MELBOURNE HIGH SCHOOL
BIOLOGY UNIT 4
PRACTICAL NOTES
Remember pay attention to all the assessment criteria and their weighting, when writing
your reports.
Table of Contents
SAC 1-1: Mendelian Inheritance
2
SAC 1-2a: Structure & Role of DNA
3
SAC 1-2b: Manipulation of DNA
4
SAC 2-1: Evolutionary Relationships
4
SAC 2-2: Applied Gene Technology - Issue
4
—2—
SAC 1-1: Mendelian Inheritance
INTRODUCTION
Depending on the nature of the gene(s) involved, inheritance often follows defined and predictable patterns, first discovered by Gregor
Mendel in 1865.
AIMS
In this experiment you will germinate some seeds, collect data regarding the colour of the offspring, and make decisions about the genetic inheritance pattern involved in the cross. The cross involves a single gene locus with two alleles, one completely recessive.
You will also use a computer program to work out the genotypes of individuals in a pedigree.
HYPOTHESIS
It is possible to use a knowledge of Mendelian inheritance patterns to determine the genotypes of either the parents, or the offspring in
a genetic cross.
MATERIALS & EQUIPMENT (PER TEAM OF 3)
Petri dish; cotton wool; 6 seeds; forceps; computer with SEXLINK.
PROCEDURE
1. Thinly cover the base of a Petri dish with cotton wool.
2. Moisten the cotton wool.
3. Place the seeds, evenly spaced, on the cotton wool.
4. Place the lid on the Petri dish and draw the appearance of the dish.
5. Mark the dish so you can later identify it as yours.
6. Place the dish in an incubator set to 24°C for 4 days.
7. After 4 days have elapsed, examine the dishes for signs of germination.
8. When germination is apparent, leave the lids off, but keep the cotton wool moist (not wet).
9. As colour becomes evident in the seedlings, score the colours present in your dish, and collect results from all other groups in your class.
10. Use the computer program called SEXLINK to determine the genotypes in a pedigree involving a rare, X-linked gene. Read the instructions relating to the program first. Capture the screen when you have everything correct, and present a print of the screen with your report for this SAC.
PROCEDURE
Open the program in the Biology section called SEXLINK
1. In the first exercise you are told the recessive gene is “rare”. What that means to the program is that if there is any doubt about that allele being
in a individual’s genotype, it is NOT!
2. After completing the exercise, record your pedigree and paste it in a Word document for inclusion with your SAC report.
EXAMINING THE RESULTS
1. What colours were present in the seedlings, and in what proportion?
2. From your results, what must have been the genotype of the parents in the cross? Explain why.
3. From your results, which phenotype is recessive? Explain why you think so.
4. Explain which coloured seedlings you think would not survive.
5. Using the allele symbols G and g, write the possible genotypes of the dominant phenotype plants?
6. How could you test some of the dominant phenotype plants’ actual genotypes? What would the parental phenotypes be for such a cross?
7. What was the class-pooled ratio of the dominant to recessive phenotypes? If it was not what you expected, why do you think it was different?
ASSESSMENT CRITERIA
Collection and presentation of results [7]
Evaluation of procedures and results [8]
Understanding of Mendelian inheritance theory [5]
Ability to interpret pedigrees [5]
Task Marked out of 25
—3—
SAC 1-2a: The Structure & Role of DNA
INTRODUCTION
DNA is the molecule of inheritance, and the molecule of gene action. In order to be translated from the nucleotide base sequence of the gene, the
cell has to transcribe a section of DNA into a closely-related molecule, mRNA, and then translate the nucleotide base sequence on the mRNA into
an amino acid sequence.
PURPOSE
To investigate the molecular structures of DNA and mRNA, and to transcribe and translate a section of DNA into an amino acid sequence, using a
computer program, capturing screen data for presentation in a report.
EQUIPMENT
Computer; commercial computer program Genetic Molecules (Hand On Genetics, 2000); floppy disc.
PROCEDURE
1. Open the program (under the Biology section) called Genetic Molecules. Read the Introduction screen then proceed to the DNA molecules screen and complete the task. To save time, notice that the
purines are cytosine and thymine; the pyrimidines are guanine and
adenine.
