IB DP Biology Topic 3: 3.3 Meiosis Question Bank SL Paper 2

Question

Outline what occurs in cells in the first division of meiosis.  [5]

▶️Answer/Explanation

Ans

a.halves the chromosome number/produces haploid cells;
b.at start of meiosis each chromosome consists of two sister chromatids attachedby a centromere;
c.prophase (I): pairing of homologous chromosomes;
d.crossing over occurs;
e.chromosomes condense by supercoiling;
f.metaphase (I): pairs of homologous chromosomes/bivalents move to equator ofspindle
OR
metaphase (I): orientation of pairs of homologous chromosomes (prior toseparation) is random;
g.anaphase (I): centromeres do not divide
OR
anaphase (I): spindle fiber pulls chromosome/whole centromere with two sisterchromatids to opposite poles;
h.telophase (I): arrival of centromere with sister chromatids at opposite poles;

Question

Meiosis in humans produces cells that participate in fertilization. Outline the processes involved in meiosis.

[5]
a.

Following fertilization, cells in the developing embryo differentiate. Outline a technique for cloning using differentiated animal cells.

[5]
b.

Discuss ethical issues of therapeutic cloning in humans.

[8]
c.
▶️Answer/Explanation

Markscheme

Remember, up to TWO “quality of construction” marks per essay.

a. meiosis reduces a diploid cell into (four) haploid cell(s);
b. (during prophase I) homologous chromosomes pair up/synapsis;
c. chromatids (break and) recombine / crossing over
d. (metaphase I) (homologous chromosomes) at the equator of the spindle / middle of cell;
e. (anaphase I) (homologous) chromosomes separate and move to opposite poles;
f. (telophase I) chromosomes reach poles and unwind WTTE;
g. (prophase II) chromosomes (condense and) become visible, new spindles form;
h. (metaphase II) chromosomes line up at the centre of the cells/equator;
i. (anaphase II) sister chromatids separate;
j. (telophase II) chromatids reach the poles and unwind;

a.

Remember, up to TWO “quality of construction” marks per essay.

a. differentiated/somatic/diploid cells taken from donor animal/sheep udder;
b. (diploid) nucleus from donor cells removed;
c. ova/eggs cells removed from (donor) animal/female sheep;
d. (haploid) nucleus removed from eggs/ova;
e. (diploid/donor’s) nucleus is fused with/inserted into egg/ovum (to form zygote);
f. embryo (from cell with donor nucleus and egg from surrogate) implanted in uterus of surrogate mother;
g. normal pregnancy and birth is completed;
h. offspring is a genetic copy/clone of the donor mother/diploid nucleus WTTE;

b.

Remember, up to TWO “quality of construction” marks per essay.

a. therapeutic cloning involves producing embryos from which embryonic stem cells can be harvested for medical use;

argument in favour:
b. (to many people) any procedure that reduces pain and suffering is ethically/morally justified;
c. stem cells can be used to replace organs/tissues that have been lost/damaged in a patient;
d. (thus) pain and suffering can be reduced/lives can be saved/life quality improved;
e. cells can be removed from embryos that have stopped developing and would have died anyway;
f. cells are removed at a stage when no pain can be felt by the embryo;
g. use embryos from IVF that would otherwise be destroyed;

Accept up to one additional reasonable argument in favour.

argument against:
h. embryonic stem cells are no longer needed as adult stem cells can be used without causing loss of life;
i. there is danger of embryonic stem cells developing into tumour cells/harmful effects are not yet known;
j. every human embryo is a potential human with the right to development;
k. more embryos may be produced than can be used and so some would be killed;
l. (to many people) any procedure that harms a life/kills is unethical/morally wrong;
Accept up to one additional reasonable argument against.

To award [8] at least one pro and one con must be addressed.

c.

Question

State three processes occurring in a cell during interphase of the cell cycle but not  in mitosis.

1.  …………………………………………………………..

2.  …………………………………………………………..

3.  ………………………………………………………….. 

[3]
a.

Explain how sexual reproduction can allow evolution to occur.

[3]
c.
▶️/Explanation

Markscheme

a. growth (of cells);
b. transcription/protein synthesis/translation;
c. DNA replication / genetic material copied;
d. production of organelles/mitochondria/chloroplasts;
e. named normal activity of cell (eg active transport, movement, secretion);
NB Do not accept G1, S, G2 unless linked to correct process.

a.

a. sexual reproduction promotes variation in species;
b. independent assortment of genes / random orientation of chromosomes in metaphase/meiosis;
c. crossing-over provides new combinations of alleles;
d. production of great variety of gametes (by meiosis) / different combinations of chromosomes in gametes;
e. (random) combination of gametes from both parents (in fertilization);
f. (genetic) variation allows natural selection which leads to evolution;

c.

Question

The following sequence of pictures, made using an electronic imaging technique, shows a cell undergoing division.

State the stage of mitosis typified by image II.

[1]
a.

List two processes that involve mitosis.

[2]
b.

State the process that results in tumour (cancer) formation or development.

[1]
c.

Explain, using one example, how non-disjunction in meiosis can lead to changes in chromosome number.

[2]
d.
▶️Answer/Explanation

Markscheme

anaphase

a.

a. growth (through increasing cell number);

b. embryonic development;

c. tissue production/repair;

d. (asexual) reproduction;

b.

uncontrolled mitosis/cell division

c.

a. pair of homologous chromosomes moves in same direction/does not separate during anaphase I / chromatids move in same direction/do not separate during anaphase II;

b. leaving a cell with an (some) extra chromosome(s)/missing chromosome(s);

c. an example; (e.g. Down syndrome where there is an extra chromosome number 21);

d.

Question

The diagram below shows the female reproductive system.

Label the diagram above with the letter U to show the uterus.

[1]
a.

Outline the role of luteinizing hormone (LH) after ovulation.

[1]
b.

Explain how sexual reproduction can lead to variation in a species.

[3]
c.
▶️Answer/Explanation

Markscheme

letter U marked/labelled on uterus

Accept in lumen or on wall.

a.

formation of the corpus luteum

b.

allows characteristics from both parents to appear in offspring;

crossing over (during prophase 1) changes chromosome composition;

produces gametes which are all different;

random chance of which sperm fertilizes ovum;

greater variation (resulting from sexual reproduction) favours survival of species through natural selection;

Accept independent assortment during meiosis from AHL.

c.
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