WGU Biochemistry Final Review

Diabetic ketoacidosis can lower blood pH, which affects the structure of important proteins like hemoglobin. Which of the following interactions are most likely affected by the change in pH? Choose the letter(s) corresponding to the interaction. (a) (b) (c) (d)

(a) (b) Feedback Correct! The interactions labeled (a) are ionic bonds while (b) are hydrogen bonds. Changes in the pH can disrupt both ionic bonds and hydrogen bonds.

Hemophilia is an X-linked recessive condition. This means that: 1. A person with at least one normal X chromosome without the hemophilia gene will not show signs of hemophilia 2. The disease is more common in females 3. Affected men can pass the condition on to sons but not to daughters 4. Women can only pass the condition on to daughters

1. A person with at least one normal X chromosome without the hemophilia gene will not show signs of hemophilia Feedback An X-linked recessive condition is inherited when a female has a recessive allele on each of her X chromosomes. Males inherit an X-linked recessive condition if they inherit a recessive allele on their one and only X chromosome. Therefore if a female has a dominant (or normal) allele on one of her X chromosomes, she will not have the disease. Because men only have one X-chromosome, they tend to inherit X-linked conditions more easily than females. Men with X-linked recessive conditions do not pass the disease on to their sons, because they pass a Y chromosome on to their sons. Men will pass an X chromosome to their daughters. Women are able to pass an X chromosome on to their son or their daughters.

The amino acid at position 150 (not shown) helps to stabilize the protein by forming disulfide bonds. What amino acid is likely located at position 150? Could this amino acid form a disulfide bond with any of the amino acids in the provided sequence above? 1. Cysteine is at 150. No, Cysteine only forms a disulfide bond with itself. There are no Cysteines in the sequence above. 2. Methionine is at 150. Yes, position 10 could form a disulfide bond. 3. Either Cysteine or Methionine is at 150. Yes, position 10 could form a disulfide bond.

1. Cysteine is at 150. No, Cysteine only forms a disulfide bond with itself. There are no Cysteines in the sequence above. Feedback Correct! Disulfide bonds form only between two cysteine amino acids. The provided image is of cysteine, which would be found at position 150. There are no cysteines within the provided protein, so no disulfide bond would form between it and the cysteine at position 150.

When the wrong nucleotide is added to a newly forming DNA strand during DNA replication 1. Distortion of the double helix structure occurs because of uncomplimentary pairing of the nucleotides 2. The DNA can not be repaired 3. The cell dies 4. Thymine dimers occur

1. Distortion of the double helix structure occurs because of uncomplimentary pairing of the nucleotides Feedback Correct! A mismatch (A with C or G, T with C or G) causes a bump to form in the DNA double helix, which is recognized by proofreading enzymes and fixed by excision repair.

Select all of the following that are involved in the process of actively transcribing a gene. 1. Epigenetic modifications to nucleosomes 2. Ribosomes 3. DNA Ligase 4. Transcription Factors 5. Promoters 6. RNA polymerase 7. DNA polymerase

1. Epigenetic modifications to nucleosomes 4. Transcription Factors 5. Promoters 6. RNA polymerase Feedback Correct! Epigenetic changes result in modifications of the nucleosomes that affect chromatin packing and transcription. Transcription Factors are specialized proteins that recognize specific promoter sequences and bind to them. Once bound to the promoters, the transcription factors recruit RNA polymerase to the transcription start site. RNA polymerase begins transcribing the gene sequence into a new RNA molecule.

The two amino acids below are part of the myosin protein. What interaction can these amino acids form, and where are they likely to be located in the protein? 1. Hydrophobic interaction, the core of the protein 2. Hydrophobic interaction, the surface of the protein 3. Hydrogen bond, the core of the protein 4. Hydrogen bond, the surface of the protein

1. Hydrophobic interaction, the core of the protein Feedback Correct! The two amino acids presented have side-chains comprised of only nonpolar C-C and C-H bonds. These amino acids belong to the nonpolar group and can form hydrophobic interactions. Because these amino acids cannot form hydrogen bonds they are hydrophobic in nature. This hydrophobic nature leads these amino acids to be in the interior/core of the protein, hidden away from the water surrounding the protein. If you chose "Hydrophobic interaction, the surface of the protein:" The surface of the protein is surrounded by water molecules, which do not interact favorably with nonpolar amino acid sidechains. These two amino acids will tend to be in the core of the protein instead. If you chose "Hydrogen bond, the core of the protein:" While the two amino acids shown will tend to be in the core of the protein they have nonpolarized C-C and C-H bonds that cannot participate in hydrogen bonding. If you chose "Hydrogen bond, the surface of the protein:" The two amino acids shown have nonpolarized C-C and C-H bonds that cannot participate in hydrogen bonding. These amino acids will not interact favorably with water and will tend to avoid the surface of the protein (which is surrounded by water) and instead be in the protein's core.

Which of the following statements about the secondary structure of proteins is true? You may select more than one answer. 1. It involves hydrogen bonding between the backbone atoms 2. It includes alpha helices as a common form. 3. It includes beta pleated sheets as a common form. 4. It involves hydrogen bonding between amino acid side-chains.

1. It involves hydrogen bonding between the backbone atoms 2. It includes alpha helices as a common form. 3. It includes beta pleated sheets as a common form. Feedback Correct! Secondary structures arise from hydrogen bonding patterns between backbone atoms. The most common secondary structures are alpha-helices and beta sheets. Hydrogen bonding between side-chains contributes to protein tertiary structure, but not secondary structure.

Which of the following are true about a misfolded protein? You may select more than one answer. 1. It will lose its normal function. 2. It can be degraded by the cell. 3. It can be the result of denaturation. 4. It can cause protein aggregation. 5. It loses its primary structure.

1. It will lose its normal function. 2. It can be degraded by the cell. 3. It can be the result of denaturation. 4. It can cause protein aggregation. Feedback Correct! The following options are correct: "It will lose its normal function:" The function of a protein is heavily dependent on its three-dimensional shape. As a protein misfolds changes in three-dimensional shape lead the protein to lose its ability to perform its normal function. "It can be degraded by the cell:" In addition to chaperone proteins being able to help misfolded protein refold, the cell also has mechanisms for identifying and breaking down misfolded proteins into amino acids to prevent these misfolded proteins from forming aggregates. "It can be the result of denaturation:" Denaturation disrupts side chain interactions, which destabilizes tertiary structure and can cause the protein to change shape, i.e. misfold. "It can cause protein aggregation:" Misfolded proteins can have sections of hydrophobic amino acid residues exposed to water. This can lead to misfolded proteins to aggregate in order to keep these hydrophobic residues away from water.

What changes can occur to the DNA (ex. methyl groups) and to the histones that will impact gene expression? Select all that apply 1. methylation 2. chromosome replication 3. acetylation 4. splicing

1. methylation 3. acetylation Feedback Correct! Methyl groups can be added to DNA (methylation) without altering the DNA sequence. DNA methylation changes the spacing of nucleosomes. Acetyl groups can be added to histones (acetylation) and this also changes the spacing of nucleosomes. Nucleosome spacing affects the transcription of genes.

Which of the following best describes the nature of protein primary structure? 1. Structural elements such as alpha helices and beta pleated sheets 2. Amino acids linked together in a specific order by peptide bonds 3. Two or more polypeptide chains coming together to form the final functional protein 4. The overall three-dimensional shape of a chain of amino acids

2. Amino acids linked together in a specific order by peptide bonds Feedback Correct! The sequence of amino acids connected by peptide bonds in a specific order defines protein primary structure. "Structural elements such as alpha helices and beta pleated sheets" refers to secondary structure. "The overall three-dimensional shape of a chain of amino acids" refers to tertiary structure. "Two or more polypeptide chains coming together to form the final functional protein" refers to quaternary structure.

