Genetics and Evolution
- Among the following characters, which one was not considered by Mendel in his experiments on pea ? Answer: 1. Trichomes - Glandular or non-glandular Key idea: Mendel studied 7 contrasting pairs in pea. Seed colour (green/yellow), pod shape... 1
- The central dogma of molecular genetics states that the genetic information flows from Answer: 2. DNA → RNA → Proteins Key idea: the central dogma: DNA is transcribed to mRNA, which is translated to protein. Information flows D... 1
- A molecule that can act as a genetic material must fulfill the traits given below, except Answer: 2. it should be unstable structurally and chemically A genetic material must: replicate itself, express itself (as Mendelian charact... 1
- If a colour-blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour-blind is Answer: 4. 0 Colour blindness is X-linked recessive. Let the normal allele be X and the defective allele X^c. Father: X^cY. Mother (homozygo... 1
- DNA-dependent RNA polymerase catalyzes transcription on one strand of the DNA which is called the Answer: 4. template strand In transcription, RNA polymerase reads one DNA strand, which acts as the template strand (it has 3' to 5' polarit... 1
- The mechanism that causes a gene to move from one linkage group to another is called Answer: 2. translocation A gene moves from one linkage group (chromosome) to another by translocation, the transfer of a chromosome segment... 1
- Taylor conducted the experiments to prove semiconservative mode of chromosome replication on Answer: 1. *Vicia faba* Taylor and co-workers (1957) used radioactive thymidine with root tip cells of Vicia faba (broad bean) to show that... 1
- A true breeding plant is Answer: 2. near homozygous and produces offspring of its own kind A true-breeding line, after repeated self-pollination, is nearly homozygou... 1
- The equivalent of a structural gene is Answer: 1. cistron A cistron is the functional unit of DNA that codes for one polypeptide, so it is equivalent to a structural gene. An oper... 1
- Which of the following rRNAs acts as structural RNA as well as ribozyme in bacteria? Answer: 2. 23 S rRNA In bacteria, the 23S rRNA of the large subunit acts as the peptidyl transferase ribozyme that forms peptide bonds, besi... 1
- In a testcross involving F_1 dihybrid flies, more parental-type offspring were produced than the recombinant-type offspring. This indicates : Answer: 3. The two genes are linked and present on the same chromosome. In a testcross with an F₁ dihybrid, independent assortment gives 1:1... 1
- Which of the following is not required for any of the techniques of DNA fingerprinting available at present ? Answer: 2. Zinc finger analysis DNA fingerprinting uses PCR (to amplify VNTR/STR regions), restriction enzymes (to cut DNA) and DNA-DNA hybr... 1
- Which one of the following is the starter codon ? Answer: 1. AUG AUG codes for methionine and is the start (initiator) codon. UAA, UAG and UGA are stop codons. 1
- Which of the following is required as inducer(s) for the expression of Lac operon ? Answer: 3. lactose Key idea: In the lac operon, lactose (as allolactose) is the inducer. It binds the repressor protein, which then leaves t... 1
- A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. When the F_1 plants were selfed the resulting genotypes were in the ratio of : Answer: 1. 1 : 2 : 1 :: Tall homozygous : Tall heterozygous : Dwarf Key idea: A TT × tt cross gives all Tt in F₁. Selfing F₁ (Tt × Tt) gives... 1
- Match the terms in Column I with their description in Column II and choose the correct option :Column I: (a) Dominance; (b) Codominance; (c) Pleiotropy; (d) Polygenic inheritanceColumn II: (i) Many genes govern a single character; (ii) In a heterozyg… Answer: 2. (ii) (iii) (iv) (i) Key idea: Match each term with its meaning. Dominance: in a heterozygote only one allele expresses: (ii) Codo... 1
- Pick out the correct statements :(a) Haemophilia is a sex-linked recessive disease.(b) Down's syndrome is due to aneuploidy.(c) Phenylketonuria is an autosomal recessive gene disorder.(d) Sickle cell anaemia is an X - linked recessive gene disorder. Answer: 4. (a), (b) and (c) are correct. Key idea: Check each statement. (a) Haemophilia is X-linked recessive: correct. (b) Down syndrome i... 1
- A complex of ribosomes attached to a single strand of RNA is known as : Answer: 1. Polysome Key idea: Several ribosomes attached to one mRNA strand make a polysome (polyribosome), so many copies of a polypeptide... 1
- Which of the following most appropriately describes haemophilia ? Answer: 2. X - linked recessive gene disorder Key idea: Haemophilia is caused by a recessive gene on the X chromosome, so it is the most pre... 1