Download Essential Biology 04: Genetics (HL) DNA structure review: draw and

Essential Biology 04: Genetics (HL)
1. DNA structure review: draw and label a section of a DNA molecule.
Include sugar-phosphate backbone, bases, double helix shape, complementary base pairing.
Label the bond between nucleotides in a strand of DNA and the bond between base pairs.
2. What is a chromosome?
3. What makes up the structure of a chromosome?
DNA & ____________
4. How many chromosomes are present in a diploid human cell?
5. Distinguish between haploid and diploid.
6. Distinguish between chromosomes and chromatids.
7. Define gene.
8. Define genome.
9. What is a gene locus?
10. Define allele.
11. Give two examples of genes and some of their possible alleles.
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Essential Biology 04: Genetics (HL)
12.
13. Define mutation.
14. What factors can increase the chance of a genetic mutation?
15. Define evolution.
16. How can mutations lead to evolution by natural selection?
17. Compare the following types of base-substitution mutation.
Silent mutation
Number of bases
substituted
Mis-sense mutation
Nonsense mutation
1
Stop codon produced
early – polypeptide
shortened
Effect on polypeptide
Example illness
Sickle cell disease
18. Describe the effects of sickle cell disease on sufferers.
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Essential Biology 04: Genetics (HL)
19. In which parts of the world could carrying a sickle cell (Hbs) gene be beneficial? Why?
20. How is the spread of the sickle cell gene an example of natural selection in action?
21. How could this be an example of a correlation which has a strong element of causality?
22. Define the term homologous chromosomes.
23. Which three visual aspects of chromosomes can be used to identify them?
a. Banding patterns
b.
c.
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Essential Biology 04: Genetics (HL)
24. Define meiosis.
25. What is meant by the term reduction division?
26. What is the function of meiosis?
27. Add chromosomes and annotate the diagram below summarizing the steps in meiosis.
Where does crossing-over occur?
28. Compare mitosis and meiosis:
Mitosis
Meiosis
Number of divisions
Number of daughter cells
Chromosome number in
daughter cells
Functions:
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Essential Biology 04: Genetics (HL)
29. Outline the major events occurring at these stages of meiosis:
Meiosis I
Meiosis II
Prophase I
Prophase II
Metaphase I
Metaphase II
Anaphase I
Anaphase II
Telophase I
Telophase II
Cytokinesis
Cytokinesis
Interphase
30. Annotate the diagram below to show what happens in non-disjunction.
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Essential Biology 04: Genetics (HL)
31. Describe what you can see in this image.
32. Distinguish between bivalents and sister chromatids.
33. During which stage of meiosis is the image in Q32 most likely to be seen?
34. During which phase of meiosis does crossing over occur?
Outline the process of crossing over.
35. What is the effect of crossing over in terms of genetic diversity?
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Essential Biology 04: Genetics (HL)
36. A diploid cell carries genes A and B. There are dominant and recessive alleles for
these genes. The cell is heterozygous for both genes.
a. What combination of gametes could be produced if there was no crossing over?
b. What combinations of gametes could be produced if a chiasma formed between the loci of
genes A and B?
37. The rough image shows chromosomes forming chismata.
How many of the following structures are present?
Chromosomes
Centromeres
Sister Chromatids
Chiasmata
38. Which event during meiosis I leads to further genetic variation? Explain how.
39. State Mendel’s Law of Independent Assortment:
40. What assumption is made here?
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Essential Biology 04: Genetics (HL)
41. Illustrate Mendel’s law of independent assortment using two different heterozygous genes.
42. How does Mendel’s law of independent assortment relate to meiosis?
43. How does sexual reproduction lead to even further genetic variation within a species?
44. How does non-disjunction lead to trisomy?
45. Find out more about these trisomy disorders:
Down Syndrome*
Klinefelter Syndrome
Patau Syndrome
Chromosome
Some effects
*this is the one reference needed for the syllabus
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Essential Biology 04: Genetics (HL)
46. Using information in the graph, outline the effect of maternal age on likelihood of Down
Syndrome:
47. A karyotype can be used to test for non-disjunction disorders. Fetal cells are taken and the
number of chromosomes counted. Outline how these cells are retrieved:
Chorionic Villus Sampling (CVS):
Amniocentesis:
48. How are chromosomes arranged in a karyotype?
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Essential Biology 04: Genetics (HL)
49. Which trisomy disorder from question 45 is shown in this karyotype?
50. Define the following terms:
Genotype
Phenotype
Dominant allele
Recessive allele
Codominant alleles
Homozygous
Heterozygous
Carrier
Test cross
51. What is a monohybrid cross?
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Essential Biology 04: Genetics (HL)
52. Complete the punnet grid below to show the outcome of the monohybrid cross that results in
peas of different colours.
53. Complete the punnet grid below to show the possible outcomes of a cross between two
members of the F1 generation.