The LEP gene codes for an anorexigenic hormone. Interestingly, breastfeeding has been shown to alter methylation of the promoter of this gene, leading to increased LEP expression. What is likely happening in response to breastfeeding: 1. Breastfeeding increases the methylation of the promoter of the LEP gene, decreasing the spacing between nucleosomes. 2. Breastfeeding decreases the methylation of the promoter of the LEP gene, increasing the spacing between nucleosomes. 3. Breastfeeding decreases the methylation of the promoter of the LEP gene, decreasing the spacing between nucleosomes. 4. Breastfeeding increases the methylation of the promoter of the LEP gene, and the tight packing of the DNA alters binding of RNA polymerase.

2. Breastfeeding decreases the methylation of the promoter of the LEP gene, increasing the spacing between nucleosomes. Feedback Correct. When histones wrap up DNA, transcription will be repressed and when histones open DNA will be available for transcription.

Glutamine at position 16 forms an important interaction with Serine in a different location in the protein. How would the protein structure be affected if the Glutamine in position 16 were mutated to Leucine? Would this increase or decrease the stability of the protein? 1. Increase. Leucine and Serine form a stronger ionic bond together 2. Decrease. Serine and Leucine do not interact 3. Decrease. Glutamine and Serine formed a hydrogen bond that stabilized the protein structure before the mutation 4. Decrease. Glutamine and Serine formed an ionic bond that stabilized the protein structure before the mutation 5. Approximately the same. The Glutamine-Serine interaction is similar to the Leucine-Serine interaction

2. Decrease. Serine and Leucine do not interact 3. Decrease. Glutamine and Serine formed a hydrogen bond that stabilized the protein structure before the mutation Feedback Correct! Glutamine and Serine are both polar and form a hydrogen bond with each other. Leucine is hydrophobic and would not want to be near polar R group of Glutamine, therefore causing a change in the shape of the tertiary structure. This change in shape would decrease stability.

As a piece of bacon is heated in a skillet on the stove, you observe that the appearance of the bacon changes. You may even notice that the bacon becomes crispy if left in the skillet. What type of bonds or interactions in proteins are susceptible to temperature changes? Why? 1. Hydrophobic interactions. Hydrophobic interactions are oily, when the bacon grease cooks away from the bacon it takes away the hydrophobic interactions. 2. Hydrophobic interactions. As the temperature increases, as it does in the skillet, the atoms in the proteins in bacon begin to move more rapidly. This causes the hydrophobic areas of the protein to become exposed. 3. Ionic bonds. As the bacon cooks, charged amino acids become neutral causing proteins to aggregate. This aggregation causes the characteristic look of crispy bacon. 4. Disulfide bonds. Disulfide bonds are associated with the smell of cooking bacon.

2. Hydrophobic interactions. As the temperature increases, as it does in the skillet, the atoms in the proteins in bacon begin to move more rapidly. This causes the hydrophobic areas of the protein to become exposed. Feedback Correct! As the temperature increases, the atoms in the proteins begin to move more rapidly. This causes the hydrophobic areas of the protein to become exposed. The bacon has protein that undergoes this phenomenon when it is cooked.

What is the proper order of the steps involved in excision repair? 1. Recognize the damage, resynthesize the sequence, remove the damage, ligate the DNA backbone. 2. Recognize the damage, remove the damage, resynthesize the sequence, ligate the DNA backbone. 3. Recognize the damage, remove the damage, ligate the DNA backbone, resynthesize the sequence. 4. Recognize the damage, ligate the DNA backbone, remove the damage, resynthesize the sequence.

2. Recognize the damage, remove the damage, resynthesize the sequence, ligate the DNA backbone. Feedback Correct! The basic steps of excision repair are given as bullet points at the very beginning of Lesson 1: DNA and RNA; Chapter - Inheritance of Genes; Subchapter - DNA Damage and Repair; Section - Excision Repair Corrects The Most Frequent DNA Lesions.

Homologous recombination: 1. Fixes single damaged nucleotides 2. Repairs a broken chromsome using genetic information from same chromosome inherited from other parent. 3. Fixes mistakes made by DNA polymerase during DNA replication 4. Fixes multiple damaged nucleotides

2. Repairs a broken chromsome using genetic information from same chromosome inherited from other parent. Feedback Correct! Homologous refers to the pair of same chromosomes (same genes in same order, except different alleles) you inherit from each parent - for example, the two chromosome 12s in your cells, one from your mother and one from your father. Homologous recombination fixes broken chromosomes using DNA in the same position on the homologous chromosome as a template to fix the broken chromosome. Homologous recombination also shuffles DNA between the pair of chromosomes adding genetic variation.

Aggregation of proteins is the main reason behind many neurodegenerative diseases. Which one of the following mutations will likely cause a neurodegenerative disease? 1. Replacing a positively charged amino acid with a negatively charged amino acid 2. Replacing a polar amino acid with a non polar amino acid 3. Replacing a polar amino acid with another polar amino acid 4. Replacing a negatively charged amino acid with a negatively charged amino acid

2. Replacing a polar amino acid with a non polar amino acid Feedback Correct! Polar amino acids like to be around water and are usually found on the exterior of a protein. Non-polar amino acids are hydrophobic and prefer to be on the interior of a protein. Aggregation within neurodegenerative diseases is caused when non-polar amino acids become exposed on the exterior of a protein due to mutation or misfolding. In their effort to hide from water, these non-polar amino acids interact with other misfolded proteins. The misfolded proteins begin to aggregate and form long, hydrophobic fibers. These fibers cause cell death, which cause neurodegenerative diseases when this death occurs in the brain.

Frameshift mutations 1. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations. 2. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations. 3. change a single nucleotide in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations 4. change a single nucleotide in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations.

2. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations. Feedback Correct! Mutations caused by insertion/deletions introduce a change in the 'reading frame', known as a frameshift mutation. Background: Errors that change the number of nucleotides in a gene (insertion/deletion) are said to 'shift' the 'reading frame' from the correct groups of three basses to new groups. For example, how the following can be read as CAT DOG RAT PIG APE- unless you deleted the 'C' from CAT. It then becomes, ATD OGR ATP IGA PE- which doesn't have any meaning.

Match the letters with the correct names of the processes of the central dogma (Replication; Transcription; Translation). 1. A) Transcription, B) Translation, C) Replication 2. A) Translation, B) Replication, C) Transcription 3. A) Replication, B) Transcription, C) Translation 4. A) Translation B)Transcription, Replication

3. A) Replication, B) Transcription, C) Translation Feedback Correct! The central dogma starts with DNA, which is able to be replicated to prepare for cell division. DNA in the nucleus can also be accessed and transcribed to mRNA. The mRNA will leave the nucleus and enter the cytoplasm where it will be translated into a protein by the ribosome.

The Punnett Squares below represent three different types of dominance. Which answer choice correctly identifies the different types of Dominance? 1. A. Complete Dominance; B. Incomplete Dominance; C. Codominance 2. A. Codominance; B. Complete Dominance; C. Incomplete Dominance 3. A. Incomplete Dominance; B. Complete Dominance; C. Codominance 4. A. Codominance; B. Incomplete Dominance; C. Complete Dominance

3. A. Incomplete Dominance; B. Complete Dominance; C. Codominance Feedback A. Incomplete Dominance (heterozygotes are a color in-between the dominant and recessive color). B. Complete Dominance (All flowers are completely the dominant color or the recessive color). C. Codominance (heterozygotes are both the dominant and the recessive color).

