Cell Biology, Molecular Genetics, and Historical Trade Networks

Flashcards covering the cell cycle, DNA structure and replication, transcription, translation, gene regulation, cell differentiation, and historical Indian Ocean trade networks.

Which phases make up Interphase in the cell cycle?

Interphase consists of the $G_1$, $S$, and $G_2$ phases, during which the cell grows and prepares to divide.

During which specific phase of the cell cycle does DNA replication occur?

DNA replication occurs during the $S$ (Synthesis) phase of Interphase.

What cellular process does a single-celled zygote undergo to divide into two identical cells?

Mitosis.

What prior mercantile activity paved the way for the expansion of Islam across the Indian Ocean during the Postclassical Era?

Arab merchants had already been traveling to South Asia for centuries in search of trading partners before Islam expanded. Later, Muslim merchants connected these routes to Dar al-Islam, utilizing environmental knowledge and sailing technology to make the Indian Ocean an economic hot spot.

What three critical events must occur before a cell can split into two identical daughter cells?

1. The cell must grow in size.
2. It must copy each DNA molecule via DNA replication.
3. It must equally divide the chromosomes so each daughter cell receives a full set of DNA.

If a sample of DNA contains $23\%$ Adenine, what percentage of Thymine must it contain according to base-pairing rules?

The sample must contain $23\%$ Thymine because Adenine pairs equally with Thymine.

If a sample of DNA is determined to have $21\%$ Adenine, what percentage of Guanine does it contain?

It contains $29\%$ Guanine. Adenine ($21\%$) and Thymine ($21\%$) account for $42\%$ total; the remaining $58\%$ is split equally between Guanine ($29\%$) and Cytosine ($29\%$).

If one strand of a DNA molecule has the sequence ATA A AGC, what is the sequence of the complementary strand?

TATTTCG

If one strand of a DNA molecule reads AATAGCG, what is the sequence of the complementary strand?

TTATCGC

What is the monomer of a DNA molecule?

A nucleotide.

What structural name is given to the twisted ladder-like shape of DNA?

Double Helix.

Why is DNA replication classified as semi-conservative?

Because each newly formed double-stranded DNA molecule consists of one original (template) strand and one newly synthesized strand.

What are the sequential steps of DNA replication?

1. An enzyme breaks the hydrogen bonds between the two strands of a DNA molecule.
2. Each separated strand acts as a template while enzymes link floating complementary nucleotides to each side.
3. The process continues until both open strands form a complete, identical double-stranded DNA molecule.

What is chromatin, and during which phase of the cell cycle is it present?

Chromatin is the form of DNA found during Interphase, where DNA molecules are wound around histone proteins and are not condensed into visible X-shapes or bar-shapes.

How does a replicated DNA molecule appear in early M-phase prior to chromosome separation?

As an X-shaped chromosome composed of two identical sister chromatids joined at a centromere.

What is a gene?

A section of DNA that contains the coded instructions for building one specific protein.

What are the chronological steps a cell takes from interphase to complete division?

1. Grow to full size
2. Make a copy of the DNA
3. Condense the DNA into X-shaped chromosomes (two sister chromatids)
4. Split the sister chromatids apart to opposite sides of the cell
5. Split the cellular material (cytokinesis) into two daughter cells

What are the sequential steps of gene expression from DNA to protein?

1. Epigenetic acetylation loosens the DNA, allowing transcription factors and regulatory proteins to turn on the gene.
2. An enzyme uses the gene's DNA code to transcribe mRNA.
3. The mRNA exits the nucleus and travels to a ribosome.
4. The ribosome reads the mRNA sequence and links amino acids in order during translation.

What does the existence of non-numbered sections between genes in a genome indicate?

Not all DNA in a genome codes for genes; significant portions consist of non-coding regions.

How can cells with identical genomes (such as neurons and skin cells) have completely different structures and functions?

Different cell types express different subsets of genes, which are selectively turned on or off by unique transcription factors and regulatory proteins.

What primary structural factor causes osteocalcin and hemoglobin to perform completely different functions?

They have different sequences of amino acids, which cause them to fold into different three-dimensional shapes with unique functions.

What is the relationship between DNA, proteins, and organismal traits?

DNA contains the instructions that code for proteins, which directly influence or produce physical, metabolic, and hormonal traits.

What is the role of mRNA, and what does the 'm' stand for?

The 'm' stands for messenger. mRNA is a mobile copy of a gene synthesized during transcription that delivers genetic instructions from the nucleus to the ribosome for translation.

In what specific way does RNA polymerase function like helicase during transcription?

It unzips and unwinds the DNA double helix to read the template strand.

If a gene sequence reads ATA GCG AGC CGT, what mRNA molecule is produced, and how many amino acids will it yield?

The transcribed mRNA is UAU CGC UCG GCA, which codes for $4$ amino acids (one for each three-nucleotide codon).

What are six major functions carried out by different proteins in the body?

1. Transporting molecules (e.g., oxygen)
2. Fighting pathogens like bacteria
3. Acting as chemical messengers
4. Linking molecules together to build larger polymers
5. Detecting molecules or light
6. Breaking down nutrients (e.g., lactose)

What is cell differentiation?

The process by which an unspecialized stem cell transforms into a specific cell type through epigenetic modifications and targeted transcription factor activity.

What are the two primary reasons multicellular organisms undergo mitosis?

1. Growth (adding more cells)
2. Repair and tissue maintenance (replacing damaged, worn-out, or dead cells)

What is a mutation, and how can it lead to cancer?

A mutation is a change in the DNA sequence. If a mutation disrupts genes that regulate the cell cycle, the cell may ignore division checkpoints and divide uncontrollably.