BIOL4210 Lecture 1: Cell & Molecular Biology – Key Concepts

A set of practice questions (Q&A flashcards) covering the main concepts from BIOL4210 Lecture 1 videos: universal features of cells, genome diversity, and model organisms.

What are the three domains of life in the three-domain system?

Bacteria (eubacteria), Archaea, and Eukaryotes.

How were the domains organized into a tree of life in the lecture notes?

By comparing ribosomal RNA sequences across species to estimate evolutionary differences.

What is the central claim of cell theory highlighted in the notes?

All life is cellular; everything is made of cells and life begins as a single cell.

What is the primary function of the plasma membrane?

To enclose the cell, regulate entry and exit of materials, and host receptors for stimuli.

What is considered the universal hereditary material and genetic language in cells?

DNA; same genetic code used across organisms; RNA transcripts are produced via transcription.

Define transcription and translation.

Transcription: DNA is copied into RNA. Translation: RNA is used to synthesize proteins; the machinery is highly conserved.

What nucleotides make up DNA and what are the base-pairing rules?

Adenine (A), Thymine (T), Cytosine (C), Guanine (G); A pairs with T, G pairs with C.

Describe the structure of double-stranded DNA.

Two strands form a double helix with a sugar-phosphate backbone on the outside and bases paired inside.

How is a gene defined in this course?

A region of DNA that codes for a distinct RNA molecule, which may be translated into a protein (including noncoding RNAs).

What does the genome refer to?

The total genetic information of a cell, including genes and noncoding DNA.

What is the approximate minimal number of genes required for a viable cell and the core set shared by all life?

About 300 genes in total are needed; a core set of about 60 genes is shared by all living species.

What is a gene family?

A set of genes related by DNA sequence due to derivation from the same ancestral gene.

What is gene duplication and why is it important?

Copying of an existing gene, creating gene families; can lead to new functions over time.

Give the approximate genome size and gene count for E. coli.

About 4.6 million base pairs and ~4,300 genes; roughly 11% of the genome is noncoding.

Give the approximate genome size and gene count for the human genome.

About 3.2 billion base pairs and ~30,000 genes (roughly 20,000 coding); ~98.5% noncoding.

Why is Saccharomyces cerevisiae (yeast) a useful model organism?

A minimal eukaryote with a small genome, mitochondria, haploid/diploid life cycles, and well-defined mutants; useful for studying cell cycle and basic eukaryotic processes.

Why is Arabidopsis thaliana used as a plant model organism?

Small, easily grown, rapid generation time, and numerous offspring; widely used to study plant biology, including circadian rhythms.

Why is Caenorhabditis elegans (C. elegans) used as a model organism?

Tiny, with a defined somatic cell count (~959), transparent for imaging, used to study aging, development, and nervous system.

Why is Drosophila melanogaster used as a genetic model organism?

Long history in genetics; large, banded chromosomes; many mutants; short generation time (~9 days); fewer gene duplicates.

Why are Zebrafish used as a model organism?

Transparent embryos for early development studies; compact genome (~half the size of humans); rapid generation; easy genetic engineering.

What are Xenopus species and why are they used in research?

Frogs used for embryonic development studies; large eggs easy to manipulate; embryos develop outside the mother; Xenopus tropicalis is diploid, laevis is not.

Why are mice considered a predominant mammalian model organism?

Inbred strains with high genetic similarity; mammals share similar anatomy; highly relevant to human biology and well-established genetics.

What ethical rationale supports using model organisms and cell lines?

They allow answering research questions without experimenting on humans, addressing ethical concerns.

What is lysozyme and its function as an enzyme?

Lysozyme hydrolyzes the polysaccharide chains in bacterial cell walls, causing lysis; an early enzyme studied by X-ray crystallography.

What does autocatalysis mean in the context of cellular biology?

Life as an autocatalytic, self-replicating process where DNA/RNA guide the production of proteins and more nucleotides, enabling growth.

What is a key difference between eukaryotic and prokaryotic gene structure mentioned in the notes?

Eukaryotes have introns and exons; prokaryotes generally do not.