Concept explainers
Chapter 21 describes a technique known as Northern blotting that is used to detect RNA transcribed from a particular gene. In this method, a specific RNA is detected using a short segment of cloned DNA as a probe. The DNA probe, which is labeled, is complementary to the RNA that the researcher wishes to detect. After the probe DNA binds to the RNA, the RNA is run on a gel and then visualized as a labeled (dark) band. As shown here, the method of Northern blotting can be used to determine the amount of a particular RNA transcribed in a given cell type. If one type of cell produces twice as much of a particular mRNA as another type of cell does, the band will appear twice as intense. Also, the method can distinguish whether alternative RNA splicing has occurred to produce an RNA that has a different molecular mass.
Lane 1 is a sample of RNA isolated from nerve cells.
Lane 2 is a sample of RNA isolated from kidney cells. Nerve cells produce twice as much of this RNA as do kidney cells.
Lane 3 is a sample of RNA isolated from spleen cells. Spleen cells produce an alternatively spliced version of this RNA that is about 200 nucleotides longer than the RNA produced in nerve and kidney cells.
Let’s suppose a researcher is interested in the effects of mutations on the expression of a particular protein-encoding gene in eukaryotes. The gene has one intron that is 450 nucleotides long. After this intron is removed from the pre-mRNA, the mRNA transcript is 1100 nucleotides in length. Diploid somatic cells have two copies of this gene. Make a drawing that shows the expected results of a Northern blot using mRNA from the cytosol of somatic cells, which were obtained from the following individuals:
Lane 1: A normal individual
Lane 2: A homozygote for a deletion that removes the
Lane 3: A heterozygote in which one gene is normal and the other gene has a deletion that removes the
Lane 4: A homozygote for a mutation that introduces an early stop codon into the middle of the coding sequence of the gene Lane
5: A homozygote for a two-
Want to see the full answer?
Check out a sample textbook solutionChapter 12 Solutions
Genetics: Analysis and Principles
- Choose 1 or more than 1 RNA are extracted from liver cells and separated in agarose gel by electrophoresis side-by-side with a molecular weight marker. The separated RNA fragments are then transferred to an RNA-binding membrane. Next, this membrane is incubated with labelled probe specific for the gene X. This experiment determines: how many copies of gene X there are in liver cells. if the gene X is translated in liver cells. if gene X has a point mutation in liver cells. the chromosomal location of gene X. the length of the transcript of gene X.arrow_forwardYou are asked to sequence a piece of DNA to determine if it is from a gene thought to be involved in the development of breast cancer. The sequence of the template strand is ATGCCCGTAATCGTTA and you are given the primer TAACGA. You take these along with a sequencing kit that contains everything else needed for sequencing. You then run the sequencing experiment and analyze the results on a sequencing gel. Which of the following gels (A-D) is the correct sequencing gel for this experiment? Answers: A-D A A BB CC DD Question #3 attachment A ATOC B с A TO C ATOC ATOCarrow_forwardAs part of the steps necessary to clone a human gene with multiple introns (so it can be expressed in a bacterial cell, which does not have the enzyme for RNA splicing), the intron sequences have to be removed first. Explain how such an intronless human gene for cloning is made.arrow_forward
- Cre-Lox system is used for site-specific modification of DNA for genetic engineering applications. The reporter gene construct shown below is used to test the Cre-Lox system. Cells are transfected with the construct shown below and the activity of the constructs is determined by visualizing the cells with a fluorescence microscope. Match the following conditions with the expected cell observations. Hint: Make sure you note the position of the Start and Stop. The GFP and RFP genes shown do not have start codons. Cre/Lox Reporter Gene ATG LoxP CMV-Pro A. No Expression GFP Stop B. GFP Only LoxP Absence of Cre Cells treated with drug that induces expression of Cre RFP C. RFP Only A. Image A B. Image B C. Image C D Image D express ? D. RFP and GFParrow_forwardThe following gene sequence of nucleotides is found on the template (non-coding) strand of a molecule of DNA from a bacterial cell. The promoter of the gene is highlighted in bold letters and the +1 is underlined. Use the genetic code at the end of this packet to answer the following questions. 3'-AGGCATATTACGATGCCGGTACTTGATGATGACGGACCCATTATAGGACATATG-5' a) What is the sequence of the mRNA strand that will be transcribed from this piece of DNA? Indicate which is the 5’ and which is the 3’ end of the mRNA. b) What is the amino acid sequence that will be translated from this piece of DNAarrow_forwardRestriction sites are palindromic; that is, they read the same in the5' to 3' direction on each strand of DNA. What is the advantage ofhaving restriction sites organized this way?arrow_forward
