biology 6 Flashcards
In one tissue, the scientists found a genetic mutation that stopped the metaphase checkpoint from working.
Suggest an abnormality the scientists might observe in the cells of this tissue.
cells do not contain the diploid number of chromosomes / cells contain different numbers of chromosomes
In the other tissue, the scientists observed cells with chromosomes that had been replicated despite containing damaged DNA.
Suggest which cell cycle checkpoint is no longer working in this tissue and justify your answer.
G1 (checkpoint) AND idea that cells (with damaged DNA) should be stopped from entering the S phase ✓
G1(checkpoint) AND idea that this is the point where DNA damage is checked ✓
Suggest what is being checked at checkpoint Y(G1) on the figure .
idea that (checking that) DNA has replicated correctly ✓
(checking) for , mutations / damage to DNA / damage to genes / errors in DNA
A transmission electron microscope image of a white blood cell was studied. It was concluded that the cell had stopped dividing at the G2 checkpoint.
Suggest two observations that would have led to this conclusion.
larger number of (named) organelles
✓
more DNA / larger nucleus ✓
no visible chromosomes ✓
nuclear membrane present ✓
Mitosis is involved in growth and repair of tissues.
State two other roles of mitosis in multicellular organisms.
asexual / vegetative , reproduction
(development of) body plan
producing gametes from haploid cells
production of new stem cells ✓
Suggest why Hydra reproduces asexually when conditions are favourable.
genetically identical offspring ✓
offspring produced , rapidly / in large numbers
(all) offspring will , find conditions favourable / have same adaptations
Explain why bone is described as a tissue and gills are described as organs.
tissue has, one / few, types of cell and performs, one / few, functions (1)
idea that bone has, one / few, types of cell
or
idea that bone performs, one / few, functions (1)
organs consist of several tissues (1)
gills contain two or more named tissues (1)
Name the type of cell present in meristematic tissue and describe how xylem vessel elements are produced from this type of cell.
Type of cell
stem (cells) (1)
Description - any three from,
by differentiation (1)
(cell) elongation (1)
deposition of lignin / lignification (of cell walls) (1)
end walls break down (1)
The cell labelled T on Fig. 23 is a parenchyma cell which carries out photosynthesis and stores starch. Suggest why cell T and the cells surrounding it, can be classified as parenchyma tissue.
(similar) cells working together with common/ same function ✓
Explain the role of embryonic stem cells in the development of the embryo.
embryonic stem cells
(are) undifferentiated / not specialised ✓
(are) a renewing source of cells / AW
✓
(can) differentiate into any cell type (of the developing foetus) ✓
Discuss the ways in which genetic variation is produced, including the role of nuclear division.
