Review Packet #5 - Genetics (Topics 3 all, Topic 10.1, 10.2)

1. If a person inherited an allele with the same base substitution mutation from both parents, what sequences could be altered from normal in the person’s cells?

A. One mRNA base sequence only

B. Two mRNA base sequences only

C. One mRNA base sequence and one polypeptide amino acid sequence only

D. Two mRNA base sequences and two polypeptide amino acid sequences only(Total 1 mark)

2. Which processes always occur in meiosis but not normally in mitosis?

I. Chiasmata formation

II. Recombination of genes

III. Separation of homologous chromosomes

A. I and II only

B. II and III only

C. I and III only

D. I, II and III(Total 1 mark)

3. Mendel crossed pure breeding (homozygous) tall pea plants that had coloured flowers with pure breeding dwarf pea plants that had white flowers. All of the resulting F1 plants were tall and had coloured flowers.

If Mendel had crossed these F1 plants with a pure breeding strain of dwarf pea plants with coloured flowers, what proportion of tall coloured plants would be expected in the offspring?

A. 41

B. 83

C. 21

D. 169

(Total 1 mark)

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4. A gene has three alleles. How many different genotypes can be found for this gene?

A. 3

B. 6

C. 9

D. 12(Total 1 mark)

5. A cross is carried out between two heterozygous individuals (AaBb) where the genes A and B are not linked genes. What would be the proportions of genotypic recombinants amongst the offspring of this cross?

A. 0

B. 25

C. 75

D. 100(Total 1 mark)

6. What is the genetic cross called between an individual of unknown genotype and an individual who is homozygous recessive for a particular trait?

A. Test-cross

B. Hybrid cross

C. Dihybrid cross

D. F1 cross(Total 1 mark)

7. What is the usual cause of Down’s syndrome?

A. 21 pairs of chromosomes

B. Trisomy 21

C. Non-disjunction of sex chromosomes

D. Fertilization of the egg by two sperm(Total 1 mark)

8. Which enzyme is used to produce complementary DNA (cDNA) from mRNA?

A. Restriction endonuclease

B. Reverse transcriptase

C. DNA ligase

D. RNA primase(Total 1 mark)

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9. If the haploid number of an organism is 8, how many different varieties of gametes are possible, not considering the effects of crossing over?

A. 16

B. 64

C. 128

D. 256(Total 1 mark)

10. How does the X chromosome differ from the Y chromosome in humans?

A. The Y chromosome is longer.

B. Some genes on the X chromosome are absent from the Y chromosome.

C. The genes are the same but some on the Y chromosome are not expressed.

D. The X chromosome determines sex.(Total 1 mark)

11. What are the functions of the polymerase chain reaction?

I. Copy fragments of DNA

II. Amplify fragments of DNA

III. Translate fragments of DNA

A. I and II only

B. I and III only

C. II and III only

D. I, II and III(Total 1 mark)

12. What procedure is used to determine whether a chromosome is in excess or missing in an organism?

A. X-ray

B. Karyotyping

C. Centrifugation

D. DNA fingerprinting(Total 1 mark)

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13. What feature demonstrates codominance in the inheritance of ABO blood groups?

A. When A antigens and B antigens are present on red blood cells.

B. When A antibodies and B antibodies are present in blood serum.

C. When IA and i alleles are expressed in homozygotes.

D. When IA and i alleles are expressed in heterozygotes.(Total 1 mark)

14. Which event occurs first in meiosis?

A. Centromere appearance

B. Chiasmata formation

C. Crossing over

D. Synapsis(Total 1 mark)

15. Alleles S and T are both dominant. In the theoretical cross ttSs Ttss, which of the following offspring would show recombination?

A. TS, tS

B. TS, Ts

C. tS, Ts

D. TS, ts(Total 1 mark)

16. Colour blindness in humans is caused by an X chromosome linked recessive allele. In the pedigree chart below which two individuals must, for certain, be carriers of colour blindness?

I

I I I I VI I

A. II and IV

B. I and III

C. II and III

D. I and II(Total 1 mark)

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17. In Drosophila the allele for normal wings (W) is dominant over the allele for vestigal wings (w) and the allele for normal body (G) is dominant over the allele for ebony body (g). If two Drosophila with the genotypes Wwgg and wwGg are crossed together, what ratio of phenotypes is expected in the offspring?

