Instructions: Answer each of the questions given below in your own words. Write
ID: 85278 • Letter: I
Question
Instructions: Answer each of the questions given below in your own words. Write in complete sentences where appropriate. A complete answer usually requires one to two sentences per mark, so a three-mark question would be answered in three to six sentences. This section is worth a total of 40 marks. (7 marks)
1. Describe the major phases of the cell cycle in a typical eukaryote. (2 marks)
2. Which major event during meiosis is most likely to produce deviations from Mendel’s laws? (6 marks)
3. Explain, with examples, the concept of jumping genes in prokaryotes. (5 marks)
4. Explain the variation of blood types in humans. (2 marks)
5. Compare prokaryotes and eukaryotes with regard to DNA that is NOT part of the nucleus/nucleoid. (4 marks)
6. Explain what it means that the genetic code is “universal” and “degenerate.” (6 marks)
7. Using the following DNA template strand sequence, answer the questions that follow: 3–TACCAGCATGACTAA–5
a. What is the complementary DNA sequence?
b. What is the final sequence of amino acids in the peptide produced?
c. If the sequence is mutated so that an adenine is inserted before position 11, how will the peptide be affected? What kind of a mutation is this? (8 marks)
8. In fruit flies, grey colour is dominant over black colour and normal sized wings are dominant over vestigial wings. Suppose a true breeding line of grey fruit flies with vestigial wings is mated with a true breeding line of black fruit flies with normal wings. The F1 generation is then crossed. Draw a Punnett square to show the genotypes of the F2 generation, and give the phenotypic ratio for the F2 generation.
Explanation / Answer
1. ANS: The cell cycle is the sequence of events that takes place in cells. It leads to cell division and replication (duplication). There are four distinct phases in the cell cycle - G1 phase, S phase (synthesis), G2 phase and M phase. The G1, S phase and G2 phase together are known as interphase.
2. ANS: Crossing over between chromosomes during meiosis is most likely to produce deviations from Mendel’s laws. But crossing over occurs in meiosis.
Mendel's law of independent assortment of allele will be deviated because of crossing over in meiosis. The law of independent assortment would have genes being independent of each other. In real life gene loci are on chromosomes and some gene loci are on the same chromosome. If crossing over occurs, the alleles may be unlinked. If crossing over does not occur, then alleles on the same chromosome will always remain linked and thus not assort independently.
3. ANS: A major variation in nearly all genomes is caused by Transposable elements (TEs), also known as "jumping genes," which are DNA sequences that move from one location on the genome to another.
Ex1: One family of TEs in the fruit fly Drosophila melanogaster is called P elements. They seem to have first appeared in the species only in the middle of the twentieth century; within the last 50 years, they spread through every population of the species.
Ex 2: Transposons in bacteria usually carry an additional gene for functions other than transposition, often for antibiotic resistance.
4. ANS: Karl Landsteiner described the original blood types--A, B and O--in 1900. The types of proteins, glycoproteins and glycolipids found (or expressed) on the surface of red blood cells define blood types. In addition, blood types, or at least the genes responsible for them, are inherited.
5. ANS: The position of DNA changes how transcription and translation occur. In eukaryotes, transcription occurs inside the nucleus, and the mRNA produced travels to the cytoplasm to continue with translation. In prokaryotes, the DNA is attached to the plasma membrane with the help of a Y fork. The mRNAs produced don't have to cross any membranes to get to the ribosomes, which are situated nearby so translation starts much faster compared to eukaryotes.
6. ANS: To elaborate more on the degenerate (which you seem to understand)...take the stop codon for instance. There are like three different possible sequences (Ex: UGA UAA or UGG...I think...those are off the top of my head) of nucleotides that can form the STOP codon.
Please remind this note: Answering to many questions is against to CHEGG RULES, so I am answering 1- 6 questions.