Of carbon dioxide that was in the atmosphere in prehistoric times. Scientists retrieved this data from air bubbles trapped in ancient ice in Vostok, Antarctica.
Carbon dioxide levels are provided in parts per million (ppm).
400
375
Graph 1: Atmospheric Carbon Dioxide BCE
(www. co2.earth)
350
325
300
Atmospheric Carbon Dioxide Levels
275
250
225
ws
200
175
400,000
300,000
100,000
200.000
Years Before Present
3. What time frame does this graph include?*
1 point
O a. about 400,000 years ago to the present
O b. from the present day to 400,000 years in the future
O c. one million years ago to the present day
O d. the graph does not provide a timeframe

the answer is:

carbon dioxide

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.