BIOL 3000- Genetics, Dr. S. Exam 3

Which of the following statements is true regarding euchromatin and

heterochromatin?

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and transcriptionally inactive.

What is the most likely effect of a mutation in the promoter region of a gene?

It can alter the binding of transcription factors or RNA polymerase, leading to increased or decreased gene expression.

*Expect there to be like this on your exam where something goes wrong with a component of DNA and having to know the effect. Ex what would happen if Preinitiation Complex stopped working?

Which of the following correctly describes the difference between the coding strand and the template strand in DNA transcription?

The coding strand has the same sequence as the mRNA (except for uracil replacing thymine), while the template strand is used by RNA polymerase to synthesize RNA.

You are a part of a research team and discover 2 nucleosomes. How many total histones and how many core histones are there?

18 total histones and 16 core histones

You are a part of a research team and find a new nucleosome in a polar bear. If your team has found it to be identical to that of a human, what are the amounts and components of the histone?

2 H2A, 2 H2B, 2H3, 2H4, and H1

DNA undergoes multiple levels of compaction to fit within the nucleus, involving interactions between histones and higher-order folding mechanisms. This process ensures proper genome organization and regulation of gene expression. Which of the following are true about the levels of DNA compaction, including nucleosome formation, solenoid, zig-zag model, chromatin loops, and condensed chromatin?

A) The nucleosome is the fundamental unit of DNA compaction, consisting of DNA wrapped around 8 of core histones and 1 linker histone.

B) The solenoid and zig-zag models describe two possible arrangements of nucleosomes in the 30 nm chromatin fiber.

C) Chromatin loops are formed by interactions between topoisomerase II compacting DNA into a functional nuclear architecture.

D) None of the above.

E) All of the above.

DNA undergoes multiple levels of organization at different points in the cell cycle to ensure proper genome function, ranging from chromatin loops to the highly condensed metaphase chromosome. These structural changes are essential for processes such as gene regulation, replication, and cell division. Which of the following are true about the differences between chromatin loops and the metaphase chromosome?

A. Only Chromatin Loops use Topoisomerase II

B. Chromatin loops and metaphase chromosome share the same level of compaction

C. metaphase chromosomes use only Topoisomerase II to reach its level of compaction of 700nm

D. All the above

E. None of the above

The nucleosome model represents the fundamental level of DNA organization, where DNA is wrapped around histone proteins to form chromatin. The structure and compaction of chromatin vary throughout the cell cycle, influencing gene expression and accessibility to regulatory factors. What stage of the cell cycle is the nucleosome model most likely to be first observed in?

The nucleosome model is most prominent during G1 when chromatin remains in a relatively decondensed state for transcription and replication.

Which is the correct order of proteins involved in the initiation of transcription in eukaryotic cells?

The transcription factors recruit RNA Polymerase II complex, to start transcription.

Which of the following statements best describes the role of alternative splicing in humans?

Alternative splicing allows a single gene to produce multiple protein isoforms by varying the inclusion or exclusion of exons.

Which of the following classes of nucleotide sequences is paired with the incorrect definition or property?

Highly Repetitive nucleotide sequences includes some coding and some noncoding regions

Which of the following types of nucleotide sequences is paired with the correct definition or property?

A. Solitary Genes: Dysfunctional relatives of genes that have lost their function. Pseudogenes definition

B. Pseudogenes: Set of several similar genes, formed by the duplication od a single original gene, and generally with similar biochemical functions. Multigene family definition

C. Repeated Genes: two copies in a diploid situation. Solitary genes definition

D. Multigene families: Multiple copies of small genes clustered throughout the genome at specific sites. Repeated genes definition

E. Duplicated Genes: Process by which a paralog gene is produced. ANSWER to the question

What is the role of the lariat formation in the splicing of pre-mRNA during transcription, and how does it contribute to the removal of introns?

It facilitates the removal of introns by forming a looped structure due to the association of U2 and U6 that is excised during splicing.

