Question
DNA fingerprinting involves identifying differences in some specific regions in DNA sequence, called as [NEET 2021]
(a) satellite DNA
(b) repetitive DNA
(c) single nucleotides
(d) polymorphic DNA
Answer/Explanation
Ans. (b)
Repetitive DNA are DNA sequences that are repeated in the genome. These sequences do not code for protein. One class termed highly repetitive DNA consists of short sequences, 5-100 nucleotides, repeated thousands of times in a single stretch and includes satellite DNA.
Other options can be explained as:
The density of DNA is a function of its base and sequence, and satellite DNA with its highly repetitive DNA has a reduced or a characteristic density compared to the rest of the genome.
Single nucleotide polymorphisms, frequently called SNPs (pronounced ‘snips’) are the most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block, called a nucleotide. DNA polymorphisms are the different DNA sequences among individuals, groups, or populations. Polymorphism at the DNA level includes a wide range of variations from single base pair change, many base pairs, and repeated sequences. DNA polymarphisms are endless, and more discoveries continue at a rapid rate. These are called as polymorphic DNA.
Question
DNA strands on a gel stained with ethidium bromide when viewed under UV radiation, appear as [NEET 2021]
(a) yellow bands
(b) bright orange bands
(c)dark red bands
(d) bright blue bands
Answer/Explanation
Ans. (b)
To make the DNA visible in the gel, ethidium bromide is added to the gel solution and the buffer. This positively charged polycyclic aromatic compound binds to DNA by inserting itself between the basepairs (intercalation). The DNA fragments when exposed to ultraviolet light appear as orange colour bands, due to the large increase in fluorescence of the ethidium bromide upon binding to the DNA.
Question
Which is the basis of genetic mapping of human genome as well as DNA fingerprinting? [NEET (Oct.) 2020]
(a) Polymorphism in DNA sequence
(b) Single nucleotide polymorphism
(c) Polymorphism in hnRNA sequence
(d) Polymorphism in RNA sequence
Answer/Explanation
Ans. (a)
Polymorphism in DNA sequence is the basis of genetic mapping of human genome as well as DNA fingerprinting. Polymorphism simply means variation at genetic level which arises due to mutations.
Question
Which of the following is not required for any of the techniques of DNA fingerprinting available at present? [NEET 2016, Phase I]
(a) Zinc finger analysis
(b) Restriction enzymes
(c) DNA-DNA hybridisation
(d) Polymerase chain reaction
Answer/Explanation
Ans. (a)
A zinc finger is a small protein structural motif that is characterised by the coordination of one or more $\mathrm{Zn}$ ions in order to stabilise the folds.
Question
Satellite DNA is important because it. [CBSE AIPMT 2015]
(a) codes for proteins needed in cell cycle
(b) shows high degree of polymorphism in population and also the same degree of polymorphism in an individual, which is heritable from parents to children
(c) does not code for proteins and is same in all members of the population
(d) codes for enzymes needed for DNA replication
Answer/Explanation
Ans. (b)
Satellite DNA forms the minor peak after centrifugation of DNA. These are repetitive DNA sequences that do not code for any protein. They show high degree of polymorphism and heritable from parents to children, thus form the basis of DNA fingerprinting.
Question
DNA fingerprinting refers to [CBSE AIPMT 2004]
(a) molecular analysis or profiles of DNA samples
(b) analysis of DNA samples using imprinting device
(c) techniques used for molecular analysis of different specimens of DNA
(d) techniques used for identification of finger-prints of individuals
Answer/Explanation
Ans. (a)
DNA fingerprinting refers to molecular analysis of DNA samples. Alec Jeffreys $[1985,86]$ discovered this technique for the first time.
Question
Nucleus of a donor embryonal cell/somatic cell is transferred to an enucleated egg cell. Then after the formation of organism, what shall be true? [CBSE AIPMT 2002]
(a) Organism will have extra-nuclear genes of the donor cell
(b) Organism will have extra-nuclear genes of recipient cell
(c) Organism will have extra-nuclear genes of both donor and recipient cell
(d) Organism will have nuclear genes of recipient cell
Answer/Explanation
Ans. (b)
The organism will have extranuclear genes of recipient cell. Since, the recipient cell has already been enucleated(its nucleus is removed) the organism developing from it would have the nuclear genes of donor cell.
Question
The basis for DNA fingerprinting is [CBSE AIPMT 1996]
(a) occurrence of Restriction Fragment Length Polymorphism (RFLP)
(b) phenotypic differences between individuals
(c) availability of cloned DNA
(d) knowledge of human karyotype
Answer/Explanation
Ans. (a)
The basis of DNA fingerprinting is the occurrence of restriction fragment length polymorphism which are distributed throughout human genome. DNA fingerprinting was developed by a British geneticist Prof. Alec Jeffreys in 1984.
The chromosomes of every human cell contain short, highly repeated 15 nucleotide segments called ‘mini-satellites’ or variable number tendem repeats scattered through their DNA.