- Bacteria can be used to produce human growth hormone (HGH - a peptide/protein) through genetic engineering. The human gene for HGH is inserted into a plasmid, which is then taken up by a bacterial cell, which divides and multiplies into a clone of cells, all of which contain the plasmid with the HGH gene. The bacteria express the HGH gene, producing HGH which can be harvested and used for treatment of humans. (See figure below) Which of the following statements is NOT true about this process? bacterium Vector, such as a DNA containing the gene of plasmid, isolated it from a different species is Gene encoding protein for pest resistance is inserted into plant cells ©2019 Pearson Education, Inc chromosome recombinant DNA (plasmid) transformed bacterium Create and harvest copies of a gene with either of two goals in mind. Gene encoding degradative enzyme to clean up toxdo waste is inserted into bacterial cells ved by an enzyme into gene of interest The desired gene is selected and…arrow_forwardIn Northern blot analysis, mRNA samples from tissues are bound to a labeled DNA probe that is complementary to the mRNA, and run on a gel to be visualized. The protein tropomyosin is known to be present in both brain and liver. When brain and liver tissue were assayed for the presence of tropomyosin mature mRNA, bands of two different sizes were seen. Tropomyosin gene diagram (3000 bp total): Shown in attatched image If the band on the Northern blot for mRNA isolated from liver tissue is 2580 bp, whereas from brain tissue the band is 2250 bp, what is most likely? a)The two mRNAs are made from different tropomyosin DNA sequences. b)Exon 2 is alternatively spliced out of the brain mRNA. c)Introns 1 and 2 are spliced out of the brain transcript but not the liver transcript. d)Exons 1 and 3 are spliced out of the brain transcript but not the liver transcript. e)Exon 2 is alternatively spliced out of the liver mRNA.arrow_forwardDescribe the process of cloning a DNA fragment into theBamHI and PstI sites of the vector pUC18. How would youscreen for clones that contain an insert? and explain the process(steps) by drawingarrow_forward
- A biologist is attempting to clone the gene encoding a particular enzyme (Enz) into a plasmid vector in E.coli. This plasmid has a gene encoding a green fluorescent protein (GFP) as well as a gene for tetracycline antibiotic resistance (TetR). The restriction site (to clone foreign DNA into) is within the GFP sequence. Which of the following would be expected when trying to see which E. coli cells acquired the recombinant plasmid (i.e., carrying the Enz gene)? Bacteria UNABLE to grow on tetracycline-containing media AND are NOT able to make green fluorescent protein are the ones that contain the recombinant plasmid. Bacteria able to grow on tetracycline-containing media AND that are NOT able to make green fluorescent protein are the ones that contain the recombinant plasmid. Bacteria able to grow on tetracycline-containing media AND are able to make green fluorescent protein are the ones that contain the recombinant plasmid. Bacteria UNABLE to…arrow_forwardDescribes a method known as Western blotting that can be used to detect a polypeptide that is translated from a particular mRNA. In this method, a particular polypeptide or protein is detected by an antibody that specifically recognizes a segment of its amino acid sequence. After the antibody binds to the polypeptide within a gel, a secondary antibody (which is labeled) is used to visualize the polypeptide as a dark band.For example, an antibody that recognizes α-galactosidase A couldbe used to specifically detect the amount of α-galactosidase A proteinon a gel. The enzyme α-galactosidase A is defective in individuals with Fabry disease, which shows an X-linked recessive pattern of inheritance. Amy, Nan, and Pete are siblings, and Pete has Fabry disease. Aileen, Jason, and Jerry are brothers and sister, and Jerry has Fabry disease. Amy, Nan, and Pete are not related to Aileen, Jason, and Jerry. Amy, Nan, and Aileen are concerned that they could be carriers of a defective…arrow_forwardSouthern blotting is a method used in molecular biology for detection of a specific DNA sequence in DNA samples while northern blotting is used for the detection of RNA in a sample. Write down the similarities and differences between both methods.arrow_forward
- Human Anatomy & Physiology (11th Edition)BiologyISBN:9780134580999Author:Elaine N. Marieb, Katja N. HoehnPublisher:PEARSONBiology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStaxAnatomy & PhysiologyBiologyISBN:9781259398629Author:McKinley, Michael P., O'loughlin, Valerie Dean, Bidle, Theresa StouterPublisher:Mcgraw Hill Education,
- Molecular Biology of the Cell (Sixth Edition)BiologyISBN:9780815344322Author:Bruce Alberts, Alexander D. Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter WalterPublisher:W. W. Norton & CompanyLaboratory Manual For Human Anatomy & PhysiologyBiologyISBN:9781260159363Author:Martin, Terry R., Prentice-craver, CynthiaPublisher:McGraw-Hill Publishing Co.Inquiry Into Life (16th Edition)BiologyISBN:9781260231700Author:Sylvia S. Mader, Michael WindelspechtPublisher:McGraw Hill Education