Cell division - mitosis + meiosis Flashcards
Discuss the ways in which genetic variation is produced, including the role of nuclear division. f215 june15 q1b
A1 independent assortment/ random segregation, of (homologous) chromosomes/ bivalents;
A2 in, metaphase I/ meiosis I;
A3 of chromatids in, metaphase II/ meiosis II;
A4 (so) homologous chromosomes, have different
alleles/ come from different parents;
A5 produces large number of allele combinations; [different combinations of, chromatids/chromosomes,
in gametes/ e.g. for humans 2^23 possible combinations]
C1 crossing over/ (formation of) chiasma(ta);
C2 in, prophase I/ meiosis I;
C3 (so) chromatids will have new combination of alleles; [shuffles/ swaps/ exchanges, alleles on chromatids]
C4 amount of variation depends on distance between
crossover points; [e.g. more variation the further apart the crossovers occur]
M1 mutation;
M2 changes the (DNA) nucleotide/ base, sequence; [deletion,/ substitution/ addition, of, base/ nucleotide]
M3 DNA checks (during duplication) did not recognise damage; [proof reading did not recognise damage]
M4 idea of differences in (named) protein(s); [e.g. change in, amino acid sequence/ primary structure]
N1 non-disjunction; [inversion/ translocation (chromosome mutation)]
N2 homologous chromosomes do not separate (in metaphase I);
N3 one, more/ less, chromosome present; [examples of chromosome changes e.g. Trisomy 21]
F1 random, mating/fusion of gametes/ fertilisation;
F2 gametes are not genetically identical; [gametes are genetically different]
F3 produces large number of (allele) combinations;
Before the division of the nucleus of a cell, the genetic material must replicate. Explain why this is essential.
cells, genetically identical / have same DNA ; so both (daughter) cells receive a full, copy / complement ; [in context of identical to each other or identical to parent; ‘same genetic information/material’; same / correct amount of DNA; same / correct number of chromosomes]
Explain what is meant by a homologous pair of chromosomes.
1 one maternal and one paternal; 2 carry same genes; 3 carry, same/ different, alleles; 4 (usually) same/ similar, length; 5 centromere in same position; 6 same banding pattern; 7 pair up in meiosis/ form bivalent; [‘same loci’; 'same shape’ ‘same size’]
State one way in which the products of meiosis are different from the products of nuclear
division in meristematic tissue.
in meiosis: (cells produced are) not genetically identical [not clones]; one set of chromosomes/ haploid [half number of chromosomes/ half genetic material]; (they are) gametes; 4 cells produced;
Outline the process of budding in yeast. [2mks] (jun11 f210 q3)
nucleus divides/ mitosis [asexual reproduction/ cloning];
cell, swells on one side / bulges;
nucleus/ cytoplasm/ organelles, move into, bud/ bulge;
pinches off/ cell wall forms, (so bud becomes a separate cell); [cytokinesis]
Name one process that occurs during stages G1 and G2.
growth of cell / growth of organelles / increase number of organelles / synthesis of proteins; [named steps in protein synthesis]
During stage S, the genetic information is copied and checked. Suggest what might happen if the genetic information is not checked
mutation / faulty DNA produced / error in copying ;
daughter cells will not receive identical genetic information ; [‘daughter cells will not be clones’]
proteins / (daughter) cells, not made / do not function; [‘proteins / daughter cells function differently]
During meiosis a cell undergoes two divisions.
Suggest how cells produced by meiosis may differ from those produced by mitosis.
haploid / half genetic information / chromosome number is n ; [use of comparative chromosome numbers as example]
genetic information not identical / produces genetically different cells ;
4 cells produced
Name the process of asexual reproduction in yeast
budding; [IGNORE mitosis/ asexual]
Outline the process of asexual reproduction in yeast. [2mks]
mitosis ; [Ensure this is in context of before nucleus moves into bud]
swelling / bulge, in (surface of) the cell ;
nucleus moves into, swelling / bulge / bud ;
idea that, bulge / bud, nips / pinches / breaks off / cleaves ;
ref to uneven distribution of cytoplasm
Even when the environmental conditions are perfect, one yeast cell rarely produces the
calculated number of potential new cells.
Suggest why the reproductive potential of the yeast cell is not reached (1mk)
new bud cannot occur, on / close to, old scar ; [idea that some of surface between scars is not used/ ref to unable to tessellate / scars not closely packed]
not enough space between scars for another bud ;
yeast cell not a true sphere ;
(gene) mutation / DNA damage ;
Yeast cells separate after cell division. In a multicellular organism, the cells do not separate
but become organised to form the body structure.
Describe how the cells in a multicellular organism are organised [5mks]
1) (cells) differentiate(d) / specialise(d) ;
2) (groups of) cells form tissue(s) ;
3) (groups of) tissues form organ(s) ;
4) (groups of organs) form organ system(s) ;
5) (group of) cells / tissues / organs / organ systems, work together / interact ; [same job/ function]
6) named example of a tissue / an organ /an organ system
[e.g. cells work together to form tissues = 2 marks
(mp2 and 5)]
independent assortment
metaphase I and metaphase II ;
formation of the spindle apparatus
prophase I ;
separation of sister chromatids
anaphase II ;
