Genomics Genetics medicine Mcdowell NSU chapter 1 Garland practice quiz

Which of the following correctly fills in the blanks in the following passage? A 1_(nonsense)___ mutation directly changes a DNA triplet so that it is transcribed to give a ____2__(premature)__ termination codon instead of the normal amino acid-specifying codon. Some other mutations also give rise to a ____2 (premature)____ termination codon, but indirectly. When a single nucleotide (or any number of nucleotides not exactly divisible by three) is deleted from, or inserted into, a coding DNA sequence, and transcribed into RNA, the altered sequence is translated differently. This is a common example of a ____3_(frameshift)___ mutation. At the RNA level, mutations can cause altered RNA ___4_(splicing)__, for example a mutation at a ___5_(splice0__ site can cause a whole exon to be omitted from the mRNA (exon ____6_(skipping)___) or a whole intron to be retained in the mRNA. Alternatively, a cryptic ___5_(splice)__ site can be activated and abnormal RNA transcripts produced in which partial exon sequences are deleted or partial intron sequences are inserted. A. 1 - nonsense; 2 - premature; 3 - frameshift; 4 - splicing; 5 - splice; 6 - skipping B. 1 - frameshift; 2 - premature; 3 - nonsense; 4 - splicing; 5 - splice; 6 - skipping C. 1- premature; 2 - nonsense; 3 - skipping; 4 - splicing; 5 - splice; 6 - frameshifting D. 1 - nonsense; 2 - premature; 3 - frameshift; 4 - skipping; 5 - splice; 6 - splicing

1 - nonsense; 2 - premature; 3 - frameshift; 4 - splicing; 5 - splice; 6 - skipping

How many different DNA molecules are there in human cells?

25 There are 24 nuclear DNA molecules (one each for the 24 different chromosomes, that is, the 22 autosomes, X and Y) and one form of mtDNA.

.Which of the following correctly fills in the blanks in the following passage? A ____1_____ tumor is localized, being completely enclosed in a protective capsule of tissue, and is self-limiting. A ____2_____ tumor can both invade neighboring tissues and have cells that break away and enter the lymphatic system or bloodstream to be carried to distant sites to form ____3_____ tumors. The process of spreading to more distant sites is known as ____4_____, and the process whereby cells migrate from tissues across the walls of blood capillaries is known as ____5_____. A. 1 - benign; 2 - malignant; 3 - secondary; 4 - metastasis; 5 - extravasation. B. 1 - malignant; 2 - benign; 3 - secondary; 4 - extravasation; 5 - metastasis. C. 1 - benign; 2 - invasive; 3 - additional; 4 - metastasis; 5 - extravasation. D. 1 - benign; 2 - malignant; 3 - secondary; 4 - extravasation; 5 - metastasis.

A. 1 - benign; 2 - malignant; 3 - secondary; 4 - metastasis; 5 - extravasation.

.Which of the following correctly fills in the blanks in the following passage? Retroviruses are single stranded RNA viruses. They make a reverse ______1_______ that converts their genome into single-stranded cDNA. The cDNA is then converted to double-stranded cDNA and is able to ______2_______ into the chromosomal DNA of host cells. Retroviruses usually cannot pass through the pores in the ______3______ _membrane and so they normally infect dividing cells only (because during mitosis the ______3______ membrane breaks down, allowing the viral DNA access to the chromosomes). However, certain types of retrovirus, notably ______4______, are able to infect both dividing and non-dividing cells because they are able to pass their genomes effectively through the pores of the ______3______ membrane. A. 1 - transcriptase; 2 - integrate; 3 - nuclear; 4 - lentiviruses. B. 1 - polymerase; 2 - integrate; 3 - nuclear; 4 - lentiviruses. C. 1 - transcriptase; 2 - integrate; 3 - cellular; 4 - lentiviruses. D. 1 - transcriptase; 2 - relocate; 3 - nuclear 4 - adenoviruses.

A. 1 - transcriptase; 2 - integrate; 3 - nuclear; 4 - lentiviruses.

Which of the following is incorrect? A. At the level of genomic DNA, exons are functional DNA sequences separated by non-functional introns. B. The exons in animal cells are generally shorter and less variable in length than introns. C. An intron of one gene can contain exons of another gene. D. Exons of a protein-coding gene may not contain coding DNA.