A. 9 × normal wings, normal body : 3 × normal wings, ebony body : 3 × vestigal wings, normal body : 1 × vestigal wings, ebony body

B. 3 × normal wings, normal body : 3 × normal wings, ebony body : 3 × vestigal wings, normal body : 1 × vestigal wings, ebony body

C. 3 × normal wings, normal body : 1 × normal wings, ebony body : 3 × vestigal wings, normal body : 1 × vestigal wings, ebony body

D. 1 × normal wings, normal body : 1 × normal wings, ebony body : 1 × vestigal wings, normal body : 1 × vestigal wings, ebony body

(Total 1 mark)

18. A gene in cattle controls whether horns develop or not. When cattle without horns are mated together, none of the offspring ever has horns. A male with horns is mated with females without horns. If half of the offspring have horns and half do not, what is the conclusion?

A. The male is homozygous dominant.

B. The male is homozygous recessive.

C. The male is heterozygous.

D. Only males have horns.(Total 1 mark)

19. Humans are in blood group M, N or MN. The alleles for blood group M (M) and blood group N (N) are co-dominant. Humans are also in blood group A, B, AB or O. The alleles controlling these blood groups are IA, IB and i.

If two parents have the genotypes ii MM and IA i MN what is the ratio of possible phenotypes of their offspring?

A. 9 group A, group M 3 group A, group N 3 group O, group M 1 group O, group N

B. 9 group O, group M 3 group O, group N 3 group A, group M 1 group A, group N

C. 3 group O, group M 3 group O, group MN 1 group A, group M 1 group A, group MN

D. 1 group A, group M 1 group A, group MN 1 group O, group M 1 group O, group MN

(Total 1 mark)

20. A cell replicates its DNA and then starts to divide by meiosis. What is the expected arrangement of chromosomes if crossing over has taken place between the two genes shown?

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A . B .

C . D .

(Total 1 mark)

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21. Which response describes the behaviour of chromosomes in metaphase I and anaphase II of meiosis?

Metaphase I Anaphase II

A. Chromosomes line up at the equator Separation of homologous chromosomes

B. Tetrads (bivalents) line up at the equator Separation of homologous chromosomes

C. Chromosomes line up at the equator Separation of sister chromatids

D. Tetrads (bivalents) line up at the equator Separation of sister chromatids(Total 1 mark)

22. In garden peas, the pairs of alleles coding for seed shape and seed colour are unlinked. The allele for smooth seeds (S) is dominant over the allele for wrinkled seeds (s). The allele for yellow seeds (Y) is dominant over the allele for green seeds (y).

If a plant of genotype Ssyy is crossed with a plant of genotype ssYy, which offspring are recombinants?

A. SsYy and Ssyy

B. SsYy and ssYy

C. SsYy and ssyy

D. Ssyy and ssYy(Total 1 mark)

23. What constitutes a linkage group?

A. Genes carried on the same chromosome

B. Genes whose loci are on different autosomes

C. Genes controlling a polygenic characteristic

D. Alleles for the inheritance of ABO blood groups(Total 1 mark)

24. The allele for red flower colour (R) in a certain plant is co-dominant with the allele for white flowers (R’). Thus a plant with the genotype RR’ has pink flowers. Tall (D) is dominant to dwarf (d). What would be the expected phenotypic ratio from a cross of RR’dd plants with R’R’Dd plants?

A. 9:3:3:1

B. 50% pink 50% white, and all tall

C. 1:1:1:1, in which 50% are tall, 50% dwarf, 50% pink and 50% white

D. 3:1(Total 1 mark)

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25. Two genes A and B are linked together as shown below.

A b

a B

If the genes are far enough apart such that crossing over between the alleles occurs occasionally, which statement is true of the gametes?

A. All of the gametes will be Ab and aB.

B. There will be 25% Ab, 25% aB, 25% ab and 25% AB.

C. There will be approximately equal numbers of Ab and ab gametes.

D. The number of Ab gametes will be greater than the number of ab gametes.(Total 1 mark)

26. A polygenic character is controlled by two genes each with two alleles. How many different possible genotypes are there for this character?

A. 2

B. 4

C. 9

D. 16(Total 1 mark)

27. A cross is performed between two organisms with the genotypes AaBb and aabb.

What genotypes in the offspring are the result of recombination?

A. Aabb, AaBb

B. AaBb, aabb

C. aabb, Aabb

D. Aabb, aaBb(Total 1 mark)

28. The diagram below shows chromosomes during prophase I of meiosis. How many chromosomes and chiasmata are visible?

Number of chromosomes Number of chiasmata

A. 2 2

B. 4 2

C. 2 4

D. 4 4(Total 1 mark)

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29. In peas the allele for round seed (R) is dominant over the allele for wrinkled seed (r). The allele for yellow seed (Y) is dominant over the allele for green seed (y).