Primary structure consists of the order of ______ in a protein. These are held together with ______ bonds that are formed by a ______ reaction. 1. Nucleotides, phosphodiester, dehydration 2. Amino acids, peptide, hydrolysis 3. Amino acids, peptide, dehydration 4. Nucleotides, peptide, dehydration

3. Amino acids, peptide, dehydration Feedback Correct! Protein primary structure is defined by the order of amino acids that make up the protein. The amino acids are linked together by peptide bonds, which are formed via dehydration reactions. Dehydration reactions involve two molecules reacting to produce H2O and another product molecule. These reactions are called dehydration reactions because it is as if the two reactant molecules were dehydrated (H2O was removed from them).

Nucleotide excision repair: 1. Fixes single damaged nucleotides 2. Fixes mistakes made by DNA polymerase during DNA replication 3. Fixes multiple damaged nucleotides 4. Repairs a broken chromosome using genetic information from same chromosome inherited from other parent.

3. Fixes multiple damaged nucleotides Feedback Correct! Nucleotide excision repair replaces several damaged nucleotides.

Which of the following statements about protein structure and stability is true? 1. Denaturation is the loss of primary, secondary, and tertiary structure 2. Denatured proteins retain their tertiary structure 3. Ionic bonds between the side chains of the charged amino acids stabilize the protein structure 4. Protein structure is not stabilized by the hydrophobic effect

3. Ionic bonds between the side chains of the charged amino acids stabilize the protein structure Feedback Correct! Ionic bonds help stabilize both the tertiary structure of a protein chain and the quaternary structure of a protein with multiple subunits.

If all of the Arginine amino acids (position 2, 5, 6, 9 and 15) in the sequence above are mutated to Lysine, would there be a significant effect on the protein's stability? 1. Yes, Lysine and Arginine would repel one another because they are both positively charged 2. Yes, mutations always destabilize the protein 3. No, not significant, Lysine and Arginine would have all the same interactions

3. No, not significant, Lysine and Arginine would have all the same interactions Feedback If you chose the option "Yes, Lysine and Arginine would repel one another because they are both positively charged," this answer is incorrect because Arginine replaces Lysine. Since it is a replacement, the two amino acids would never interact. If you chose the option, "Yes, mutations always destabilize the protein," the answer is incorrect because mutations can sometimes have a minimal effect. The side chains of Lysine and Arginine are both long with a positive charge at the end. If Lysine is forming an ionic bond with another amino acid elsewhere in the protein, Arginine would be able to make that same ionic bond. The protein would therefore be stable, even with this mutation.

The LCT gene codes for Lactase, which is responsible for the breakdown of lactose. Which of the following statements could explain how Lactase activity is increased in the presence of lactose? 1. Lactose blocks RNA polymerase from binding the promoter sequence, facilitating transcription of the LCT gene. 2. Lactose prevents binding of transcription factors at the transcription start site of the LCT gene. 3. The presence of lactose causes nucleosomes to separate, exposing the LCT gene. 4. The presence of lactose causes nucleosomes to pack together tightly, exposing the LCT gene.

3. The presence of lactose causes nucleosomes to separate, exposing the LCT gene. Feedback Correct! In this case, the presence of lactose in the diet is an environmental stimulus. In response to this stimulus, DNA may be modified by the addition or removal of methyl groups and histones may be modified by the addition or removal of acetyl groups. These changes can alter the spacing of nucleosomes and therefore, affect gene expression.

A nonsense mutation 1. inserts or deletes nucleotides in a mutant gene compared to a normal gene. 2. causes a double-stranded break in a chromosome. 3. changes a codon to introduce a premature stop codon. 4. has no effect on an amino acid sequence.

3. changes a codon to introduce a premature stop codon. Feedback Correct! A mutation that introduces a premature stop codon is a nonsense mutation. Background: A nonsense mutation occurs when a point mutation (change in single nucleotide) changes a codon to a STOP codon- which causes the protein synthesis to prematurely terminate. For example, UGC (codes for Cys) changed to UGA (STOP) would cause the protein synthesis to stop early resulting in a truncated protein (non functional).

A missense mutation 1. inserts or deletes nucleotides in a mutant gene compared to a normal gene. 2. causes a double-stranded break in a chromosome. 3. changes a single amino acid in a protein. 4. has no effect on an amino acid sequence.

3. changes a single amino acid in a protein. Feedback Correct! A codon change that changes the amino acid that is being coded is a missense. Background: A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA such that it codes for a different amino acid that it did before is called a missense mutation. The missense mutation changes one amino acid in the amino acid sequence of a protein. For example, changing the codon UUU (codes for Phe) to UUA (codes for Leu) is a missense mutation.

Histone proteins can be chemically modified by addition of an methyl group. If this causes nucleosomes to pack _________ , the process of ___________ is decreased at those DNA sites. 1. more loosely; transcription 2. more loosely; translation 3. more tightly; transcription 4. more tightly, translation

3. more tightly; transcription Feedback Correct! Changes to histone proteins or to DNA that result in tighter nucleosome packing make the DNA less available for transcription. Therefore, transcription is decreased.

Assuming there is one copy of the target DNA sequence before PCR, how many copies of DNA are there after 5 PCR cycles? 256 6 65,536 16 32

32 Feedback Each cycles double the numbers of DNA copy. Round 1: 1->2. Round 2: 2 ->4. Round 3: 4 -> 8. Round 4: 8 ->16. Round 5: 16 ->32.

Label the lettered strands of nucleic acid below. The possible words to use in labeling strands are: Coding Strand, Non-template Strand, Non-coding Strand, Template Strand, and mRNA. Note: A and B refer to one strand of DNA; C and D refer to the other strand of DNA. 1. A) Template B) Coding C) Non-template D) Non-Coding E) mRNA 2. A) Template B) Non-coding C) Non-template D) Coding E) mRNA 3. A) Non-template B) Non-Coding C) Template D) Coding E) mRNA 4. A) Non-template B) Coding C) Template D) Non-coding E) mRNA

4. A) Non-template B) Coding C) Template D) Non-coding E) mRNA Feedback Correct! The coding and the non-template strands are the same strand (blanks A and B). The non-coding and the template strands are the same strand (blanks C and D).

Mismatch repair: 1. Repairs a broken chromsome using genetic information from same chromosome inherited from other parent. 2. Fixes single damaged nucleotides 3. Fixes multiple damaged nucleotides 4. Fixes mistakes made by DNA polymerase during DNA replication

4. Fixes mistakes made by DNA polymerase during DNA replication Feedback Correct! Mismatch repair fixes errors in DNA replication made by DNA polymerase.

Which of the following statements about epigenetics is false? 1. Environmental stimuli control gene expression. 2. Gene expression is influenced by chemical modifications of the DNA and/or histone proteins. 3. Access to the promoter gene by transcription factors is affected. 4. The DNA sequence is permanently altered.

4. The DNA sequence is permanently altered. Feedback Correct! Epigenetics involves reversible changes to the DNA or to histone proteins. These changes, such as adding or removing methyl groups from DNA or acetyl groups from histone proteins, respond to environmental stimuli. Such changes can increase or decrease nucleosome spacing, which can make the promoter of a gene accessible or inaccessible. In this way, epigenetic changes influence gene expression.

Which of the following statements about the different levels of protein structure is true? 1. Two or more polypeptides each with their own secondary structures come together to form a single larger tertiary structure of a protein 2. Peptide bonds between amino acids make up the secondary structure of a protein 3. The interactions between the side chains of the amino acids make up the secondary level structure of a protein 4. The interactions between the side chains of the amino acids make up the tertiary level structure of a protein

4. The interactions between the side chains of the amino acids make up the tertiary level structure of a protein Feedback Correct! The interactions between the side chains of the amino acids make up the tertiary level structure of a protein.