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Essential Biology 04: Genetics (HL)
54. In the examples above, identify individuals which are:
a. Homozygous dominant
b. Heterozygous
c. Homozygous recessive
55. The allele for red flower colour (R) is dominant over white (r).
A student suspects that a red flower is heterozygous. Explain how she could use a test cross to
verify this.
With complete dominance, a carrier is totally unaffected by the recessive allele – but can pass it on.
People who are heterozygous for the sickle cell allele display incomplete dominance – the single allele
causes some sickle cells to be produced, protecting them against malaria. If they are homozygous
recessive, they produce a lot of sickle cells and suffer from sickle cell disease .
56. Complete a punnet grid to show the results of a cross between two carrier parents.
What ratio of phenotypes do you expect in the offspring? How many will be:
- Sickle cell sufferers?
- Protected against malaria?
- Unprotected against malaria?
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Essential Biology 04: Genetics (HL)
57. Some genes have multiple alleles.
What does this mean?
58. Complete the table below to show how blood types are inherited.
59. Which blood type is an example of codominance?
60. Distinguish between autosomes and sex chromosomes.
61. Distinguish between the female (X) and male (Y) chromosomes in humans, in terms of size and
number of genes.
62. Complete a punnet grid to show how gender is determined in humans.
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Essential Biology 04: Genetics (HL)
63. A dihybrid cross considers two genes at the same time.
When Mendel came upon his law of independent assortment, he was studying sweet pea colour
and shape. These traits are carried on separate chromosomes.
The colour yellow (Y) is dominant over green (y). Smooth peas (S) are dominant over rough (s).
What are the possible genotypes for the following phenotypes:
Yellow, Smooth
Yellow, rough
Green, Smooth
Green, rough
64. Use the punnet grid to predict the ratio of phenotypes of offspring in a cross between two
completely heterozygous peas.
Ratios:
Smooth Yellow :
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Rough Yellow
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Essential Biology 04: Genetics (HL)
65. A researcher has some smooth yellow peas. He wants to find out if they are homozygous or
heterozygous for these dominant characteristics, so he performs a test cross.
a. What must be the genotype must he use as the other individual in the test cross?
b. Complete a series of punnet grids for this cross. What phenotypic ratios would he expect to see
if the smooth yellow peas were:
i.
Heterozygous for both colour and shape?
ii.
Homozygous for both colour and shape?
iii.
Heterozygous for colour, homozygous for shape?
iv.
Homozygous for colour, heterozygous for shape?
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Essential Biology 04: Genetics (HL)
c. In the cross, the student found 120 yellow-smooth and 124 green-smooth.
Which genotype is most likely to have been that of the unknown pea?
d. What statistical test could be used to test the significance of this result?
66. Define gene interaction.
67. Complete a punnet grid for a cross between two ‘agouti’ (brown) mice.
What phenotypic ratio is expected?
Why does this differ from the normal 9:3:31 ratio of a heterozygous cross?
Key: C = coat has colour,
c = coat has no colour (albino).
A = agouti (brown) colour, a = black coat
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Essential Biology 04: Genetics (HL)
68. Define linkage group.
69. What is the consequence of gene linkage in terms of the movement of alleles in anaphase I?
70. Give two plant examples of linked genes.
71. The notation shows genes of Zea mays (corn). It is described as
“heterozygous at both loci”.
Draw the other possible combinations of these linked genes.
a. Homozygous at both loci
b. Homozygous at locus 1.
c.
(write the description)
72. Complete a punnet grid to show the possible phenotypes produced by a cross between the corn
that is heterozygous at both loci.
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Essential Biology 04: Genetics (HL)
73. Which combinations of alleles would be ‘impossible’ in the cross above? Why?
74. What can we assume has happened if a small number of ‘impossible’ phenotypes have
appeared in the cross?
75. At which point of meiosis does recombination due to crossing over occur?
76.
77.
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78. A cross is carried out between two organisms with genotypes GgHh and gghh. Which offspring
below are recombinants? The genes G and H are linked.
A. GgHh, gghh
B. Gghh, ggHh
C. GGhh, ggHH
D. gghh, Ggh
Can you explain why the other three options were not correct?
79. In sweet peas (Lathyrus odoratus), pollen grain shape and flower colour are
linked genes. P=purple, p = white L=long pollen, l = short pollen.
The genes are far enough apart that crossing-over occurs occasionally.
a. Which statement is true of the gametes?
A. They will be all Pl and pL
B. They will be 25% each of Pl, pL, PL and pl
C. There will be more pL gametes than PL gametes.
D. There will be an equal number of PL and pL gametes.
b. Complete a punnet grid in the space below to show the possible genotypes and phenotypes
of a test cross with the individual above. Assume no crossing over.
