HURDLE

Question 1

What is the relationship between nucleic acids and protein?

Answer 1

Nucleic acids encode instructions for the synthesis of proteins

This includes the structure of DNA and RNA, and the process of gene expression.

Question 2

Identify the type of nucleic acid represented by the sequence: 3’ TAC AGC TAG GGA CCG CCA 5’ and justify your answer.

Answer 2

DNA

The presence of ‘Thymine’ indicates it is DNA, as Thymine is not found in RNA.

Question 3

Describe one other difference between DNA and RNA nucleotides.

Answer 3

DNA nucleotides contain deoxyribose; RNA nucleotides contain ribose

This difference is crucial for their respective functions.

Question 4

State one structural similarity between DNA and RNA.

Answer 4

• Both have a sugar phosphate backbone
• Both are composed of nucleotides
• Both contain the bases cytosine, guanine, and adenine

These similarities highlight their roles as nucleic acids.

Question 5

Compare the roles of mRNA and tRNA in translation.

Answer 5

mRNA contains codons; tRNA has anticodons that carry amino acids

This interaction is essential for protein synthesis.

Question 6

How do the mRNA and amino acid sequences demonstrate that the genetic code is degenerate?

Answer 6

Codons GGC and GGU both code for the same amino acid

This shows that multiple codons can specify the same amino acid.

Question 7

True or false: If the same gene sequence is found in three different species, each would produce a different polypeptide.

Answer 7

FALSE

The genetic code is universal, so the same gene sequence produces the same polypeptide.

Question 8

In which type of cell does RNA processing occur?

Answer 8

Eukaryotes

Eukaryotes have introns and exons; prokaryotes do not.

Question 9

What occurs during splicing and why is it necessary before translation?

Answer 9

Introns are removed, and exons are joined

This ensures only the coding sequence is translated.

Question 10

State two other modifications that occur during RNA processing.

Answer 10

• A 5’ cap is added
• A poly-A-tail is added

These modifications enhance mRNA stability and translation efficiency.

Question 11

Explain how alternative splicing can result in a proteome larger than the number of genes.

Answer 11

Different combinations of exons produce multiple mRNA transcripts

This allows one gene to produce multiple proteins.

Question 12

What are amino acids in relation to polypeptide chains?

Answer 12

Monomers of a polypeptide chain

They are the building blocks that form proteins.

Question 13

Identify the highest level of protein structure shown in Rubisco.

Answer 13

Quaternary structure

Rubisco consists of multiple polypeptide sub-units.

Question 14

Name two types of secondary structure likely present in Rubisco.

Answer 14

• Beta-pleated sheets
• Alpha helices

These structures are stabilized by hydrogen bonds.

Question 15

What type of bond stabilizes secondary structures?

Answer 15

Hydrogen bond

These bonds are crucial for maintaining protein structure.

Question 16

How could a mutation changing one amino acid in the primary structure affect Rubisco?

Answer 16

It alters R-group interactions during folding

This can change the protein’s three-dimensional shape and function.

Question 17

What change in protein shape can occur at high temperature?

Answer 17

Denaturation

This process disrupts weaker bonds, altering protein structure.

Question 18

Why is Rubisco’s primary structure usually unchanged by denaturation?

Answer 18

Peptide bonds are strong covalent bonds

Denaturation disrupts weaker bonds, not peptide bonds.

Question 19

Identify one factor, other than temperature, that may result in a change in protein shape.

Answer 19

• Extreme pH
• Detergents
• Organic solvents
• High salt concentration
• Radiation
• Heavy metals

These factors can also lead to denaturation.

Question 20

Suggest three other general functional categories of proteins.

Answer 20

• Immunological (e.g., antibody)
• Signalling molecule (e.g., hormone)
• Structural protein (e.g., cytoskeleton)

These categories highlight the diverse roles of proteins.

Question 21

Complete the flow chart for the pathway of a protein destined for secretion.

Answer 21

Ribosome → Rough endoplasmic reticulum → transport vesicle → Golgi body → secretory vesicle → Secretion (exocytosis)

This pathway outlines the protein secretory pathway.

