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Passage The K-Ras Gene Codes for a Small Guanine Nucleotide-Binding Protein

Question 113

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The K-ras gene codes for a small guanine nucleotide-binding protein, which acts as a molecular activator in numerous signaling pathways that promote DNA replication along with cell growth and survival.  K-ras mutations at codons 12 and 13 function as biological markers for diagnosis of tumors.  The DNA of SW-480 cells, a line originating from a colon adenocarcinoma, is the standard positive control used to identify codon 12 mutations in K-ras testing.
Passage The K-ras gene codes for a small guanine nucleotide-binding protein, which acts as a molecular activator in numerous signaling pathways that promote DNA replication along with cell growth and survival.  K-ras mutations at codons 12 and 13 function as biological markers for diagnosis of tumors.  The DNA of SW-480 cells, a line originating from a colon adenocarcinoma, is the standard positive control used to identify codon 12 mutations in K-ras testing. <strong>Figure 1</strong>  Structural comparison of K-ras codon 12 in wild-type cells and SW-480 cellsPCR sequence analysis has been the preferred method for studying genetic mutations such as those in K-ras.  However, challenges in analyzing PCR amplicons have prompted the development of DNA melting curve analysis (MCA) .  In the MCA technique, DNA is extracted from clinical samples and amplified by PCR.  The amplified DNA is then melted (30-70°C) and analyzed by assessing the fluorescence (at 640 nm) of LC Green Plus, an intercalating dye that fluoresces when bound to double-stranded DNA (Figure 2) . <strong>Figure 2</strong>  Melting curves of wild-type (WT) and SW-480 K-ras DNA.To study K-ras activity in colorectal cancer cells, short tandem repeats (STRs) were introduced into the K-ras gene.  STRs are short stretches of DNA with repeating nucleotides, and four different STR sequences were inserted into the K-ras gene and analyzed via MCA under different experimental conditions (Table 1) .<strong>Table 1</strong>  Sequences Studied in K-ras DNA MCA Analysis. Liu YP, Wu HY, Yang X, et al. Diagnostic accuracy of high resolution melting analysis for detection of KRAS mutations: a systematic review and meta-analysis. Sci Rep. 2014;4:7521. -What are the physical states of wild-type (WT) and SW-480 K-ras DNA at 55°C? A) 100% of SW-480 DNA is double-stranded and 50% of WT DNA is single-stranded. B) 100% of SW-480 DNA is single-stranded and 50% of WT DNA is single-stranded. C) 50% of SW-480 DNA is double-stranded and 100% of WT DNA is double-stranded. D) 50% of SW-480 DNA is single-stranded and 100% of WT DNA is double-stranded. Figure 1  Structural comparison of K-ras codon 12 in wild-type cells and SW-480 cellsPCR sequence analysis has been the preferred method for studying genetic mutations such as those in K-ras.  However, challenges in analyzing PCR amplicons have prompted the development of DNA melting curve analysis (MCA) .  In the MCA technique, DNA is extracted from clinical samples and amplified by PCR.  The amplified DNA is then melted (30-70°C) and analyzed by assessing the fluorescence (at 640 nm) of LC Green Plus, an intercalating dye that fluoresces when bound to double-stranded DNA (Figure 2) .
Passage The K-ras gene codes for a small guanine nucleotide-binding protein, which acts as a molecular activator in numerous signaling pathways that promote DNA replication along with cell growth and survival.  K-ras mutations at codons 12 and 13 function as biological markers for diagnosis of tumors.  The DNA of SW-480 cells, a line originating from a colon adenocarcinoma, is the standard positive control used to identify codon 12 mutations in K-ras testing. <strong>Figure 1</strong>  Structural comparison of K-ras codon 12 in wild-type cells and SW-480 cellsPCR sequence analysis has been the preferred method for studying genetic mutations such as those in K-ras.  However, challenges in analyzing PCR amplicons have prompted the development of DNA melting curve analysis (MCA) .  In the MCA technique, DNA is extracted from clinical samples and amplified by PCR.  