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Date November 2017 Marks available 3 Reference code 17N.2.SL.TZ0.06
Level Standard level Paper Paper 2 Time zone TZ0 / no time zone
Command term Outline Question number 06 Adapted from N/A

Question

Reproduction in eukaryotes can be sexual or asexual.

Describe the origin of eukaryotic cells according to the endosymbiotic theory.

[4]
a.

Explain how hormones are used to control the human menstrual cycle.

[8]
b.

Outline natural methods of cloning in some eukaryotes.

[3]
c.

Markscheme

a. mitochondria and chloroplasts are similar to prokaryotes

b. «host» cell took in another cell by endocytosis/by engulfing «in a vesicle»

Allow “taking in” in place of “engulfing”

c. but did not digest the cell/kept the «ingested» cell alive

    OR

    symbiotic/mutualistic relationship «between engulfed and host cell»

d. chloroplasts and mitochondria were once independent/free-living «organisms»

e. DNA «loop» in chloroplast/mitochondrion

f. division/binary fission of chloroplast/mitochondrion

g. double membrane around chloroplast/mitochondrion

h. 70s ribosomes «in chloroplast/mitochondrion»

Award up to [2] for evidence from mpe to mph

[Max 4 Marks]

a.

a. FSH stimulates the development of follicles

b. follicles produce estrogen

c. estrogen stimulates the repair of the uterus lining

d. estrogen stimulates LH secretion

e. LH causes/stimulates ovulation

f. LH causes/stimulates the development of the corpus luteum

g. corpus luteum secretes progesterone

h. progesterone causes/stimulates thickening of the uterus lining

    OR

    prepares uterine lining for implantation

    OR

    maintains the endometrium

i. progesterone/estrogen inhibits the secretion of LH/FSH

j. falling progesterone levels at the end of the cycle allow FSH production/menstruation

k. negative/positive feedback «control» described correctly

l. LH/FSH are pituitary hormones

[Max 8 Marks]

b.

a. clones are genetically identical organisms

    OR

    group of cells derived from a single parent cell

b. asexual reproduction in plants such as tubers/runners/bulbs

Allow other verifiable examples of plants

c. common in non-vertebrates such as budding in hydra

Allow other verifiable examples of invertebrates

d. budding in yeast/fungi

Allow other verifiable examples of fungi

e. identical twins «in humans» are clones because they originate from
the same cell

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Core » Topic 3: Genetics » 3.5 Genetic modification and biotechnology
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