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Date May 2018 Marks available 3 Reference code 18M.2.SL.TZ1.3
Level Standard level Paper Paper 2 Time zone Time zone 1
Command term Explain Question number 3 Adapted from N/A

Question

Using the Punnett grid, explain how two parents can have children with any of the different ABO blood groups.

[3]
a.

Distinguish between the structure of arteries and the structure of veins.

[3]
b.

Explain how cuts in the skin are sealed by blood clotting.

[2]
c.

Markscheme

a. correct gametes of one parent as IA AND i in header line/column
AND
correct gametes of other parent as IB AND i in header column/line 

b. correct corresponding genotypes in inner squares as IAIB, IAi, IBi, ii 

c. corresponding phenotypes of children identified as AB, A, B and O 

d. ratio of phenotypes is 1:1:1:1  OWTTE

Allow ECF.

a.

a. arteries have thicker (muscular) walls/layer/tunica (media)
OR
veins have thinner (muscular) walls/layer/tunica (media) 

b. arteries have no valves
OR
veins have valves 

c. arteries have thicker elastic layer
OR
veins have thinner elastic layer 

d. arteries have a smaller lumen/bore
OR
veins have a larger lumen/bore 

Accept answers presented in a table.

b.

a. clotting factors released from platelets 

b. clotting process involves a cascade/series of reactions 

c. produces thrombin 

d. causes rapid conversion of fibrinogen into fibrin 

e. fibrin makes a mesh to seal the wound OWTTE

c.

Examiners report

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

Syllabus sections

Core » Topic 3: Genetics » 3.4 Inheritance
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