Molecular Basis Of Inheritance Flashcards
Statement 1: RNA though it also acts as a genetic material in some viruses, mostly functions as a messenger.
Statement 2: RNA has additional roles as well. It functions as adapter, structural, and in some cases as a catalytic molecule.
Both are correct
Bacteriophage φ ×174 has……..nucleotides
5386
Bacteriophage lambda has………. base pairs
48502
Escherichia coli has………bp
4.6 × 10*6
Haploid content in human DNA is……….. bp
3.3 x 10*9 base pairs
………….. is common for both DNA and RNA
Cytosine
Thymine is also known as…….
5-methyl uracil
DNA as an acidic substance present in nucleus was first identified by Friedrich Meischer in……….. He named it as………
1869
Nuclein
In …………. James Watson and Francis Crick, based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin
1953
Erwin Chargaff that for a double stranded DNA, the ratios between…………. and Thymine and Guanine and…………..are constant and equals one.
Adenine
Cytosine
The pitch of the helix is……. nm and distance between a bp in a helix is approximately……….nm as there are……… base pairs in one single turn
3.4 nm
0.34 nm
10
…………….. proposed the Central dogma in molecular biology,
Francis Crick
Reverse transcription aka Teminism is seen in some viruses name some of them
(4)
Rous sarcoma virus
HIV
Tobacco mosaic virus
QB bacteriophage
Statement 1: In prokaryotic cells the DNA is scattered throughout the cell
Statement 2: The DNA in nucleoid is organised in small loops held by proteins.
Both are incorrect
Though they do not have a defined nucleus, the DNA is not scattered throughout the cell. DNA (being negatively charged) is held with some proteins (that have positive charges) in a region termed as ‘nucleoid’. The DNA in nucleoid is organised in large loops held by proteins.
Histones are………. charged proteins rich in two basic amino acids…..&……..
Positively
Arginine and Lysine
Histones are organised to form a unit of…….molecules called histone…….
eight
octamer
The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called
nucleosome
A typical nucleosome contains………. bp of DNA helix
200
Statement 1: The beads-on-string structure in chromatin is packaged to form chromatin fibers
Statement 2: These are further coiled and condensed at metaphase stage of cell division to form chromosomes
Both are correct
By year…….. the quest to determine the mechanism for genetic inheritance had reached the molecular level
1926
In 1928……………… in a series of experiments with Streptococcus pneumoniae (bacterium responsible for pneumonia), witnessed a miraculous transformation in the bacteria
Frederick Griffith
Prior to the work of………/……../…….. (1933-44), the genetic material was thought to be a protein.
Oswald Avery
Colin MacLeod
Maclyn McCarty
The unequivocal proof that DNA is the genetic material came from the experiments of ………/………. (1952)
Alfred Hershey and Martha Chase
Radioactive elements used in Hershey Chase experiment
Radioactive sulphur in proteins S35
Radioactive phosphorus in DNA P32
Molecule that can act as a genetic material must fulfill the following criteria:
4 given in NCERT
(i) It should be able to generate its replica (Replication).
(ii) It should be stable chemically and structurally.
(iii) It should provide the scope for slow changes (mutation) that are required for evolution
(iv) It should be able to express itself in the form of ‘Mendelian Characters’.
‘‘It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material’’
This was statement of
Watson and Crick, 1953
Matthew Meselson and Franklin Stahl performed experiment in year…….. to prove that the DNA replicates ………….
1958
Semi conservatively
Matthew Meselson and Franklin Stahl used radioactive N15 isotope in their experiments
False
It was just a heavy isotope and not any radioactive isotope
Similar experiments involving use of radioactive……. to detect distribution of newly synthesised DNA in the chromosomes was performed on………. (faba beans) by Taylor and colleagues in 1958
thymidine
Vicia faba
E. coli that has only 4.6×106 bp completes the process of replication within……..minutes
18
The average rate of polymerisation in E.coli has to be approximately………..bp per second
2000
Assertion: For long DNA molecules replication occurs in small opening of helix
Reason: In such long molecules two strands of DNA cannot be separated in its entire length due to very high energy requirement
The DNA-dependent DNA polymerases catalyse polymerisation only in one direction, that is………
5’ to 3’.
Why both the strands are not copied during transcription
First, if both strands act as a template, they would code for RNA molecule with different sequences and if they code for proteins, the sequence of amino acids in the proteins would be different. Hence, one segment of the DNA would be coding for two different proteins
Second, the two RNA molecules if produced simultaneously would be complementary to each other, hence would form a double stranded RNA. This would prevent RNA from being translated
The RNA polymerase is only capable of catalysing the process of…….
elongation
The RNA polymerase I transcribes
The RNA polymerase II transcribes
RNA polymerase III transcribes.
rRNAs (28S, 18S, and 5.8S)
precursor of mRNA, the heterogeneous nuclear RNA (hnRNA).
tRNA, 5srRNA, and snRNAs (small nuclear RNAs)
In capping an unusual nucleotide…………. is added to the………. end of hnRNA.
methyl guanosine triphosphate
5’-end
In tailing, adenylate residues are added at 3’-end in a template………….manner
200-300
independent
The presence of……….. is reminiscent of antiquity, and the process of splicing represents the dominance of………..-world.
introns
RNA
It was………….. a physicist, who argued that since there are only 4 bases and if they have to code for 20 amino acids, the code should constitute a combination of bases.
George Gamow
The chemical method developed by………………was instrumental in synthesising RNA molecules with defined combinations of bases (homopolymers and copolymers)
Har Gobind Khorana
……………… cell-free system for protein synthesis finally helped the code to be deciphered
Marshall Nirenberg’s
……………….. (polynucleotide phosphorylase) was also helpful in polymerising RNA with defined sequences in a template independent manner (enzymatic synthesis of RNA)
Severo Ochoa enzyme
Statement 1: 61 codons code for amino acids and 3 codons do not code for any
Statement 2: Codon is read in mRNA in a contiguous fashion. There are no punctuations.
Both are correct
Statement 1: One specific codon codes for one specific amino acid, this is known as degeneracy
Statement 2: Some amino acids can be coded by more than one codons this is known as unambiguous nature of codon
Both are incorrect vice versa is true
The code is nearly universal like from bacteria to human UUU would code for Phenylalanine
But there are some exceptions to this
Paramecium (Protozoa)
Termination codons UAA UGA code for Glutamate in
Mitochondria
AGG AGA generally coding for arginine works as stop codons in mitochondria
UGA a stop codon codes for tryptophan in mitochondria
AUA generally coding Isoleucine codes for methionine in mitochondria
…./…../…….. are stop terminator codons.
UAA, UAG, UGA
NCERT question intext
-AUG UUU UUC UUC UUU UUU UUC-
Give order of amino acids formed
Met-Phe-Phe-Phe-Phe-Phe-Phe
