Answer:
major evolutionary change
Explanation:
Cirrostratus:This sheet, or layer, of high-level cloud is made of ice crystals and is often the forerunner of rain. The sun may shine weakly through the cloud, and a ring or halo can often be seen around the sun or moon.
Answer:
Option B, Most communities never become completely stable
Explanation:
In an ecological succession, most of the species are unstable and they keep on changing continuously. The succession is primarily of two types –
a) Primary Succession – In this, community of species occur on a new habitat which had been never occupied earlier. Or it can be said that it is entirely a new habitat.
b) Secondary Succession – In this, community of species occur in a habitat where earlier life existed but it was disturbed or damaged by some environmental condition.
Hence , the correct answer is option B
Answer:
The correct answer is ''All three are caused by disparate genes, but each gene was found to contain repeats of a unique trinucleotide sequence.''
Explanation:
Four groups of trinucleotide repeats related to DNA expansion have been characterized in the human genome. CGGI GCC, CAGIGTC, CTGIGAC and recently GW CTT sequences. The CGGl GCC sequences are usually located in the noncoding regions of different genes and when expanded they associate with fragile sites on the chromosomes. The CAGIGTC repeats are part of the coding region and are related to different neurodegenerative disorders. You can try to make a classification depending on the unit that is repeated, having on one side a group that are caused by repeats of the CAG trinucleotide (cytosine, adenine, guanine). Huntington's disease (HD) is a progressive disorder of motor, cognitive and psychic function. The disease is inherited in an autosomal dominant manner, and is caused by the expansion of CAG trinucleotide repeats in exon 1 of the gene called huntingtin (HTT or IT-15). Unstable mutations have also been found in which the repeat unit does not is composed of three nucleotides, if not four, such as type 2 myotonic dystrophy, where the tetranucleotide CCTG repeats. Fragile X Syndrome consists of an abnormal expansion of the cytosine-guanine-guanine trinucleotide (CGG) in the FMR1 gene, which prevents intellectual disability and also influences the formation of connective tissue
