The double helix is a description of the molecular shape of a double-stranded DNA molecule. In 1953, Francis Crick and James Watson first described the molecular structure of DNA, which they called a "double helix," in the journal Nature.
An indicator species<span> is an organism whose presence, absence or abundance reflects a specific environmental condition. </span>Indicator species<span> can signal a change in the biological condition of a particular ecosystem, and thus may be used as a proxy to diagnose the health of an ecosystem.
</span>
<span>During the twentieth century, absolute date was added to the relative time scale. </span>Geologic time scale uses both relative and absolute dating techniques. <span>Soon after the discovery of radioactivity, geologists used radioactive isotope decay to develop a method for determining absolute ages of rocks</span>
The purple spots on the colorless background of corn kernels observed by Barbara McClintock were the result of the transposition of the Ds elements out of the color gene.
<h3>What are the genetic elements found in corn?</h3>
- A transposable element is removed from one spot in the DNA and inserted into a different site in the DNA during the process of genetic transposition, which allows genes to shift their location on chromosomes.
- The first recognized genetic instability was caused by genetic transposition.
- The size of the tissue patch displaying the reversion phenotype increases as a reversion event happens earlier in the kernel development.
- Barbara McClintock saw purple dots on maize kernels with an otherwise colorless background.
- These spots were caused by the Ds components of the color gene being transposed.
- The wild-type (purple) phenotype manifests itself in cells where Ds from the color gene "C" sequence has been lost.
Hence, Barbara McClintock discovered purple patches on the colorless backdrop of maize kernels due to the transposition of the Ds elements out of the color gene.
To learn more about Transposition refer to:
brainly.com/question/13447171
#SPJ4
