Cell division Flashcards
G1/G2
-Organelles replicate
-Cell size grows
-Protein synthesis
-Respiration
S
DNA synthesis
Checkpoints
G1/G2/Metaphase
G1 checkpoint
-Checking size
-DNA errors - prevents synthesis
G2 checkpoint
-DNA replication
-Errors
Metaphase checkpoint
Checks spindle fibre is positioned correctly and the chromatids are attached properly so equal amounts of chromatids each side
Mitosis/cytokinesis
Mitosis - nucleus splits
Cytokinesis - cytoplasm splits
Meiosis 1
Interphase - chromatids to chromosomes
P1:
-Homologous chromosomes pair up
-Crossing over: swapping alleles
M1:
-Line up in homologous pairs along equator
-Independent assortment: random arrangement of female/male chromosomes ether side of spindle
A1:
-Carry swapped alleles to each pole
-Homologous pairs of chromosomes separate
-No separation at centromere
T1:
-Nuclear envelope reforms
What has resulted at the end of meiosis 1
Haploid - half the original set of chromosomes (n2)
Meiosis/mitosis
Meiosis: Haves the genetic material to make haploid gametes for reproduction
Mitosis: Cell division where cells make genetically identical daughter cells
Meiosis 2:
P2:
-Nuclear envelope breaks down
-Chromatin condenses
M1:
-Line up in pairs along the spindle region
-Independent assortment: crossed over alleles could be on the same or different sides
A1:
-Separates sister chromatids
-Splitting of centromere
T1:
-Nuclear envelope reforms
-DNA becomes no longer visible
What results at the end of meiosis 2
4 Haploid
Sperm specialisations
Hydrolytic enzymes in the sperm head so that it can penetrate the egg
SEM
Black and white but can add colour on the computer
Reasons for mitosis
-Body plan development
-Asexual reproduction
-Repair and growth of tissues
Explain why the type of nuclear division in a zygote is mitosis and not meiosis
Mitosis for the growth of zygote /needs to be genetically identical/ gametes not produced
Suggest three ways in which the use of embryonic stem cells in research has practical benefits to
biological knowledge
1) can be grown into different tissues
to) test how effective new medicinal
drugs are (1)
2) (can be grown into different tissues
to) test for side effects / toxicity of
new drugs (1)
3) (can be grown and) studied to see
how they develop into different cell
types (developmental research)
4) cell function can be studied to find
out what can make it fail to work
properly in certain (named) diseases
Explain the difference between muscle tissue and a muscle
1) muscle tissue is a group of cells
which contract together (1)
2) a muscle is an organ that consists of
muscle tissue and other (named)
tissues working together (1)
Explain the role of embryonic stem cells in the development of the embryo
1) embryonic stem cells
(are) undifferentiated / not
specialised
2) (are) a renewing source of cells / AW
3) (can) differentiate into any cell type
(of the developing foetus)
Explain why the cells of the inner cell mass are not totipotent stem cells.
1) not totipotent stem cells
as cannot form whole organism
2) cannot give rise to extra-embryonic
tissues / AW
Why is the cell wall thicker on the inner side of the stoma
so the cell
does not change shape symmetrically as its volume changes
shows that gills are adapted for efficient gas exchange
1) many / AW, lamellae / structure A,
provide large surface area (1)
2) presence of) secondary lamellae on
main lamellae provide large surface
area (1)
3) short distance between blood and,
water / outside (1)
4) idea that blood maintains diffusion
gradient (1)
any of above linked to
faster diffusion (of oxygen, carbon
dioxide) (1)
. Name the type of cell present in meristematic tissue and describe how xylem vessel elements are produced from this type of cell.
1) Description - any three from,
by differentiation (1)
2) (cell) elongation (1)
3) deposition of lignin / lignification (of
cell walls) (1)
4) end walls break down (1)
Homologous chromosomes
A pair of chromosomes in which each chromosome contains the same genes