When comparing a normal and mutant gene sequence, how do you identify a frameshift mutation? 1. The number of nucleotides between the normal and mutant gene sequences is identical and the amino acid sequence is different. 2. The number of nucleotides between the normal and mutant gene sequences is identical and the amino acid sequence is identical. 3. The number of nucleotides between the normal and mutant gene sequences is different and the amino acid sequence is identical. 4. The number of nucleotides between the normal and mutant gene sequences is different and the amino acid sequence is different.

4. The number of nucleotides between the normal and mutant gene sequences is different and the amino acid sequence is different. Feedback Correct! Frameshift mutations are caused by changing the number of nucleotides in a sequence Background. Errors that increase or decrease the number of nucleotides in a gene cause frameshift mutations. The insertion of an extra base or the removal of one of the bases will change which groups of three bases that the ribosome reads when it translates the message. This is said to 'shift' the 'reading frame' from the correct groups of three bases to different groups of three. To visualize what a frameshift is, imagine you are given a string of letters and told to start at the beginning and read every group of three letters: CATDOGRATPIGAPE. You would get "cat dog rat pig ape". But if we add an extra letter, say CATDFOGRATPIGAPE, following our "read every group of three" rule, we would get "cat dfo gra tpi gap e". Shifting our 'reading frame' by adding one more letter completely changes what we read. This is similar to what happens with a frameshift mutation.

Point mutations 1. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations. 2. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations. 3. change a single nucleotide in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations 4. change a single nucleotide in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations.

4. change a single nucleotide in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations. Feedback Correct! A single nucleotide change in the DNA is a point mutation. Background: A single nucleotide change in the DNA is a point mutation. For example, changing an A for a C would be a point mutation. Point mutations do not increase or decrease the number of nucleotides in a gene, and they might (missense and nonsense mutations) or might not (silent mutations) change the amino acid sequence of the protein.

A mutation in the protein A gene results in a negatively charged amino acid, Glutamate, being replaced with the nonpolar amino acid Leucine. This is an example of a _______ mutation that could potentially interrupt __________. 1. nonsense, a hydrogen bond 2. missense, a disulfide bond 3. nonsense, a hydrophobic interaction 4. missense, an ionic bond

4. missense, an ionic bond Feedback Correct! Point mutations resulting in a change in the amino acid sequence are called missense mutations. Since Glutamate is negatively charged, it likely participates in an ionic bond. Mutation to Leucine, a non-polar amino acid, would disrupt this ionic bond.

What happens to oxygenated hemoglobin as the amount of CO2 increases? 1. pH increases, Hb shifts more to the R state, oxygen affinity increases 2. pH increases, Hb shifts more to the T state, oxygen affinity decreases 3. pH decreases, Hb shifts more to the R state, oxygen affinity increases 4. pH decreases, Hb shifts more to the T state, oxygen affinity decreases

4. pH decreases, Hb shifts more to the T state, oxygen affinity decreases Feedback Correct! As the amount of CO2 increases, the CO2 combines with water to form H+ and bicarbonate. The increased H+ decreases the pH, which causes hemoglobin to shift more to the T state. Hemoglobin in the T state has a low affinity for oxygen

During DNA replication, which of the following sequences can be used as a primer for the following DNA sequence: 3' AGT GGA TCA CTA GGC TCT 5'? (Recall that DNA replication uses RNA primers whereas PCR uses DNA primers). 5' UCA CCU AGU GAU 3' 5' TCA CCT AGT GAT 3' 3' UCA CCU AGU GAU 5' 3' TCA CCT AGT GAT 5'

5' UCA CCU AGU GAU 3' Feedback Correct! During DNA replication, RNA is used as a primer for the DNA polymerase. Recall that primers are complementary and antiparallel to the strand of DNA that is being copied. The complementary RNA sequence for 3' AGT GGA TCA CTA GGC TCT 5'? is 5' UCA CCU AGU GAU CCG AGA 3'. Thus 5' UCA CCU AGU GAU 3', which is contained within the sequence above (beginning at the 5' end), could serve as a complementary primer for DNA synthesis.

Which of the following is the correct tRNA anticodon for the mRNA codon 5' GCA 3' ? 5' UGC 3' 5' CGU 3' 5' TGC 3' 5' CGT 3'

5' UGC 3' Feedback Correct. mRNA binding to tRNA is also complementary and antiparallel.

DNA polymerase can synthesize new DNA strands in which direction? 3' to 5' 5' to 3' any direction N-terminus to C-terminus

5' to 3' Feedback DNA needs a free 3' end to bind to and initiate synthesis of a DNA. It synthesizes in a 5' to 3' direction.

What is the expected probability that a child will have an autosomal dominant disease if their father is heterozygous for the allele and their mother is homozygous for the normal allele? 0% 25% 50% 100%

50% Feedback Aa X aa => 50% Aa diseased, 50% aa normal

Epigenetics. Given the following modification of the nucleosomes, discuss how the transcription and gene expression is impacted. In A the the nucleosomes are less condensed, and in B they are more tightly wound. Would A or B foster the ability to have more active transcription of genes? A (less condensed) B (tightly wound)

A (less condensed) Feedback Correct. When the histones of the nucleosomes have DNA wound tightly around them, less DNA is available to be bound and activated by transcription factors.

When Estrogen binds to the binding pocket of the Estrogen Receptor, it is stabilized by hydrogen bonds. Which amino acids listed below could stabilize the interaction with Estrogen in the binding pocket of the Estrogen Receptor? Check all that apply. Amino Acid 1 Amino Acid 3 Amino Acid 10 Amino Acid 16

Amino Acid 16 Feedback Correct! Amino acid 16 is polar, as evidenced by the -NH as part of the side chain. Polar amino acids participate in hydrogen bonds. In this case, polar amino acids within the estrogen receptor would participate in hydrogen bonds with estrogen.

Mutations in the FANCA gene (located on chromosome 16) can lead to Fanconi Anemia. A healthy individual inherited one mutant and one normal allele of the FANCA gene. Which of the following describes the inheritance pattern of Fanconi Anemia? Autosomal Dominant Autosomal Recessive X-linked Dominant X-linked Recessive

Autosomal Recessive Feedback Chromosome 16 is an autosome because it is a numbered chromosome. For a healthy individual to have a mutant allele, the mutant allele must be recessive.

Which of the following amino acids would you expect to find in the interior of a protein rather than on its exterior? A B C D

B Feedback Correct! Answer choice B represents a nonpolar amino acid, with a side-chain comprised of only nonpolar C-C and C-H bonds that is hydrophobic. This hydrophobic nature leads this amino acid to be in the interior of the protein, hidden away from the water surrounding the protein. If you chose A: The side-chain of this amino acid contains an O-H bond which allows it to form hydrogen bonds. This amino acid side-chain can interact favorably with water and is hydrophilic, so it can be on the surface of the protein next to water without issue. If you chose C: The side-chain of this amino acid contains an N-H bond which allows it to form hydrogen bonds. This amino acid side-chain can interact favorably with water and is hydrophilic, so it can be on the surface of the protein next to water without issue. If you chose D: The side-chain of this amino acid contains an O-H bond which allows it to form hydrogen bonds. This amino acid side-chain can interact favorably with water and is hydrophilic, so it can be on the surface of the protein next to water without issue.

In order to fulfill their function, proteins must fold in proper, three-dimensional conformations. Which one of the following molecules, available in a cell, is likely to help a protein fold properly? Cysteine Glycine Chaperone Polymerase

Chaperone Feedback Correct! Chaperones bind to newly made polypeptides and enable proper folding. Chaperones can also bind to misfolded proteins and work to refold them to their correct form.

