Trait Expression: Transcription

Amy Hauver Author

07/19/2022 Added

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Trait expression is the process by which genes becomes proteins, and it occurs in two parts: transcription and translation. This video describes the process of transcription.

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[00:00:09.090]In this video,
[00:00:10.110]we'll be discussing trait expression.
[00:00:12.540]An important part of understanding herbicide resistance
[00:00:15.420]is learning how resistance traits originate in populations.
[00:00:19.680]Traits that influence resistance originate
[00:00:21.930]as a gene that is expressed in an individual.
[00:00:25.170]The ultimate effect of a trait will be influenced
[00:00:27.720]by the individual's growing environment.
[00:00:30.780]Trait expression is the process by which a gene
[00:00:33.300]is used to generate a protein.
[00:00:35.490]The protein will serve some function within the individual.
[00:00:39.031]Gene expression occurs in two parts.
[00:00:41.430]First, transcription, followed by translation.
[00:00:44.760]In this video, we'll specifically talk about transcription,
[00:00:48.330]but before we describe transcription,
[00:00:51.000]we're going to review the relationships between genes,
[00:00:53.580]chromosomes, and cells.
[00:00:55.920]A chromosome is a large macromolecule
[00:00:58.200]consisting of one DNA molecule
[00:01:00.840]that is thousands of nucleotide subunits long
[00:01:03.390]wrapped around stabilizing proteins.
[00:01:05.850]A chromosome may contain hundreds or thousands of genes.
[00:01:09.330]In total, plants have around 30,000 different genes
[00:01:12.150]on their chromosomes.
[00:01:13.830]One gene is a sequence of DNA that provides instructions
[00:01:17.310]to make a specific protein needed by the plant.
[00:01:23.340]Because chromosomes are housed
[00:01:25.050]in the nucleus of the plant cell
[00:01:26.550]and proteins are built in the cytoplasm of a cell,
[00:01:29.520]the gene expression process requires two main steps.
[00:01:33.720]First, transcription.
[00:01:35.340]It's the first step in gene expression
[00:01:37.050]where a specific section of the DNA sequence,
[00:01:39.690]otherwise known as the gene,
[00:01:41.370]is read to build a complementary segment
[00:01:43.680]of messenger RNA.
[00:01:45.540]This messenger RNA sequence has the coded information
[00:01:48.630]for building a specific protein
[00:01:50.513]and building a specific protein occurs during translation.
[00:01:55.680]DNA stores its genetic code as a sequence
[00:01:58.350]of four different DNA subunits called nucleotides.
[00:02:01.796]These nucleotides are thymine, guanine,
[00:02:06.060]adenine, and cytosine.
[00:02:08.190]There's also an RNA nucleotide called uracil
[00:02:10.890]that is used when building RNA.
[00:02:13.560]The enzyme RNA polymerase is responsible
[00:02:16.200]for reading the DNA nucleotide sequence
[00:02:18.570]and synthesizing the complementary
[00:02:20.370]messenger RNA nucleotide sequence.
[00:02:23.550]The RNA polymerase enzyme will read one of the gene strands
[00:02:27.840]and build a corresponding RNA nucleotide sequence.
[00:02:31.830]The guanine in a DNA sequence will signal for a cytosine
[00:02:35.690]in the RNA sequence.
[00:02:37.560]Cytosine encodes G, guanine, thymine encodes an adenine,
[00:02:43.350]and adenine in the DNA encodes a uracil RNA nucleotide.
[00:02:48.450]The pairing of nucleotides can be seen
[00:02:50.340]in this following example.
[00:02:52.020]The nucleotides in this segment of a gene
[00:02:54.420]are cytosine, adenine, guanine, thymine,
[00:02:57.330]and two more adenine.
[00:02:59.700]These six nucleotides are read and converted
[00:03:02.130]to complementary messenger RNA nucleotides.
[00:03:06.930]The DNA cytosine is read and matched with RNA guanine.
[00:03:11.850]DNA adenine is read and matched with RNA uracil.
[00:03:17.460]Another guanine is read and matched
[00:03:19.440]with complementary cytosine
[00:03:22.530]and thymine is matched with adenine
[00:03:24.870]and the last adenine is matched with uracil.
[00:03:31.260]Remember, transcription occurs
[00:03:33.060]within the nucleus of the plant.
[00:03:35.910]RNA polymerase builds to the promoter region of the gene
[00:03:40.560]and begins to read the DNA nucleotide sequence of the gene
[00:03:44.010]and transcribes it to a messenger RNA strand.
[00:03:48.630]Once it reaches the termination sequence,
[00:03:50.730]the RNA polymerase stops the process.
[00:03:54.510]The resulting complementary strand of messenger RNA
[00:03:57.630]is then transported out of the nucleus,
[00:04:00.660]which begins the next stage of trait expression,
[00:04:03.420]translation, which we'll discuss in the next video.

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Trait Expression: Transcription

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