Final Exam

Question 1

What are the phases of the cell cycle and what is happening in each phase?

Answer 1

• In phase G1, The G1 phase is a time of expansion. A lot of protein is made and water is pumped in so that a cell increases in volume.
• In phase S, the cell replicates its DNA. All chromosomes are copied so that DNA content doubles.
• In phase G2, is the time when a cell duplicates its organelles.
• In phase M (mitosis), is the phase during which the cell physically separates into two daughter cells.

Question 2

In Hypotonic, which way does water and solutes will osmose/diffuse?

Answer 2

The free net movement of water move inside the cell, causing it to swell up and explode. 
The spectrum of water movement based on solute concentration through the process of
osmosis.

Question 3

In Hypertonic, which way does water and solutes will osmose/diffuse?

Answer 3

When placing a red blood cell in any hypertonic solution, there will be a movement of free water out of the cell and into the solution. This movement occurs through osmosis because the cell has more free water than the solution.

Question 4

In Isotonic, which way does water and solutes will osmose/diffuse?

Answer 4

In isotonic solution, the cell has no effect, and the solution moves inside and
outside the cell. In an isotonic solution, no net movement of water will take place. If the solution surrounding a cell is isotonic, water molecules diffuse in and out of the cell at the same rate by the process of osmosis.

Question 5

What is going on in the prep phase of Glycolysis?

Answer 5

Investment phase (prep phase)- In this phase, there are two phosphates added to glucose. Glycolysis begins with hexokinase phosphorylating glucose into glucose-6 phosphate (G6P). This step is the first transfer of a phosphate group and where the consumption of the first ATP takes place. Also, this is an irreversible step. This phosphorylation traps the glucose molecule in the cell because it cannot readily pass the cell membrane. From there, phosphoglucose isomerase isomerizes G6P into fructose 6-phosphate (F6P). Then, phosphofructokinase (PFK-1) adds the second phosphate. PFK-1 uses the second ATP and phosphorylates the F6P into fructose 1,6-bisphosphate. This step is also irreversible and is the rate-limiting step. In the following step, fructose 1,6-bisphosphate undergoes lysis into two molecules, which are substrates for fructose-bisphosphate aldolase to convert it into dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (G3P). DHAP is turned into G3P by triosephosphate isomerase. DHAP and G3p are in equilibrium with each other, meaning they transform
back and forth

Question 6

What is going on in the payoff phase of Glycolysis?

Answer 6

It is critical to remember that there is a total of two 3-carbon sugars for
every one molecule of glucose at the beginning of this phase. The enzyme glyceraldehyde-3-phosphate dehydrogenase metabolizes the G3P into 1,3-diphosphoglycerate by reducing NAD+ into NADH. Next, the 1,3-diphosphoglycerate loses a phosphate group through phosphoglycerate kinase to make 3-phosphoglycerate and creates an ATP through substrate-level phosphorylation. At this point, there are 2 ATP produced, one from each 3-carbon molecule. The 3-phosphoglycerate turns into 2-phosphoglycerate by phosphoglycerate mutase, and then enolase turns the 2-phosphoglycerate into phosphoenolpyruvate (PEP). In the final step, pyruvate kinase turns PEP into pyruvate and phosphorylates ADP into ATP through substrate-level phosphorylation, thus creating two more ATP. This step is also irreversible. Overall, the input for 1 glucose molecule is 2 ATP, and the output is 4 ATP and 2 NADH and 2 pyruvate molecules.

Question 7

What happens in the Acetyl-CoA pathway

Answer 7

The acetyl-CoA pathway begins with the reduction of a carbon dioxide to carbon monoxide. The other carbon dioxide is reduced to a carbonyl group. Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production.

Question 8

What happens in the Krebs Cycle

Answer 8

The Krebs Cycle (aka The Citric Cycle), is production of intermediate compounds important in the synthesis of substances such as amino and fatty acids, and the formation of large quantities of ATP that provides energy for various synthetic processes. Pyruvic Acid is broken down into Carbon Dioxide, in a series of energy extracting reactions.

Question 9

How does the electron transport work to make ATP?