What category does this amino acid belong to? Polar Charged Nonpolar

Charged Feedback If you selected polar, you are incorrect. The amino acid depicted is charged. There is a COO- group displayed as the R group of this amino acid. Polar amino acids have nitrogen and oxygen atoms at the end of their R groups, but no visible charges. If you selected charged, you are correct. The amino acid depicted is charged. There is a COO- group displayed as the R group of this amino acid with a visible charge. If you selected nonpolar, you are incorrect. The amino acid depicted is charged. There is a COO- group displayed as the R group of this amino acid. Nonpolar amino acids have carbon atoms bonded to hydrogen atoms at the end of their R groups and do not have a charge present.

Which kind of interaction can the following pair of amino acids form between their side chains (R-groups)? Hydrogen bond Ionic bond Disulfide bond Hydrophobic interaction

Correct! Hydrogen bonds are made between R groups that have polar bonds within them N-H, O-H, C-O or C-N but do not display a visible charge (+/-) on their R group. If you selected Ionic, you are incorrect. Amino acids with opposite charged R groups will be attracted to each other and form an ionic bond. If you selected Disulfide, you are incorrect. This is a very specific interaction between two cystiene amino acids where their sulfur atoms (S) bond to each other covalently (S-S). If you selected Hydrophobic, you are incorrect. Hydrophobic interactions are made by amino acids that have carbon and hydrogen atoms bonded to each other on the outer-most portions of their R groups.

Sickle Cell Anemia is inherited in an autosomal recessive pattern. Choose the set of chromosomes of a person that has inherited the disease. Green boxes represent normal alleles and yellow boxes represent mutant alleles. Captionless Image A. Chromosome 12 (Blue) vs. Chromosome 11 (Red) B. Chromosome X (Blue) vs. Chromosome Y (Red, Short) C. Chromosome 11 (Blue) vs. Chromosome 11 (Red w/green stripe) D. Chromosome 11 (Blue) vs. Chromosome 11 (Red w/yellow stripe)

D. Chromosome 11 (Blue) vs. Chromosome 11 (Red w/yellow stripe) Feedback This question depicts chromosomes and asks which pair represents an Autosomal Recessive inheritance pattern. Each of the chromosomes are pictured carrying an allele from each parent, which is depicted by a yellow or green box. The green box represents a normal or dominant allele, while the yellow box represents a mutant or recessive allele. An Autosomal trait will be carried on a numbered chromosome and both chromosomes should have the same number. An X-linked trait will be carried on an X-chromosome. This allows us to rule out answer choices A and B. To inherit a recessive trait, we need to inherit two recessive (or mutant alleles), which would be shown as two yellow boxes. A dominant trait can be inherited when one or two dominant alleles are present. Answer choice C depicts an Autosomal Dominant inheritance, while answer choice D is the correct answer because it depicts an Autosomal Recessive inheritance pattern.

The following are steps involved in a polymerase chain reaction. Which is the correct order: Elongation, denaturation, and annealing Denaturation, annealing, and elongation Annealing, elongation, and denaturation Elongation, annealing, and denaturation

Denaturation, annealing, and elongation Feedback PCR uses repeated cycles of temperature to amplify particular DNA segments. In the first step, the reaction mixture is heated to separate the DNA strands (denaturation). The reaction is then cooled to allow the DNA primers, which define the sequence to be amplified, to anneal (base pair) with the template DNA. In the third step, DNA polymerase extends the DNA primers to create a copy of the target DNA sequence. Heating the reaction to stop polymerization and separate the DNA strands starts the cycle over again

A toddler mistakenly swallows a bathroom cleaning solution, containing a strong reducing agent. Which interaction is most likely to be disrupted within a glycoprotein in the lining of the toddlerʼs esophagus? Hydrogen Bond Disulfide Bond Hydrophobic interactions Ionic Bonds

Disulfide Bond Feedback Correct! Reducing agents disrupt disulfide bonds.

Some changes to the DNA do not modify the coding sequence of the DNA but do affect its winding and unwinding from nucleosomes. These changes can increase or decrease the availability of DNA and hence, the transcription of a gene. These are called _________ changes? Genetic Epigenetic Epidermal Hypogenetic

Epigenetic Feedback Correct. Epigenetic changes result from modifications of the DNA that affect nucleosome spacing and, therefore, transcription. They do not alter the DNA sequence itself.

Which of the following changes can NOT be detected using PCR? Differences in DNA sequence Epigenetic changes Deletions Insertions

Epigenetic changes Feedback Epigenetic changes do not affect the sequence of the DNA. PCR is used to look at the DNA sequence.

1. The polymerase chain reaction is a tool used to study protein structure. True False

False Feedback PCR is a tool used to amplify a specific segment of DNA.

This amino acid would prefer to interact with oil over water. True False

False Feedback If you selected false, you are correct. The amino acid depicted in this problem is polar/hydrophilic because the end of the amino acid R group has a nitrogen bound to a hydrogen. Other polar amino acids can have oxygen bound to hydrogen, carbons bound to oxygens or carbons bound to nitrogens. Water is also polar, and that is why this amino acid would like to interact with water. And, why the amino acid is categorized as hydrophilic (water loving). Oils are nonpolar and polar amino acids don't like nonpolar molecules.

Both pedigrees show the inheritance of von Willebrand disease, a bleeding disorder in which platelets fail to clot properly. There are different types of von Willebrand disease that exhibit different inheritance patterns. Type I is inherited in an autosomal dominant fashion, while type III is autosomal recessive. Which of the following statements best describes the families depicted in the pedigrees below? Family 1 has type III and Family 2 is unlikely to have either of these two types. Family 1 has type I and Family 2 has type III Both families have type I. Family 1 has type III and Family 2 has type I

Family 1 has type III and Family 2 has type I Feedback Family 1 has carrier parents present and both males and females are affected, so it is type III, autosomal recessive. Family 2 does not have carrier parents and affected males do have unaffected daughters, so it is type I, autosomal dominant.

Base excision repair: 1. Fixes single damaged nucleotides 2. Repairs a broken chromosome using genetic information from same chromosome inherited from other parent. 3. Fixes mistakes made by DNA polymerase during DNA replication 4. Fixes multiple damaged nucleotides

Fixes single damaged nucleotides Feedback If you chose, 'Repairs a broken chromosome using genetic information from same chromosome inherited from other parent', that is incorrect. This is the description of a different repair mechanisms, homologous recombination. Homologous recombination occurs to repair a double stranded break in DNA. If you chose, 'Fixes mistakes made by DNA polymerase during DNA replication', this is incorrect. This is the description for DNA Polymerase Proofreading and mismatch repair. This occurs during DNA replication. If you chose, 'Fixes multiple damaged nucleotides', this is incorrect. This is the description for nucleotide excision repair, which occurs to repair DNA damage involving multiple bases. Background. Base excision repair is the repair mechanisms utilized for replaced a single damaged nucleotide

Does oxygenated hemoglobin have a high or low affinity for carbon monoxide (CO)? High affinity for CO Low affinity for CO

High affinity for CO Feedback Correct! Carbon monoxide (CO), which is similar in shape to oxygen (O2), binds to the iron (Fe) atom in the heme group when hemoglobin is in the R state and the heme group is planar, just like oxygen does. Hemoglobin binds to carbon monoxide with 200 times the affinity of oxygen, which means it is very difficult to get rid of the carbon monoxide once it is bound to hemoglobin.

Proteins that promote coiling of DNA and help prevent DNA strands from "tangling" are called? Histones Enzymes Polymerase Chaperones

Histones Feedback Correct! The combination of DNA and histone proteins creates nucleosomes.

A diabetic patient is suffering from ketoacidosis. Which interaction(s) could be disrupted within the patientʼs hemoglobin due to this condition. (Click all that apply) Hydrogen Bond Disulfide Bond Hydrophobic Interactions Ionic Bonds

Hydrogen Bond Ionic Bonds Feedback Correct! Diabetic ketoacidosis leads to a lower pH than normal. Changes in pH can disrupt both hydrogen bonds and ionic bonds inside of a protein.

