Ethiopia Grade 12 Biology: Unit 3 Genetics Questions Answers for Ethiopian University Entrance exam. This page contains multiple choice question answers.
Grade 12 Biology: Unit 3 Genetics
- Genetic crosses
- Molecular genetics
- Protein synthesis
- Mutations
Ethiopia Grade 12 Biology: Unit 3 Genetics Quiz
Grade 12 Biology: Unit 3 Genetics Review Questions Answers
Q1. Two parents of genotype Aa are cross-bred. The alleles do not show codominance. What proportion of the offspring will look
like their parents?
- A. none
- B. ¾
- C. ¼
- D. ½
Answer: C
Q2. A woman with blood group A and a man with blood group B could potentially have offspring with which of the following blood groups?
- A. A
- B. B
- C. O
- D. all blood groups
Answer: D
Q3. In an organism of genotype Aa, half the gametes carry the A allele and half carry the a allele. This is due to:
- A. dominance
- B. recessiveness
- C. independent assortment
- D. segregation
Answer: D
Q4. The genotype of a homozygote could be:
- A. AA
- B. aa
- C. Aa
- D. XX
Answer: A
Q5. A plant has a genotype AaBb. There is no linkage of the genes. The gametes it will produce are:
- A. AB and ab
- B. Aa and Bb
- C. AA, aa, BB and Bb
- D. AB, Ab, aB and ab
Answer: 5
Q6. A tall pea plant with purple flowers (both determined by dominant alleles) is crossed with a short plant with white flowers. There is no linkage of the genes. If the tall, purple-flowered plant is heterozygous for both traits, the offspring will be:
- A. 1 purple tall:1 white short
- B. 3 purple tall:1 white short
- C. 9 purple tall:3 purple short:3 white tall:1 white short
- D. 1 purple tall:1 purple short:1 white tall:1 white short
Answer: B
Q7. Cross-breeding results in:
- A. an increase in heterozygosity
- B. hybrid vigour
- C. an increase in the number of dominant alleles
- D. all of the above
Answer: D
Q8. Which of the following statements concerning multiple allele inheritance is not true?
- A. A gene has more than two alleles.
- B. An individual will have more than two alleles of the gene.
- C. There are more than two alleles in the population.
- D. The alleles may be dominant, recessive or codominant.
Answer: B
Q9. Which of the following is not true of sex limited traits?
- A. They are determined by genes on the autosomes.
- B. They are expressed in only one sex (male or female).
- C. They are carried on the X chromosome.
- D. They often result in sexual dimorphism (very different physical appearance in male and female animals).
Answer: A
Q10. It is characteristic of sex-linked traits that they:
- A. occur more frequently in males than in females
- B. rarely skip a generation
- C. are always determined by genes found on the Y chromosome
- D. none of the above
Answer: A
Q11. DNA consists of two polynucleotide strands in which:
- A. the percentage of adenine is the same in each strand
- B. the percentage of adenine is the same as that of thymine in each strand
- C. the percentage of adenine is the same as that of thymine in the whole molecule
- D. the percentage of adenine is 50% of that of thymine in the whole molecule
Answer: B
Q12. Ligase is an enzyme that:
- A cuts DNA molecules, leaving sticky ends
- B joins sticky ends of DNA fragments
- C copies DNA fragments
- D separates DNA fragments
Answer: B
Q13. A gene probe could be:
- A. a short length of single-stranded DNA that has been made radioactive
- B. a tRNA molecule that has been made radioactive
- C. a short length of double-stranded DNA that has been made radioactive
- D. all of the above
Answer: A
Q14. Viruses and plasmids are examples of:
- A. vectors
- B. transformed bacteria
- C. restriction enzymes
- D. liposomes
Answer: A
Q15. Which of the following statements about genetic fingerprinting is not accurate?
- A. Genetic fingerprinting involves the analysis of the DNA to identify an individual.
- B. Genetic fingerprinting can be used to identify criminals and also the real parents of a child when the identity is in doubt.
- C. Only coding DNA is used to make a genetic fingerprint.
- D. Genetic fingerprinting has become faster and more detailed over time.
