PROTO-ONCOGENES are corresponding normal cellular genes to an oncogene that is responsible for normal cell growth and division.
An oncogene refers to a gene that is capable of causing cancer due to damage to the DNA molecule either by virus or other DNA damaging agents. A proto oncogene is the normal version of the gene while an oncogene is the abnormal version of the concerned gene.
Answer: The correct answer is-
an agent that causes a mutation in DNA.
Mutagen is an agent or a substance that causes permanent change in the genetic material of living organisms ( DNA, deoxyribonucleic acid). This process is called mutation.
A mutagen can be a chemical, physical or biological agent that causes mutation in the DNA.
Example- Physical agents such as -
- Ionizing radiations like alpha particles, gamma rays, X-rays that brings break in the DNA and cause other damages.
- Ultraviolet radiations that creates pyrimidine dimers ( T=T) and causes replication errors if damage is not repaired.
Answer:
The correct answer is "1. cornea 2. retina 3. rods and cones 4. ganglion cells
5. optic nerve 6. thalamus 7. primary visual cortex"
Explanation:
Light must pass a series of structures for the brain being able to interpret the data that comes from the eyes. The order that light stimuli travels from the eye to the brain is as follows:
1. cornea
2. retina
3. rods and cones
4. ganglion cells
5. optic nerve
6. thalamus
7. primary visual cortex
Light enters trough the cornea, the transparent front part of the eye that covers two-thirds of its total optical power; then it goes to the retina which receives the image that could go to the rods or the cones (depending if the light is at low or high levels, respectively). Then, ganglion cells increase the rate of the impulse within the optic nerve, and finally thalamus passes the sensory signal to the primary visual cortex. In this area of the brain, the basic visual features are extracted and interpreted.
A possible reason for the transition of algae from unicellularity
to multicellularity would be the evolution of multicellularity allowed algae to
develop traits that keep them close to the land and thus a source of nutrients.
The correct answer between all the choices given is the last choice. I
am hoping that this answer has satisfied your query and it will be able to help
you in your endeavor, and if you would like, feel free to ask another question.