If two pea plants with the genotypes YyRr and Yyrr are crossed together, what ratio of phenotypes is expected in the offspring?

A. 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green

B. 3 round yellow : 3 round green : 1 wrinkled yellow : 1 wrinkled green

C. 3 round yellow : 1 round green : 3 wrinkled yellow : 1 wrinkled green

D. 1 round yellow : 1 round green : 1 wrinkled yellow : 1 wrinkled green(Total 1 mark)

30. What is a difference between autosomes and sex chromosomes?

A. Autosomes are not found in gametes but sex chromosomes are.

B. Sex chromosomes are found in animal cells and autosomes are found in plant cells.

C. Autosomes are diploid and sex chromosomes are haploid.

D. Sex chromosomes determine gender and autosomes do not.(Total 1 mark)

31. The diagram below shows a cell in meiosis. What can be deduced from this diagram?

[Source: J W Saunders, (1968), Animal Morphogenesis, MacMillan, page 7]

Stage of meiosis shown Haploid number ofchromosomes in this cell

A. Metaphase I 6

B. Prophase I 3

C. Prophase I 6

D. Metaphase I 3(1)

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32. If red (RR) is crossed with white (rr) and produces a pink flower (Rr), and tall (D) is dominant to dwarf (d), what is the phenotypic ratio from a cross of Rr dd and rr Dd?

A. 9:3:3:1

B. 50% pink, 50% white and all tall

C. 1:1:1:1, in which 50% are tall, 50% dwarf, 50% pink and 50% white

D. 3:1(1)

33. What is the locus of a gene?

A. The proportion of the population that have the gene

B. The part of the phenotype that is affected by the gene

C. The position of a gene on a chromosome

D. The predicted effect of natural selection on the frequency of the gene(Total 1 mark)

34. The diagram below shows the life cycle of a moss. The haploid chromosome number is shown as n and the diploid number as 2n. At which stage in the life cycle does meiosis take place?

A. I

B. II

C. III

D. IV(Total 1 mark)

35. Which human trait shows a pattern of polygenic inheritance?

A. ABO blood type

B. Sickle cell anemia

C. Skin colour

D. Co-dominant alleles(Total 1 mark)

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36. How does recombination normally occur for unlinked genes?

A. Crossing-over in Prophase I

B. Random chromosome assortment

C. Failure of spindles to form

D. Random gene mutations(Total 1 mark)

37. Why is it sometimes difficult to identify how certain characteristics are inherited in humans.

A. Most genes are linked.

B. Rates of mutation are high.

C. The inheritance may be polygenic.

D. The environment varies so little.(Total 1 mark)

38. The diagram below shows a cell undergoing meiosis. What is this stage of meiosis?

A. Anaphase I

B. Prophase I

C. Anaphase II

D. Telophase II(Total 1 mark)

39. A pure breeding tall plant with smooth seeds was crossed with a pure breeding short plant with wrinkled seeds. All the F1 plants were tall with smooth seeds. Two of these F1 plants were crossed and four different phenotypes were obtained in the 320 plants produced.

How many tall plants with wrinkled seeds would you expect to find?

A. 20

B. 180

C. 60

D. 30(Total 1 mark)

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40. What constitutes a linkage group?

A. Genes whose loci are on different chromosomes

B. Genes carried on the same chromosome

C. Genes controlling a polygenic characteristic

D. Genes for the inheritance of ABO blood groups(Total 1 mark)

41. What are the possible outcomes of recombination?

I. A different combination of unlinked genes not seen in the parentsII. A different combination of linked genes not seen in the parentsIII. The same combination of genes seen in the parents

A. I and II only

B. I and III only

C. II and III only

D. I, II and III(Total 1 mark)

Short Answer Questions

1. The following diagram represents a two generation pedigree showing the blood groups of the individuals. The female has been married to two different individuals.

1 s t g en e ra tio n

2 n d g en e ra tio n

O A A B

1 2 3

1 2 3 4

B O A A B

K ey

M ale

F em a le

(a) Define the term co-dominant alleles.

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(b) Deduce with a reason the probable father of 2nd generation–1.

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(2)

(c) If 2nd generation–3 marries a man with blood group AB, predict the possible genotypes of the children.

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(Total 6marks)

2. (a) State the names of the parts of the chromosome labelled (i) and (ii) on the diagram below.

(2)

[Source: adapted from Hartwell (editor) (2003), Genetics: from Genes to Genomes, 2nd edition, McGraw Hill, page 81]

(b) Explain how the inheritance of chromosome 21 can lead to Down’s syndrome.

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(c) Explain how meiosis promotes variation in a species.

