Refer to the figure to answer these questions: a. Add labels...

Refer to the figure to answer these questions: a. Add labels for mRNA (including the $5^{\prime}$ and $3^{\prime}$ ends) and tRNA. In addition, draw in the RNA polymerase enzyme and the ribosomes, including arrows indicating the direction of movement for each. b. What are the next three amino acids to be added to polypeptide $b$ ? c. Fill in the nucleotides in the mRNA complementary to the template DNA strand. d. What is the sequence of the DNA complementary to the template strand (as much as can be determined from the figure)? e. Does this figure show the entire polypeptide that this gene encodes? How can you tell? f. What might happen to polypeptide $b$ after its release from the ribosome? g. Does this figure depict a prokaryotic or a eukaryotic cell? How can you tell?

Refer to the figure to answer these questions: a. Add labels for mRNA (including the $5^{\prime}$ and $3^{\prime}$ ends) and tRNA. In addition, draw in the RNA polymerase enzyme and the ribosomes, including arrows indicating the direction of movement for each.
b. What are the next three amino acids to be added to polypeptide $b$ ?
c. Fill in the nucleotides in the mRNA complementary to the template DNA strand.
d. What is the sequence of the DNA complementary to the template strand (as much as can be determined from the figure)?
e. Does this figure show the entire polypeptide that this gene encodes? How can you tell?
f. What might happen to polypeptide $b$ after its release from the ribosome?
g. Does this figure depict a prokaryotic or a eukaryotic cell? How can you tell?

Key Concepts

Protein Processing and Post-translational Modifications

After a polypeptide is synthesized and released from the ribosome, it often undergoes further processing. This may include folding into its correct three-dimensional shape, cleavage of specific segments, and various chemical modifications that are essential for the protein’s final function and regulation.

Complementary Base Pairing

Complementary base pairing is a fundamental principle of nucleic acid chemistry where specific bases pair with one another (adenine with uracil in RNA or thymine in DNA, and cytosine with guanine). This concept is critical in transcription when forming the RNA strand and in translation when tRNA anticodons pair with mRNA codons.

Prokaryotic vs. Eukaryotic Gene Expression

The genetic mechanisms of transcription and translation can differ between prokaryotic and eukaryotic cells. In prokaryotes, these processes are often coupled—meaning transcription and translation occur simultaneously in the cytoplasm—whereas in eukaryotes they are compartmentalized, with transcription occurring in the nucleus and translation in the cytoplasm. This distinction is crucial for understanding gene regulation and the overall flow of genetic information.

RNA Polymerase Enzyme

RNA polymerase is the enzyme that synthesizes RNA from a DNA template during transcription. It binds to the DNA at specific promoter regions and catalyzes the sequential addition of ribonucleotides, effectively 'reading' the template strand and producing a complementary RNA strand.

Translation

Translation is the process of decoding the information carried by mRNA to assemble a chain of amino acids into a polypeptide. Ribosomes facilitate this process by moving along the mRNA, reading sets of three nucleotides called codons, and matching them with the appropriate tRNA molecules that carry the corresponding amino acids.

tRNA and Anticodon-Codon Pairing

Transfer RNA (tRNA) is essential for translation because each tRNA molecule carries a specific amino acid and contains an anticodon region that is complementary to the mRNA codon. This base-pairing between the anticodon and the codon ensures that the correct amino acid is incorporated into the growing polypeptide chain.

Ribosome Function

Ribosomes are complex molecular machines responsible for translating mRNA into protein. They consist of two subunits and move along the mRNA strand, facilitating the interaction between mRNA codons and tRNA anticodons. This coordinated movement and binding drive the synthesis of polypeptides in a sequential, directional manner.

Transcription

Transcription is the process by which a segment of DNA is used as a template to synthesize a complementary strand of RNA. This process is carried out by the enzyme RNA polymerase, and it follows a specific direction along the DNA template (usually 3' to 5') resulting in an mRNA strand that has a defined 5' to 3' orientation. It is the first step in expressing genetic information from DNA into functional products.

mRNA Structure and Directionality

Messenger RNA (mRNA) molecules have distinct 5' and 3' ends that determine their direction and functionality during translation. The 5' end often includes a cap (in eukaryotes), while the 3' end may possess a poly-A tail, and the overall polarity is crucial for the sequential reading of codons during protein synthesis.

Transcript

00:02 Hi, welcome to another numerate video.

00:06 The purpose of this video is to kind of give a visual representation of the processes of transcription and translation.

00:16 It's kind of kind of help understand it a little bit better.

00:19 It may sound like i'm kind of rambling, but i am actually trying to answer some questions that come at the end of chapter 7 in the book, biology concepts and investigations, third edition.

00:31 So there is an order to it.

00:36 Hopefully it will appear that way.

00:39 Transcription is the process of taking the dna, a strand of dna, and using it to build a strand of rna.

00:52 Translation then is the process of taking that rna and using it to build a polypeptide.

01:01 And so in this picture, the blue material is the dna, and the green material is the messenger rna that we're building from the dna.

01:20 Now, it's getting kind of messy, so i won't draw it in.

01:27 Oops, didn't mean to do that.

01:34 It's getting a little messy, so i won't draw it in.

01:37 But there would be a molecule of rna polymerase involved in this.

01:44 Now, on the dna over to the left, you see that's the three prime end, and the right is a five prime end.

01:52 So on the messenger rna, it's said to be anti -parallel.

01:57 So the right is going to be the three -prime end of the messenger rna, and the far left would be the five -prime end.

02:07 And so it's the three prime end where the transcription is happening.

02:13 And so this end down here is where the polymerase, the rna polymerase would be polymerase.

02:20 Anytime you hear that ase ending, you know you're talking about an enzyme.

02:25 Polymer is a molecule made of multiple parts, multiple subunits bonded together.

02:35 And so rna polymerase is an enzyme that is bonding the subunits of rna together.

02:41 It's building the rna.

02:44 So the rna polymerase would be working on that end.

02:48 Now, there are a couple of things we can tell from looking at this picture.

02:53 The first is that transcription is happening along the dna strand.

03:00 So the dna strand is opened up, and it is.

03:06 Is using that to build a messenger rna strand, and we could actually tell which bases are going to be added next if we follow this sequence.

03:20 So here we have guanine and the dna, and that is going to pair with a cytosine.

03:29 So on the rna strand, you're going to put a cytosine right here.

03:32 Next is adenine and what would bind with adenine is thymine, except thymine is not found in messenger or in rna.

03:47 Instead, it's going to be uracil.

03:52 And so then another uricil would go here.

03:56 And this thymine is going to pair up with an adenine.

04:04 This cytosine is going to pair up with the guanine, this cytosine with a guine, this thymine with an atomene, this guine with cytosine...

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