1.	Outline the differences between the behaviour of the chromosomes in mitosis and meiosis.
(Total 5 marks)

2.	(a)	Define the term sex linkage.
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(1)
 
(b)	A male and female with normal colour vision each have a father who is colour blind. They are planning to have children. Predict, showing your working, the possible phenotypes and genotypes of male and female children.

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(3)

(c)	Explain the relationship between Mendel’s law of segregation and meiosis.
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(3)
 
(d)	Distinguish the differences between animal cells and plant cells undergoing mitosis and cytokinesis.
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(2)
(Total 9 marks)

3.	Up to two additional marks are available for the construction of your answers.
(2)
	(a)	Outline how the process of meiosis can lead to Down’s Syndrome.
(4)
(b)	Discuss the advantages and disadvantages of genetic screening for chromosomal and genetic disorders.
(8)
(c)	Describe the technique for the transfer of the insulin gene using E. coli.
(6)
(Total 20 marks)

4.	What is the relationship between Mendel’s law of segregation and meiosis?
A.	Only one of a pair of alleles appears in a gamete.
B.	The separation of “paternal” and “maternal” chromosomes shows no pattern.
C.	Gametes contain all dominant or all recessive alleles.
D.	Variation only results from two divisions.
(Total 1 mark)

5.	Which fluid is sampled to try to detect chromosomal abnormalities in a fetus?
A.	Placental
B.	Umbilical
C.	Amniotic
D.	Spinal
(Total 1 mark)

6.	Up to two additional marks are available for the construction of your answers.
(2)
	(a)	Draw and label a generalized prokaryotic cell as seen under the electron microscope.
(4)
(b)	Outline the process of meiosis.
(6)
(c)	Explain the role of the following hormones in the menstrual cycle: estrogen, progesterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH).
(8)
(Total 20 marks)

7.	What does a karyotype show?
A.	Gel electrophoresis bands from DNA
B.	The number and appearance of chromosomes
C.	A pair of alleles controlling a specific character
D.	All the genes possessed by a living organism
(Total 1 mark)

8.	A diploid cell in a gorilla has 48 chromosomes. How many chromosomes will be present in a haploid gorilla cell?
A.	96
B.	48
C.	24
D.	12
(Total 1 mark)

9.	What are homologous chromosomes?
A.	Two chromosomes with differing sets of genes, in the same sequence, with the same alleles
B.	Two chromosomes with the same set of genes, in a different sequence, with the same alleles
C.	Two chromosomes with a different set of genes, in the same sequence, with different alleles
D.	Two chromosomes with the same set of genes, in the same sequence, sometimes with different alleles
(Total 1 mark)

10.	Which processes result in the greatest amount of genetic variation in a population?
A.	Natural selection and meiosis
B.	Meiosis and mutation
C.	Mutation and mitosis
D.	Mitosis and natural selection
(Total 1 mark)

11.	The diagram below shows the cell of an organism going through the first division of meiosis.

How many different combinations are possible for these chromosomes in the haploid cells formed by meiosis?
A.	2
B.	6
C.	8
D.	9
(Total 1 mark)

12.	If the amount of DNA in a haploid gamete is represented by ´, what is the net quantity of DNA in a cell from the same organism at the start of meiosis?
A.	0.5 ´
B.	´
C.	2 ´
D.	4 ´
(Total 1 mark)

13.	two divisions in meiosis, only one in mitosis;
meiosis results in haploid cells, mitosis in diploid cells;
crossing over only occurs in meiosis;
no S phase precedes meiosis II;
chromosome behaviour in meiosis II and mitosis is similar / chromosome
behaviour in meiosis I and mitosis is different;
chiasmata only form during meiosis;
homologous chromosomes move to the equator in pairs only in meiosis;
Do not accept number of cells produced - it is a result not a behaviour.
[5]

14.	(a)	genes found on the sex chromosomes / X / Y chromosome	1
Characteristics or traits are unacceptable replacement for genes.
 
(b)	parent genotypes (XCY and XCXc) / same genotypes using alternative symbols / 
four offspring genotypes (XCXc, XCXC, XCY,XcY);
Punnett square showing cross / other acceptable working;
all / 100% daughters normal colour vision (phenotype);
half / 50% the sons normal and half / 50% are colour blind (phenotype);	3 max
Award [0] for autosomal analysis.
 