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Essential Biology 04: Genetics (HL)
80. Define sex-linkage.
81. Distinguish between sex linkage and gene linkage.
82. Explain briefly why sex-linked traits are more common in males than females.
83. The allele for colour blindness (n) is recessive to the allele for normal vision (N). This gene is
carried on the X chromosome. Complete the table below to show the genotypes and
phenotypes of individuals with regard to colour blindness.
Female
Normal
Male
XN XN
Affected
Not possible! Why?
Carrier
84. In the space below, complete a punnet grid to show a cross between a normal male and a
carrier female. What is the expected ratio of phenotypes?
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Essential Biology 04: Genetics (HL)
85. Hemophilia is a blood-clotting disorder that is also sex-linked.
Use the pedigree chart to answer these questions.
a. What is the genotype of Leopold? Why?
b. What is the genotype of Helen? Why?
c. Which two females’ symbols need to be amended? Why?
d. What are the possible genotypes of Bob?
Stephen Taylor
Bandung International School
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Essential Biology 04: Genetics (HL)
86. Use the pedigree chart of the mystery trait below to answer these questions.
Create your own key: symbols are standard.
a. Is this trait dominant or recessive? How do you know?
b. Is this trait autosomal or sex-linked? How do you know?
c. How could you determine whether an affected female was homozygous or heterozygous for
the mystery trait?
87. Define polygenic inheritance.
88. Give some examples of polygenic inheritance in humans and in plants.
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Essential Biology 04: Genetics (HL)
89. What is a contributing allele?
90. Polygenic inheritance gives rise to continuous variation within a population.
Explain what this means, using skin colour as an example.
91. Assume that two genes (A and B) are responsible for inheritance of skin colour, with two alleles
each and that they are unlinked.
a. How many genotypes are possible?
b. What are the phenotypes associated with these genotypes?
c. Why is there a normal distribution of phenotypes?
92. Using a punnet grid, explain why it is possible for children to have skin which is darker or lighter
than both parents.
Stephen Taylor
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Essential Biology 04: Genetics (HL)
93. Compare the advantages and disadvantages of light and dark skin.
Light Skin
Dark Skin
Cold Climate
Hot Climate
94. What measures could be taken for
a. Pale skinned people to avoid the dangers of hot climates?
b. Dark skinned people to reduce the disadvantage of a cold climate?
95. Compare the effects of a change in a single allele on Mendelian (monohybrid) crosses and on
polygenic characteristics.
96. A characteristic is controlled by three genes with two alleles each. How many genotypes are
possible in a cross between a homozygous recessive father and a homozygous dominant
mother?
Stephen Taylor
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Essential Biology 04: Genetics (HL)
97. What does PCR stand for?
98. How is PCR useful in investigations?
99. Outline briefly how gel electrophoresis works.
100.
What are two main uses of DNA profiling by electrophoresis?
101.
Use the gel electrophoresis results below to answer these questions.
a. Which criminal, Rob McCarr or Nick Allott, left their dribbly cigarette-end at the crime scene?
How do you know?
b. Colour in bands to show where the ‘standard’ fragments would be observed.
c. What evidence is there to suggest that Nick and Rob are related?
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Essential Biology 04: Genetics (HL)
102.
This father thinks that the second child is not his – he looks too different from him!
He has seen the mother and the mailman chatting and is suspicious. He stole some hair from all
family members and swabbed a cup the mailman used and ran a gel electrophoresis to confirm
his suspicions.
103.
What is the Human Genome Project?
104.
How did the HGP develop knowledge in the following fields?
Evolutionary research
Medicine
Bioinformatics
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Essential Biology 04: Genetics (HL)
105.
What is meant by the term ‘the genetic code is universal’?
106.
What is a transgenic organism?
107.
State three uses for gene transfer technology.
108.
What is the role of the following in gene transfer:
Restriction enzymes
E. coli plasmids
Ligase
Vector
109.
How is gene transfer used in industrial production of insulin?
110.
Give three examples of genetically modified plant crops and the effects of their new
genes.
New properties
Advantages
‘Golden Rice’
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Essential Biology 04: Genetics (HL)
111.
Outline how genetically modified sheep can help hemophiliacs.
112.
Explain how gene transfer can be used to cure SCID.
113.
Discuss the benefits and potential dangers of one type of genetic modification used in
agriculture.
114.
Define clone.
115.
Give three examples of naturally occurring clones.
116.
Dolly the Sheep was produced by cloning using a differentiated nucleus.
a. What is a differentiated nucleus?
b. Why was the differentiated nucleus taken from an udder cell?
c. Suggest one reason why Dolly died younger than normal, but of age-related illnesses.
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Essential Biology 04: Genetics (HL)
117.
Outline the method used to clone Dolly the Sheep.
118.
Distinguish between reproductive cloning and therapeutic cloning.
119.
Discuss the ethical considerations of therapeutic cloning in humans.
120.
How might stem-cell reprogramming mitigate the negative opinions of human
therapeutic cloning?
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