Molecular Biology: DNA & RNA Polymerases

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Questions and Answers

What happens to the epigenome of monozygotic twins as they grow older?

It becomes identical to their parents' epigenome.

It becomes more identical over time.

It remains unchanged throughout life.

It diverges due to different lifestyles. (correct)

What does Mendel’s law of independent assortment imply about unlinked genes?

They can influence each other's inheritance.

They always assort together during gamete formation.

Their allele presence in a gamete is unrelated. (correct)

They are located on the same chromosome.

What conclusion was drawn from Martha Chase and Alfred Hershey's experiment using radioactive isotopes?

Both DNA and protein can carry genetic information.

Isotopes have no role in genetic material identification.

Proteins are the genetic material.

DNA, not protein, is the genetic material. (correct)

How did Chargaff’s findings challenge the tetranucleotide hypothesis?

It showed that base ratios vary across different species. Signup and view all the answers

What is the application of knockout technology in gene editing?

To target specific genes for removal or replacement. Signup and view all the answers

What is the orientation of the two strands in the DNA double helix?

One strand runs 5’ to 3’, and the other runs 3’ to 5’ Signup and view all the answers

Which base pairs are correctly matched according to their type?

Adenine-Thymine and Cytosine-Guanine Signup and view all the answers

What structure holds the nucleosome together?

H1 histone Signup and view all the answers

What is the main role of highly conserved DNA sequences?

They require natural selection to maintain essential gene products Signup and view all the answers

Why is cell proliferation critical in organisms?

It contributes to growth, tissue repair, and cell replacement Signup and view all the answers

During which subphase of interphase does DNA replication occur?

S phase Signup and view all the answers

How do cyclins regulate the cell cycle?

By changing in concentration to trigger checkpoints Signup and view all the answers

What might slow rates of mutation in certain DNA regions lead to over time?

Preservation of closely related gene sequences Signup and view all the answers

What role do cyclins play in the cell cycle?

They phosphorylate target proteins in conjunction with CDKs. Signup and view all the answers

How do mutations in proto-oncogenes contribute to cancer?

They can turn into oncogenes, leading to excess cell proliferation. Signup and view all the answers

What differentiates malignant tumors from benign tumors?

Malignant tumors can invade neighboring tissues while benign tumors cannot. Signup and view all the answers

What is the primary level of control for gene expression?

Transcription regulation via RNA polymerase binding. Signup and view all the answers

What factor can influence the longevity and expression levels of a gene?

The degradation rate of mRNA molecules. Signup and view all the answers

Which statement accurately describes the genome and its components?

The genome contains both coding and non-coding DNA. Signup and view all the answers

Which component of gene expression plays a critical role in the assembly of proteins?

Messenger RNA (mRNA). Signup and view all the answers

What is a characteristic feature of metastatic tumors?

They arise from cells that have traveled from a primary tumor site. Signup and view all the answers

What role does lactose play in the regulation of the lac operon?

It converts to allolactose, which changes the shape of the lac repressor. Signup and view all the answers

How does estradiol influence gene expression?

It binds to a receptor in the cytoplasm, forming a hormone-receptor complex. Signup and view all the answers

What is the effect of methylation on gene expression in relation to epigenetics?

It represses transcription by methylating cytosine in promoter regions. Signup and view all the answers

Which of the following statements about epigenetic changes is true?

They can affect phenotype without changing genotype. Signup and view all the answers

What was the finding from Meany's work on rats related to maternal care?

Maternal care type influenced epigenetic changes in subsequent generations. Signup and view all the answers

What is characteristic of imprinted genes?

They inherit only one working copy, with one allele silenced. Signup and view all the answers

What is a consequence of environmental effects on epigenetics mentioned in the content?

Widespread decrease in DNA methylation from air pollution. Signup and view all the answers

What is the impact of paternal versus maternal imprinting according to the genetic conflict hypothesis?

Paternal imprinting favors larger offspring, while maternal imprinting favors smaller offspring. Signup and view all the answers

which genotype would normally found in a gamete?