What bonds can the R group of this amino acid form to stabilize tertiary structure? Hydrogen bonds and ionic bonds Ionic bonds and disulfide bonds Hydrogen bonds and disulfide bonds

Hydrogen bonds and disulfide bonds. Feedback Correct! Charged amino acids have R groups with visible positive or negative charges and form ionic bonds. Polar amino acids have R groups with S-H, N-H, O-H, C-N, or C=O bonds and can form hydrogen bonds. Cysteine can also form a disulfide bond with its terminal S-H. Non-polar amino acids have R groups with C-H bonds and hide from water on the inside (or core) of proteins

3. Which type of bonding or interaction is correctly paired with a chemical or change in environment that will disrupt/break the interaction or bond? Peptide bonds: Reducing agents Hydrophobic interactions: Change in pH Peptide bonds: Change in pH Hydrogen bonds/ionic bonds: Change in pH

Hydrogen bonds/ionic bonds: Change in pH Feedback Correct! Hydrogen bonds and ionic bonds can be disrupted by changes in pH. High salt concentrations can also disrupt ionic bonds / hydrogen bonds, heat disrupts hydrophobic interactions, and reducing agents disrupt sulfide bonds.

What type of reaction breaks peptide bonds apart? Condensation Reaction Methylation Reaction Hydrolysis Reaction Oxidation/Reduction Reaction

Hydrolysis Reaction Feedback Correct! Peptide bonds are formed by dehydration reactions (named for the loss of water that occurs) and broken via hydrolysis (named for the addition of water: "hydro-" meaning water, and "-lysis" meaning cutting, i.e. water cuts the peptide bond).

Alzheimer disease is caused by aggregation of the Amyloid beta peptide and tangle formation by the tau protein. What kinds of amino acids are likely to drive the formation of these protein aggregates? Hydrophobic Hydrophilic Polar Cysteine

Hydrophobic Feedback Correct! The Amyloid beta plaque and tau protein become misfolded, exposing hydrophobic amino acids on their exterior. When hydrophobic amino acids are exposed to water, they actively seek out ways to avoid that water. One way to do this is to find other exposed hydrophobic amino acids, located on other misfolded proteins. When misfolded proteins begin to gather, they form aggregates, ultimately resulting in neuronal cell death.

A patient presents with a fever of 110°F. Which interaction(s) would be disrupted within a neuronal protein if the fever is not resolved quickly. Hydrogen Bond Disulfide Bond Hydrophobic Interactions Ionic Bonds

Hydrophobic Interactions Feedback Correct! The patient's temperature is much higher than normal. High temperatures disrupt hydrophobic interactions.

As a piece of bacon is heated in a skillet on the stove, you observe that the appearance of the bacon changes. You may even notice that the bacon becomes crispy if left in the skillet. What types of bonds or interactions in proteins are susceptible to temperature changes? Ionic Bonds Hydrogen Bonds Hydrophobic interactions Disulfide Bonds

Hydrophobic interactions Feedback Correct! Just as protein structure is stabilized primarily by the hydrophobic effect, disruption of the hydrophobic effect and hydrophobic interactions is the simplest way to denature a protein. This is generally done by applying heat. High temperatures cause the atoms in a protein to move so quickly that the structure loosens and causes the hydrophobic core to open up and expose the nonpolar residues to water.

A black female mouse mates with a white male mouse and produces a litter of all gray mice. Which inheritance pattern can be used to describe this situation? Complete Dominance Recessive Incomplete Dominance Codominance

Incomplete Dominance Feedback Incomplete dominance produces a blended phenotype.

If the coding (non-template) DNA sequence of a normal gene is 5' GTC GCA TGG TGA 3', what kind of mutation would create the mutant gene sequence 5' GTC GAC ATG GTG A 3'? Deletion mutation Silent mutation Insertion mutation Nonsense mutation

Insertion mutation Feedback Correct! Nucleotides were inserted into the original sequence Background. An insertion mutation inserted an A in the second position of the second codon (GCA). Notice that there are now more nucleotides in the mutant gene compared to the normal gene.

The following is the mRNA sequence for actin, a protein that provides structure to a cell: 5' ACU AGA CGU UUU UAA 3'. A mutation to the actin gene results in the production of the following mRNA: 5' ACU AGA CAU UUU UAA 3' What type of mutation is this? Silent Missense Nonsense Frameshift

Missense Feedback If you chose, Nonsense mutation, this is incorrect. A nonsense mutation is a point mutation that results in a change to a stop codon, the change here is to a different amino acid (His). If you chose, Silent mutation, this is incorrect. A silent mutation changes the codon, however, it doesn't change the resulting amino acid encoded. If you chose, frameshift mutation, this is incorrect. Frameshift mutations are not point mutations and are usually the result of an insertion or deletion. As such, inserting or deleting nucleotides will change the number of nucleotides present causing a shift in the reading frame. For example, if we read the sentences CAT HAT DOG and deleted the 'A' in CAT we would change the reading frame to CTH ATD OG. Background: CGU in the normal gene is mutated to CAU, changing the amino acid from arginine (Arg) to histidine (His). A change in a codon that also changes one amino acid in the protein is a missense mutation.

Which characteristic correctly describes the amino acid shown below? Charged Polar Non-polar

Non-polar Feedback Correct! Side chains that are predominantly carbon and hydrogen are nonpolar.

Several components of cigarette smoke, including benzopyrene, insert themselves (intercalate) into the DNA and lead to several types of mutations such as frameshift mutations, including both insertions and deletion. Which of the following repair pathways would be used to repair this type of damage? Base excision repair Mismatch Repair Nucleotide Excision Repair Homologous Recombination

Nucleotide Excision Repair Feedback Correct! Nucleotide excision repair is used to repair deletions, insertions, and helix-distorting lesions, such as thymine dimers.

Antibodies that enable our body to fight bacterial infections must bind to antigens on the surface of the bacterial cell. If the antigen on the surface of the bacterial cell has several negatively charged amino acids, which of the following amino acids would you expect to find on the portion of the antibody that binds to the antigen? Option 1 Option 2 Option 3 Option 4

Option 1 Feedback If you selected option 1, you are correct. Positive charged amino acids will be attracted to the negatively charged amino acids.

A missense mutation resulting in a change from asparagine to leucine at a specific position on an enzyme leads to a neurodegenerative disease. Is there an alternate amino acid substitution of a missense mutation listed below that would have less of an impact on the protein structure and consequently its function than the proposed leucine substitution would? Option 1 Option 2 Option 3 Option 4

Option 2 Feedback Correct! Glutamine is a polar amino acid and so is asparagine,. They are polar because they contain C-N, C-O, O-H or N-H bonds on the outside surface of their R groups. A replacement of one category of amino acid for another in the same category has the best chance of being tolerated and not affecting the protein.

Craniofrontonasal Dysplasia is an X-linked Dominant disorder. This condition is very rare and is caused by mutations in the Ephrin B-1 gene. Which one of the following pedigrees portrays the familial inheritance pattern of this X-linked Dominant disorder? Option 1 Option 2 Option 3 Option 4

Option 4 Feedback To first differentiate between dominant and recessive, check to see if any carriers are present in any generation. Options 1 and 3 are Recessive inheritance patterns because they both contain the pattern where two parents are unaffected and have a child that is affected. Option 1 is X-linked Recessive because only males are affected in the entire pedigree. Option 3 is Autosomal Recessive because there is an affected female. Since Options 2 and 4 are both Dominant, we look to see which one has a pattern where an affected father has daughters that are all affected. Option 2 has an affected father with an affected son, so this must be Autosomal Dominant. Option 4 demonstrates an affected father passing the disease down to all of his daughters, so the answer is Option 4.

