Question

2. Which of the following pairs of molecules alternate to form the backbone of a polynucleotide chain?

1. adenine and thymine
2. cytosine and guanine
3. sugar and phosphate
4. base and sugar
5. base and phosphate

3. Which of the following is FALSE concerning the human genome?

1. It contains about 25,000 genes.
2. It contains about 3.2 billion base pairs.
3. Only 2% of the genome codes for proteins.
4. It has very few introns.
5. 25,000 genes may produce up to 100,000 proteins.

4. Which of the following terms is not related to histones?

1. chromosomes
2. proteins
3. prokaryotes
4. nucleosomes
5. solenoid

5. Generation time refers to

1. the number of years it takes for a generation to die.
2. the amount of time required to replicate the DNA in a cell.
3. the time it takes to complete one cell cycle.
4. the time required for an individual in a species to achieve sexual maturity.
5. the time it takes for meiosis to go to completion.

6. Two chains of DNA must run in ________ direction(s) and must be ________ in order to bond with each other.

1. the same; uncomplementary
2. opposite; uncomplementary
3. parallel; uncomplementary
4. parallel; complementary
5. antiparallel; complementary

Answer 1

Answer for the first question : Option C - Sugar and phosphate

Explanation : A polynucleotide chain is formed by joining multiple nucleotides together with the help of polymerase enzymes. In polynucleotide chain alternative molecules of sugar and phosphate forms the backbone and the bases protrudes inward. In a completed polynucleotide chain the sugar molecule is usually present at the 3' end and the phosphate at the 5 ' end.

From the above explanation it is clear that Option C is the right answer while others are not.

Answer for second question : OptionD- It has very few introns.

Explanation : Majority of the human genome is consists of introns which is often referred to as junk DNA. So, this statement is false and all the other statements listed above in the question are true.

Answer for third question : Option C - Prokaryotes

Explanation : Histones are involved in the solenoid structure of chromatin which is a form of chromosomal packing. Histones are present in the nucleosome structure inside solenoid organisation. In nucleosome the DNA is coiled around histone octamer. Such type of chromosome organisation /chromatin compaction is not present in Prokaryotes.

So, Option C- Prokaryotes is not related to histones.

Answer for fourth question : Option C - the time it takes to complete one cell cycle.

Explanation : Generation time refers to the time it takes for a cell to divide into two. Generally the completion of one cell cycle means that the cell has divided to produce two daughter cells. So, Option C is the correct explanation for generation time.

Option A, B, D and E are not applicable.

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Answer for fifth question : Option E - Antiparallel and complementary

Explanation : In DNA double stranded structure one strand runs in 5 ' to 3' directions and the other strand runs in 3' to 5 ', which makes it an antiparallel orientation of two strands. The bases attached with each of the strands are complementary in nature that makes the DNA double helix a stable structure.

So, Option E is the right answer while Option A, B, C and D are not.