A. At the level of genomic DNA, exons are functional DNA sequences separated by non-functional introns. Because: The introns of many genes often contain functional DNA sequences, including both regulatory sequences and sometimes other genes that are usually transcribed from the opposite DNA strand.

Which of the following statements is incorrect? A. Because centromeres and telomeres are critically important for chromosome function their DNA has been very highly conserved during evolution. B. Centromeres are important for correct segregation of chromosomes during cell division. C. The DNA of both centromeres and telomeres consist of repetitive DNA sequences. D. The DNA of our chromosomes may have multiple replication origins but their sequences are not very well conserved

A. Because centromeres and telomeres are critically important for chromosome function their DNA has been very highly conserved during evolution. because:The sequences of telomeres have been very highly conserved during evolution but centromere sequences are rapidly evolving and are poorly conserved between species.

Regarding human meiotic recombination frequencies, which of the following statements is correct? A. Recombination frequencies may differ significantly between individual meioses in the same person, irrespective of sex. B. Recombination frequencies are on average lower in male meiosis than female meiosis but do not differ significantly between individual meiosis. C. Recombination frequencies are on average higher in male meiosis than female meiosis but do not differ significantly between individual meiosis. D. On average, recombination frequencies do not differ substantially between male and female meioses, but can show significant differences between individual meioses.

A. Recombination frequencies may differ significantly between individual meioses in the same person, irrespective of sex.

Which of the following statements is incorrect? A. Segregation of mtDNA molecules into daughter cells needs to be equal. B. The copy number of nuclear DNA molecules is tightly controlled. C. Hundreds or thousands of mtDNA molecules are found in human cells. D. The replication of nuclear DNA and mtDNA molecules is not co-ordinated.

A. Segregation of mtDNA molecules into daughter cells needs to be equal. Because:Unlike the segregation of nuclear DNA which is very tightly controlled, the segregation of mtDNA into daughter cells is not tightly controlled and can be unequal.

What does "the germ line" refer to? A. The lineage of cells from fertilized oocyte to the gametes. B. The gametes. C. All the haploid cells. D. Primordial germ cells and their descendants.

A. The lineage of cells from fertilized oocyte to the gametes

.Which of the following statements is incorrect? A. The most important stages of the cell cycle are M phase and S phase because the cell does most of its work during these stages. B. The Go phase is a form of G1 phase where cells can exit the cell cycle, sometimes temporarily. C. Interphase means all parts of the cell cycle other than mitosis. D. A cell at the G2 phase has twice as many chromosomes as when it is in the G1 phase. previous question next question

A. The most important stages of the cell cycle are M phase and S phase because the cell does most of its work during these stages. Beacause: Although we are very conscious of these M and S phases because of the structural differences they bring about in chromosomes, most of the work done by a cell takes place in the other phases of the cell cycle.

With reference to recombination between human chromosomes, which of the following statements is correct? A. The recombination between the X and the Y chromosomes is largely restricted to a small region on the tips of the short arms. B. The recombination frequency varies between chromosomes but is uniform across a chromosome except in the case of recombination between the X and Y. C. The recombination frequency does vary between individuals across chromosomes, but not between different meioses in a single person. D. Exclusively because of recombination, no two people who originated from different zygotes are genetically identical.

A. The recombination between the X and the Y chromosomes is largely restricted to a small region on the tips of the short arms. Because: The X and Y have very different DNA sequences and recombination is restricted to the pseudoautosomal regions at the ends of the short and long arms. Recombination between the major pseudoautosomal regions at the tips of the short arms of the X and Y is obligatory during male meiosis, but sometimes there is also recombination between the shorter minor pseudoautosomal regions at the tips of the long arms of the X and Y.

The sequence at the beginning of a human protein-coding gene is shown below. The sequence shown in capital letters is exon 1, and the ATG triplet shown in bold is translated to give the initiation codon of an mRNA. Which of the following definitions of a to d is correct? 1 gtcagggcag agccatctat tgcctACATT TGCTTCTGAC ACAACTGTGT TCACTAGCAA a 61 CCTCAAACAG ACACCATGGT GCACCTGACT CCTGAGGAGA AGTCTGCCGT TACTGCCCTG b c 121 TGGGGCAAGG TGAACGTGGA TGAAGTTGGT GGTGAGGCCC TGGGCAGgtt ggt d A. a: 5′ flanking sequence b: 5′ untranslated sequence c: 5th codon d: donor splice site B. a: 3′ untranslated sequence b: acceptor splice site c: 5th codon d: donor splice site C. a: acceptor splice site b: 5′ untranslated sequence c: acceptor splice site d: donor splice site D. a: 5′ flanking sequence b: 5′ untranslated sequence c: donor splice site d: 3′ untranslated sequence

