Genetics and Evolution
- In Antirrhinum (Snapdragon), a red flower was crossed with a white flower and in F_1 generation, pink flowers were obtained. When pink flowers were selfed, the F_2 generation showed white, red and pink flowers. Choose the incorrect statement from the… Answer: 4. Law of Segregation does not apply in this experiment. Key idea: Flower colour in snapdragon shows incomplete dominance, but segre... 1
- Purines found both in DNA and RNA are : Answer: 2. Adenine and guanine The purines are adenine and guanine, and both are present in DNA and RNA. Thymine and cytosine are pyrimidine... 1
- Select the incorrect statement. Answer: 3. In domesticated fowls, sex of progeny depends on the type of sperm rather than egg. We look for the incorrect statement. Male fru... 1
- All of the following are part of an operon except Answer: 2. an enhancer Key idea: A prokaryotic operon has structural genes, a promoter and an operator (and a regulatory gene nearby). An en... 1
- A woman has an X-linked condition on one of her X chromosomes. This chromosome can be inherited by Answer: 4. Both sons and daughters Key idea: A woman has two X chromosomes and passes one at random to each child. Each child (son or daught... 1
- Many ribosomes may associate with a single mRNA to form multiple copies of a polypeptide simultaneously. Such strings of ribosomes are termed as Answer: 1. Polysome Key idea: A string of ribosomes on one mRNA, each making a copy of the polypeptide, is a polysome (polyribosome). A nucl... 1
- AGGTATCGCAT is a sequence from the coding strand of a gene. What will be the corresponding sequence of the transcribed mRNA ? Answer: 1. AGGUAUCGCAU The coding strand has the same sequence as the mRNA, with U in place of T (the template strand is the one complementa... 1
- Which of the following characteristics represent 'Inheritance of blood groups' in humans ?a. Dominanceb. Co-dominancec. Multiple alleled. Incomplete dominancee. Polygenic inheritance Answer: 3. a, b and c Key idea: ABO blood group inheritance is controlled by one gene with three alleles I^A, I^B, i . Multiple alleles: thr... 1
- Select the *correct* statement : Answer: 3. Punnett square was developed by a British scientist. The Punnett square, a tool to show gamete combinations in a cross, was devis... 1
- Which of the following pairs is *wrongly* matched ? Answer: 1. Starch synthesis in pea : Multiple alleles Starch synthesis in pea is an example of pleiotropy (one gene, many effects), not mult... 1
- Select the *correct* match : Answer: 4. Francois Jacob and Jacques Monod – *Lac* operon Jacob and Monod proposed the lac operon model of gene regulation in E. coli. Jeff... 1
- The experimental proof for semiconservative replication of DNA was first shown in a Answer: 3. Bacterium Meselson and Stahl showed semiconservative replication in 1958 using E. coli. They grew the bacteria in ¹⁵ N medium, sh... 1
- Select the *correct* match : Answer: 1. Ribozyme – Nucleic acid A ribozyme is an RNA molecule with catalytic activity, so it is a nucleic acid. Morgan is linked to linka... 1
- Which one from those given below is the period for Mendel's hybridization experiments ? Answer: 4. 1856 - 1863 Mendel carried out his hybridization experiments on garden pea from 1856 to 1863. He published the results in 1866. 1
- Which of the following RNAs should be most abundant in animal cell ? Answer: 4. r-RNA Among cellular RNAs, rRNA makes up about 80% of the total RNA, so it is the most abundant. tRNA is about 15%, and mRNA only... 1
- The genotypes of a Husband and Wife are I^AI^B and I^Ai.Among the blood types of their children, how many different genotypes and phenotypes are possible ? Answer: 2. 4 genotypes ; 3 phenotypes Write the Punnett cross of the parents and count the distinct genotypes and blood groups. Gametes: I^A... 1
- The final proof for DNA as the genetic material came from the experiments of : Answer: 1. Hershey and Chase Hershey and Chase used radioactive ³²P (labels DNA) and ³⁵S (labels protein) in bacteriophages. Only the DNA en... 1
- If there are 999 bases in an RNA that codes for a protein with 333 amino acids, and the base at position 901 is deleted such that the length of the RNA becomes 998 bases, how many codons will be altered ? Answer: 2. 33 Deleting one base causes a frameshift, so every codon after the deletion point is read differently. Codon 300 covers bases 898... 1
- During DNA replication, Okazaki fragments are used to elongate : Answer: 3. The lagging strand away from the replication fork. Key idea: DNA polymerase can add nucleotides only in the 5' to 3' direction. O... 1
- A disease caused by an autosomal primary non-disjunction is : Answer: 4. Down's Syndrome Key idea: Non-disjunction of an autosome gives a trisomy or monosomy of an autosome. Down's syndrome is trisomy 2... 1
- Thalassemia and sickle cell anemia are caused due to a problem in globin molecule synthesis. Select the correct statement. Answer: 2. Thalassemia is due to less synthesis of globin molecules. Key idea: The two disorders differ in the type of globin defect. Thalas... 1
- Spliceosomes are not found in cells of : Answer: 3. Bacteria Key idea: Spliceosomes remove introns from hnRNA (pre-mRNA) in eukaryotes. Fungi, animals and plants are eukaryotes and... 1
- The association of histone H1 with a nucleosome indicates : Answer: 2. The DNA is condensed into a Chromatin Fibre. Key idea: Histone H1 is the linker histone that seals the nucleosome. H1 binds the l... 1
- DNA replication in bacteria occurs : Answer: 2. Prior to fission Key idea: Bacteria have no nucleus and no defined cell cycle phases. They have no nucleolus and no S phase (that... 1