3.1 – Genes

1.Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is based on DNA sequences and the cladogram on the right is based on comparing protein sequences. What is the reason that cladograms based on DNA sequences are more reliable predictors of the phylogenetic relationship of species than cladograms based on protein sequences?

2. What distinguishes an allele from a gene?

3. The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive system. The graph shows the percentage of samples in which this bacterium showed resistance to six antibiotics over a period of ten years. What is a possible explanation for the total percentage resistance being larger than 100% in 2010?

4. What is the effect of dominant alleles? I.   They mask the effect of recessive alleles. II.  They become more frequent than recessive alleles in a population. III. They have a joint effect with recessive alleles when characteristics are co-dominant.

5. What is the name given to a heritable factor which controls a specific characteristic?

6. The sequence of the first six amino acids of the normal β hemoglobin (HbA) chain are listed. valine – histidine – leucine – threonine – proline – glutamic acid Which sequence of amino acids could there be in the first six amino acids of the sickle-cell β hemoglobin (HbS) chain?

7. What is a gene mutation?

8. The sequence of the first six amino acids of the normal β hemoglobin (HbA) chain are listed. valine – histidine – leucine – threonine – proline – glutamic acid Which sequence of amino acids could there be in the first six amino acids of the sickle-cell β hemoglobin (HbS) chain?

9. What is a gene mutation?

10. Which statement is a definition of a gene?

11. A human cell has between 20 000 and 25 000 genes whereas an E. coli cell has approximately 4000 genes. Which of the following statements is true?

12. What is the difference between the alleles of a gene?

13. In some people, hemoglobin always contains the amino acid valine in place of a glutamic acid at one position in the protein. What is the cause of this?

14. Which of the following is the cause of sickle-cell anemia?

15. The Human Genome Project allowed the first accurate estimates of the number of different genes in the human genome. What was a typical estimate, based on the results of the Human Genome Project?

16. What is the set of alleles that an individual possesses?

17. Which of the following is an inherited disease that is due to a base substitution mutation in a gene?