Nextstep 1 Bio

Question 1

A peptide bond is forms what kind of functional? And why is it so stable?

Answer 1

A peptide bond forms an amide linkage between the amine group of one amino acid and the carboxylic acid group of another.

Amides are stable because they show resonance stabilization.

Question 2

In prokaryotes, genes can exist as operons that are transcribed into a polycistronic mRNA, containing multiple genes in a single transcript. In eukaryotes, transcripts exist only as monocistronic mRNA containing a single gene. What fundamental genetic difference is responsible for this distinction?

Answer 2

Eukaryotes mRNA contain a single gene because each gene contains their own transcription site.

Question 3

Start codons refers to translation or transcription?

Answer 3

Start codons refers to translation of mRNA.

Question 4

What is the definition of hybridization?

Answer 4

Hybridization describes the process of binding to complementary strands such as in the silencing of mRNA by miRNA

Question 5

What is defined as RNA polymerization?

Answer 5

Polymerization is the process by which a series of nucleotides are strung together to form a single-stranded RNA strand. NOT THE JOINING OF TWO COMPLEMENTARY ONES.

Question 6

If a protein is cationic at physiological pH it must have more of which amino acids and why?

Answer 6

If the protein is positive at neutral pH, the protein must have more amino acids that are basic than acidic.

Question 7

The innate immune system includes what and what are its responses?

Answer 7

The innate immune system includes nonspecific immune responses. Its responses provide general protection. Inflammation is a function of the innate immune system.

Question 8

The adaptive immune system includes what and what are its responses?

Answer 8

The adaptive immune system is directed against a particular pathogen to which the body had been exposed before. “remembering” this exposures that lead to quicker future responses. Vaccines are an example of this.

Question 9

Passive immunity involves?

Answer 9

Passive immunity involves the transfer of one individual to another.

Question 10

Which form of genetic change best explains the loss of the majority of genes from the Y chromosome?

Answer 10

Genetic drift. Genetic drift is a term from population gentics, and encompasses the fact that that an adult male that has only female offsprings will not pass its Y chromosome. The repeated random loss of the well-adapted Y chromosomes can result in the degeneration of the chromosome as a whole.

Question 11

Researchers showed that the Y chromosome experiences a much higher mutation rate than the X chromosome. This is likely due to the fact that?

Answer 11

Given that sperm undergoes many divisions during gametogenesis, each cellular division makes mutations more likely in the Y chromosome.

Also, sperm develops in the testes an environment that is under unusually oxidative conditions; promoting mutations.

Finally, the X chromosome undergoes fewer total number of replications do to limited replication rounds during oogenesis, and females have crossing-over events that restore the function to damaged X chromosomes.

Question 12

Stimulation of the iris dialator muscle is a result of?

Answer 12

Sympathetic motor neurons. Motor because are originated in the brain and sent to the muscle and sympathetic because pupil dilation is a classic response to fight-flight type of situations.

Question 13

Increasing plasma concentration of aldosterone is most likely to be followed by which of the following?

Answer 13

B is correct. Aldosterone is released from the adrenal cortex in response to low blood pressure. Its primary function is to increase sodium reabsorption in the distal tubule and collecting duct. Aldosterone upregulates the sodium-potassium pumps along the lining of the nephron, pumping three sodium ions OUT of the nephron lining (and toward the blood) for every two potassium ions it pumps IN (toward the nephron and away from the blood). Since we have a net solute movement out of the nephron, aldosterone also increases the gradient that favors water reabsorption.

Question 14

When normal human cells are grown in culture, they will divide a limited number of times – typically 50 rounds of mitosis. After this number is reached, the cells become apoptotic. This cell death is a result of:

Answer 14

Chromosomal telomeres shortening after each round of replication.

As cell undergoes mitosis, its telomeres, the repeating portions of DNA at the end of the chromosomes gets progressively shorter. Eventually the cell looses its telomeres entirely and is unable to reproduce. The cell then undergoes mitosis.

Question 15

The process of arranging nuclear DNA in preparation for transmission to offspring is cyclical or non cyclical?

Answer 15

The arraging of nclear DNA otherwise known as meosis is a noncyclical process. It happens once and terminates in gamete creation (sperm or ova).

Question 16

Is the growth of cell cultures cyclical or non-cyclical?

Answer 16

Cell culture growth occurs through mitosis which is a cyclical process.

Question 17

III. Growth of cell cultures requires transformation of diploid cells into haploid cells, while genetic transmission of nuclear DNA to offspring requires transformation of haploid cells into diploid cells.

Is the above statement true or false and why?

Answer 17

It is false. Because the process of cell culture is a mitotic process that results in diploid cells, whereas the process described ends in haploid ones (meiosis).

Question 18

What aspects separate single-crossover events from double-crossover events?

