provides large surface area, no nucleus so more space for haemoglobin,
what is the structure and function of epithelial cells
f: cover the surfaces of organs
s:cilated epithelia have Cilia to beat particles away, squamous epithelia are thin for short diffusion pathway
what is the structure and function of sperm cells
f: to fertilise the egg
s: have flagellum to swim to the egg, lots of mitochondria to provide it with energy, acrosome has digestive enzymes to allow it to penetrate the surface of the egg
what is the structure and function of palisade mesophyll cells
f: carry out most of photosynthesis
s: many chloroplasts , thin walls for short diffusion pathway of co2
what is the structure and function of root hair cells
f: absorb water and mineral ions from the soil
s: large surface area for absorption, thin cell wall for entry of water and ions, cytoplasm has extra mitochondria for energy for active transport
where are embryonic stem cells found and what do they differentiate into
in the inner embryo, any type of cells
what is totipotent cells
totipotent cells can develop into any cell type, including extra-embryonic tissues;
what is Pluripotent cells
Pluripotent cells can form almost all cell types but cannot form extra-embryonic tissues;
what is Multipotent cells
Multipotent cells can give rise to a limited range of related cell types.
