All Free Biology MCQs with Answers

• A. Change in Phenotype
• B. No change in Phenotype
• C. Synthesis of 3 amino acids.
• D. Synthesis of 4 amino acids.

Explanation: A deletion changes the DNA sequence by removing at least one nucleotide in a gene.Phenotypic effects of deletions depend on the size and location of deleted sequences on the genome. If the nucleotide is deleted this effect amino acid sequence thus primary secondary or tertiary structure is disturbed protein becomes non functional.

• A. Protein→DNA
• B. RNA →DNA
• C. DNA→RNA
• D. RNA Protein

Explanation: A reverse transcriptase(RT) is an enzyme used to generate complementary DNA(cDNA) from an RNA template, a process termed reverse transcription.

• A. 3.6 turns
• B. 100 turns
• C. 360 turns
• D. The number of turns can not be determind

Explanation: An alpha(α) helix contains 3.6 amino acids per turn of the helix. If a polypeptide consists of 360 amino acids, the turns in the helix would be 100. 360÷3.6=100 amino acids.

• A. PKU
• B. Alkaptunuria
• C. Anuria
• D. Dluria

Explanation: Phenylketonuria occurs when parents pass the defective phenylalanine hydroxylase (PAH) gene that causes this disorder on to their children. This gene helps create the enzyme needed to convert phenylalanine to tyrosine. Phenylketonuria is a disorder of amino acid metabolism that occurs in infants born without the ability to normally break down an amino acid called phenylalanine. Phenylalanine, which is toxic to the brain, builds up in the blood.

• A. Klinefelter's Syndrome
• B. Down's Syndrome
• C. Turner's Syndrome
• D. Jacob's Syndrome

Explanation: Down's Syndrome involves a child receiving an extra copy of their 21st chromosome.Klinefelter's syndrome is a genetic disorder that occurs in males and is characterized by the presence of an extra X chromosome, resulting in a chromosomal configuration of XXY.Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21 Turner's syndrome, also known as monosomy X, is a genetic disorder that affects females. It occurs when one of the sex chromosomes is missing or partially missing, resulting in a chromosomal configuration of X0.Jacob's syndrome, also known as XYY syndrome, is a genetic condition that affects males. It is caused by the presence of an extra Y chromosome, resulting in a chromosomal configuration of XYY.

• A. Both are due to a quantitative defect in globin chain synthesis
• B. Thalassemia is due to less synthesis of globin molecules
• C. Sickle cell anaemia is due to a quantitative problem of globin molecules
• D. Both are due to a qualitative defect in globin chain synthesis

Explanation: Sickle cell anemia is caused due to point mutation in which at the 6th position of the beta-globin chain, glutamic acid is replaced by valine. Thus, it is a qualitative defect in the functioning of globin molecules. Sickle cell anemia is caused due to point mutation in which at the 6th position of the beta-globin chain, glutamic acid is replaced by valine. Thus, it is a qualitative defect in the functioning of globin molecules. Thalassemia is caused due to either mutation or deletion which ultimately results in a reduced rate of synthesis of one of the globin chains that make up hemoglobin. Hence, it is a quantitative defect in the functioning of globin molecules.ing of globin molecules.

• A. It should be able to express itself in the form of 'Mendelian characters'
• B. It should be able to generate its replica
• C. It should be unstable structurally and chemically
• D. It should provide the scope for slow changes that are required for evolution

Explanation: Genetic material should be structurally and chemically stable otherwise its expression will change. This will lead to a loss of several metabolic functions, etc. The genetic material in any living organism consists of the fundamental information required to carry out various life processes related to development, growth, metabolism, reproduction, etc. DNA (deoxyribose nucleic acid) and RNA (ribonucleic acid) are known to constitute the genetic material in all organisms. The genetic material is stabilized using various interactions like van der Waals forces, hydrophobic interactions, and hydrogen bonds. The structural and chemical instability of the genetic material will result in impairment of cell function, mutations, and transformation to cancerous cells, or diseases.

• A. Lactose
• B. Lactose and Galactose
• C. Glucose
• D. Galactose

Explanation: In Lac operon, lactose is an inducer. It binds with a suppressor and inactivates it. It allows RNA polymerase to access the promoter and transcription proceeds. The lac z, lac y, and lac genes in the lac operon are the structural genes that code for beta-galactosidase which converts lactose into glucose and galactose. In lac operon, Lactose acts as an inducer for the synthesis of protein. Lactose goes and binds with the repressor protein, causing an allosteric shift. This altered repressor cannot bind to the operator, thereby making the promoter region accessible. As the promoter region gets activated, the RNA polymerase enzyme initiates the transcription of the lac operon. Thus, lactose is required for the expression of the lac operon.

• A. The inducer
• B. A terminator
• C. A promoter
• D. The structural gene

Explanation: A transcription unit is a part of DNA that is able to transcribe a complete RNA. It consists of a promoter region (where RNA polymerase binds to start transcription), the structural gene (coding region) and the terminator region (that signals release of RNA polymerase and newly formed RNA strand).

• A. One strand turns clockwise
• B. One strand turns anti­-clockwise
• C. The phosphate groups of two DNA strands, at their ends, share the same position
• D. The phosphate groups at the start of two DNA strands are in opposite positions (poles)

Explanation: DNA is a type of nucleic acid that forms genetic material in many organisms. It consists of a long polymer of nucleotides that transcribes the coded information in the form of a triplet code of nucleotides in mRNA. It is a double helical molecule. The two strands of DNA run in opposite directions to one another with hydrogen bonds between them. One strand of DNA has a 5'-­3' direction and the other strand has a 3'-5' direction, so they are antiparallel. This direction is determined by the presence of a free phosphate or OH group at the end of the strand.