Question 22

Describe the role of the rough endoplasmic reticulum in protein processing.

Answer 22

Ribosomes synthesize polypeptides, which enter the lumen for folding and modification

This is the initial step in protein processing.

Question 23

Describe the role of the Golgi apparatus in protein processing.

Answer 23

Receives proteins from transport vesicles, modifies, sorts, and packages them

This is crucial for proper protein secretion.

Question 24

What advantage does E. coli gain from regulating the production of tryptophan?

Answer 24

Conserves energy/resources

This regulation allows E. coli to adapt to environmental conditions.

Question 25

What is the role of the **promoter** in transcription?

Answer 25

Region where RNA polymerase binds to initiate transcription ## Footnote This is essential for starting the transcription process.

Question 26

What is the role of the **operator** during repression of the trp operon?

Answer 26

Site where the activated repressor binds, blocking RNA polymerase ## Footnote This prevents transcription of structural genes.

Question 27

How does **tryptophan** act as a co-repressor during repression of the trp operon?

Answer 27

Binds with the repressor protein to activate it ## Footnote This allows the repressor to bind to the operator and block transcription.

Question 28

Name the second regulatory mechanism used to regulate the production of tryptophan.

Answer 28

Attenuation ## Footnote This mechanism involves the formation of hairpin structures in mRNA.

Question 29

What hairpin structure forms when tryptophan levels are high?

Answer 29

Terminator hairpin ## Footnote This structure regulates transcription by causing RNA polymerase to detach.

Question 30

Explain the significance of the two tryptophan codons in region 1 of the leader sequence.

Answer 30

Act as a sensor of tryptophan levels ## Footnote Their presence influences the formation of hairpin structures that regulate transcription.

Question 31

How does preventing transcription of structural genes in the trp operon prevent the synthesis of **tryptophan**?

Answer 31

Without transcription, enzymes for tryptophan synthesis are not produced ## Footnote This halts the synthesis pathway for tryptophan.

Question 32

True or false: A **nucleotide** with the subunit labelled uracil can be found in DNA.

Answer 32

FALSE ## Footnote Uracil is present in RNA, not DNA.

Question 33

True or false: A **nucleotide** with the subunit labelled thymine will have a pentose sugar subunit.

Answer 33

TRUE ## Footnote All DNA nucleotides contain a pentose sugar (deoxyribose).

Question 34

What are the components of **DNA nucleotides**?

Answer 34

* phosphate group * deoxyribose sugar * nitrogenous base (A, T, C, G) ## Footnote RNA uses uracil instead of thymine.

Question 35

In an experiment investigating the effect of different temperatures on DNA structure, what is the **independent variable**?

Answer 35

temperatures at which the experiment is conducted ## Footnote The independent variable is manipulated by the scientist.

Question 36

What marks the **end of transcription** in eukaryotic cells?

Answer 36

RNA polymerase reaches a termination sequence on the DNA template ## Footnote At this point, RNA polymerase detaches and the mRNA strand is released.

Question 37

How many **codons** are required to code for 100 amino acids?

Answer 37

100 ## Footnote Each codon codes for one amino acid.

Question 38

What are the modifications that occur during **mRNA processing**?

Answer 38

* removal of introns * joining of exons * addition of a 5′ cap * addition of a poly-A tail ## Footnote These modifications result in a mature mRNA molecule.

Question 39

What is an **operon**?

Answer 39

A cluster of genes under the control of a single promoter, transcribed together into mRNA ## Footnote This is a feature of prokaryotic gene regulation.

Question 40

What is the difference between **repression** and **attenuation** in gene regulation?

Answer 40

* Repression: activated repressor binds to operator, blocking transcription * Attenuation: transcription stops early due to hairpin loop formation ## Footnote Both mechanisms occur when tryptophan levels are high.

Question 41

What group of biological monomers does **tryptophan** belong to?

Answer 41

amino acid ## Footnote Tryptophan contains an amine group, a carboxyl group, and a variable R group.