(c)	law of segregation states that one half of the alleles enter one gamete 
and the other half enter the other gamete;
meiosis reduces the chromosome number by half / diploid to haploid;
homologues carrying alleles separate (in anaphase I);
end result is four cells, half with one allele / homologue and the other half 
with the other allele;	3 max

(d)	plant cells lack centrioles / animals cells have centrioles;
plants form a cell plate / new cell wall to divide cells / animal cells from 
a cleavage furrow;	2
[9]

15.	(a)	Accept any of the points below if clearly drawn and correctly
labelled in a diagram.
in metaphase homologues in centre of cell / spindles attached;
homologues are separating;
one pair doesn’t separate / non-disjunction;
in telophase cells divide into two;
cells have either one more / one less chromosome;
can occur in second division of meiosis;
sister chromatids fail to separate;
fertilization with one gamete / sperm / egg carrying extra chromosome;
Down’s syndrome is trisomy of chromosome 21;	4 max
 
(b)	genetic screening is testing for the presence or absence of gene / 
chromosome;
screening for chromosomes can involve karyotyping;
genetic screening is controversial;
advantages: [4 max]
parents can choose to avoid having children with disorder;
parents can prepare for a child with a disorder;
parents can use IVF to select embryos that are normal;
can use gene therapy to correct the problem;
treatment can start to prevent symptoms;
fewer children with the disorder are born;
disadvantages: [4 max]
frequency of abortion can increase;
parents can select embryos for sex of the child;
	can have harmful side effects such as depression if you know you will
develop a disorder later;
can create a genetic underclass;
health insurance / treatment can be denied if there is genetic predisposition;	8 max
 
(c)	mRNA is extracted;
DNA copy of RNA is made using reverse transcriptase;
plasmids are cut open with endonucleases (at specific sequences);
insulin gene and plasmid are mixed together;
	addition of “sticky ends” to the DNA copy (so that it will combine with
the cut plasmid);
DNA ligase will seal the plasmid;
recombinant plasmid is inserted into E. coli;
E. coli is cultured;
E. coli begins to make insulin;	6 max
 
(Plus up to [2] for quality)
[20]

16.	A
[1]

17.	C
[1]

18.	(a)	Award [1] for any of the following clearly drawn and correctly labelled.
	Award [2 max] if two or more eukaryotic structures are given and if a nucleus
is included award [0].
cell wall / capsule / slime wall / layer;
plasma / cell membrane;
mesosome,
cytoplasm;
ribosomes;
nucleoid / naked DNA;
flagella;
pili;
plasmid;
size stated 1 to 10 μm;	4 max
 
(b)	two cell divisions / reduction-division / diploid to haploid / meiosis I
and meiosis II;
produce four (haploid) cells;
for production of sex cells / gametes / spores;
daughter cells are different from parent cells;
homologous chromosomes / two chromatids pair up;
line-up on equator;
(spindle fibres) pull homologous chromosomes to opposite poles;
two haploid cells are formed;
second division / like mitosis, separates chromatids to opposite poles;	6 max
Accept any of the above points if clearly explained in a
labelled diagram.

(c)	FSH stimulates (in first few / five days) follicle development (in ovary);
(FSH stimulates) follicles to secrete estrogen, (positive feedback);
low levels of estrogen initially inhibit FSH (and LH) secretion;
	rapid increase in estrogen stimulates FSH / LH production, (positive
feedback);
estrogen also starts to repair / thicken endometrium / uterine lining;
LH stimulates ovulation;
	LH causes follicle to produce less estrogen (negative feedback) / more
progesterone (positive feedback);
LH stimulates follicle to become corpus luteum;
	corpus luteum secretes (more estrogen and) large level of progesterone
(positive feedback);
	estrogen and / or progesterone stimulate thickening of endometrium / 
uterus lining;
	estrogen and / or progesterone inhibit FSH and LH secretion (by
negative feedback);
	estrogen and / or progesterone levels fall after day 21-24 if no embryo
 / fertilization;
	lower concentrations of estrogen and / or progesterone allow
disintegration of endometrium / menstruation occurs;
FSH secretion begins a new cycle;	8 max
Award [6 max] if only three hormones are explained.
 
(Plus up to [2] for quality)
[20]

19.	B
[1]

20.	C
[1]

21.	D
[1]

22.	B
[1]

23.	C
[1]

24.	D
[1]