Molecular Biology and Genetics Fundamentals | Scholarly

What constitutes the genome of an organism?

All the genetic content of an organism, encompassing the complete set of DNA sequences that define its hereditary information.

What is supercoiling in the context of bacterial DNA?

The condensation of bacterial DNA through twisting, which compacts the genome into a manageable size within the cell.

How is euchromatin characterized in terms of structure and function?

Decondensed DNA strands that are accessible to enzymes and transcription factors, allowing for active gene expression.

What are the components and structure of a nucleosome?

A core chromatin unit formed by $8$ histone protein subunits with DNA wrapped around them approximately $1.65$ times.

Define a gene as it relates to molecular biology.

A particular stretch of nucleotides that produce a protein product when translated by a cell.

What is the role of a promoter in DNA?

It is the DNA region where RNA polymerase binds to initiate transcription, allowing for control over gene expression.

What are introns?

Regions within a gene that are not translated into protein and are spliced out during mRNA processing.

Define epigenetics according to the lecture notes.

Heritable changes in gene expression that occur without altering the DNA sequence, such as DNA methylation or histone modification.

What is the maximum rate of an enzymatic reaction called?

$V_{max}$, which occurs when all active sites of the enzyme are saturated with substrate.

Define $K_m$ in enzyme kinetics.

The substrate concentration at which the reaction velocity is $50\%$ of $V<em>{max}$; lower $K</em>m$ indicates higher affinity.

What does $K_{cat}$ measure?

The catalytic efficiency of an enzyme, defined as the number of substrate molecules turned over by a single enzyme molecule per unit time.

Describe heterochromatin.

Condensed DNA that is typically inaccessible to enzymes and transcription factors, thereby silencing gene expression.

What is an operator in prokaryotic gene regulation?

A DNA region where repressor proteins bind to inhibit transcription, often found in operons like the lac operon.

Define polycistronic mRNA.

A single mRNA transcript common in bacteria that encodes for two or more separate proteins.

What are transposons?

Known as "jumping genes," these are mobile DNA sequences that can relocate within the genome and cause mutations.

Contrast synonymous and non-synonymous point mutations.

Synonymous mutations are silent and result in the same amino acid, while non-synonymous mutations result in an amino acid change (missense) or a premature stop (nonsense).

What are germline mutations?

Changes in cells producing gametes that are heritable to offspring, as opposed to somatic mutations.

Define ploidy and provide examples.

The number of chromosome sets in a cell, such as haploid ($1$ set) or diploid ($2$ sets).

What is heterosis?

Also known as hybrid vigor, it is the phenomenon where progeny outperform parental genotypes due to allele complementation.

Compare the primary purposes of mitosis and meiosis.

Mitosis produces identical daughter cells for growth and repair, while meiosis halves chromosome numbers for gamete production and introduces genetic variation.

What is a locus?

The specific position of a gene on a chromosome, used as a standard reference for mapping alleles and traits.

Define RuBisCO and its role in carbon fixation.

Ribulose $1,5$-bisphosphate carboxylase/oxygenase; it is the most abundant enzyme and catalyzes $CO_{2}$ fixation in the Calvin cycle.

What is a pyrenoid?

A subcellular structure in algae that contains RuBisCO, scaffolding proteins, and carbonic anhydrase to boost photosynthetic efficiency.

What is the difference between weathering and mineralization?

Weathering is the physical/chemical breakdown of rocks releasing nutrients like phosphorus, while mineralization is the microbial conversion of organic nutrients to inorganic forms.

Identify the major greenhouse gases (GHGs) associated with farming.

$N<em>{2}O$ (from soil and manure), $CH</em>{4}$ (from livestock and manure), and $CO_{2}$ (from energy and land use).