Which of the following components is NOT used in PCR? DNA template DNA nucleotides RNA polymerase Primers

RNA polymerase Feedback PCR makes a DNA copy, so DNA polymerase is used.

What color is the primer in the following diagram? Red Purple Blue

Red Feedback Recall from the section on DNA replication that DNA polymerase needs a primer to begin DNA synthesis. This requirement means the primers will direct the DNA polymerase to only synthesize complementary strands of the target DNA. (Note: In DNA replication, the primers are RNA primers, while PCR generally uses DNA primers because they are more stable.)

If lysine is required at position #150 in the peptide chain in order for a protein to properly fold and function, what happens if amino acid #150 is mutated from lysine to alanine? The protein will fold properly-no change The protein will not fold properly

The protein will not fold properly Feedback Correct! Changing lysine (positively charged amino acid, forms ionic bonds, is hydrophilic) to alanine (a non-polar amino acid, does not form ionic bonds, is hydrophobic) eliminates one or more important interactions and will prevent the protein from properly folding.

DNA polymerase is used in DNA replication and in PCR. True False

True Feedback Both PCR and DNA replication require DNA polymerase to make new copies of DNA.

A thermocycler is a machine used for PCR that varies the temperature of a sample. True False

True Feedback For PCR, in each cycle, the two strands of the duplex DNA are separated by heating, then the reaction mixture is cooled to allow the primers to anneal (or pair) to their complementary segments on the DNA. Next, the DNA polymerase directs the synthesis of the complementary strands. The use of a heat-stable DNA polymerase eliminates the need to add fresh enzyme after each round of heating (heat inactivates most enzymes). Hence, in the presence of sufficient quantities of primers and dNTPs, PCR is carried out simply by cycling through the different temperatures for strand separation, primer annealing, and DNA synthesis. The thermocycler is the machine that is used to vary the temperature of the samples.

This amino acid is polar. True False

True Feedback If you selected true, you are correct. The amino acid depicted in this problem is polar/hydrophylic because the end of the amino acid R group has an oxygen bound to a hydrogen. Other polar amino acids can have nitrogen bound to hydrogen, carbons bound to oxygens or carbons bound to nitrogens.

dNTPs are DNA nucleotides used in PCR. True False

True Feedback dNTPs stands for deoxynucleotide triphosphates, which are the nucleotides used in DNA synthesis.

A woman is homozygous for an abnormal allele on Chromosome 2 that codes for an autosomal dominant disease. This means that she: Will have the disease Will not have the disease Has one normal gene and one abnormal gene Can pass on two genes to any daughters and one gene to any son

Will have the disease Feedback Homozygous means that the woman will have two copies of the abnormal allele. An abnormal allele is the allele that can lead to disease. Since the disease is dominant, then the abnormal allele is dominant in this case. With two copies of a dominant allele, an individual will inherit a dominant disease.

Which of the following would be considered a point mutation to a DNA strand that consists of a nucleotide sequence: 5' CTG ACG TAT CTT AAT 3' a. 5' CTG ACG TAA CTT AAT 3' b. 5' CTG ACG TAT TTA AT 3' c. 5' CTG ACG TAT TCT TAA T 3' d. 5' CTG ACG TAT CTT AAT 3'

a. 5' CTG ACG TAA CTT AAT 3' Feedback Correct! A point mutation changes a single nucleotide in a codon, in this case, changing the T in the third position of the third codon to an a (TAT > TAA).

If the coding (non-template) DNA sequence of a normal gene is 5' GTC GCA TGG TGA 3', which DNA sequence would represent a nonsense mutation? q. 5' GTC GCA TAG TGA 3' b. 5' ATC GCA TGG TGA 3' c. 5' GTC GCA TGT GA 3' d. 5' GTA GCG TGG TGA 3'

a. 5' GTC GCA TAG TGA 3' Feedback If you chose, 5' GTC GCA TGT GA 3', this is incorrect because the change here (TGG in the third codon to TGT) results from the loss of a single base (G) at the end of the third codon. Then, the first T from the 4th codon becomes the third base of the third codon, 'shifting' the reading frame. This is a deletion mutation in the DNA. If you chose, 5' GTA GCG TGG TGA 3', this is incorrect because the change here (GTC to GTA in the first codon) would change one Val codon to another Val codon. This is a point mutation in the DNA that would result in a silent mutation in the protein. If you chose, 5' ATC GCA TGG TGA 3', this is incorrect because the change here (GTC to ATC in the first codon) would change a Val codon into an Ile codon. This is a point mutation in the DNA that would result in a missense mutation in the protein. Background. A point mutation (single nucleotide change in a codon) that changed the G in the second position of the third codon (TGG) into an A (TAG) changed the amino acid tryptophan (Trp) into a premature stop codon - This is a point mutation in the DNA that would result in a a nonsense mutation in the protein.

What would the amino acid sequence be from this coding strand sequence: 5'-GGA AGG CCC-3'? a. Gly Arg Pro b. Lys Pro Ser c. Pro Gly Arg d. Val Ala Pro

a. Gly Arg Pro Feedback Correct! The mRNA transcribed from the template strand is complementary and antiparallel to it. The coding strand of DNA (also called the non-template strand) is also complementary and antiparallel to the template strand. Thus, translating 5'-GGA AGG CCC-3' gives us Gly Arg Pro

The RNA sequence 5'-CUC AUA GCC UGA CCC-3' is mutated to 5'-CUC AUA GCC UAA CCC-3' What kind of mutation is this? a. Silent b. Missense c. Nonsense d. Frameshift

a. Silent Feedback If you chose, Nonsense Mutation, this is incorrect. A nonsene mutation is when a codon is changed from coding an amino acid to coding for a stop codon. For example, UGC (Cys) to UGA (stop codon), this usually causes truncated, non-functional proteins. If you chose, Missense Mutation, this is incorrect. A missense mutation changes the codon to code for a different amino acid. For example, if we changed UUC (Phe) to UUA (Leu). If you chose, Frameshift, this is incorrect. Frameshift mutations are not point mutations and are usually the result of an insertion or deletion. As such, inserting or deleting nucleotides will change the number of nucleotides present causing a shift in the reading frame. For example, if we read the sentences CAT HAT DOG and deleted the 'A' in CAT we would change the reading frame to CTH ATD OG. Background. The A in the second position of the third codon is mutated to a G, changing the codon from UAA to UGA. This changes one STOP codon into another STOP codon, so there is a STOP codon where there should be a STOP codon. This is not a premature STOP codon. Since the amino acid sequence doesn't change, this a silent mutation.

If one strand of chromosome 2 has a DNA sequence that consists of this: 5' AAG CGG TAC GTA 3' What will be the composition of the complementary DNA strand? (Select all that apply) a. 5' TTC GCC ATG CAT 3' b. 3' TTC GCC ATG CAT 5' c. 5' TAC GTA CCG CTT 3' d. 3' AAG CGG TAC GTA 5'

b. 3' TTC GCC ATG CAT 5' c. 5' TAC GTA CCG CTT 3' Feedback Correct! All complementary base pairing must be antiparallel. The complementary strand to 5' AAG CGG TAC GTA 3' is 3' TTC GCC ATG CAT 3'. If we simply 'flip' the sequence, we get 5' TAC GTA CCG CTT 3'. Thus, these are the correct answers.

What would be the resulting mRNA sequence from a template strand with this sequence: 5'-CAG CTC GTC-3'? a. 5'-GUC GAG CAG-3' b. 5'-GAC GAG CUG-3' c. 3'-GAC GAG CUG-5' d. 3'-GUG GAG GAG-5'

b. 5'-GAC GAG CUG-3' Feedback Correct! Sequences that bind each other (are complementary) must also be antiparallel (running in opposite directions). The sequence that is complementary to 5'-CAG CTC GTC-3' is 3'-GUC GAG CAG-5'. Since the possible answers in the list to choose from are presented with their 5' ends on the left, we simply 'flip' the sequence to get 5'-GAC GAG CUG-3'.

