Biology 1030 Unit 3: DNA, Genes, and Cell Division

Comprehensive vocabulary flashcards covering the structure of DNA, gene function, transcription and translation, gene regulation, mutations, the cell cycle, DNA replication, mitosis, and meiosis based on the Biology 1030 lecture notes.

Nucleotide

The basic building block of DNA, composed of three components: a phosphate group, a deoxyribose sugar, and a nitrogenous base (adenine, thymine, cytosine, or guanine).

Complementary Base Pairing

The rule in DNA structure where adenine (A) on one strand pairs via hydrogen bonding specifically with thymine (T) on the opposing strand, and guanine (G) pairs with cytosine (C).

Chromatin

The nuclear complex formed by DNA and all the associated proteins (such as histones) attached to it.

Gene

A specific sequence or stretch of DNA nucleotides that holds instructions to code for a protein; in humans, genes average a length of $3,000$ nucleotides.

Dystrophin

The protein coded by the longest gene in human DNA ($2.4\text{ million}$ nucleotides); it aids in muscle contractions, and defects in it are linked to muscular dystrophy.

Alleles

Different versions of the same gene that code for the same trait, originating from minor differences in their nucleotide sequences.

Introns

Noncoding sections of DNA located within a gene that are transcribed into RNA but spliced out and removed before translation.

Exons

The protein-coding regions of a gene that are spliced together to form the mature messenger RNA used in translation.

Genome

A complete set of chromosomes or the entire genetic material contained within an organism.

Central Dogma of Biology

The two-step biological process of producing functional proteins from genetic instructions in DNA via transcription and translation.

Transcription

The process occurring inside the nucleus where RNA polymerase unwinds DNA and matches complementary RNA nucleotides to synthesize a single-stranded messenger RNA (mRNA) copy of a gene.

Translation

The process where ribosomes bind mRNA outside the nucleus and read its codons three nucleotides at a time to assemble amino acids into a polypeptide chain.

Template Strand

The single strand of double-stranded DNA that RNA polymerase binds to and reads during transcription to synthesize an mRNA copy.

Promoter

A specific, non-transcribed DNA sequence located upstream of a gene that acts as a recognition landing site for RNA polymerase.

Terminator

A specialized DNA sequence situated downstream of a gene that signals RNA polymerase to stop transcribing.

Codon

A sequence of three consecutive nucleotides on an mRNA strand that specifies a single amino acid or a stop signal.

Transfer RNA (tRNA)

A highly folded T-shaped RNA molecule that carries a specific anticodon on one end and its corresponding amino acid on the other end to deliver to the ribosome.

Start Codon (AUG)

The mRNA codon sequence AUG, which codes for the amino acid methionine (Met) and instructs the ribosome to initiate translation.

Gene Expression

The active process by which a gene's coded information is transcribed into mRNA and translated into a functional protein.

Transcription Factors

Regulatory proteins that bind directly to DNA sequences near gene promoters to either recruit (activators) or block (repressors) RNA polymerase.

Activators

Transcription factors that turn genes on by assisting RNA polymerase in binding to promoters to initiate transcription.

Repressors

Transcription factors that turn gene expression off by blocking RNA polymerase from accessing the promoter site.

HFN1

An activator transcription factor that binds near the promoter to switch on the lactase gene in intestinal cells.

Epigenetics

The regulation of gene expression through modifications to chromatin structure—such as chemical tags on histone tails—without altering the underlying DNA nucleotide sequence.

Alternative Splicing

A post-transcriptional mechanism where different combinations of exons from a single gene are joined together, allowing humans to produce over $100,000$ proteins from approximately $20,000$ protein-coding genes.

Troponin

A muscle contraction protein that exists in distinct forms across different muscle cell types as a result of alternative splicing.

Point Mutation

A genetic mutation involving a change to a single nucleotide within a gene, categorized into substitutions, insertions, or deletions.

Frameshift Mutation

A mutation caused by the insertion or deletion of nucleotides that shifts the reading frame of all subsequent codons, typically yielding a nonfunctional protein.

Chromosomal Aberrations

Large-scale alterations to chromosome structure, classified as gene deletions (loss of an entire gene), gene duplications (extra copies), or gene relocations (movement to another chromosome).

Telomeres

Protective terminal caps of noncoding DNA on eukaryotic chromosomes that shorten with each round of DNA replication, ultimately preventing the loss of essential coding sequences.

Binary Fission

A form of asexual reproduction in prokaryotic organisms where a single parent cell replicates its circular DNA and divides into two genetically identical daughter cells.

$$G_0\text{ Phase}$$

A non-dividing resting state outside the cell cycle in which a cell pauses and can remain for days or years.

S Phase (Synthesis Phase)

The stage of interphase during which the cell replicates all of its DNA, taking approximately $8\text{ hours}$ in human cells.

DNA Helicase

The enzyme responsible for unwinding and separating the two strands of the parent DNA double helix at the replication fork.

DNA Polymerase

The enzyme that synthesizes new complementary DNA strands in the $5'$ to $3'$ direction by adding nucleotides to the free $3'\text{ -OH}$ group and proofreading errors.

Sister Chromatids

Two identical copies of a chromosome produced during S phase that remain physically linked at the centromere until anaphase.

Homologous Chromosomes

Pairs of matching chromosomes in a diploid cell that contain the same genes in the same positions, one inherited from the mother and one from the father.

Diploid

Cells containing two complete sets of chromosomes ($2n$), totaling $46$ chromosomes in human somatic cells.

Haploid

Cells carrying only one copy of each chromosome ($n$), such as the $23$ chromosomes present in human gametes (sperm and egg cells).

Synapsis

The pairing and physical alignment of replicated homologous chromosomes alongside each other during prophase I of meiosis.

Crossing Over

The exchange of corresponding genetic segments between non-sister chromatids of homologous chromosomes during prophase I, generating genetic diversity in gametes.