Ascientist is studying a cell and can clearly see that it has ribosomes and mitochondria. which statement best describes how the cell could be classified?
a) the cell is prokaryotic because it contains ribosomes.
b) the cell is prokaryotic because it contains mitochondria.
c) the cell is eukaryotic because it contains ribosomes.
d) the cell is eukaryotic because it contains mitochondria.

The cell studied by the scientist under the microscope contains both ribosomes and mitochondria. Both the prokaryotic and the eukaryotic cells contain ribosomes. However, the ribosomes in prokaryotes are 70S, while eukaryotes have 80S ribosomes. Nonetheless, they are present in both the cells. Their presence will not establish the classification of cells.

On the other hand, the mitochondria are present only in the eukaryotic cells. The prokaryotic cells contain no cell organelles and hence, have no mitochondria. The cell observed by the scientist contains mitochondria, hence, it is an eukaryotic cell.

Hence, the correct answer is 'Option D - The cell is eukaryotic because it contains mitochondria'.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.