Answer:
The type of mutation responsible for changing a base in the mRNA strand, without changing the coding aminoacid or protein, is called a <u>silent</u> mutation.
Explanation:
In a silent mutation occurs the change of a nitrogenous base in one of the codons that encodes an aminoacid, without changing the aminoacid or altering the structure or function of the protein to be synthesized.
In this type of mutations the change of the base does not mean the change of the aminoacid, because some aminoacids can be coded with more than one codon. In the case of Leucine, the codons that encode it are CUU, CUC, CUG or CUA, so even if a base changes, the final protein will be the correct one.
For the other options:
- <u><em>Missense</em></u><em>: the change of the base in the DNA chain implies the change of the codon in the mRNA and of the encoded aminoacid, in that way a structural and functional alteration of the synthesized protein occurs. </em>
- <u><em>Nonsense</em></u><em>: the change in the nitrogenous base in the DNA leads to the coding of a termination codon, so that the protein is ultimately incomplete.</em>
- <u><em>Insertion</em></u><em>: in this case there is the addition of more nitrogenous bases to the DNA chain, with respect to the original one.</em>
Organisms that originated in a certain geographic region and can only be found in that region are said to be endemic.
Explanation:
Endemic organisms are taxonomic species (plants and animals) which originates and distributed only in specific geographic regions. This state of evolution is called endemism.
They are said to be native or indigenous to that particular region which can be an ecological habitat, an entire nation, an island, a mountain range etc. Certain parts are known for majority of their species being endemic like St. Helen Island, New Caledonia Island, Hawaiian Islands, Southern regions of Africa, and Australia.
The species becomes endemic to a particular region because of the presence of certain bio-geographical environmental qualities of that habitat which are favorable to that species.
When these conditions become unfavorable, then species becomes restricted leading to endangerment or extinction of the species.
Examples:
- Kangaroo - Australia
- Nilgiri Tahr, - Nilgiri Hills, India
- The Redwood trees of West Coast of the USA
- Plants like kalo, sumac of Hawaii
Well, you failed to mention which one is the recessive trait in this instance. But, let’s say red hair is recessive, denoted by r and brown hair is dominant denoted by R. Mom is rr and dad is RR. All children are going to be Rr and so heterozygous. They will all carry the trait for red hair but will express brown hair themselves, so 0% probability of having a child with red hair from the initial parents
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.
Answer:
4 percent (4%)
Explanation:
A single crossover occurs between two (non-sister) chromatids belonging to homologous chromosomes. In this case, 16 percent of the meioses have a single crossover, thereby it will produce 8 percent of the chromosomes with the original (parental) combination in the progeny and the remaining 8 percent should be recombinants. From this result, it is reasonable to conclude that half of these recombinants should be 'Br' (and the other remaining 4 percent should be recombinants 'bR'), and therefore the answer is 4 percent (4%).
