Answer:
A. stratified squamous epithelium; absorption
Explanation:
Stratified squamous epithelium are composed of multiple layers of cells which rest on a basement membrane. Superficial layers are made of squamous cells and underlying layers can also be made of cuboidal or columnar cells.
Stratified squamous epithelium is generally present in area where there is frequent physical or chemical abrasion. It protects the underlying structures from the stress. Hence, it is found wherever the body comes in contact with the outer environment like skin, digestive system and respiratory system. It also prevents water loss and desiccation.
More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described.
Answer:
Normal Strand: alanine - methionine - histidine
Mutated Strand: glutamine - cysteine - no third amino acid.
Explanation:
<h3>mRNA Structure</h3>
Messenger ribonucleic acid (mRNA) is the RNA that is used in cells for protein synthesis. It has a single strand made by the transcription of DNA by RNA polymerase. It contains four nucleotides: Adenine (A), Guanine (G), Cytosine (C), and Uracil (U).
<h3>DNA Replication</h3>
Before transcribing, we need to create the complementary strand of the DNA. We're going to write out the nucleotides of the complementary strand by matching the nucleotides in these pairs: (A & T) and (C & G).
Normal Strand: GCA ATG CAC
Complementary Strand: CGT TAC GTG
Next, we can transcribe this to find our mRNA. We're going to do the same thing to the complementary DNA strand, but with Uracils instead of Thymines. So our pairs are: (A & U) and (C & G)
Complementary DNA Strand: CGT TAC GTG
mRNA Strand: GCA AUG CAC
You'll notice that the mRNA strand is almost exactly like the new mRNA strand, but with Uracil instead of Thymine.
<h3>Reading Codons</h3>
Each set of three nucleotides is known as a codon, which encodes the amino acids that ribosomes make into proteins. To read the codons, you need to have a chart like the one I attached. Start in the middle and work your way to the edge of the circle. Some amino acids have multiple codons. There are also "stop" and "start" codons that signify the beginning and ends of proteins.
mRNA Strand: GCA AUG CAC
Amino Acids: Ala Met His
Our sequence is alanine, methionine, and histidine.
<h3>Frameshift Mutations</h3>
A frameshift mutation occurs when a nucleotide is either added or removed from the DNA. It causes your reading frame to shift and will mess up every codon past where the mutation was. This is different than a point mutation, where a nucleotide is <em>swapped</em> because that will only mess up the one codon that it happened in. Frameshift mutations are usually more detrimental than point mutations because they cause wider spread damage.
<h3>Mutated Strand</h3>
Let's repeat what we did earlier on the mutated strand to see what changed.
Mutated Strand: CAA TGC AC
Complementary Strand: GTT ACG TG
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Complementary DNA Strand: GTT ACG TG
mRNA Strand: CAA UGC AC
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mRNA Strand: CAA UGC AC
Amino Acids: Glu Cys X
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Our amino acid sequence is glutamine, cysteine, and no third amino acid.
As you can see, removing the first nucleotide of the strand caused every codon to change. The last codon is now incomplete and won't be read at all. If this happened in a cell, the protein that was created from this mutated strand would be incorrect and may not function completely or at all.
Electrons are found outside the nucleus.
Starch cannot diffuse across the membrane because starch molecules are too large to fit through the pores in the dialysis tubing, whereas iodine is a smaller molecule and therefore can diffuse across.