Lifeforms have changed throughout Earth's geologic history. Scientists learn about these changes by studying the fossil record.
For example, scientists have learned when different groups of organisms first appeared. These events can be placed within specific periods on the geologic time scale, which is shown below.
Fishes with jaws first appeared during the Silurian period, and dinosaurs first appeared during the Triassic period. Large mammals first appeared after both dinosaurs and fishes with jaws.
Using this information and the geologic time scale above, choose the period in which large mammals first appeared.
A.
Permian
B.
Ordovician
C.
Tertiary
D.
Cambrian
Fishes with jaws first appeared during the Silurian period, and dinosaurs first appeared during the Triassic period. Large mammals first appeared after both dinosaurs and fishes with jaws.
Using this information and the geologic time scale above, choose the period in which large mammals first appeared.
A.
Permian
B.
Ordovician
C.
Tertiary
D.
Cambrian
1 answer:
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Hi!
Hypothesis:
<em>Proteins are built from the translation of messenger RNA (mRNA) molecules</em>
RNA, or ribonucleic acid, is a structure that is similar to DNA, except that it exists as a single strand, consists of a ribose sugar instead of a deoxyribose sugar and has the base uracil (U) instead of thyamine (T).
<h3><u>From DNA to RNA</u></h3>
RNA is generated through transcription of the DNA molecule, resulting in a <em>complementary </em>molecule of the template DNA strand. For instance, if the sequence of the DNA was:
ATGCGCAGTTATTGCGAT
The corresponding RNA sequence will be:
UACGCGUCAAUAACGCUA <em>(complementary with U instead of T)</em>
<h3><u>From RNA to Protein</u></h3>
The RNA molecule in our case is known as the mRNA. After transcription the mRNA molecule is transported to the cytoplasm, where a ribosome binds to it for another molecule to translate the sequence. This translation is mediated by an RNA molecule known as the tRNA molecule which enters the ribosome to catalyze the reaction.
These molecules identify a sequence of 3 bases (codon) and for specific codon sequences, the tRNA allocates specific amino acid. For instance, for the codon <em>UCA</em>, the tRNA will allocate a <em>Serine residue.</em>
This translation process starts at specific three base sequences, known as start codons, and terminates at specific three base sequences known as stop codons.
In this manner, a sequence of amino acids respective to the mRNA codon sequence is synthesized, and as we identify proteins as chains of amino acids that are covalently linked together through peptide bonds, we can clearly see that proteins are built directly from RNA, and indirectly from DNA.
Hope this helps!
