LAMARCK's THEORY
Jean Baptiste Lamarck (1744-1829) proposed a theory which was published in "<em>Philosophie Zoologique"</em> (1809). This theory is simply known as Lamarckism. It has two main postulates:
1. Use and disuse of organs
2. Inheritance of acquired characters.
Example
He explained his theory by giving the examples:
1. Neck length of Girrafes
2. Webbed toes of water birds, and
3. Wings of penguins
Explanation
Lamarck explained that water birds use toe for swimming, with the passage of time webbed were developed in their toes. these features were then transferred to their offspring.
Drawback
Lamarck theory was based on natural observation. It did not explain the genetic basis of such characteristics.
Answer:
Genetic drift happens when its adapted organisms survive and reproduce more often than poorly-adapted organisms
1. differential reproduction, that is, not all organisms are able to reproduce to their fullest capacity because nature cannot simply sustain it
2. acquire genes that is heredity.
Question 1:
Exons are gene fragments whose DNA sequence after transcription is found in mature mRNAs. This part of the gene is most often coding.
The size of the exons in the genomes follows a log-normal distribution, with an average length of about 150 nucleotides, knowing that in eukaryotes, each gene contains several exons and introns (an average of 8) so the size is 8*150 = 1200 bp.
Question 2:
Introns are fragment of a gene located between two exons. Introns are present in immature mRNA and absent in mature mRNA. "Non-coding" fragment of the gene.
The introns average in a gene is 3365 bp including 3'UTR and 5'UTR and intermediate introns.