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(Total 7 marks)

3. A gene in humans called APC is located on chromosome 5. This gene controls cell division and is known as a tumour suppressor gene. Mutations of APC cause a genetic disease called FAP (Familial Adenomatous Polyposis).

(a) State, with a reason, whether FAP is a sex-linked genetic disease or not.

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50% of the gametes produced by a person with FAP have an APC gene with the mutation.

(b) Identify, with a reason, whether FAP follows a dominant or recessive pattern of inheritance.

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In a person with FAP, each cell contains a copy of the APC gene with the mutation. If a mutation occurs on the cell’s other copy of the APC gene, the cell becomes a tumour cell. Almost everyone with FAP develops cancer before the age of 50.

(c) Explain why almost everyone with FAP eventually develops cancer.

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In 2004, doctors in Britain were given permission to test embryos to see whether an APC gene with the mutation is present. This test can be used where one of the parents is known to have FAP. The procedure involves the parents using in-vitro fertilisation (IVF) to produce embryos, testing the embryos for the gene and implanting only embryos that do not have the mutation.

(d) (i) State the name of this type of test.

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(ii) State one advantage and one disadvantage of testing embryos in this way.

Advantage: ...................................................................................................

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Disadvantage:..................................................................................................

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(Total 8 marks)

4. (a) State one advantage and one disadvantage of genetic modification technology for crop plants.

Advantage: ........................................................................................................

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Disadvantage: ........................................................................................................

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(b) Explain the effect of base substitution mutation in sickle cell anemia.

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(Total 5 marks)

5. (a) (i) Define allele.

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(ii) Outline the consequences of a base substitution mutation.

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(b) (i) Mendel crossed tall, round-seeded plants with short, wrinkled-seeded plants.All F1 produced were tall, round-seeded plants. When F1 plants were crossed with other F1 plants, the F2 generation produced many more than 1/16 short, wrinkled-seeded plants. Deduce, with reasons, the inheritance of these genes.

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(ii) The same cross was later repeated but gave fewer F2 short, wrinkled-seeded plants although still more than 1/16. Outline a named statistical test that could indicate if your deduction about the inheritance of these two genes is likely to be correct.

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(Total 7 marks)

6. In Zea mays, the allele for coloured seed (C) is dominant over the allele for colourless seed (c). The allele for starchy endosperm (W) is dominant over the allele for waxy endosperm (w). Pure breeding plants with coloured seeds and starchy endosperm were crossed with pure breeding plants with colourless seeds and waxy endosperm.

(a) State the genotype and the phenotype of the F1 individuals produced as a result of this cross.

genotype .............................................................................................................................

phenotype .............................................................................................................................(2)

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(b) The F1 plants were crossed with plants that had the genotype c c w w. Calculate the expected ratio of phenotypes in the F2 generation, assuming that there is independent assortment. Use the space below to show your working.

Expected ratio .....................................................................................................(3)

The observed percentages of phenotypes in the F2 generation are shown below.

coloured starchy 37% colourless starchy 14%

coloured waxy 16% colourless waxy 33%

The observed results differ significantly from the results expected on the basis of independent assortment.

(c) State the name of a statistical test that could be used to show that the observed and the expected results are significantly different.

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(d) Explain the reasons for the observed results of the cross differing significantly from the expected results.

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(Total 8 marks)

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7. (a) A farmer has rabbits with two particular traits, each controlled by a separate gene. Coat colour brown is completely dominant to white. Tailed is completely dominant to tail-less. A brown, tailed male rabbit that is heterozygous at both loci is crossed with a white, tail-less female rabbit. A large number of offspring is produced with only two phenotypes: brown and tailed, white and tail-less, and the two types are in equal numbers.

(i) Deduce the pattern of inheritance of these traits.

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(ii) State both parents’ genotypes and the gametes that are produced by each during the process of meiosis.

Male genotype: ........................................................................................

Female genotype: ........................................................................................

Male gametes: ........................................................................................

Female gametes: ........................................................................................(2)

(iii) Predict the genotypic and phenotypic ratios of the F2 generation. Show your working.

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(b) Outline the biotechnology used to transfer genes from one organism to another.

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(Total 9 marks)

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8. (a) State the two classes of compounds that compose chromosomes in animal cells.

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(b) Outline how meiotic division results in almost an infinite genetic variation in the gametes produced.

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(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 tallt allele for short

R allele for round seed

r allele for wrinkled seed.

Determine the phenotypes and genotypes of the offspring of this cross.

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(d) State how chromosome number can increase in human beings.

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(1)(Total 6 marks)

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