Topic 3/10 A [60 marks]
1.
In some people, hemoglobin always contains the amino acid valine in place of a glutamic acid at one position in the protein. What is [1 mark]
the cause of this?
A. An error in transcription of the hemoglobin gene
B. An error in translation of the mRNA
C. Lack of glutamic acid in the diet
D. A base substitution in the hemoglobin gene
Markscheme
D
2.
What is the set of alleles that an individual possesses?
[1 mark]
A. A gene
B. A genotype
C. A genome
D. A genus
Markscheme
B
3.
Which is a characteristic of the pairs of sister chromatids that are visible during meiosis?
[1 mark]
A. They result from the replication of DNA before meiosis.
B. They are only present in meiosis I.
C. They split apart during metaphase I in meiosis.
D. They are only present in meiosis II.
Markscheme
A
4.
What is a possible source of the chromosomes used for pre-natal karyotype diagnosis?
A. The mother’s lymphocytes
B. The mother’s cheek cells
C. The cells from chorionic villi
D. The fetal hair root cells
[1 mark]
Markscheme
C
5.
What causes the presence of three chromosomes 21 in Down syndrome?
A. Crossing over
B. Allele change
C. Non-disjunction
D. Gene mutation
[1 mark]
Markscheme
C
6.
The micrographs show four different phases from meiosis II. What is the correct order?
[1 mark]
A. 3-4-2-1
B. 2-3-4-1
C. 4-3-2-1
D. 4-2-3-1
Markscheme
C
7.
What causes genetic variety in the formation of gametes during meiosis?
A. Crossing over in prophase I and random orientation of homologous chromosomes in metaphase I
B. Crossing over in metaphase I and random orientation of homologous chromosomes in metaphase II
C. Linkage of genes in prophase I and crossing over in metaphase I
D. Linkage of genes in metaphase I and random orientation of homologous chromosomes in metaphase II
Markscheme
A
[1 mark]
8.
In the following diagram, which pair represents homologous chromosomes?
[1 mark]
A. 1 and 2
B. 3 and 4
C. 2 and 5
D. 4 and 6
Markscheme
D
9.
Which genotypes are possible when a male with blood group AB and a female with blood group O have offspring?
A. IAi only
B. IAi and IBi
C. IAi and ii
D. IAi, IBi and ii
[1 mark]
Markscheme
B
10.
The diagram shows a pedigree.
[1 mark]
According to the pedigree shown, which pattern of inheritance is indicated?
A. Sex-linked recessive trait
B. Autosomal recessive trait
C. Autosomal dominant trait
D. Codominant alleles
Markscheme
C
11.
What would be the expected result if a woman carrier for colour blindness and a colour blind man had many children?
A. All offspring will be colour blind.
B. All male offspring will be colour blind and all females normal.
C. All males will be normal and all females will be colour blind.
D. All females will be carriers of colour blindness or colour blind
[1 mark]
Markscheme
D
12.
Which is a possible risk associated with a genetic modification of crops?
[1 mark]
A. Crop plants will become weaker with time.
B. It can increase mutations in the organisms that consume them.
C. Starch obtained from genetically modified plants will be more difficult to digest.
D. Resistance to herbicide genes can be transferred to weeds.
Markscheme
D
13.
Which sequence of DNA would be suitable in DNA profiling?
[1 mark]
A. ---ATTCGTGAATCAGCC-B. ---ATTCGTGAATTTGCC-C. ---ATTCGTGATTGCAGC-D. ---ATTCGTGATTCGTGA--
Markscheme
D
14. The flow chart summarizes methods of gene transfer.
Which enzymes are used in steps I and II?
[1 mark]
Markscheme
B
15.
Which gametes can result from the following crossover?
Markscheme
D
[1 mark]
16. The genetic determination of dogs’ coats can be quite complex, with many different genes acting at the same time.
[1 mark]
• The dominant allele E gives brown tones. The recessive allele e results in red tones.
• The colour intensity is due to another gene. The dominant allele B gives a dark colour, whereas the recessive allele b results in a light
colour.
What would be the genotype of a light brown dog produced from a cross between a dark brown dog and a light red dog?
A. EEbb
B. EeBb
C. eeBb
D. Eebb
Markscheme
D
17.
How many autosomes are there in a human sperm?
A. 1
B. 22
C. 23
D. 46
[1 mark]
Markscheme
B
18.
Skin colour is a trait controlled by polygenic inheritance. Which statement is correct?
A. Skin colour shows discontinuous variation
B. Individuals show a wide range of phenotypes for skin colour
C. No two people have the same skin colour
D. Children always have the same skin colour as one of their parents
[1 mark]
Markscheme
B
19. Why do humans inherit continuous variation with regard to height?
[1 mark]
A. The trait for tallness is dominant.
B. The height phenotype is polygenic.
C. This is a case of multiple alleles.
D. Height in humans is polyclonal with multiple alleles.
Markscheme
B
20. Which of the following processes result in the production of recombinants?
I. Crossing over between linked genes
II. Reassortment of non-linked genes
III. Mutation
A. I only
B. I and II only
C. I and III only
D. I, II and III
[1 mark]
Markscheme
B
21a.