Answer 9

The electron transport chain (ETC) is a collection of proteins bound to the inner mitochondrial membrane and organic molecules, which electrons pass through in a series of redox reactions, and release energy. The energy released forms a proton gradient, which is used in chemiosmosis to make a large amount of ATP by the protein ATP-synthase

Question 10

How does oxidative phosphorylation work to make ATP?

Answer 10

Oxidative phosphorylation produces ATP (energy) in our cells. NADH, a molecule
produced during cellular respiration, gets oxidized and releases electrons. These electrons pass through a series of acceptors in the electron transport chain, releasing energy

Question 11

The chemical equation of the breakdown of glucose

Answer 11

C6H12O6+6O2→6CO2+6H2O+energy.

Question 12

Why does fermentation happen and how does fermentation work?

Answer 12

• Fermentation occurs in the absence of oxygen (anaerobic conditions), and in the presence of beneficial microorganisms (yeasts, molds, and bacteria) that obtain their energy through fermentation
• Fermentation begins with glycolysis which breaks down glucose into two pyruvate molecules and produces two ATP (net) and two NADH. Fermentation allows glucose to be continuously broken down to make ATP due to the recycling of NADH to NAD+.

Question 13

How do we make and burn fats using the Acetyl-CoA pathway?

Answer 13

• Acetyl-CoA is formed into malonyl-CoA by acetyl-CoA carboxylase, at which point malonyl-CoA is destined to feed into the fatty acid synthesis pathway.
• Fatty acid oxidation is the mitochondrial aerobic process of breaking down a fatty acid into acetyl-CoA units. Fatty acids move in this pathway as CoA derivatives utilizing NAD and FAD

Question 14

What are the phases of mitosis and what is happening in each

Answer 14

• Prophase is when the nuclear membrane degrades and the chromosomes thicken.
• Metaphase is when the chromosomes align in the middle of the cell.
• Anaphase is when the chromosomes split in half; one part goes to
  each side.
• Telophase is when the middle of the cell pinches together to create two independent cells.

Question 15

The different checkpoints that control the cell cycle

Answer 15

● The G1 checkpoint, at the G/S transition.
● The G2 checkpoint, at the G/M transition.
● The spindle checkpoint, at the transition from metaphase to anaphase.

Question 16

What is a tumor, and what are the differences between a benign and malignant one.

Answer 16

• An abnormal mass of tissue that forms when cells grow and divide more than they should or do not die when they should.
• Tumors may be
  ● Benign (not cancer)
  ● Malignant (cancer).

Question 17

Why sexual reproduction is important?

Answer 17

Sexual reproduction has been favored by evolution probably because the random recombination of genetic information improves the chances of producing at least some offspring that will survive in an unpredictably variable environment. The variation that sexual reproduction creates among offspring is very important to the survival and reproduction of the population.

Question 18

What are the different ploidy levels?

Answer 18

● Monoploidy (1 set)
● Diploid (2 sets)
● Triploid (3 sets)
● Tetraploid (4 sets)
● Pentaploid (5 sets)
● Hexploid (6 sets)
● Heptaplouid or Septaploid (7 sets)

Question 19

When does the cell become haploid as opposed to diploid

Answer 19

During meiosis I, the cell is diploid because the homologous chromosomes are still located within the same cell membrane. Only after the first cytokinesis, when the daughter cells of meiosis I are fully separated, are the cells considered haploid.

Question 20

How does crossing over contributes to genetic variation?

Answer 20

It creates gametes that contain new combinations of genes, which helps maximize the genetic diversity of any offspring that result from the eventual union of two gametes during sexual reproduction.

Question 21

What can go wrong during meiosis

Answer 21

The most common error of meiosis is nondisjunction, when chromatids fail to separate during either anaphase I or II, creating imbalances in the number of chromosomes in each daughter cell.

Question 22

What are the base pairing of DNA and RNA

Answer 22

• In DNA:
  Adenine (A) - Thymine (T)
  Cytosine (C) - Guanine (G)
• In RNA:
  Adenine (A) - Uracil (U)
  Cytosine (C) - Guanine (G)

Question 23

What holds DNA and RNA molecules together?

Answer 23

Ester bonds. DNA and RNA are composed of nucleotides that are linked to one another in a chain by chemical bonds, called ester bonds.