The amplified DNA is then melted (30-70°C) and analyzed by assessing the fluorescence (at 640 nm) of LC Green Plus, an intercalating dye that fluoresces when bound to double-stranded DNA (Figure 2) . <strong>Figure 2</strong>  Melting curves of wild-type (WT) and SW-480 K-ras DNA.To study K-ras activity in colorectal cancer cells, short tandem repeats (STRs) were introduced into the K-ras gene.  STRs are short stretches of DNA with repeating nucleotides, and four different STR sequences were inserted into the K-ras gene and analyzed via MCA under different experimental conditions (Table 1) .<strong>Table 1</strong>  Sequences Studied in K-ras DNA MCA Analysis. Liu YP, Wu HY, Yang X, et al. Diagnostic accuracy of high resolution melting analysis for detection of KRAS mutations: a systematic review and meta-analysis. Sci Rep. 2014;4:7521. -What are the physical states of wild-type (WT) and SW-480 K-ras DNA at 55°C? A) 100% of SW-480 DNA is double-stranded and 50% of WT DNA is single-stranded. B) 100% of SW-480 DNA is single-stranded and 50% of WT DNA is single-stranded. C) 50% of SW-480 DNA is double-stranded and 100% of WT DNA is double-stranded. D) 50% of SW-480 DNA is single-stranded and 100% of WT DNA is double-stranded. Figure 2  Melting curves of wild-type (WT) and SW-480 K-ras DNA.To study K-ras activity in colorectal cancer cells, short tandem repeats (STRs) were introduced into the K-ras gene.  STRs are short stretches of DNA with repeating nucleotides, and four different STR sequences were inserted into the K-ras gene and analyzed via MCA under different experimental conditions (Table 1) .Table 1  Sequences Studied in K-ras DNA MCA Analysis.
Passage The K-ras gene codes for a small guanine nucleotide-binding protein, which acts as a molecular activator in numerous signaling pathways that promote DNA replication along with cell growth and survival.  K-ras mutations at codons 12 and 13 function as biological markers for diagnosis of tumors.  The DNA of SW-480 cells, a line originating from a colon adenocarcinoma, is the standard positive control used to identify codon 12 mutations in K-ras testing. <strong>Figure 1</strong>  Structural comparison of K-ras codon 12 in wild-type cells and SW-480 cellsPCR sequence analysis has been the preferred method for studying genetic mutations such as those in K-ras.  However, challenges in analyzing PCR amplicons have prompted the development of DNA melting curve analysis (MCA) .  In the MCA technique, DNA is extracted from clinical samples and amplified by PCR.  The amplified DNA is then melted (30-70°C) and analyzed by assessing the fluorescence (at 640 nm) of LC Green Plus, an intercalating dye that fluoresces when bound to double-stranded DNA (Figure 2) . <strong>Figure 2</strong>  Melting curves of wild-type (WT) and SW-480 K-ras DNA.To study K-ras activity in colorectal cancer cells, short tandem repeats (STRs) were introduced into the K-ras gene.  STRs are short stretches of DNA with repeating nucleotides, and four different STR sequences were inserted into the K-ras gene and analyzed via MCA under different experimental conditions (Table 1) .<strong>Table 1</strong>  Sequences Studied in K-ras DNA MCA Analysis. Liu YP, Wu HY, Yang X, et al. Diagnostic accuracy of high resolution melting analysis for detection of KRAS mutations: a systematic review and meta-analysis. Sci Rep. 2014;4:7521. -What are the physical states of wild-type (WT) and SW-480 K-ras DNA at 55°C? A) 100% of SW-480 DNA is double-stranded and 50% of WT DNA is single-stranded. B) 100% of SW-480 DNA is single-stranded and 50% of WT DNA is single-stranded. C) 50% of SW-480 DNA is double-stranded and 100% of WT DNA is double-stranded. D) 50% of SW-480 DNA is single-stranded and 100% of WT DNA is double-stranded. Liu YP, Wu HY, Yang X, et al. Diagnostic accuracy of high resolution melting analysis for detection of KRAS mutations: a systematic review and meta-analysis. Sci Rep. 2014;4:7521.
-What are the physical states of wild-type (WT) and SW-480 K-ras DNA at 55°C?


A) 100% of SW-480 DNA is double-stranded and 50% of WT DNA is single-stranded.
B) 100% of SW-480 DNA is single-stranded and 50% of WT DNA is single-stranded.
C) 50% of SW-480 DNA is double-stranded and 100% of WT DNA is double-stranded.
D) 50% of SW-480 DNA is single-stranded and 100% of WT DNA is double-stranded.

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