A. a: 5′ flanking sequence b: 5′ untranslated sequence c: 5th codon d: donor splice site

.Certain methylated and acetylated lysine residues in histone proteins are important in conferring transcriptionally active or repressive states on chromatin. Which of the following statements is incorrect? A. Methylation of histones is consistently associated with transcriptionally repressive chromatin states and heterochromatin. B. Acetylation of histones is consistently associated with transcriptionally active chromatin. C. Acetylation of histones is mostly associated with transcriptionally active chromatin but some acetylated histones are markers of transcriptionally repressive chromatin states and heterochromatin. D. Methylation of histones is mostly associated with transcriptionally repressive chromatin states but some methylated histones are markers of transcriptionally active chromatin.

A. is correct - Methylation of histones is consistently associated with transcriptionally repressive chromatin states and heterochromatin. Because: Methylation of H3K4 is associated with transcriptionally active chromatin states but generally methylation of other lysines in histones is associated with transcriptional inactivity

25.Which of the following correctly fills in the blanks in the following passage? ____1_____ is the study of how variation in genes affects how the body metabolizes and responds to drugs. It includes ____2_____, the study of what the body does with, and to, the drug, plus ____3_____, the study of how a person is affected by the drug. Drug metabolism is mostly carried out in the liver, but significant drug metabolism also occurs in the ____4_____ and ____5_____. A. 1 - pharmacokinetics; 2 - pharmacogenetics; 3 - pharmacodynamics; 4 - intestines; 5 - kidneys. B. 1 - pharmacogenetics; 2 - pharmacokinetics; 3 - pharmacodynamics; 4 - intestines; 5 - kidneys. C. 1 - pharmacogenetics; 2 - pharmacodynamics; 3 - pharmacokinetics; 4 - intestines; 5 - kidneys. D. 1 - pharmacogenetics; 2 - pharmacokinetics; 3 - pharmacodynamics; 4 - pancreas; 5 - kidneys. previous question next question

B. 1 - pharmacogenetics; 2 - pharmacokinetics; 3 - pharmacodynamics; 4 - intestines; 5 - kidneys.

Which of the following options correctly matches the chromosomal abnormality with the technique best suited to identifying it? A. Any inversion - chromosome painting. A change in copy number for any chromosome - array comparative genome hybridization. Any small (1 Mb) interstitial deletion - array comparative genome hybridization. Any balanced translocation - chromosome-banding on metaphase chromosomes stained with Giemsa. A gross change in karyotype in a tumor sample - chromosome-banding on metaphase chromosomes stained with Giemsa. B. Any inversion - chromosome-banding on metaphase chromosomes stained with Giemsa. A change in copy number for any chromosome - array comparative genome hybridization. Any small (1 Mb) interstitial deletion - array comparative genome hybridization. Any balanced translocation - chromosome-banding on metaphase chromosomes stained with Giemsa. A gross change in karyotype in a tumor sample - chromosome painting. C. Any inversion - chromosome-banding on metaphase chromosomes stained with Giemsa. A change in copy number for any chromosome - chromosome painting. Any small (1 Mb) interstitial deletion - array comparative genome hybridization. Any balanced translocation - chromosome-banding on metaphase chromosomes stained with Giemsa. A gross change in karyotype in a tumor sample -array comparative genome hybridization. D. Any inversion - chromosome-banding on metaphase chromosomes stained with Giemsa. A change in copy number for any chromosome - array comparative genome hybridization. Any small (1 Mb) interstitial deletion - chromosome-banding on metaphase chromosomes stained with Giemsa. Any balanced translocation - array comparative genome hybridization. A gross change in karyotype in a tumor sample - chromosome painting.

B. Any inversion - chromosome-banding on metaphase chromosomes stained with Giemsa. A change in copy number for any chromosome - array comparative genome hybridization. Any small (1 Mb) interstitial deletion - array comparative genome hybridization. Any balanced translocation - chromosome-banding on metaphase chromosomes stained with Giemsa. A gross change in karyotype in a tumor sample - chromosome painting.

