All Free Biology MCQs with Answers

• A. It increases frequency of an allele.
• B. It is the same as disruptive selection.
• C. It increases genetic diversity.
• D. It removes variation from the population.

Explanation: The statement that best describes the impact of purifying selection is: "It removes variation from the population." Purifying selection, also known as negative or stabilizing selection, is a type of natural selection that operates to eliminate deleterious or harmful alleles from a population. It favors the preservation of advantageous alleles and the removal of deleterious ones, leading to a reduction in genetic diversity within the population over time. Essentially, purifying selection acts to "purify" the gene pool by removing harmful genetic variants and maintaining or increasing the prevalence of beneficial ones.

• A. Mitosis
• B. Meiosis
• C. Cytoplasm
• D. Nucleus

Explanation: The doubling of DNA material occurs in the process of mitosis as parent cell divides into two daughter cells having same number of chromosomes as present in parent cell.

• A. Mendel
• B. Boweri
• C. Sutton
• D. Fleming

Explanation: The term was discovered by the German scientist Heinrich Wilhelm Waldeyer in 1888, it referred to chromatin at the time which was later named by Walther Flemming.

• A. Sutton
• B. Sutton and Walther Flemming
• C. Correns and Robert Brown
• D. Einstein and Mendel

Explanation: The chromosomal theory of inheritance was proposed by Walter Sutton which states that chromosomes are the units of genetic heredity.

• A. Telomeres
• B. Centromeres
• C. Kinetochores
• D. Satellites

Explanation: The ends of chromosomes are called telomeres. They consist of repeating non-coding nucleotide sequences.

• A. 3 pairs
• B. 4 pairs
• C. 2 pairs
• D. 1 pair

Explanation: Humans have 2 sex chromosomes (1 pair), i.e. the X and Y chromosomes. Females have XX chromosomes whereas males have XY chromosomes.

• A. Waldeyer
• B. Coloumb
• C. Strasburger
• D. Flemming

Explanation: Walther Flemming was the first person to observe chromosomes while examining the rapidly dividing cells of salamander larvae and described chromosomal behaviour during cell division.

• A. Sutton
• B. Flemming
• C. Boweri
• D. Mendel

Explanation: The term 'chromosome' was first time proposed by Walther Flemming. Chromosomes are thread-like structures that appear inside the nucleus at the time of cell division. They were first observed by the German embryologist Walther Flemming in 1882 when he was examining the rapidly dividing cells of salamander larvae.

• A. DNA dependent DNA polymerase
• B. DNA dependent RNA polymerase
• C. RNA dependent DNA polymerase
• D. RNA dependent RNA polymerase

Explanation: Conversion of - ssRNA to +ssRNA is mediated by "RNA-dependent RNA Polymerase". This conversion is responsible for the translation and synthesis of protein using host machinery.

• A. Chromatic body
• B. Nuclear region
• C. Nuclear Body
• D. All of above

Explanation: Nucleotides are present in chromosomes that are located in the nucleus. All these options are true because all of these contain genetic information.