Indicate true (T) and false (F) statements below regarding a genome and its evolution. Your answer would be a four-letter string composed of letters T and F only, e.g. FFTF.
( ) The genome of the last common ancestor of mammals can be investigated only if a DNA sample of the ancestor can be obtained.
( ) All of the "ultraconserved" elements found in the human genome have been shown to encode long noncoding RNAs.
( ) If a mouse carrying a homozygous deletion of a highly conserved genomic sequence survives and shows no noticeable defect, the highly conserved sequence has to be functionally unimportant.
( ) The "human accelerated regions" are genomic regions that are found in humans with no homologs in chimpanzees or other animals.

Question

Indicate true (T) and false (F) statements below regarding a genome and its evolution. Your answer would be a four-letter string composed of letters T and F only, e.g. FFTF.
( )	The genome of the last common ancestor of mammals can be investigated only if a DNA sample of the ancestor can be obtained.
( )	All of the "ultraconserved" elements found in the human genome have been shown to encode long noncoding RNAs.
( )	If a mouse carrying a homozygous deletion of a highly conserved genomic sequence survives and shows no noticeable defect, the highly conserved sequence has to be functionally unimportant.
( ) 	The "human accelerated regions" are genomic regions that are found in humans with no homologs in chimpanzees or other animals.

Quizplus · Accepted Answer

By comparing genomic DNA sequences from various existing mammals, as well as non-mammals, much can be inferred about the genome of the last common ancestor that lived about 100 million years ago. Although some of the ultraconserved elements may encode long noncoding RNAs, the function of the majority of these elements is still a mystery. Since even a tiny selective advantage can support the conservation of a particular DNA sequence, lack of an "obvious" defect in a laboratory strain of mouse does not preclude functional importance. The "human accelerated regions" show accelerated genetic changes during recent evolution in the human lineage, but are not entirely novel genetic elements; in fact, they had been highly conserved before the sudden spurt of nucleotide changes.

Indicate True (T) and False (F) Statements Below Regarding a Genome