Tropopause is the boundary between the troposphere and stratosphere.
Explanation:
- Tropopause marks the transition region between troposphere and stratosphere.
- As we move up from the Earths surface , the temperature gets colder but when we reach the tropopause the temperature becomes constant and the temperature does not fall further.
- It is at a height of about 9Km at the polar region while at a height of 17 Km at the equitorial region.
Answer:
The duplication of a cluster of four Hox genes is equally likely as the duplication of a single Hox gene.
Explanation:
This comes from the definition of the parsimony principle, which is the action of choosing the simplest scientific explanation fitting the given evidence, meaning that all other elements are equal when evaluating the hypothesis. In biology the best hypothesis is the one that requires the fewest evolutionary changes.
Since three independent duplications of an individual Hox gene is in evolutionary terms, more complex than a single duplication or a cluster, then that hypothesis would be the most parsimonious.
Answer:
A = Activator
B = Effector
Explanation:
An activator is a protein which typically binds to a short (50–1500 bp) region of DNA which might be located either upstream (mainly) or downstream of a gene so as to cause increased transcription. This particular region of DNA is known as enhancer and activator is also known as transcription factor. Activator is a trans-acting factor which binds to the cis-acting factor which is enhancer so as to enhance transcriptional expression.
But another protein named as effector may restrict activator from binding to the enhancer leading to a decrease in transcriptional expression by binding to the activator allosterically. Allosteric binding of effector to the activator causes conformational change in activator so it can no longer bind the enhancer.
The pattern that explains why polygenes are called additive are the dominant and recessive genes incorporated.