Question 42

What is an organism's **proteome**?

Answer 42

The complete set of proteins produced by that organism or by a particular cell type ## Footnote Different cell types express different sets of genes, leading to diverse functions.

Question 43

What is the **primary structure** of a protein?

Answer 43

amino acid sequence ## Footnote This is the first level of protein structure.

Question 44

What is the **secondary structure** of a protein?

Answer 44

local folding (α-helix / β-sheet) ## Footnote This involves the initial folding of the polypeptide chain.

Question 45

What is the **tertiary structure** of a protein?

Answer 45

full 3D folding ## Footnote This describes the overall shape of a single polypeptide chain.

Question 46

What is the **quaternary structure** of a protein?

Answer 46

multiple polypeptides ## Footnote This structure involves the assembly of multiple polypeptide chains.

Question 47

What is the **typical protein secretion pathway**?

Answer 47

* RER * Golgi * vesicle * plasma membrane ## Footnote This pathway outlines the general route proteins take for secretion from the cell.

Question 48

Fill in the blank: **Ovalbumin** is synthesized in the __________.

Answer 48

rough endoplasmic reticulum ## Footnote This is the site where ovalbumin is produced before being transported to the Golgi apparatus.

Question 49

What are the roles of the **Golgi apparatus** in protein export?

Answer 49

* Modification of proteins * Packaging into vesicles ## Footnote The Golgi apparatus is crucial for processing proteins before they are secreted.

Question 50

What process releases ovalbumin from the plasma membrane?

Answer 50

Exocytosis ## Footnote This is the mechanism by which proteins are expelled from the cell.

Question 51

What is the role of **single guide RNA (sgRNA)** in the CRISPR-Cas9 system?

Answer 51

To direct the cutting of DNA ## Footnote sgRNA binds to Cas9 and guides it to the target DNA sequence for cleavage.

Question 52

In the CRISPR-Cas9 system, what is created when a bacteriophage infects bacteria?

Answer 52

Spacers of viral DNA ## Footnote These spacers are inserted into the CRISPR array, providing a genetic memory of the virus.

Question 53

Which hypothesis would Charpentier and Doudna likely propose regarding **CRISPR-Cas9 technology**?

Answer 53

CRISPR-Cas9 can be guided to edit DNA by combining crRNA and tracrRNA into a single guide RNA ## Footnote This hypothesis is supported by experimental results showing the necessity of guide RNA for DNA targeting.

Question 54

What is the significance of **gel electrophoresis** in the context of CRISPR-Cas9?

Answer 54

To interpret DNA fragment patterns ## Footnote Gel electrophoresis helps visualize whether DNA has been successfully cut by CRISPR-Cas9.

Question 55

What ethical concern is raised regarding **intensive farming methods**?

Answer 55

Welfare of chickens ## Footnote Intensive farming can lead to stress and injury due to overcrowded conditions.

Question 56

What is a feasible solution to improve **animal welfare standards**?

Answer 56

Provide larger living spaces and stricter regulations ## Footnote This approach aims to ensure humane treatment of chickens in farming.

Question 57

What does the ethical concept of **non-maleficence** entail?

Answer 57

Avoiding harm ## Footnote This principle emphasizes minimizing harm to animals in farming practices.

Question 58

What is the role of **DNA ligase** in recombinant DNA technology?

Answer 58

Joins the human insulin gene to the plasmid DNA ## Footnote DNA ligase forms phosphodiester bonds, creating recombinant plasmids.

Question 59

What is the outcome when **amino acid chains A and B** combine?

Answer 59

A functional insulin protein ## Footnote This combination is essential for producing active insulin.

Question 60

What is the definition of a **transgenic organism**?

Answer 60

Contains genes from another species ## Footnote This definition applies to organisms modified through recombinant DNA technology.

Question 61

What is a common mistake students make when interpreting **DNA profiling**?

Answer 61

Comparing offspring directly to possible fathers without identifying maternal bands ## Footnote Proper analysis requires recognizing which bands are inherited from the mother.