1. DNA Structure Review: Draw and Label a Section of a DNA Molecule s1

Essential Biology 04: Genetics

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.

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.

18.  Describe the effects of sickle cell disease on sufferers.

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

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.  What is the effect of crossing over?

29.  Compare mitosis and meiosis:

30.  Outline the major events occurring at these stages of meiosis:

31.  Annotate the diagram below to show what happens in non-disjunction.

32.  How does non-disjunction lead to trisomy?

33.  Find out more about these trisomy disorders:

*this is the one reference needed for the syllabus

34.  Using information in the graph, outline the effect of maternal age on likelihood of Down Syndrome:

35.  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:

36.  How are chromosomes arranged in a karyotype?

37.  Which trisomy disorder from question 33 is shown in this karyotype?

38.  Define the following terms:

Genotype

Phenotype

Dominant allele

Recessive allele

Codominant alleles

Homozygous

Heterozygous

Carrier

Test cross

39.  What is a monohybrid cross?

40.  Complete the punnet grid below to show the outcome of the monohybrid cross that results in peas of different colours.

41.  Complete the punnet grid below to show the possible outcomes of a cross between two members of the F1 generation.

42.  In the examples above, identify individuals which are:

a.  Homozygous dominant

b.  Heterozygous

c.  Homozygous recessive

43.  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 .

44.  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?

45.  Some genes have multiple alleles.

What does this mean?

46.  Complete the table below to show how blood types are inherited.

47.  Which blood type is an example of codominance?

48.  Distinguish between autosomes and sex chromosomes.

49.  Distinguish between the female (X) and male (Y) chromosomes in humans, in terms of size and number of genes.

50.  Complete a punnet grid to show how gender is determined in humans.

51.  Define sex-linkage.

52.  Explain briefly why sex-linked traits are more common in males than females.

53.  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.

54.  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?

55.  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?

56.  Use the punnet grid 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?

57.  What does PCR stand for?

58.  How is PCR useful in investigations?

59.  Outline briefly how gel electrophoresis works.

60.  What are two main uses of DNA profiling by electrophoresis?

61.  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?

62.  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.

63.  What is the Human Genome Project?

64.  How did the HGP develop knowledge in the following fields?

Evolutionary research

Medicine

Bioinformatics

65.  What is meant by the term ‘the genetic code is universal’?

66.  What is a transgenic organism?

67.  State three uses for gene transfer technology.

68.  What is the role of the following in gene transfer:

Restriction enzymes

E. coli plasmids

Ligase

Vector

69.  How is gene transfer used in industrial production of insulin?

70.  Give three examples of genetically modified plant crops and the effects of their new genes.

71.  Outline how genetically modified sheep can help hemophiliacs.

72.  Explain how gene transfer can be used to cure SCID.

73.  Discuss the benefits and potential dangers of one type of genetic modification used in agriculture.

74.  Define clone.

75.  Give three examples of naturally occurring clones.

76.  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.

77.  Outline the method used to clone Dolly the Sheep.

78.  Distinguish between reproductive cloning and therapeutic cloning.

79.  Discuss the ethical considerations of therapeutic cloning in humans.

80.  How might stem-cell reprogramming mitigate the negative opinions of human therapeutic cloning?