Review #4: Genetics, Meiosis, and Biotechnology Short Answer and Extended Response Released IB Questions
1.	 
(a)	Explain, using an example, how females but not males can be carriers of some recessive alleles.
(4)
(b)	Explain the causes and consequences of sickle-cell anemia.
(5)
(Total 9 marks) 
2.	(a)    Describe the causes of Down syndrome.
(5)
(b)	Describe how human skin colour is determined genetically.
(5)
(c)	Explain the causes of sickle-cell anemia.
(8)
(Total 18 marks)
3.	 Explain the methods and aims of DNA profiling.
(8) 
4.	(a)	In some maize plants the seed is enclosed in a green sheath called a tunica.
The allele (T) for this is dominant to the allele (t) for normal, unenclosed seeds.
The endosperm of the seed can be starchy (allele E) or sugary (allele e). The genes for these two characteristics are linked. The table below shows the outcome of crosses between a plant heterozygous for both characteristics and one that is homozygous recessive for both characteristics.

Phenotype	Number	
Tunica present, starchy	326	
Unenclosed seeds, starchy	111	
Tunica present, sugary	118	
Unenclosed seeds, sugary	295	

(i)	State the genotype of the heterozygous parent using the correct notation.
 (1)
(ii)	Identify which individuals are recombinants in this cross.
 (1)
(iii)	Explain what has occurred to cause these results.
 (2)
 (Total 4 marks)
5.	Which are the possible recombinants in a dihybrid test cross involving the linked genes ?
A.	
B.	
C.	
D.	
(Total 1 mark) 
6.	
Outline the method that can be used to amplify small quantities of DNA to obtain large enough quantities for DNA profiling.
 (2)
7.	The diagram below shows a pair of chromosomes during meiosis in a cell in the human testis.
The position of the alleles of some genes is indicated.
		
(a)	Deduce, with reasons for your answer, whether the chromosomes are
(i)	autosomes or sex chromosomes.
 (1)
(ii)	homologous or non-homologous.
 (1)
(b)	State the stage of meiosis of a cell if it contains pairs of chromosomes as shown in the diagram.
 (1)
(c)	At the end of meiosis, each of the chromatids shown in the diagram will be in a different haploid cell. The diagrams below represent the chromatids inside the haploid cells.
Determine the combinations of alleles that would be present on each chromatid. Use the diagrams to indicate your answer.

(2)
(d)	State the pattern of inheritance shown by the three genes.
 (1)
(Total 6 marks)
8.	(a)   Describe karyotyping and one application of its use.
(4)
(b)	Describe a technique used for gene transfer.
(5)
(c)	Using a named example, discuss the benefits and harmful effects of genetic modification.
(9)
(Total 18 marks) 
9.	(a)	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)
(b)	The diagram below shows a cut circle of DNA into which a gene is being inserted. Before it can be transferred into a bacterium, the 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.
 (2)
(c)	Discuss the potential benefit and possible harm of one named example of gene transfer between species.
 (3)
(Total 6 marks)
10.	(a)	State the name of the technique that is used to separate fragments of DNA according to their size, during DNA profiling.
 (1)
(b)	The diagram below represents the results of a paternity investigation. Track A is the profile of the mother of a child, track B is the profile of the child and track C is the profile of a man who might be the father.
		
	Explain, using evidence from the diagram, whether this man is the father or not.
 (3)
(Total 4 marks)

11.	The karyotype below shows the chromosomes from a person with Down syndrome.

(a)	State the evidence provided by the karyotype that shows this person has Down syndrome.
(1)
(b)	Outline how Down syndrome occurs due to meiosis.
 (2)
(c)	Determine, giving a reason, the sex of the person in the karyotype.
 (1)
(d)	Explain briefly why males are more likely to inherit colour blindness than females.
 (2)
(Total 6 marks)
12.	(a)	State two procedures used for the preparation of a DNA profile.
 (1)
	The following part of a DNA profile was used as evidence in a criminal investigation. DNA profiles of two suspects labelled S1 and S2 were compared to the DNA profile taken from the scene of the crime labelled E.

(b)	Analyse the profiles to determine which suspect was present at the crime scene.
 (2)
(Total 3 marks)
13.	(a)	State the two classes of compounds that compose chromosomes in animal cells.
 (1)
(b)	Outline how meiotic division results in almost an infinite genetic variation in the gametes produced.
 (2)
(c)	In a species of plant, tall is dominant to short and the production of round seeds is dominant to that of wrinkled seeds. The alleles are unlinked.
	A plant heterozygous for both characteristics is crossed with a plant homozygous for tall with wrinkled seeds.
Use the letters:
T—allele for tall
t — allele for short
R — allele for round seed
r—allele for wrinkled seed.
Determine the phenotypes and genotypes of the offspring of this cross.
 (2)
(d)	State how chromosome number can increase in human beings.
 (1)
(Total 6 marks)
14.	Outline a basic technique for gene transfer.
(6)
15.	In the red squirrel (Tamiasciurus hudsonicus), the allele for grey fur colour (G) is dominant to the allele for red fur colour (g) and the allele for a fluffy tail (F) is dominant to hairless tail (f).
(a)	The genes described above form a linkage group. Define linkage group.
 (1)
(b)	A cross is made between squirrels of the following genotypes.
		
	Using a similar format, identify the genotypes of offspring which are recombinants.
 (2)
(c)	Explain how the recombinants are formed during meiosis.
 (3)
(Total 6 marks)
16.	Which processes result in recombination?

	Meiosis	Crossing over	Independent assortment	Mutation	
A.	yes	yes	yes	no	
B.	yes	no	yes	no	
C.	yes	yes	no	yes	
D.	no	no	no	yes	
(Total 1 mark)
17.
A boy inherited red-green colour-blindness from one of his grandfathers. Deduce, giving your reasons, which of his two grandfathers was also colour-blind.
 (Total 3 marks)
18.	(a)	Define the term polygenic inheritance.
 (1)
(b)	Explain, using a named example, how polygenic inheritance gives rise to continuous variation.
 (2)
(c)	Describe the inheritance of colour blindness in humans.
 (3)
(Total 6 marks)
19.	Explain how sexual reproduction can eventually lead to evolution in offspring.
(8)
20.	(a)   Outline the formation of chiasmata during crossing over.
(5)
(b)	Explain how an error in meiosis can lead to Down syndrome.
(8)
(Total 13 marks)
21.	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)
22.	If the haploid number of a species is 14, how many chromatids will there be in metaphase I in a dividing diploid cell?
A.	7
B.	14
C.	28
D.	56
(Total 1 mark)
23.	The diagram below shows a pair of chromosomes immediately after pairing in prophase I of meiosis in a cell. What combinations of alleles are possible in haploid cells produced by meiosis in this cell?

(Total 1 mark)

24.	What do all human males inherit from their mother?
I.	An X chromosome
II.	A Y chromosome
III.	Mitochondrial DNA
A.	I and II only
B.	II only
C.	I and III only
D.	I, II and III
(Total 1 mark)