Genetics — Set 4
Biology · आनुवंशिकी · Questions 31–40 of 50
How many chromosomes does a person with Down Syndrome typically have?
Correct Answer: A. 47
Down Syndrome is caused by the presence of an extra copy of chromosome 21, also known as Trisomy 21. This results in a total of 47 chromosomes instead of the usual 46. It is one of the most common chromosomal abnormalities in humans.
Which of the following is the 'Universal Recipient' blood group?
Correct Answer: B. AB+
People with AB+ blood have all major antigens on their red blood cells. Because they have no antibodies against A, B, or Rh antigens, they can safely receive blood from any type. This makes AB positive the universal recipient in medical practice.
Who coined the term 'Gene' in 1909?
Correct Answer: B. Wilhelm Johannsen
Wilhelm Johannsen introduced the word 'gene' to replace Mendel's 'element'. He also coined the terms 'genotype' and 'phenotype' during his studies on inheritance. His terminology clarified the distinction between inherited factors and visible traits.
In the DNA double helix, the two strands are held together by?
Correct Answer: B. Hydrogen bonds
Hydrogen bonds form between the complementary nitrogenous bases of the two strands. These bonds are weak enough to allow the strands to separate for replication. The backbone of each strand is held by strong covalent phosphodiester bonds.
The 'Law of Segregation' states that during gamete formation, the two alleles for a trait?
Correct Answer: A. Separate from each other
Mendel's Law of Segregation explains that each parent passes only one allele for a trait to their offspring. This separation occurs during the process of meiosis. As a result, each gamete carries only one copy of each gene.
Which organism did Thomas Hunt Morgan use for his genetic research on linkage?
Correct Answer: A. Fruit fly
Morgan used Drosophila melanogaster, the common fruit fly, due to its short life cycle and visible traits. His work provided the first evidence that genes are located on specific chromosomes. He received the Nobel Prize for his discoveries regarding heredity.
What is a 'Cistron'?
Correct Answer: B. A functional unit of a gene
A cistron is the smallest unit of genetic material that codes for a single polypeptide. The term is often used synonymously with 'gene' in molecular biology. Seymour Benzer introduced this term through his studies on bacteriophages.
The process of protein synthesis from an mRNA template is called?
Correct Answer: C. Translation
Translation occurs at the ribosomes where the genetic code in mRNA is read to assemble amino acids. This process requires tRNA and rRNA to function correctly. It is the final step in the central dogma of molecular biology.
Which of the following is a 'Stop Codon' during translation?
Correct Answer: A. UGA
Stop codons signal the end of the polypeptide chain during translation. There are three stop codons: UAA, UAG, and UGA. Unlike other codons, they do not code for any amino acid.
In genetics, 'Dominance' refers to a trait that?
Correct Answer: B. Is expressed in the heterozygote
The correct answer is 'Is expressed in the heterozygote'. A dominant allele masks the effect of a recessive allele in an individual. For example, if 'T' is dominant for tallness, 'Tt' will result in a tall plant. This concept helps explain why some traits appear more frequently in a population.