Identify the phases labelled X and Y.
[1 mark]
X:
Y:
Markscheme
X: plateau phase
Y: exponential growth / log phase
(both needed)
21b. Distinguish between the terms genotype and phenotype.
[1 mark]
Markscheme
genotype is the genetic make-up/set of alleles (of an organism) while phenotype is the characteristics (expressed/shown in an organism)
21c. Outline a structural difference between the chromosomes of Helicobacter pylori and Homo sapiens.
[1 mark]
Markscheme
chromosome from bacteria has no protein associated/naked DNA / bacteria is circular, H. sapiens is linear / (chromosomes of) H.
sapiens are much bigger/have many more base pairs than bacteria
N.B.: Answer must refer to "chromosomes" not genomes of the two organisms.
21d.
Deduce the percentage of adenine in Oryza sativa if the proportion of guanine in that organism is 30 %.
[1 mark]
Markscheme
20 %
21e. Deduce the possible phenotypes of individual X.
[1 mark]
Markscheme
A, B, AB and O
All four phenotypes must be shown to award the mark.
21f. Describe ABO blood groups as an example of codominance.
[1 mark]
Markscheme
allele I A and the allele IB are (co)dominant as they are both expressed in the heterozygote/AB type blood / OWTTE
[1 mark]
22a. Determine the phenotype of Aabb.
Markscheme
tall and yellow
22b. Compare the information that could be deduced when the genotypes are presented as AaBb or
[2 marks]
Markscheme
22c.
[1 mark]
Deduce one possible recombinant offspring of individual
after a test cross.
Markscheme
23a. Meiosis in humans produces cells that participate in fertilization. Outline the processes involved in meiosis.
[5 marks]
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;
23b.
Following fertilization, cells in the developing embryo differentiate. Outline a technique for cloning using differentiated animal cells. [5 marks]
Markscheme
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;
23c. Discuss ethical issues of therapeutic cloning in humans.
Markscheme
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.
[8 marks]
24a.
(i) State the technique used to collect cells for pre-natal testing.
[3 marks]
(ii) State the method used to arrange the chromosomes in a karyotype.
(iii) State at what stage in the cell cycle the cells would be when this photograph was taken.
Markscheme
(i) amniocentesis/sampling amniotic liquid/fluid (via needle)/chorionic villus sampling
(ii) chromosomes are grouped by pairs according to size and structure/band pattern/location of centromeres
(iii) metaphase/late prophase of mitosis
24b. Albinism is inherited as a recessive trait; the alleles of the gene involved are A and a. An individual with albinism produces little or [3 marks]
no pigment in the eyes, skin and hair. In a family, one sister has albinism while the parents and other sister have
normal pigmentation.
(i) Determine, using a Punnett grid to show your reasoning, the possible genotypes of the sister with normal pigmentation.
(ii) Deduce the probability that the next child of this couple will have albinism.
Markscheme
(i) Punnett grid shows the gametes (A and a) on one axis and the gametes (A and a) on the other axis and genotypes (AA, Aa, Aa, and
aa) of offspring;
AA/homozygous dominant and Aa/heterozygous (show normal
pigmentation); Both needed
Do not award marks to any answer suggesting sex linkage.
(ii) 1/4 /25 %/0.25 probability of albinism / 1 in 4 chance
25a. Gene transfer to bacteria often involves small circles of DNA into which genes can be inserted. State the name of a small circle of
DNA, used for DNA transfer, in bacteria.
[1 mark]
Markscheme
plasmid
25b.
The diagram below shows a cut circle of DNA into which a gene is being inserted. Before it can be transfered into a bacterium, the [2 marks]
ring must be altered, using an enzyme.
Outline what must be done next to complete the process of gene insertion into the DNA circle, including the name of the enzyme that is used.
Markscheme
DNA ligase involved; (DNA required to be consistent with syllabus)
seals gaps/nicks in DNA (strands);
makes sugar-phosphate bonds;
25c.
Discuss the potential benefit and possible harm of one named example of gene transfer between species.
[3 marks]
Markscheme
named example of DNA source and organism to which it is transferred;
benefit of the example of gene transfer;
possible harm from the example of gene transfer;
Example:
gene transfer details [1 max]
e.g. Bt gene transferred from bacterium/Bacillus to maize
specific benefit [1 max]
e.g. corn borer/insect pest killed by Bt toxin increasing crop production;
e.g. less pesticides/fertilizers/chemicals needed so better for environment;
specific harmful effect [1 max]
e.g. non-target insects may be killed as well;
e.g. risk of cross-pollination may introduce gene to unintended species;
Examiners may have to consult resources for legitimate alternative examples.
© International Baccalaureate Organization 2018
International Baccalaureate® - Baccalauréat International® - Bachillerato Internacional®
Printed for Dubai American Academy