Level 2 Bio Genetics 2010

1. Level 2 Bio Genetics 2010 Feedback to students

2. OVERALL • Very poor attempt by many students. • LOTS OF REVISION NEEDED! • Often you must answer all parts of a question correctly to gain the achieved grade for that question.

3. OVERALL Q1 generally completed well but without getting an achieved or higher in a question relating to gene pool you will not pass the external exam. You MUST show knowledge across all areas of the standard to pass (i.e. mendelian genetics AND population genetics)

4. YOU MUST LEARN DEFINITIONS!!! • Writing just the names of the terms should be done only when the question states IDENTIFY or NAME. • DESCRIBE or DEFINE: means basically “give the definition for the key terms”. • N.B. If in doubt give the definition of the key words in the question. This is often all that is required for the Achieved grade.

5. DEFINITIONS YOU MUST KNOW N.B. There are more definitions that you should know for this genetics topic. However these are just the ones that were in the particular set of questions used in this school exam. • Allele • Gene • Organism • Species • Population • Community • Gene pool • Evolutionary process • Genetic Drift • Natural Selection • Test cross • Inbreeding The following terms were often misused or incorrectly defined in student exam answers:

6. QUESTION ONE N.B. Each question was made up of parts. Each part was assigned a grade and these grades were then totalled for your overall grade for each question.

7. QUESTION ONE a) Most answered correctly Required genotype of parents – NOT their gametes therefore needed 2 B/b alleles AND 2 W/w alleles

8. QUESTION ONE b) Again learn your definitions! Many on the right track but what was written was not correct. N.B. pure breeding is a term used to describe an individual – it is not the mating process!

9. QUESTION ONE c) Most did this well If you did not get an M then you must get some help to get this right in the future. There will definitely be a dihybrid cross to complete in the external.

10. QUESTION ONE d) Many repeated bbWw

11. QUESTION ONE e) Most did this correctly

12. QUESTION ONE f) Many failed to identify that a TEST CROSS was required

13. QUESTION ONE f) cont Red is recessive therefore only appears when there is no B allele present. Punnet squares can therefore be simplified to monohybrid crosses of W/w alleles. Many did not read the information provided to recognise the desired pure breeding phenotype for this question was red with a white band.

14. QUESTION ONE f) cont Many failed to mention that lots of crosses would be needed to make “almost certain” that the unknown individual was bbWW Many did not say that if only one offspring of the test cross had recessive “no band” phenotype then the unknown parent was heterozygous so should be kulled as not pure breeding.

15. QUESTION TWO

16. QUESTION TWO a) DESCRIBE does NOT mean “only name” A Mutation does NOT make a new GENE – it makes a new allele Source = where it comes from

17. QUESTION TWO b) Question was flawed as a) was regarding a species and b) was regarding a gene pool hence alteration in italics above.

18. QUESTION TWO c) NS acts on PHENOTYPE (NOT genotype/allele/gene). This leads to increase/decrease of the ALLELES for that phenotype in the next generation

19. QUESTION TWO c) cont Most answers lacked link to gene pool NS is NOT mate selection NS still occurs even in a stable (i.e. non-changing) environment

20. QUESTION THREE

21. QUESTION THREE a) Majority of students did not know what an evolutionary process was. Many did not read the question so did not give three processes or only named them and did not give a description.

22. QUESTION THREE a) cont Descriptions for this example include: Bottleneck effect – eg numbers of robins were greatly reduced so likely loss / reduction in allele frequency with likely a reduction in genetic diversity.

23. QUESTION THREE a) cont Founder effect – eg only 6 breeding pairs introduced to Ulva so alleles present in their gene pool not liely to be representative of the mainland / ancestral population so likely reduced genetic diversity.

24. QUESTION THREE a) cont Genetic drift – loss / reduction in specific alleles due to chance which is likely to be more pronounced in the small robin population so corresponding [increased] loss of genetic diversity. Mutation – changes to genetic code creating new alleles. If occurring in gamete producing cells will enter gene pool as inherited.

25. QUESTION THREE a) cont Natural selection – changes in the environment cause change in selection pressures on robins so favourable alleles will be selected for and increase in frequency in gene pool.

26. QUESTION THREE b)

27. QUESTION THREE b) cont Definition of inbreeding often too basic or poorly worded. Many did not recognise that the main problem with inbreeding is that it increases the chances of (harmful) recessive alleles coming together in offspring and being expressed thus reducing the fitness of the individual. Others, because of lack of recall on evolutionary processes, failed to achieve second part of question.

28. QUESTION ONE • Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Vivamus et magna. Fusce sed sem sed magna suscipit egestas. • Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Vivamus et magna. Fusce sed sem sed magna suscipit egestas.

29. JUDGEMENT STATEMENT

30. REMEMBER: READ THE INFORMATION PROVIDED READ THE QUESTION – underline the key terms ATTEMPT ALL PARTS OF ALL QUESTIONS! If you are not sure then simply put the definitions of the key terms.

31. QUESTION ONE