For some of the genes in our cells, only one allele is normally expressed in a diploid cell. The decision as to whether the maternal allele or the paternal allele is silenced can be random, or consistently biased. In which of the following phenomena is monoallelic expression biased? A. Immunoglobulin gene expression. B. Imprinting. C. T cell receptor gene expression. D. X-inactivation.

B. Imprinting

.Which of the options correctly match the technique with the desired objectives? A. Multiplex ligation-dependent probe amplification (MLPA) - identify very large-scale expansion of an oligonucleotide repeat Oligonucleotide ligation assay (OLA) - scan for nucleotide substitutions in a defined DNA region RT-PCR (reverse transcriptase-PCR) - confirm a putative splicing mutation Amplification refractory mutation system (ARMS) - scan for nucleotide substitutions in a defined DNA region DNA sequencing - distinguish between alleles that differ by a single nucleotide substitution Pyrosequencing - distinguish between alleles that differ by a single nucleotide substitution Southern blot-hybridization - screen for deletions and duplications in each of multiple exons at a time B. Multiplex ligation-dependent probe amplification (MLPA) - screen for deletions and duplications in each of multiple exons at a time Oligonucleotide ligation assay (OLA) - distinguish between alleles that differ by a single nucleotide substitution RT-PCR (reverse transcriptase-PCR) - confirm a putative splicing mutation Amplification refractory mutation system (ARMS) - distinguish between alleles that differ by a single nucleotide substitution DNA sequencing - scan for nucleotide substitutions in a defined DNA region Pyrosequencing - distinguish between alleles that differ by a single nucleotide substitution Southern blot-hybridization - identify very large-scale expansion of an oligonucleotide repeat C. Multiplex ligation-dependent probe amplification (MLPA) - screen for deletions and duplications in each of multiple exons at a time Oligonucleotide ligation assay (OLA) - distinguish between alleles that differ by a single nucleotide substitution RT-PCR (reverse transcriptase-PCR) - distinguish between alleles that differ by a single nucleotide substitution Amplification refractory mutation system (ARMS) - confirm a putative splicing mutation DNA sequencing - scan for nucleotide substitutions in a defined DNA region Pyrosequencing - distinguish between alleles that differ by a single nucleotide substitution Southern blot-hybridization - identify very large-scale expansion of an oligonucleotide repeat D. Multiplex ligation-dependent probe amplification (MLPA) - screen for deletions and duplications in each of multiple exons at a time Oligonucleotide ligation assay (OLA) - distinguish between alleles that differ by a single nucleotide substitution RT-PCR (reverse transcriptase-PCR) - identify very large-scale expansion of an oligonucleotide repeat Amplification refractory mutation system (ARMS) - distinguish between alleles that differ by a single nucleotide substitution DNA sequencing - distinguish between alleles that differ by a single nucleotide substitution Pyrosequencing - scan for nucleotide substitutions in a defined DNA region Southern blot-hybridization - confirm a putative splicing mutation

B. Multiplex ligation-dependent probe amplification (MLPA) - screen for deletions and duplications in each of multiple exons at a time Oligonucleotide ligation assay (OLA) - distinguish between alleles that differ by a single nucleotide substitution RT-PCR (reverse transcriptase-PCR) - confirm a putative splicing mutation Amplification refractory mutation system (ARMS) - distinguish between alleles that differ by a single nucleotide substitution DNA sequencing - scan for nucleotide substitutions in a defined DNA region Pyrosequencing - distinguish between alleles that differ by a single nucleotide substitution Southern blot-hybridization - identify very large-scale expansion of an oligonucleotide repeat

.Regarding how common deleterious alleles have been maintained in the population, which of the following is incorrect? A. A common disease allele might have been selectively advantageous some time in the past but in response to environmental changes, such as dietary changes, it has recently become a disease allele. B. The ancestral APOE*ε4 allele is present at high frequencies in many populations because although it is now associated with a harmful phenotype, the phenotype is not adversely affected until late in life, and does not affect reproductive capacity. C. A common susceptibility allele for one complex disease might be an important protective factor for another. D. A common disease allele might be maintained at a high frequency by balancing selection.