Which of the following is NOT a step in base excision repair? a. Ligation to restore continuity of the DNA backbone b. Synthesis of an RNA primer c. Recognition of the damage d. Removal of the damage by excising part of one strand to leave a gap

b. Synthesis of an RNA primer Feedback Synthesis of an RNA primer is part of DNA replication, not DNA repair.

A patient with xeroderma pigmentosum is prone to developing multiple skin cancers starting in childhood. This occurs because of a mutation in a gene that codes for enzymes that help repair DNA damage through the nucleotide excision repair (NER) pathways. How does NER differ from other repair mechanisms? In NER: a. Only one nucleotide is removed and DNA polymerase replaces the one abnormality b. The error in one strand of DNA is removed as well as several nucleotides on either side of the error. The gap that was removed is filled in by DNA polymerase c. The entire homologous chromosome is used to repair the double stranded DNA error d. The affected DNA strand and its complementary strand is discarded and a new double stranded DNA is created

b. The error in one strand of DNA is removed as well as several nucleotides on either side of the error. The gap that was removed is filled in by DNA polymerase Feedback Correct! Nucleotide excision repair replaces several damaged nucleotides plus additional nucleotides and uses the DNA on the opposite strand as a template to fill in the gap.

The following sequence is the coding DNA strand of the collagen gene: 5' ATG GCG TTC GAA 3' What is the sequence of the corresponding mRNA? a. 3' ATG GCG TTC GAA 5' b. 5' AUG GCG UUC CUU 3' c. 5' AUG GCG UUC GAA 3' d. 5' UTG GCG TTC GUU 3'

c. 5' AUG GCG UUC GAA 3' Feedback Correct. The coding strand and the mRNA both go in the same direction, but do not both contain Ts.

If the coding (non-template) DNA sequence of a normal gene is 5' GTC GCA TGG TGA 3', which DNA sequence would represent a deletion mutation? a. 5' GTC GCA TAG TGA 3' b. 5' ATC GCA TGG TGA 3' c. 5' GTC GCA TGT GA 3' d. 5' GTA GCG TGG TGA 3'

c. 5' GTC GCA TGT GA 3' Feedback Correct! A deletion mutation removed a G from the fourth codon (TGG). Notice that there are now fewer nucleotides in the mutant gene compared to the normal gene.

What is the coding strand sequence if the non-template strand sequence is 5'-AGC CTT TAA CTA-3' a. 5'-TCG GAA ATT GAT-3' b. 5'-TAG TTA AAG GCT-3' c. 3'-AGC CTT TAA CTA-5' d. 3'-ATC AAT TTC CGA-5'

d. 3'-ATC AAT TTC CGA-5' Feedback Correct! The names "coding strand" and "non-template strand" refer to the exact same piece of DNA. Therefore, if the non-template strand is 5'-AGC CTT TAA CTA-3', then the coding strand is exactly the same sequence (because it is the same piece of DNA: 3'-ATC AAT TTC CGA-5'.

What would be the amino acid sequence that would result from this template sequence: 5'-TGC AAG CCA-3'? a. Pro Leu Trp b. Thr Phe Gly c. Gly Phe Thr d. Trp Leu Ala

d. Trp Leu Ala Feedback Correct! The RNA polymerase enzyme makes mRNA by antiparallel and complementary basepairing with the template strand of DNA. Therefore, the mRNA transcribed from this template would be 3'—ACG UUC GGU-5'. mRNA codons are read 5' --> 3' on the genetic code table. 'Flipping the sequence gives us 5'-UGG CUU GCA-3'. Using the genetic code table, we see that UGG encodes Trp; CUU encodes Leu; and GCA encodes Ala.

In the organization of DNA into chromosomes, DNA is wrapped around _________ to form nucleosomes. Nucleosomes are organized further to form _____________. RNA; triple helix histones; nucleus histones; chromatin promoters ; histones

histones; chromatin Feedback Correct! DNA is wrapped around proteins called histones to prevent tangling, and the combination of DNA and histone proteins creates nucleosomes. The histones promote coiling of the nucelosomes into a larger chromatin fiber.

Which of the following forces can lead to aggregation as a result of protein misfolding? disulfide bonds hydrogen bonds ionic bonds hydrophobic interactions

hydrophobic interactions Feedback Correct! Misfolded proteins can have sections of hydrophobic amino acid residues exposed to water. This can lead to misfolded proteins to aggregate in order to form favorable hydrophobic interactions between nonpolar amino acids in adjacent protein chains and to keep these hydrophobic residues away from water.

Which of the following interactions can occur between two positively charged amino acids? hydrogen bond hydrophobic interaction disulfide bond ionic bond none of these

none of these Feedback If you selected none of these, you are correct. Two positively charged amino acids would repel each other. Only opposite charged attract.

Which of the following interactions involve a covalent bond? (check all that apply) peptide bond hydrogen bond hydrophobic interaction ionic bond disulfide bond

peptide bond disulfide bond Feedback Correct! A covalent bond is a bond between to atoms involving the electrons being shared between them. In proteins, these include peptide bonds and disulfide bonds.

The negatively charged amino acid, Glutamate, is replaced with the negatively charged amino acid Aspartate. Which level of protein structure is most significantly impacted by this change? primary structure secondary structure tertiary structure quaternary structure

primary structure Feedback Correct! The original and substitute amino acid both have a negative charge and can both form an ionic bond with a positively charge amino acid, so contributions to quaternary and tertiary structure, which are dependent on side-chain interactions, are most likely unaffected. The secondary structure of a protein depends on backbone interactions, and is also probably unaffected. The amino acid sequence, however, has been altered, and so the primary structure has certainly been changed.

Two healthy individuals give birth to a child that has Bloom Syndrome. From this information, it can be concluded that Bloom syndrome is inherited in a ________ manner. recessive dominant sex-linked

recessive Feedback Carrier parents are parents who do not have a particular trait, such as a disease, but that trait shows up in their offspring. The presence of carrier parents signifies that the trait is recessive.

A mutation in the DNA that changes the sequence of a codon but does NOT change the amino acid sequence of the protein describes a _____ _____. frameshift mutation. missense mutation. nonsense mutation. silent mutation.

silent mutation. Feedback -If you chose 'Frameshift Mutation', this is incorrect. Errors that increase or decrease the number of nucleotides in a gene cause frameshift mutations. The insertion of an extra base or the removal of one of the bases will change which groups of three bases that the ribosome reads when it translates the message. This is said to 'shift' the 'reading frame' from the correct groups of three bases to different groups. To visualize what a frameshift is, imagine you are given a string of letters and told to start at the beginning and read every group of three letters: CATDOGRATPIGAPE. You would get "cat dog rat pig ape". But if we add an extra letter, say CATDFOGRATPIGAPE, following our "read every group of three" rule, we would get "cat dfo gra tpi gap e". Shifting our 'reading frame' by adding one more letter completely changes what we read. This is similar to what happens with a frameshift mutation. -If you chose 'Missense Mutation',this is incorrect. A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA such that it codes for a different amino acid, changes one amino acid in the amino acid sequence of a protein. This is called a missense mutation. See Figure 1-19 in the Module 1 text for more information. - If you chose 'Nonsense Mutation', this is incorrect. A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA from one that codes for an amino acid into one that specifies the STOP signal is a nonsense mutation. The protein will terminate prematurely. Background: When a point mutation (single nucleotide change) occurs it changes the mRNA codon (triplet sequence that codes for amino acid), however, it doesn't affect the amino acid it codes for. For example, if a point mutation caused UUU (codes for Phe) to change to UUC-