Sometimes cattle or human beings give birth to their young ones that are having different sets of oranges like limbs/position of eye, etc.It happens due to the disturbance in coordinated regulation of expression in sets of genes, which are associated with organ development

1. The genetic codes are universal, with few exceptions and mitochondrial DNA includes some of these exceptions.For most organisms the 'stop codons are 'UAA',UAG and 'UGA'.In vertebrate mitochondria 'UGA', which codes for tryptophan instead.Another codon 'AUA' codes for isoleucine in most organisms but for methionine in vertebrate mitochondrial mRNA.
2. There are many variations among the codes used by other mitochondrial mRNA, which are not harmful to these organisms,and can be used as atool (along  with other mutations among the mtDNA/RNA of different species) to determine relative proximity of common ancestry of related species.
3. The more related any two species are, the more mtDNA/RNA mutations will be the same in their mitochondrial genome.From this, it is estimated that the first mitochondria arose around 1.5 billion years ago.A generally accepted hypothesis is that mitochondria originated as an aerobic prokaryote in a symbiotic relationship within an anaerobic eukaryote.

(i) Transcription unit

(ii) RNA transcribed

Significance of satellite DNA in DNA fingerprinting
A DNA satellite is a region that consists of short DNA sequence repeated many times. The variation between individuals in the lengths of their DNA satellites forms the basis of DNA fingerprinting.
DNA satellite are of two types, i.e microsatellites and minisatellites.Their characteristic that makes them useful for identification is that they are highly polymorphic.The length of each satellite in DNA is inherited.
The length of satellite regions are highly variable between people.These form small peaks during density gradient centrifugation and thus are invaluable for identification purpose.

(i) Francis Crick
(ii) (a) ,(b)

(c) tRNA looks like inverted L.

Transformation, The phenomenon by which the DNA isolated from one type of cell when introduced to another type of cell, is able to bestow some of its properties to the former, it is termed transformation
A transformation was experimentally proved by Griffith with his experiments on Diplococcus pneumoniae. These experiments were further continued by Avery, MacCleod and McCarty and proved that transforming agent is DNA. It led to prove that DNA is the genetic material.

The estimate of a total number of human genes was very high (about 1,40,000 genes) because of a large size of the human genome. However, most of the human genome is made of noncoding repetitive sequences and single nucleotides. Only 2% of the genome actually consist of structural genes which are now estimated to be <25000. some of them are believed to form more than one type of proteins due to alternating splicing.

1. The sequence of human genome helped in enhancing the basic understanding of genetics and immunity to various disorders. various genes that cause genetic disorders were identified with the help of this project
2. It was found that more than 1200 genes are responsible for the common human cardiovascular disease, endocrine disease (like diabetes), neurological, disorder (like Alzheimer's disease), cancers and much more. These diseases can be treated easily by knowing the particular gene responsible for the particular disease.

1. Use of \({ 15 }_{ N }\) will not give any conclusive result because it is only a heavy isotope of nitrogen
2. \({ 15 }_{ N }\) will be incorporated into proteins as well as in DNA and hence it would appear both in the supernatant and in the sediment

RNA is more liable and prone to degradation (owing to the presence of 2'OH group in its ribose) Hence, heat-killed S-strain may not have retained its ability to transform the R-strain into virulent form if RNA was its genetic material.