B. The ancestral APOE*ε4 allele is present at high frequencies in many populations because although it is now associated with a harmful phenotype, the phenotype is not adversely affected until late in life, and does not affect reproductive capacity. Because: The APOE*ε4 allele is believed to be an ancestral allele (it was present before the split between humans and the great apes; the other alleles, APOE*ε2 and APOE*ε3 arose in the human lineage) but it contributes to cardiovascular disease as well as late-onset Alzheimer disease. It may instead have been advantageous to early humans (who had a low calorie, low fat diet), but is more harmful to modern humans who have comparatively high calorie, high fat diets).

Which of the following correctly fills in the blanks in the following passage? The zygote and some cells from the very early mammalian embryos are completely unspecialized and are said to be ______1_______. By the blastocyst stage, the cells of the inner cell mass have become a little more specialized. They can be cultured to make a line of embryonic stem cells that are flexible enough to give rise to all cells of the body and so are said to be _____2_____ (stem cells have two important characteristics: they can ____3_____ and they can give rise to cells that are more ____4_____ than they are). Later, during development and growth, cells become highly specialized, becoming neurons, lymphocytes, hepatocytes; they are said to be terminally ______4_______. A. 1 - pluripotent 2 - totipotent; 3 - self-replicate; 4 - differentiated. B. 1 - totipotent 2 - pluripotent; 3 - self-differentiate; 4 - replicated. C. 1 - totipotent 2 - pluripotent; 3 - self-replicate; 4 - differentiated. D. 1 - omnipotent 2 - pluripotent; 3 - self-replicate; 4 - stabilized.

C. 1 - totipotent 2 - pluripotent; 3 - self-replicate; 4 - differentiated.

Which of the following correctly fills in the blanks in the following passage? _____1_____ means an altered number of chromosomes and can arise at meiosis and mitosis because of errors in chromosome _____2_____. The most common form is _____3_____, having an additional copy of a single chromosome. It is often lethal in humans and is viable just for a few chromosomes that have a low _____4_____ content, and for the X chromosome (because of _____5_____). The clinical effects of _____1_____ arise because of problems with gene _____6_____. A. 1- aneuploidy; 2 - segregation; 3 - trisomy; 4 - gene; 5 - Y-inactivation; 6 - dosage. B. 1- polyploidy; 2 - replication; 3 - trisomy; 4 - gene; 5 - X-inactivation; 6 - dosage. C. 1- aneuploidy; 2 - segregation; 3 - trisomy; 4 - gene; 5 - X-inactivation; 6 - dosage. D. 1- aneuploidy; 2 - segregation; 3 - triploidy; 4 - gene; 5 - X-inactivation; 6 - mutations

C. 1- aneuploidy; 2 - segregation; 3 - trisomy; 4 - gene; 5 - X-inactivation; 6 - dosage.

.With reference to widespread genome instability in cancer, which of the following statements is false? A. Genome-wide DNA hypomethylation results in chromosome instability. B. Defects in some DNA repair pathways leads to global DNA instability. C. Global DNA instability arising from defective mismatch repair is found in the great majority of cancers. D. Chromosome instability is found in the great majority of cancers.

C. Global DNA instability arising from defective mismatch repair is found in the great majority of cancers. Because:Global DNA instability is a feature of defective mismatch repair but is found in a minority of cancers, notably colorectal cancers.

Which of the following statements is the most accurate? A. Mutations in tumor suppressor genes are inactivating mutations that introduce a premature termination codon by one means or another. B. Oncogene mutations are always missense mutations. C. Missense mutations are generally more common in oncogenes than in tumor suppressor genes. D. Oncogene mutations always occur post-zygotically but inherited tumor suppressor mutations are found in familial cancer cases.

C. Missense mutations are generally more common in oncogenes than in tumor suppressor genes. Because: Missense mutations (which are not obviously inactivating mutations) are common in some tumor suppressor genes, such as TP53. Oncogenes can also be activated by mutations that cause increased gene expression, as a result of translocations, gene amplification, and mutations in regulatory sequences. Some familial cancers show inherited mutations in oncogenes, such as mutations in the MET and RET proto-oncogenes in certain cancers.

Regarding RNA splicing in human cells, which of the following statements is correct? A. RNA splicing is not confined to the nucleus; it can also occur when mitochondrial genes are transcribed. B. Alternative splicing means that genes at different loci can have different numbers of exons and introns. C. RNA splicing is carried out by ribonucleoprotein complexes called spliceosomes. D. The exon-intron splice junctions have preferred consensus sequences that include invariant AG and GT dinucleotides at, respectively, the start and end of introns.