Which of the following transcriptional processes only occur post transcriptionally?

3' Polyadenylation

You and a group of scientists are observing a strange piece of RNA that lacks a 5' Cap. What is/are the fate(s) of this MRNA molecule?

A)Will not be recognized by the 40s ribosome

B)Will be degraded in the cytoplasm

C)A and B

What is the function of Histone Acetyltransferase (HAT) in gene expression regulation?

It adds acetyl groups to histones, leading to a more relaxed chromatin structure and increased transcription.

What is the function of Histone Deacetylase (HDAC) in gene expression regulation?

It removes acetyl groups from histones, leading to chromatin condensation and transcriptional repression.

What is the order of compaction from least to most compact?

I, III, II, IV

Which of the following best describes the differences between mRNA, hnRNA, and tRNA?

mRNA carries the genetic code for protein synthesis, hnRNA is the precursor to mRNA, and tRNA helps translate mRNA into protein

What is the C-value paradox in genetics?

It describes the lack of correlation between genome size and organism complexity.

What stage of the cell cycle does translation occur in?

G1 and G2

Which of the following correctly describes the different sites in the 60S ribosomal subunit during translation in eukaryotes?

The A site binds to the mRNA, the P site holds the tRNA carrying the growing polypeptide chain, and the E site releases the tRNA.

Which of the following statements about termination is true?

A) A release factor binds to the stop codon, causing the ribosome to release the polypeptide chain.

B) Termination occurs when the ribosome reaches the start codon, signaling the end of translation.

C) The ribosome continues translating the mRNA until it reaches a stop codon then brings in the complementary Amino Acid.

D) A tRNA with an anticodon complementary to the stop codon enters the A site to release the polypeptide chain.

mRNA sequence:5' - AUG GCU UAA - 3'

Is there a START codon present?

Is there a STOP codon present?

How many amino acids will be added and what is the sequence?

What is the anticodon sequence of the individual tRNAs?

- Yes, AUG

- UAA

- 2 and methionine (met), alanine (ala)

- For AUG (Start codon), the anticodon is 3'- UAC- 5'

- For GCU (codon for alanine), the anticodon is 3'- CGA- 5'.

Given the following template strand of DNA, what will be the effect on the amino acid sequence if the reading frame is shifted by +1?

Template strand:5' - TAC GGC ATG TAA - 3'

A +1 frameshift occurs when the ribosome shifts its reading frame by one nucleotide to the right (3' end) during translation. This means that the codons are read starting one nucleotide later than the original frame.

What kind of bond holds the amino acids together in the P site of the ribosome during translation?

Peptide Bond

Which of the following correctly pairs the secondary protein structure with its definition?

Alpha helices - Loops of polypeptide chains that allow for sharp turns, often found connecting regions of secondary structure.

Which of the following best describes the activation step in translation?

The amino acid is covalently attached to its corresponding tRNA by the enzyme aminoacyl-tRNA synthetase, preparing it for use in translation.

Which of the following statements about protein structure is false?

Secondary structure - The overall 3D shape of the protein, stabilized by interactions between side chains.

Which of the following correctly describes the components of an individual amino acid?

A) An amino acid consists of a carboxyl group, an amino group, a central carbon, and a side chain (R group) that varies between different amino acids.

B) An amino acid consists of a carboxyl group, a hydrogen atom, and a nitrogen atom that forms the side chain.

C) An amino acid consists of a phosphate group, a carboxyl group, and a ribose sugar.

D) An amino acid consists of an amino group, a hydroxyl group, and a variable peptide bond sequence

Where are hydrophilic amino acids likely to be found in the tertiary structure of a protein?

On the exterior of the protein, interacting with the surrounding water or aqueous environment.

Where does the peptide bond form between two amino acids?

Between the amino group of one amino acid and the carboxyl group of another amino acid.

Which of the following accurately describes the difference between protein domains and motifs?

Domains are independent, stable, and functional units of a protein, whereas motifs are short, specific sequences that contribute to a protein's overall structure.