Download Q1 The freshwater mussel, Margaritifera margaritifera, is a mollusc

Q1 The freshwater mussel, Margaritifera margaritifera, is a mollusc which lives in rivers
and streams.
When the mussel reproduces, gametes are released into the water and fertilisation takes
place.The embryos, in the form of larvae, attach themselves to the gills of fish and
develop there for a few months.
The larvae then release themselves and grow in sand in the river, feeding by filtering
food from the water.
The number of mussels is falling due to human predation and the species is threatened
with extinction.
(a) The mussel belongs to the group known as the molluscs. State two features you
would expect the mussel to have.[2]
(b) Explain how the species name of the freshwater mussel can be distinguished from its
genus.[1]
(c) State the type of reproduction shown by the mussel.
Explain your answer. [2]
(d) (i) Fish gills have the same function as lungs. Suggest one advantage to a mussel
larva of attaching itself to fish gills. [1]
(ii) The mussel develops on the fish gills. Define the term development. [1]
(e) The mussel is threatened with extinction. Name another organism which is also
threatened with extinction and outline how it could be conserved. [3] [Total: 10]
Q2 O/N/05 (a) Describe the effect sickle cell anaemia has on red blood cells.[2]
(b) (i) The allele for normal haemoglobin production is IN. The allele for sickle cell
haemoglobin production is IS. Two parents who are heterozygous have a child.
With the help of a genetic diagram, predict the probability that this child would be
heterozygous.[4]
(ii) Explain why, under some circumstances, people who are heterozygous for this
condition have a greater chance of survival than homozygous people.[3][Total: 9]
Q3 Nov 2002(a) Distinguish between each of the following pairs of terms:
(i) phenotype and genotype;
(ii) dominant and recessive;
(iii) homozygous and heterozygous. [7]
(b) Using a suitable named example, explain how the following phenotypic ratios can be
obtained from a genetic cross.
(i) 1 : 1
(ii) 3 : 1 [8]
Q4 MJ 03 (a) Explain the term codominance. [3]
(b) Using a suitably labelled genetic diagram, explain how a baby can have blood group
O
(IoIo) when its mother is group A and its father is group B. [6]
(c) (i) Describe and explain what could happen when blood of different groups is mixed.
[3]
(ii) Describe and explain the role of the placenta in relation to this problem. [3]
[Total : 15]
Q5 MJ 04One variety of cat can have short hair or long hair. The allele for short hair (H)
is dominant to the allele for long hair (h).
A cat breeder has a short haired cat. Its genotype can be HH or Hh: there is no visible
difference between these genotypes.
This short haired cat is crossed with a long haired cat, hh.
(a) Construct genetic crosses to predict the ratios produced if the short haired cat is:
(i) heterozygous, Hh;[3]
(ii) homozygous, HH.[3]
(b) Suggest how the offspring from (a)(ii) would be different if the alleles were codominant.
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[Total : 7]