Amino acids are selected, collected, and carried to the ribosome by transfer RNA (tRNA) molecules,a - 4 Messenger RNA (mRNA) is a large family of RNA molecules that convey genetic information from DNA to the ribosome, b - 2 Nucleolar organizer regions (NORs) are chromosomal landmarks that consist of tandemly repeated sequences of ribosomal genes (rRNA) c - 3 Peptidyl transferase is an enzyme that catalyzes the addition of amino acid residue in order to grow polypeptide chain in protein synthesis. d - 1 Answer : (a)

Avery, MacLeod and McCarty identified DNA as the "transforming principle" while studying Streptococcus pneumoniae, bacteria that can cause pneumonia. Answer : (b)

The sequence of amino acids in a polypeptide is determined by the sequence of the corresponding codons in the mRNA molecule that was translated, where one mRNA codon “codes for” one amino acid. The sequence of the mRNA is a modified copy of the gene's DNA. Answer : (b)

Promoters are DNA sequences whose purpose is not to encode information about the organism itself, but rather they serve as a kind of "On" switch to initiate the biological process of transcription for the genes which follow the promoter DNA sequence. Answer : (b)

DNA gyrase, or simply gyrase, is an enzyme within the class of topoisomerase and is a subclass of Type II topoisomerases that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA-polymerase or by helicase in front of the progressing replication fork. Answer : (a)

Messenger RNA (mRNA) carries the genetic information copied from DNA in the form of a series of three-base code “words,” each of which specifies a particular amino acid. Translation is the whole process by which the base sequence of an mRNA is used to order and to join the amino acids in a protein. Answer : (a)

In eukaryotes, transcription and translation take place in different cellular compartments: transcription takes place in the membrane-bounded nucleus, whereas translation takes place outside the nucleus in the cytoplasm. Answer : (b)

AUG =Methionine ; UAA =Termination ; UUU =Phenylalanine ;UGG=Tryptophan Answer of question 1 or NCERT Text book table 6.1 Answer : (d)

Transposons are small pieces of DNA (500–1500 bp long) capable of moving themselves from one place to another within a genome. Answer : (c)

Mutation is a sudden heritable change in the genetic material of an organism. Change in environoment can cause mutation. Reverse is not possible. Answer : (d)

Tryptophan is unique because it is the only amino acid specified by a single codon. Tryptophan coded Only by UGG The remaining 19 amino acids are specified by between two and six codons each. Answer : (d)

DNA replication is semi-conservative because each helix that is created contains one strand from the helix from which it was copied. The replication of one helix results in two daughter helices each of which contains one of the original parental helical strands. It is semi- conservative because half of each parent helix is conserved in each daughter helix. Semi-discontinuous nature of replication is attributed to the fact that one strand is replicated continuously whereas the other strand in discontinuous fashion. Answer : (b)

DMD, the largest known human gene, provides instructions for making a protein called dystrophin This protein is located primarily in muscles used for movement (skeletal muscles) and in heart (cardiac) muscle. Small amounts of dystrophin are present in nerve cells in the brain The INS gene provides instructions for producing the hormone insulin, Answer : (a)

The composition of DNA varies from one species to another, are now known as Chargaff's Rules. The first rule holds that a double-stranded DNA molecule, globally has percentage base pair equality Answer : (d)

The three STOP codons have been named as amber (UAG), opal or umber (UGA) and ochre (UAA) If these codons are present in mRNA. The protein synthesis stops abruptly whether the protein synthesis is complete or not. AUG and GUG are called initiation codons because they initiate the polypeptide chain. Answer : (a)

Inducers bind to repressors, causing them to change shape and preventing them from binding to DNA. Therefore, they allow transcription, and thus gene expression, to take place. Answer : (a)

AAA AAG are codes for lysine Answer : (b)

chromonema (plural chromonemata) (genetics) The central coiled filament of a chromatid upon which the chromomeres lie. Answer : (b)

Stop codons are also called nonsense codons because they do not code for an amino acid and instead signal the end of protein synthesis. UAA, UAG, UGA are stop codon Answer : (c)

DNA analysis intended to identify a species, rather than an individual, is called DNA barcoding. DNA profiling is a forensic technique in criminal investigations, comparing criminal suspects' profiles to DNA evidence so as to assess the likelihood of their involvement in the crime. Answer : (a)

Peptidyl transferase is an enzyme that catalyzes the addition of amino acid residue in order to grow polypeptide chain in protein synthesis. It is located in the large ribosomal subunit, where it catalyzes the peptide bond formation. It is composed entirely of RNA. Answer : (d)

The Hershey–Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase that helped to confirm that DNA is genetic material. Answer : (d)

The nitrogenous bases are purines and pyrimidines. The purines are adenine and guanine. The pyrimidines are thymine and cytosine. Purines pair with the pyrimidines by hydrogen bonds. Adenine pairs with thymine by two hydrogen bond while the cytosine pairs with the guanosine by three hydrogen bonds. Experiments have shown that double bonds are stronger than single bonds, and triple bonds are stronger than double bonds. Therefore, the strand having least number of C and G will melt at the lowest temperature Answer : (a)

Overlapping genes represent a fascinating evolutionary puzzle, since they encode two functionally unrelated proteins from the same DNA Typically, one gene will code for one polypeptide – however there are exceptions to this rule: Genes may be alternatively spliced to generate multiple polypeptide variants. Genes encoding tRNA sequences are transcribed but never translated. Genes may be mutated (their base sequence is changed) and consequently produce an alternative polypeptide sequence An overlapping gene is a gene whose expressible nucleotide sequence partially overlaps with the expressible nucleotide sequence of another gene. In this way, a nucleotide sequence may make a contribution to the function of one or more gene products. Answer : (a)

DNA →	mRNA →	tRNA
A	U	A
C	G	C
T	A	U
G	C	G

DNA → mRNA Transcription mRNA → tRNA Translation ∴ Sequence UAC, AUG, GCU, CCG or badc Answer : (b)

The goal of transcription is to make a RNA copy of a gene's DNA sequence Answer : (a)

Transformation was discovered in Streptococcus pneumoniae in 1928 by Frederick Griffith; in 1944, Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty demonstrated that the “transforming principle” was DNA. Answer : (b)

In 1941 Beadle and Tatum published their results in "Genetic control of biochemical reactions in Neurospora," in which Beadle proposed the one gene–one enzyme hypothesis. Answer : (c)

polymerases	polymerase activity (for all enzymes 5'→ 3)	exonuclease
DNA polymerase I		5' → 3' and 3' → 5'
DNA polymerase II	DNA repair	3' → 5'
DNA polymerase III	Filling if gap after removal RNA primer, DNA repair removal of RNA primers	3' → 5'

During DNA elongation, an enzyme called DNA polymeraseIII adds DNA nucleotides to the 3′ end of the newly synthesized polynucleotide strand. Answer : (d)

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