C. RNA splicing is carried out by ribonucleoprotein complexes called spliceosomes. Because: Transcription of both mitochondrial DNA strands produces long multigenic transcripts that are simply cleaved to generate specific rRNAs, tRNAs and mRNAs. Alternative splicing applies to different splicing patterns for individual genes. The invariant dinucleotides are GT at the start of an intron and AG at the end of an intron.

Regarding exomes, which of the following statements is incorrect? A. By definition, an exome is the collective term for all exons in a genome, including those in protein-coding genes and RNA genes. B. An exome can be captured from a genomic DNA sample by a hybridization-based enrichment strategy using a reference exome as bait. C. The protein-coding exome accounts for only 10% of the human genome but 90% of pathogenic mutations. D. In practice, captured exomes predominantly consist of exons from protein-coding genes with short flanking intron sequences.

C. The protein-coding exome accounts for only 10% of the human genome but 90% of pathogenic mutations.

Regarding autosomal recessive inheritance, which of the following is correct? A. A compound heterozygote has two different mutant alleles and will normally be affected. B. Affected individuals have two mutant alleles, but a heterozygote with one mutant allele not infrequently shows mild clinical symptoms. C. Affected individuals often have affected parents. D. Each child born to unaffected carrier parents has a 50% risk of being affected.

Correct A. A compound heterozygote has two different mutant alleles and will normally be affected

16.Regarding cis-acting and trans-acting regulation of gene expression, which of the options are correct for the following statements? Several alternative promoters regulate expression of the dystrophin gene. The promoters are said to be (____1____) regulators. The PAX6 transcription factor binds to multiple regulatory elements in genomic DNA to regulate many genes important in early development. It is a (___2____) regulator. Regulatory sequences within the untranslated regions of ferritin mRNA are important in controlling ferritin protein production; they are (____3____) regulators. The neighboring H19 and IGF2 genes on chromosome 11 are regulated by a common imprinting control region located in the intervening space. The imprinting control region is a (___4___) regulator. Many miRNAs bind to recognition sequences in untranslated regions of mRNAs from target genes, thereby regulating their expression. The miRNAs are (____5___) regulators. A. 1: trans-acting 2: trans-acting 3: cis-acting 4: trans-acting 5: trans-acting B. 1: cis-acting 2: trans-acting 3: cis-acting 4: trans-acting 5: cis-acting C. 1: cis-acting 2: trans-acting 3: cis-acting 4: cis-acting 5: trans-acting D. 1: trans-acting 2: trans-acting 3: cis-acting 4: cis-acting 5: cis-acting

Correct C. 1: cis-acting 2: trans-acting 3: cis-acting 4: cis-acting 5: trans-acting

With reference to autosomal dominant inheritance, which of the following statements is correct? A. An affected person must have had an affected parent. B. An affected homozygote always shows the same phenotype as an affected heterozygote. C. If one parent is affected, each child has a 50% chance of having inherited the mutant gene D. An affected homozygote always shows a more severe phenotype than that of an affected heterozygote.

Correct C. If one parent is affected, each child has a 50% chance of having inherited the mutant gene

.Which of the following correctly matches the classes of noncoding RNAs with their function in providing general assistance, either directly or indirectly, in the expression of protein-coding genes? A. Small nuclear RNAs (snRNAs) - assist in codon interpretation and amino acid insertion. Small nucleolar RNAs (snoRNAs) - important in maturation of ribosomal RNAs. Small Cajal body RNAs (scaRNAs) - important in maturation of snRNAs. Transfer RNAs (tRNAs) - assist in RNA splicing. B. Small nuclear RNAs (snRNAs) - assist in RNA splicing. Small nucleolar RNAs (snoRNAs) - important in maturation of ribosomal RNAs. Small Cajal body RNAs (scaRNAs) - important in maturation of snRNAs. Transfer RNAs (tRNAs) - assist in codon interpretation and amino acid insertion. C. Small nuclear RNAs (snRNAs) - important in maturation of ribosomal RNAs. Small nucleolar RNAs (snoRNAs) - assist in RNA splicing. Small Cajal body RNAs (scaRNAs) - important in maturation of snRNAs. Transfer RNAs (tRNAs) - assist in codon interpretation and amino acid insertion. D. Small nuclear RNAs (snRNAs) - assist in RNA splicing. Small nucleolar RNAs (snoRNAs) - assist in codon interpretation and amino acid insertion. Small Cajal body RNAs (scaRNAs) - important in maturation of ribosomal RNAs. Transfer RNAs (tRNAs) - important in maturation of snRNAs.