2. Continue through the program, recording the nucleotide base sequence on the DNA strand and its corresponding mRNA base se-
quence at the transcription stage; and the amino acid sequence at
the translation stage.
3. Before you translate your mRNA, go to the Information Genetic
Code menu and record the amino acids corresponding to the
mRNA codons UUU and ACC. Then translate your mRNA.
4. Complete the Overview screen from the Information Menu.
5. Present as Observations the information recorded during the program, including the Overview in step 4, above.
DISCUSSION
1.
2.
3.
4.
5.
6.
What are the names of the compounds represented by the letters A, C, G and T, and what kinds of compounds are they all?
Which of the compounds in Question 1 are purines?
In a DNA molecule, which “building-block” units are covalently-bonded to which; and where are there hydrogen bonds?
Describe three differences between the structures of DNA and mRNA?
Which enzyme(s) is(are) involved in the transcription of a gene into an mRNA strand?
Describe everything that happens to the original mRNA strand produced when a gene is “read”, before the mRNA leaves the
nucleus?
7. What are the amino acids corresponding to the codons UUU and ACC respectively?
8. Where in the cell is mRNA translated?
9. Describe the process of mRNA translation.
10. What is(are) the role(roles) of the mRNA codon AUG?
—4—
SAC 1-2b: The Manipulation of DNA
INTRODUCTION
Increasingly, since the mid-1970s it has been possible for biologists to manipulate DNA, learn about the DNA profile of an individual organism, and
modify the DNA component of a chromosome by either deleting some of its DNA, or by inserting new DNA into the chromosome, not necessarily
from the same species. Your SAC report must follow the standard format for a practical report. Write a little about the structure of DNA and how it
can be manipulated by 'genetic engineering', in particular, the techniques used at the GTAC session.
PURPOSE To visit the G.T.A.C. facility in Parkville to obtain hands-on experience manipulating the DNA of bacterial cells
MATERIALS & METHODS See GTAC DNA Manipulation Tasks Option 1
DISCUSSION
For Part 2
1. What is a buffer, and why was one needed in the electrophoresis experiment?
2. What did you have to add a 'loading dye'?
3. What would have happened to your DNA samples if you
had connected the battery terminals to the wrong electrophoresis tank terminals?
4. Why did the DNA solution stay in the wells and not rise to
the surface of the gel as the buffer did?
For Part 3
5. Where do plasmids occur in nature?
6. What does the term 'competent cells' mean?
7. Why must you use competent cells in this experiment?
8. How did you make the E. coli cells competent?
9. Why did we have to invert the culture plates during incubation?
NB there will be another batch of discussion questions released during the report writing session.
ASSESSMENT CRITERIA
Knowledge of the structure of DNA [5]
Knowledge of procedures used in DNA manipulation [7]
Presentation of results [5]
Interpretation of results of the procedures used [8]
Task Marked out of 25
SAC 2-1: EVOLUTIONARY RELATIONSHIPS
After viewing the video program Islands of the Vampire Birds, complete a report of about 1000 words in which you investigate aspects of evolution
in the various finch species on the Galápagos Islands, in a way that demonstrates a sophisticated level of understanding of the mechanisms and
processes of evolution, and addresses all assessment criteria shown above. Be careful to use the correct names of investigators (attribution) and
their investigation methods, species involved [including scientific names] and relevant islands, events and dates mentioned in the video.
Please prepare your report in Comic Sans MS 10 point font.
ASSESSMENT CRITERIA
Knowledge of relevance of data presented, to evolution suggested by the data [6]
Indication of techniques used to study evolution suggested by the data [5]
Indication & explanation of types of evolution suggested, and species involved [7]
Indication of relationships between abiotic & biotic factors influencing species involved [7]
Task Marked out of 25
SAC 2–2: Report: Response to an Issue
Related to Applied Gene Technology
Information and guidelines will be issued later in the Semester.
ASSESSMENT CRITERIA
Understanding the impact of the issue on the evolutionary process [6]
Understanding the reason(s) for human intervention [8]
Evaluation of arguments relating to the issue [6]
Skill in comuunicating information [5]