Botany MCQs for NEET — Practice Questions with Answers

A gene consists of several regions including a promoter, which is the binding site for RNA polymerase to initiate transcription; initiation and termination sites, which mark the beginning and end of transcription; and the coding sequence, which is the part of the gene that is transcribed into mRNA and then translated into a protein. Therefore, all the mentioned components are part of a gene.

The enzymes needed for the catabolism of lactose in E. coli include β-galactosidase, permease, and transacetylase. β-galactosidase breaks down lactose into glucose and galactose, permease facilitates the entry of lactose into the cell, and transacetylase is involved in the removal of toxic byproducts of lactose metabolism.

An operon is a functioning unit of genomic DNA that contains a cluster of genes under the control of a single promoter. It contains a regulator gene, promoter gene, operator gene, and structural genes. The regulator gene produces a repressor protein that can bind to the operator region to control the transcription of the structural genes.

E. coli produces β-galactosidase, thiogalactoside transacetylase, and lactose permease during lactose catabolism. Lactose dehydrogenase is not involved in this process. Thus, option o3 is the correct answer.

The Human Genome Project (HGP) is not an Indian scientific research project. It was an international research project with the aim of mapping all the genes of the human genome. Thus, option o1 is the correct answer as it is the incorrect statement.

Humans have approximately 50 times more genes than E. coli. E. coli has about 4,000 genes, while humans have around 20,000-25,000 genes. Thus, option o4 is the correct answer.

1. Ligase: Joins short segments of DNA together, which is correct.
2. Helicase: Breaks the hydrogen bonds between complementary pairs during DNA replication, which is also correct.
3. DNA Polymerase: It synthesizes DNA molecules from nucleotides, not cuts DNA at specific sequences.
4. Gyrase: It relieves the strain while double-strand DNA is being unwound by helicase, not joins weak hydrogen bonds.

In eukaryotes, DNA replication is bidirectional and has multiple origins of replication. This allows the large quantity of DNA to be replicated quickly and accurately.

Eukaryotes typically have Okazaki fragments that are 100 to 200 nucleotides long, whereas fragments in prokaryotic E. coli can be 2,000 nucleotides long. The reason for this discrepancy is unknown. Each eukaryotic chromosome is composed of many replicating units of DNA with multiple origins of replication.