Question 24

What is the semi-conservative model of DNA replication

Answer 24

Semi-conservative replication means that during DNA replication, the two strands of nucleotides separate. Both strands then form the template for free nucleotides to bind to to create the two identical daughter strands. Hence each daughter strand has half of the DNA from the original strand and half newly-formed DNA.

Question 25

What is the entire process of how DNA replicates?

Answer 25

Replication occurs in three major steps.

● DNA replication initiates at specific points, called origins, where the DNA double helix is unwound.

● A short segment of RNA, called a primer, is then synthesized and acts as a starting point for new DNA synthesis.

● An enzyme called DNA polymerase next begins replicating the DNA by matching bases to the original strand.

Once synthesis is complete, the RNA primers are replaced with DNA, and any gaps between newly synthesized DNA segments are sealed together with enzymes.

Question 26

The different enzymes involved in DNA replication.

Answer 26

● DNA helicase
● RNA primase
● DNA polymerase
● DNA ligase.

Question 27

The difference between the leading and lagging strand.

Answer 27

The major difference between a lagging and leading strand is that the lagging strand replicates discontinuously forming short fragments, whereas the leading strand replicates continuously.

Question 28

What does 5’ and 3’ mean.

Answer 28

One end of the DNA molecule is known as 5′ (five prime), and the other end is known as 3′. (three prime). The numbers 3′ and 5′ refer to the number of carbon atoms in a deoxyribose sugar molecule that a phosphate group binds to.

Question 29

How does DNA get damaged and what are the different repair mechanisms

Answer 29

• Endogenous sources of DNA damage include hydrolysis, oxidation, alkylation, and mismatch of DNA bases; sources for exogenous DNA damage include ionizing radiation (IR), ultraviolet (UV) radiation, and various chemicals agents
• At least five major DNA repair pathways:
  ● base excision repair (BER)
  ● nucleotide excision repair (NER)
  ● mismatch repair (MMR)
  ● homologous recombination (HR)
  ● non-homologous end joining (NHEJ)

Question 30

The central dogma of biology

Answer 30

The central dogma of molecular biology is a theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly to protein

Question 31

What is the one gene one protein hypothesis?

Answer 31

The one gene–one enzyme hypothesis is the idea that genes act through the production of enzymes, with each gene responsible for producing a single enzyme that in turn affects a single step in a metabolic pathway

Question 32

What is a codon and how it’s used?

Answer 32

• A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis.
• To use this chart you first locate the first nucleotide in the codon, then the second, and then the third. The chart will then reveal which amino acid is coded for by which codon.

Question 33

The whole process of transcription, including which enzymes are involved.

Answer 33

It involves copying a gene’s DNA sequence to make an RNA molecule. Transcription is performed by enzymes called RNA polymerases, which link nucleotides to form an RNA strand (using a DNA strand as a template). Transcription has three stages: initiation, elongation, and termination

Question 34

How is the mRNA is modified after transcription?

Answer 34

This transcript must undergo processing (splicing and addition of 5’ cap and poly-A tail) while it is still in the nucleus in order to become a mature mRNA. The mature mRNA is exported from the nucleus to the cytosol, where it is translated at a ribosome to make a polypeptide.

Question 35

The different types of RNA.

Answer 35

Three main types of RNA are involved in protein synthesis are:

● Messenger RNA (mRNA)
● Transfer RNA (tRNA)
● Ribosomal RNA (rRNA)

Question 36

The difference between the coding and template strands of DNA.

Answer 36

• The coding strand of DNA is the strand that codes for the gene of interest.
• The template strand is complementary to this and can be transcribed to produce a piece of RNA with an identical nucleotide sequence to the coding strand

(except T’s will be U’s in RNA).

Question 37

The structure of a ribosome

Answer 37

A ribosome is made out of RNA and proteins, and each ribosome consists of two separate RNA-protein complexes, known as the small and large subunits. The large subunit sits on top of the small subunit, with an RNA template sandwiched between the two

Question 38

The whole process of translation and all the cellular machinery involved

Answer 38

Translation is the process whereby mRNA is converted into proteins by ribosomes. Translation occurs in ribosomes, which are cellular structures made of proteins and ribosomal RNA (rRNA). Here, mRNA is converted into amino acid sequences, forming polypeptides

Question 39

What happens to the polypeptide after translation.