RS Signup and view all the answers

What is the role of a "promoter" in the process of transcription?

It serves as the starting point for RNA polymerase to bind and initiate transcription Signup and view all the answers

Which of the following statements about the promoter is true?

It is part of the gene's regulatory region but not transcribed into RNA Signup and view all the answers

How are the genome and proteome connected?

The genome directly determines the specific proteins produced, while the proteome is the actual set of proteins present in a cell at a given time Signup and view all the answers

Which of the following best describes the proteome?

The complete collection of proteins actively expressed in a cell or organism at a given time Signup and view all the answers

Study Notes

DNA and RNA Polymerases

Polymerases catalyze phosphodiester linkage between nucleotides
DNA structure is antiparallel (5' to 3' and 3' to 5')
5' to 3' direction ensures accurate sequence copying during replication, transcription, and translation
Purine (A-T) and pyrimidine (C-G) base pairs maintain consistent DNA helix structure
Nucleosome structure: histone octamer wrapped by chromatin, with H1 histone holding the core together; linker DNA connects nucleosomes

DNA Sequences and Conservation

Highly conserved DNA sequences remain similar over evolutionary time, often related to conserved gene products essential for survival
Conservation may also be due to slower mutation rates in certain regions
Cell proliferation is essential for growth, tissue repair, and replacement

Cell Cycle Regulation

Cyclins are regulatory proteins that control the cell cycle
Cyclin concentrations fluctuate during the cell cycle
Cyclins bind to cyclin-dependent kinases (CDKs) to regulate cell cycle checkpoints.
Phosphorylation by the cyclin-CDK complex activates or deactivates target proteins, acting as an on/off switch

Gene Expression

Gene expression is primarily controlled at the level of transcription, particularly affecting which mRNA is made from a gene.
Transcription factors bind to enhancer sequences on DNA and ultimately modulate how much mRNA is produced
Gene expression can also be controlled by regulating translation by mRNA degradation rates

DNA Replication and Gene Expression

The genome contains all genetic info, including coding and non-coding DNA
The transcriptome is the set of all RNA transcripts (mRNA, rRNA, tRNA)
The proteome is the set of all proteins
Gene expression differences explain cellular differentiation

Lactose and the Lac Operon

Lactose influences gene expression in prokaryotes (e.g. the Lac operon)
The Lac operon regulates lactose uptake and metabolism
Absence of lactose: the lac repressor prevents transcription
Presence of lactose: allolactose binds to the repressor, changing its shape, allowing transcription

Hormone Steroids and Epigenetics

Steroid hormones (e.g., estradiol) are lipid-soluble; easily passing lipid bilayer
Hormone-receptor complex binds to specific DNA sequences, altering gene expression
Epigenetics involve phenotypic changes without altering nucleotide sequences.
Methylation of cytosine (in DNA promoters) or amino acids (in histone proteins) affects transcription

Imprinting and Gene Expression

Imprinted genes (one maternal or paternal copy is silenced)
Epigenetic changes during gamete development can affect offspring
Genetic conflict hypothesis: imprinting arose from competition for maternal resources during development

DNA and Gene Editing

Radioactive isotopes (e.g., Phosphorus, Sulfur) can be used to study DNA and protein function
The experiment of Hershey and Chase demonstrated that DNA is the genetic material
Gene editing technologies (e.g., Knockout technology, CRISPR-Cas9) allow the manipulation of DNA
Random assortment and orientation of homologous chromosomes contribute to genetic variation

Mendel's Laws

Mendel's Law of Segregation: alleles separate during gamete formation.
Mendel's Law of Independent Assortment: allele combinations of different genes are independent.

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Description

This quiz covers essential topics in molecular biology, focusing on the roles of DNA and RNA polymerases in catalyzing nucleotide linkage and the structure of nucleotides. Additionally, it discusses the conservation of DNA sequences and the regulation of the cell cycle by cyclins. Test your understanding of these critical concepts!