[Unit 6 FRQ] Gene Expression and Regulation

Answer this tricky question from CollegeBoard on Gene Expression and Regulation. Be sure to read carefully, and don’t overthink it! Feedback will be provided.

Copyright: CollegeBoard, 2019

a) Gene G most likely encodes a protein essential to glycolysis. Glycolysis is a crucial part in cellular respiration (and is the first step), which provides ATP and energy for many functions to occur in our bodies. All of the tissues need to use energy and therefore require cellular respiration to provide the ATP it needs. Since only gene G is present in every tissue, it is most likely encoding the protein that the important process, glycolysis, needs.

b) Gene H could be more important to some tissues than others. The gene could still be transcribed by DNA polymerase and form pre-mRNA, but gene H may be removed during mRNA splicing if it is not needed, so there will be no gene H protein.

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a) The most likely gene to encode a protein that is an essential component of glycolysis is gene G. The reasoning is that it is the only Gene that is actively producing mRNA in all tissues.
b) Just because the gene is present does not mean it is being translated and transcribed. It is most likely methylated, or super coield, and unable to be transcribed into a protein.

Hi Angela,

Great work on your response. You received 2/2 points for part a by successfully identifying gene G and explaining your rationale behind your choice. You received 1/1 points for part b by explaining that gene H may be removed during RNA processing. GREAT work!

Thank you for sharing your work! You received 2/2 points for part a by identifying gene G and explaining your rational. You also received 1/1 points for part b by explaining the possible rationale for the presence of the gene without transcription and translation. Nice work!

A. Gene G is most likely to encode a protein that is essential for glycolyisis. The reason that it is gene g is that glycoyilis an essential part of cellular respiration and is carried out in every type of cell. Gene G has to encode for a protein essential for glycolsis as in is the only gene produced in all cells.
B. The protein may not be important but the RNA polymerase may still create the mRNA. The H gene could be removed as an intron in post transcriptional modification where it would then br broken down and sued to create more mRNA.

a) Gene G is most likely to encode a protein that is an essential component of glycolysis. Glycolysis is the first step in cellular respiration and is responsible for the breakdown of glucose into a more usable form by plants/animals, to which it converts it into ATP and two pyruvate molecules which later gets broken down into more energy for the cell. All cells require energy to survive as it is one of the main characteristics of living things. ATP is the energy that drives our bodies’ numerous metabolic processes, and so all of our tissues/organs require this energy in order to be able to perform their daily functions. Since all of the tissues contain gene G (presence in the mRNA), this indicates that it’s an important gene that is most likely responsible for encoding a protein responsible for cellular respiration in some way, shape, or form.

b) The lack of a gene H protein in the presence of a high gene mRNA level could indicate that the protein may be unessential or not needed in those tissues more so than others. What ends up happening is that the gene that codes for the H protein could still be transcribed by RNA polymerase and included in the premature mRNA, but it ends up being excised from the sequence as an intron, and would stay inside the nucleus, following post-transcriptional modifications such as mRNA splicing during the process of being transformed into a fully mature messenger RNA. Thus, since gene H stays inside the nucleus and does not travel to the ribosome in the cytoplasm, it does not get translated into a gene H protein.

a) Gene G is the gene that is most likely to encode a protein that is an essential component of glycolysis. This is because glycolysis is an essential part of cellular respiration, a process performed in all cells, and gene G is the only gene that is present in all tissues. Thus, it would be the most likely gene to encode a protein essential to glycolysis.
b) Gene H mRNA levels may be present in certain tissues without having the gene H protein because the protein may not be needed in the cell/tissue. If it is unnecessary for the cell/tissue, it will not be translated or transcribed, or could be removed during post-transcriptional modifications. For example, the gene H mRNA may be spliced out of the mRNA chain and the gene H protein would not be formed.

  1. Gene G codes for the protein essential to glycolysis because of how glycolysis is the first step to cellular respiration, an important biological process used for obtaining energy. If all organs shown above are producing a good amount of mRNA, then it’s likely that Gene G is the cause of it.
  2. Having high mRNA levels of gene H but no gene H protein signifies that gene H may not be essential to the survival of the cell at that moment. In order to save energy, the gene can be “cut out” in the post-transcriptional modification process, which explains why there’s high mRNA levels but no protein.
  1. Gene G most likely codes for glycolysis. All of the cells exhibit this gene as shown in the chart. Because glycolysis is essential in all cells, this suggests that this is the gene that codes for glycolysis.
  2. Gene H was most likely an intron that got removed during RNA splicing. This gene may have coded for an RNA segment that was removed as it underwent modifications. Because introns are removed during RNA splicing, it can be stated that Gene H was removed during splicing, assuming that Gene H was an intron.

You received 2/2 points for part a. You received 1/1 points for mentioning that gene H may be transcribed but removed as an intron.

Great work!

Hi Tony,

You received 2/2 points for your response to part A. You received 1/1 points for your response to part B. I am thoroughly impressed by the quality of information that you have included. Great work!

Hi Mazie,

You received 2/2 points for part a and 1/1 points for part b. GREAT job.

Hi Monica,

You received 3/3 points for your response. Great work!

You received 3/3 points for your response. Great use of vocabulary!

a) The gene most likely to encode a protein essential to glycolysis is gene G, this is because all tissues play a role in cellular respiration in varying degrees. Since it is present in all cells, Gene G is most likely to be apart of glycolysis.
b) A tissue can have high gene H mRNA levels but no gene H protein when the mRNA is terminated or denatured before translation. This can be accomplished by RNA processing by a spliceosome that changes the function of the mRNA, or by microRNAs that denature the mRNA.

a) Gene G because it is present in all tissues and glycolysis is necessary in every part of the body because it produces ATP, which is used almost everywhere in our body.
b) Just because a gene is expressed, doesn’t mean a protein will always be produced. If the protein is not necessary for the tissue, the protein could have been degraded after synthesis.

a) Gene G is most likely to encode a protein that is an essential component of glycolysis. Glycolysis is the first step of cellular respiration, in which glucose is broken down to be turned into ATP, energy used for numerous biological processes, pyruvate, and, later, even more ATP. Since Gene G is found in all tissues, it is most likely that Gene G encodes for an essential component of glycolysis, because it would be able to provide ATP for these tissues.

b) Although some tissues had the Gene H mRNA, it is likely that some tissues did not form Gene H proteins because the protein was not necessary to them. It is likely that after transcription, Gene H may have been spliced out of the pre-mRNA as an intron during splicing in post-transcriptional modification. Because it was spliced out, Gene H would not be able to leave the nucleus to be transcribed into a protein by the ribosomes.

(a) Gene G is the most likely to encode a protein that is an essential component of glycolysis. This is because it is present in some quantity in all of the tissues in the mice, meaning that that gene is necessary for them to have energy/survive. Also, every single one of these have glycolysis occurring in their tissues because they are used very often.
(b) Tissues with high gene H mRNA levels can have no protein simply because those genes do not need to necessarily be expressed. After mRNA is created, the processing for a protein can still be regulated by molecules like miRNA and RNAi, which can quickly degrade the gene H mRNA. So, if the mRNA were to be degraded or destroyed in some way before it went to the ribosome and was translated into a protein, then the gene H protein would not be expressed, even in the event that there was a high amount of gene H mRNA levels.

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