Correct matches B. Small nuclear RNAs (snRNAs) - assist in RNA splicing. Small nucleolar RNAs (snoRNAs) - important in maturation of ribosomal RNAs. Small Cajal body RNAs (scaRNAs) - important in maturation of snRNAs. Transfer RNAs (tRNAs) - assist in codon interpretation and amino acid insertion.

Which of the following statements is incorrect? A. Nucleic acids are always negatively charged. B. Cellular DNAs are structured as a double helix. C. The only structural difference between DNA and RNA strands is that they have different sugars, respectively deoxyribose and ribose. D. Cellular RNAs are single-stranded.

Correct! C. The only structural difference between DNA and RNA strands is that they have different sugars, respectively deoxyribose and ribose. DNA and RNA also have different bases, thymine in DNA and uracil in RNA

In the following structures, lines indicate covalent bonds and letters indicate chemical groups as follows: P - phosphate; B - base; S - sugar; OH (or HO) - hydroxyl. Which of the structures is the correct representation of a double-stranded nucleic acid?

Correct! D. 5′ P-B-P-B-P-B-P-B-OH 3′ | | | | S S S S S S S S | | | | 3′ P-B-P-B-P-B-P-B-OH 5′

Which of the following statements is incorrect? A. Purines are nitrogenous bases with a double ring structure. B. Base pairs may form between bases on a single nucleic acid strand. C. Two types of stable base pairing occur in DNA but a third type of base pairing is common in RNA-RNA and RNA-DNA base pairing. D. A-T base pairs are stronger than G-C base pairs.

Correct! D. G-C base pairs are maintained by three hydrogen bonds and are stronger than A-T base pairs which are maintained by two hydrogen bonds.

.Which of the following statements is true? A. A non-synonymous substitution has precisely the same meaning as a missense mutation. B. A nucleotide substitution at the first base position of a codon always causes an amino acid change. C. A nucleotide substitution at the third base position of a codon never causes an amino acid change. D. A nucleotide substitution at the second base position of a codon always causes an amino acid change.

D. A nucleotide substitution at the second base position of a codon always causes an amino acid change. Because: A missense mutation means that a codon which specifies an amino acid is changed so that it now specifies an alternative amino acid. It is one of three classes of non-synonymous substitution (Table 7.1). A small minority (theoretically 4%) of substitutions at the first base position of codons are silent and roughly 1 in three substitutions at the third base position of a codon change the amino acid.

With reference to epigenetic dysregulation in cancer, which of the following statements is true? A. Inactivating mutations in genes encoding epigenetic regulators are the source of all types of epigenetic dysregulation. B. Epigenetic dysregulation is important in silencing oncogenes. C. Epigenetic dysregulation is important in cancer progression but not in cancer initiation. D. Epigenetic dysregulation does not just change chromatin states; it can also cause widespread chromosome instability.

D. Epigenetic dysregulation does not just change chromatin states; it can also cause widespread chromosome instability. Because: Epigenetic dysregulation can also be induced by non-genetic factors such as inflammation (which results in altered cell signalling that can then result in altered chromatin states) Oncogenes are not activated by silencing (but epigenetic dysregulation is important in silencing tumor suppressor genes). DNA hypomethylation causes chromosome instability.

.Concerning gene delivery in gene therapy, which of the following statements is incorrect, and why? A. Physiochemical methods usually have poor gene transfer efficiencies but are comparatively safe. B. Gene transfer using modified virus vectors generally have high gene transfer efficiencies but pose greater safety risks. C. Genes can be selectively transferred to specific cell types using virus vectors that originate from virus strains that are tropic for the cells of interest. D. Gene transfer needs to be targeted to dividing cells to help the gene integrate into a chromosome and be vertically transmitted to descendants of the transfected cell. previous question next question

D. Gene transfer needs to be targeted to dividing cells to help the gene integrate into a chromosome and be vertically transmitted to descendants of the transfected cell. For cells with comparatively short lifetimes, such as blood cells, the best hope is to get the therapeutic gene integrated into the chromosomal DNA of stem cells that can continuously divide and form new blood cells. For long-lived cells, gene therapies can be conducted without the need for the therapeutic gene to integrate into chromosomal DNA.