Answer 39

Termination is the stage in which the finished polypeptide chain is released. It begins when a stop codon (UAG, UAA, or UGA) enters the ribosome, triggering a series of events that separate the chain from its tRNA and allow it to drift out of the ribosome.

After termination, the polypeptide may still need to fold into the right 3D shape, undergo processing (such as the removal of amino acids), get shipped to the right place in the cell, or combine with other polypeptides before it can do its job as a functional protein.

Question 40

The different types of mutations and the different types of errors.

Answer 40

Class of Mutation

Point mutation

• Substitution: One base is incorrectly added during replication and replaces the pair in the corresponding position on the complementary strand / Sickle-cell anemia
• Insertion: One or more extra nucleotides are inserted into replicating DNA, often resulting in a frameshift / One form of beta-thalassemia
• Deletion: One or more nucleotides is “skipped” during replication or otherwise excised, often resulting in a frameshift / Cystic fibrosis

Chromosomal mutation

• Inversion: One region of a chromosome is flipped and reinserted / Opitz-Kaveggia syndrome
• Deletion: A region of a chromosome is lost, resulting in the absence of all the genes in that area/ Cri du chat syndrome
• Duplication: A region of a chromosome is repeated, resulting in an increase in dosage from the genes in that region / Some cancers
• Translocation: A region from one chromosome is aberrantly attached to another chromosome / One form of leukemia

Copy number variation

• Gene amplification: The number of tandem copies of a locus is increased / Some breast cancers
• Expanding trinucleotide repeat: The normal number of repeated trinucleotide sequences is expanded / Fragile X syndrome, Huntington’s disease

Question 41

The levels where genes can be regulated

Answer 41

Regulation is divided into five levels:

● Epigenetic
● Transcriptional
● Post-transcriptional
● Translational
● Post-translational

Question 42

What is a promotor, operator, enhancer do, and what transcription factors, and the various types, do

Answer 42

• A promoter is a region of DNA where transcription of a gene is initiated. they control the binding of RNA polymerase to DNA
• Operator is the DNA segment where the repressor molecule binds to the operon model. In eukaryotes, it facilitates the binding of transcription factors and RNA polymerase for gene transcription.
• Enhancers are DNA-regulatory elements that activate transcription of a gene or genes to higher levels than would be the case in their absence.
• Transcription factors are proteins involved in the process of converting, or transcribing, DNA into RNA. Transcription factors include a wide number of proteins, excluding RNA polymerase, that initiate and regulate the transcription of genes.

Question 43

How cells regulate post-transcription mRNAs and post-translational proteins.

Answer 43

• First, transcription is controlled by limiting the amount of mRNA that is produced from a particular gene. The second level of control is through post-transcriptional events that regulate the translation of mRNA into proteins. Even after a protein is made, post-translational modifications can affect its activity
• Post-translation, which occur after the completion of protein translation, regulate protein structures and functions by covalent addition of functional groups, peptides or other complex molecules reversibly or irreversibly, leading to extend and diversify protein properties and enhance the ability of modulating protein stability

Question 44

How does Mendel’s Laws apply to genetics?

Answer 44

This is known as the law of segregation. A Punnett square can be used to predict genotypes (allele combinations) and phenotypes (observable traits) of offspring from genetic crosses. A test cross can be used to determine whether an organism with a dominant phenotype is homozygous or heterozygous

Question 45

The different forms of gene dominance work

Answer 45

In genetics, there are three main dominance patterns:

● Complete dominance (only one dominant allele appears in the phenotype),
● Codominance (both alleles are visible in the phenotype)
● Incomplete dominance (a mix of alleles creates a new phenotype)

Question 46

What is a linkage map?

Answer 46

It describes the methods used to identify the location of a gene on a chromosome and the distances between genes. Gene mapping can also describe the distances between different sites within a gene

Question 47

Understand x-inactivation and how it might affect an individual

Answer 47

• A dosage compensation strategy to equalize X-linked gene expression between XX females and XY males.
• In X inactivation, each cell ‘switches off’ one of its X chromosomes, chosen at random, to ensure the correct number of genes are expressed, and to prevent abnormal development. X-inactivation ensures that females, like males, have one functional copy of the X chromosome in each body cell.