Answer: C
Q16. In gel electrophoresis of DNA:
- A. the DNA fragments migrate towards the positive electrode and are separated according to their molecular mass
- B. the DNA fragments migrate towards the negative electrode and are separated according to their molecular mass
- C. the DNA fragments migrate towards the negative electrode and are separated according to their electric charge
- D. the DNA fragments migrate towards the positive electrode and are separated according to their electric charge
Answer: B
Q17. One advantage of genetic engineering over conventional selective breeding is that genetic engineering:
- A. is quicker
- B. has fewer side effects
- C. cannot harm the environment
- D. none of these
Answer: A
Q18. The best definition of a transgenic organism is:
- A. a bacterium that contains genes from another organism
- B. a plant that has been genetically modified
- C. an animal that has been ‘pharmed’
- D. any organism that has had a foreign gene added to its genome
Answer: D
Q18. tRNA differs from DNA because it is:
- A. smaller, single stranded and shows no base pairing
- B. smaller, single stranded with thymine replaced by uracil
- C. smaller, single stranded and with deoxyribose instead of ribose
- D. smaller, single stranded and linear in shape
Answer: B
Q19. The genetic code is:
- A. a triplet code, degenerate and overlapping
- B. a doublet code, degenerate and universal
- C. a doublet code, degenerate and non-overlapping
- D. a triplet code, degenerate and universal
Answer: D
Q20. The DNA triplet AAT would code for an amino acid carried by tRNA with the anticodon:
- A. AAU
- B. TTA
- C. AAT
- D. UUA
Answer: A
Q21. In a ribosome, when the two amino acids that are held adjacent to each other form a peptide bond, the tRNA molecules are in
the:
- A. A and P sites
- B. A and E sites
- C. E and P sites
- D. none of the above
Answer: A
Q22. Post-transcriptional modification of mRNA is carried out in order to:
- A. remove exons
- B. remove introns
- C. alter its shape so that it can bind with a ribosome
- D. alter its shape so that it can bind with an amino acid
Answer: B
Q23. Which of the following statements about transcription factors is correct?
- A. They are always produced within cells.
- B. They bind with promoter sequences of DNA next to the gene.
- C. They are the same in all cells.
- D. All of the above.
Answer: B
Q24. Gene silencing by siRNA is referred to as a form of posttranscriptional repression because:
- A. it stops transcription of genes by RNA polymerase
- B. it only allows certain genes to be expressed
- C. it destroys the mRNA formed by transcription of a gene
- D. none of the above
Answer: C
Q25. Essential amino acids:
- A. must be taken in as part of our diet
- B. cannot be synthesised by transamination
- C. are found in large amounts in quinoa, meat and buckwheat
- D. all of the above
Answer: A
Q26. When comparing protein synthesis in eukaryotic cells and prokaryotic cells it is correct to say that transcription and translation are:
- A. separate in both
- B. coupled in both
- C. separate in prokaryotes and coupled in eukaryotes
- D. separate in eukaryotes and coupled in prokaryotes
Answer: D
Q27. Which of the following statements about transcription is correct?
- A. RNA polymerase assembles DNA nucleotides into a single strand.
- B. RNA polymerase assembles DNA nucleotides into a double strand.
- C. RNA polymerase assembles RNA nucleotides into a double strand.
- D. RNA polymerase assembles RNA nucleotides into a single strand.
Answer: D
Q28. Which of the following is an example of a chromosomal mutation:
- A. a base duplication
- B. a base insertion
- C. a translocation
- D. none of these
Answer: C
Q29. Which of the following is a frameshift mutation?
- A. point replacement
- B. Inversion
- C. Insertion
- D. substitution
Answer: C
Q30. The only source of new genetic material during evolution is:
- A. crossing over
- B. segregation
- C. random assortment
- D. mutation
Answer: D
Q31. The increase in bacterial resistance to penicillin is due to:
- A. mutation
- B. natural selection
- C. the increased use of penicillin
- D. a combination of all the above
Answer: D
Q32. If a substitution occurs in the DNA of an organism, which of the following will also occur?
- A. The mRNA will also be altered.
- B. All the triplets after the mutation will be altered.
- C. All the triplets before the mutation will be altered.
- D. A frameshift will occur.
Answer: A
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