Lab exam review

Question 1

What was the purpose of the detergent added to the crushed strawberries during lab 1?

Answer 1

• The detergent helps lyses the cell membranes and denatures proteins of the strawberry cells
• Does this by breaking protein-protein interactions
• Makes it easier to access the DNA

Question 2

What was the purpose of the NaCl added to the crushed strawberries during lab 1?

Answer 2

• The positive sodium ions are attracted to the negatively charged DNA, while the negative chloride ions are attracted to the positively charged histones
• Helps separate the DNA from the histones

Question 3

What two substances make up the DNA extraction buffer added to the crushed strawberries in lab 1?

Answer 3

• The detergent and the NaCl (table salt)

Question 4

In lab 1, what substance was added in order to precipitate the DNA out of the solution?

Answer 4

• Isopropanol
• It helps decrease the polarity of the water, which is good since DNA is a very polar molecule, to begin with
• DNA in the presence of sodium is highly soluble in water because water and DNA are both highly polar molecules

Question 5

Why were strawberries used in the lab 1 experiment?

Answer 5

• Strawberries are polyploid, making it easier to extract DNA because there’s so much of it

Question 6

How does the fluorescent dye called SYBR gold work on DNA? (used in lab 1)

Answer 6

• Gives off a bright yellow-gold light when bound to DNA
• Only gives off light when bound to double-stranded DNA
• The dye interacts closely with the stacked bases

Question 7

What was used to denature DNA as one of the treatments applied in lab 1?

Answer 7

• Sodium hydroxide was used
• It disrupts the hydrogen bonding that occurs between the bases which is required to stabilize and join the two strands of DNA together

Question 8

What was the purpose of the ethanol used in lab 1?

Answer 8

• Ethanol was used to “clean” the DNA on the glass rod and wash it of any remaining proteins or lipids and salts attached to the surface of the DNA

Question 9

What are the general purposes of plasmids found in bacteria during lab 2?

Answer 9

• Usually contain genes for traits that are not essential for the survival of the bacteria but may be beneficial for the bacterium

Question 10

What does the term “transformation” signify during lab 2?

Answer 10

• The process in which a bacterial cell takes up DNA from its environment

Question 11

What were the 5 different DNA sequence elements found in the pGLO plasmid?

Answer 11

• Origin of replication - bacterial DNA sequences that are required for replicating the plasmid prior to cell division
• GFP gene - originally a DNA sequence from a jellyfish that provides the proteins for GFP
• Promotor - DNA sequence from a bacterial gene promotor that allows for the production of mRNA from the GFP gene
• Inducer (araC) - DNA sequence from a bacterial gene regulatory operator that allows transcription of the GFP gene only when the sugar arabinose is present
• Selectable marker (ampR) - DNA sequence from a bacterial source that allows the transformed bacterium to make an enzyme that catalyzes the breakdown of ampicillin, an antibiotic that normally prevents E. coli from growing (i.e., allows the bacteria to continue growing)

Question 12

What components of DNA does radiation interact with?

Answer 12

• It interacts with the bonding of the nitrogenous bases, causing them to change their chemical structure and bind to other bases

Question 13

Why was yeast used in the UV radiation experiment?

Answer 13

• Yeast is a unicellular eukaryote, so it shares many of the same molecular processes found in human cells

Question 14

What are the main phases of mitosis?

Answer 14

• Interphase - the cell is growing and DNA is being replicated
• Prophase - replicated DNA condenses into chromosomes and gets attached to spindles
• Metaphase - the chromosomes align along the equator of the cell
• Anaphase - the chromosomes are then pulled apart to the separate poles of the cell
• Telophase and cytokinesis - organelles form and the chromosomes are enveloped into a nucleus again. Cleavage of cytoplasm occurs

Question 15

How do increased concentrations of caffeine affect the rate of cell division in onion root tips?

Answer 15

• Increased concentrations of caffeine decrease the rate and productivity of mitosis, leading to cell death

Question 16

What was the purpose of the bacterial evolution experiment?

Answer 16

• Investigating the response of bacterial populations to increasing salinity in their environment using salinity gradient agar plates done over the course of three weeks
• E. aerogenes bacteria was used for this experiment

Question 17

What was the general impact of the treatments applied in the bacterial evolution experiment?

Answer 17

• With the exception to spontaneous mutations, they all increased the mutation rate of the bacteria, allowing for faster adaptability to the saline environment

Question 18

What’s the purpose of a Chi-square test?

Answer 18

• Used to determine the goodness of fit between the observed results and the expected results based on a hypothesis, and whether or not the results were impacted by other factors than chance alone

Question 19

What’s the null hypothesis used when performing a Chi-square test? What does the p-value signify?

Answer 19

• There will be no statistically significant difference in any differences we observe (no difference between observed and expected)
• The p-value helps determine how large the chi-square value needs to be in order to reject the null hypothesis

Question 20

What are the degrees of freedom and how are they calculated for the Chi-Square test?

Answer 20

• Used to indicate any variance within the data, any deviation from the sample mean
• Always one less than the number of categories of possible outcomes for a chi-square test

Question 21

How does a salinity gradient impact the growth and survival of organisms?

Answer 21

• Salts affect the osmotic balance of an organism as well as direct effects on proteins
• Only a few organisms can survive in extremely high-saline environments

Question 22

How was the bacteria treated prior to inoculation?

Answer 22

• The bacteria were inoculated into a nutrient broth and incubated at 30 degrees Celsius

Question 23

What’s some important genotype nomenclature?

Answer 23

• A/a = slash indicates the separation of alleles
• A/a; B/b = semi-colon indicates the separation of different traits

Question 24

What’s the difference between a metacentric chromosome and an acrocentric chromosome?

Answer 24

• Metacentric - has arms on either side of the centromere of equal length
• Acrocentric - has one arm longer on one side of the centromere than the other

Question 25

How do researchers determine which traits are recessive or dominant?

Answer 25

• By performing a monohybrid cross for the specific trait

Question 26

What are some of the primary differences between mitosis and meiosis?

Answer 26

• In mitosis, the alleles are not separated while in meiosis they are
• Meiosis also leads to the formation of new gametes

Question 27

What should a t-test be used for?

Answer 27

• Used to determine whether the difference between two measured means is in fact statistically significant, which then decides whether to reject or fail to reject the null hypothesis

Question 28

What are some important notes in regard to a t-test?

Answer 28

• Never say that the hypothesis is proven
• The larger the calculated t-value, the more likely it is that the difference between the two means is statistically significant
• Only 2 groups can be compared using a t-test
• Degrees of freedom can be calculated by (n(a) + n(b)) - 2