Answer 18

Single-crossover events affect only the ends of chromosome arms. Double-crossover events affect segments in the middle of chromosome arms.

Question 19

If a compound travels more towards the positive side or negative what does it mean about the composition of the isoenzyme?

Answer 19

The compounds with more positive (basic) amino acids will travel the most towards the negative side. Whereas, amino acids with the most negative charge (acidic) will travel towards the positive side the most. The ones that are a combination of both will stay relatively in the middle or slightly to one side.

Question 20

Cathode is what?

Answer 20

Cathode is where positive charges go into, which makes it the negative electrode.

Question 21

Anode is what?

Answer 21

Anode is the where negative charges go into, making it the positive electrode.

Question 22

In gel electrophoresis and galvanic cells anode and cathode differ in what ways?

Answer 22

In a galvanic cell, the anode is (-), and the focus is on pushing away electrons from the anode to supply power. In an electrolytic cell and gel electrophoresis, the anode is (+) and the focus is on attracting the negative ions in solution from inputted power.

Question 23

CK isoforms containing M1 and M2 subunits migrate nearer the anode than do CK isoforms containing the unmodified M subunit. The region near the C-terminus of the unmodified M subunit is enriched in which of the following amino acids?

“CK M subunits are slowly converted into two modified subunits, M1 and M2, by plasma carboxypeptidases via successive cleavage of C-terminal amino acid residues.”

Answer 23

A is correct. The passage states that once released from tissue, the CK M subunits are converted into modified subunits M1 and M2 by successive cleavage of C-terminal amino acid residues. If the modified subunits migrate nearer the positive electrode than do unmodified subunits, then modified subunits possess a lower pI than unmodified subunits and should be enriched in lower-pI amino acids via the removal of higher-pI residues. Only choice A—lysine, asparagine, arginine—contains three higher-pI, basic residues and is the correct answer. Choices B, C, and D all contain some combination of non-basic amino acids and are incorrect.

Question 24

Troponin enzymes are used as an alternative biomarker in the diagnosis of heart attack. On which muscle type does the troponin complex function in contraction?

Answer 24

Troponin is a complex of three proteins required for muscle contraction in skeletal and cardiac muscle, but not smooth muscle.

Question 25

Which statements is true regarding peptide bonds?

Answer 25

The peptide bonds displays partial double bond character because of the delocalization of electron density from the peptide (amide) nitrogen through the peptide carbonyl carbon and onto the peptide carbonyl oxygen

Question 26

Injection of insulin into the bloodstream is LEAST likely to result in which of the following?

• Increased glycogen synthesis
• Decreased lipid synthesis
• Increased esterification of fatty acids
• Decreased gluconeogenesis

Answer 26

B is correct. Insulin is secreted in response to high blood sugar. If the body detects that there’s plenty of blood sugar, then it would want to stop making more sugar (eliminate Decreased gluconeogenesis), to store that sugar as glycogen (eliminate Increased glycogen synthesis), and to build up fatty acids into fats for storing up energy (Increased esterification of fatty acids).

Question 27

If during a chemical reaction you produce FADH2 and s NADH + H+?

Answer 27

It means that the compound was oxidized.

Question 28

Which of the following is most likely NOT a symptom of acylcarnitine translocase deficiency?

From the beginning of the passage you can deduce that the enzyme is in charge of fatty acid catabolism.

Answer 28

Given that acylcarnitine translocase is is essential for the catabolism of amino acids. It means that without it there will be agreat abundance of fatty acids and less energy available. Glucose will relied upon much more heavily as a source of ATP. Therefore, HYPERGLYCEMIA will not be a problem.

As a result of acylcartine translocase deficiency muscle weakness (less fatty energy through fatty acid catabolism) and liver damage (due to drastic changes in fat levels often being stored in the liver: fatty liver disease).

Question 29

In a population of Amish people, the frequency of the recessive autosomal allele for polydactyly is 1.2%. What percent of the population are carriers for this gene?

Answer 29

C is correct. We can use the Hardy-Weinberg equation to solve this question. Remember that the total number of alleles in the population has to add up to 1:

A + a = 1

And the total number of genotypes in the population must also add up to 1:

AA + 2Aa + aa = 1

We’re told that a = 0.012. By the first equation above, A = 0.988.

The carriers are the heterozygotes with the genotype Aa. Their frequency is:

2Aa = 2 x 0.988 x 0.012 = 0.988 x 0.024

At this point we’ve got what looks like a tough calculation to do, so we should probably back up and start estimating. Our calculation is telling us to take 98.8% of 0.024, so our answer is going to be really close to 0.024 (since 100% of any number is just that number itself [e.g. 100% of 56.7 is 56.7]). If we look at the answer choices, the only one that’s remotely close is 0.0237, or 2.37%.