DNA, Genes, Chromosomes, Gene Expression, and the Cell Cycle

Comprehensive vocabulary flashcards covering DNA structure, chromosome anatomy, gene expression (transcription and translation), and the stages and enzymes of the eukaryotic cell cycle and DNA replication.

Double Helix

The structural form of DNA consisting of two nucleotide polymer strands held together by hydrogen bonds and twisted.

Complementary Base Pairs

Specific nitrogenous bases in DNA that pair via hydrogen bonds: adenine pairs with thymine ($A\text{–}T$) and cytosine pairs with guanine ($C\text{–}G$).

Gene

A region of tightly coiled DNA within a chromosome that codes for the unique order or sequence of amino acids in a polypeptide.

Centromere

The specific region of a eukaryotic chromosome that maintains a consistent location within a given chromosome type.

Homologous Pairs

Matched pairs of chromosomes sharing the same length and arm, the same centromere location, and the same genes in the same order, but differing in their alleles.

Allele

A variation in a gene's nucleotide sequence leading to a variation in the protein made, which results in a variation of a trait.

Sex Chromosomes

The chromosomes that determine sex within the human genome's $23$ paired types ($46$ total chromosomes), configured as $XX$ in females and $XY$ in males.

mRNA (Messenger RNA)

The type of RNA that complementary pairs with the template strand of a gene's DNA to capture its coding strand instructions for protein synthesis.

Codon

A triplet of consecutive nucleotides in DNA or RNA that codes for a specific amino acid.

tRNA (Transfer RNA)

The type of RNA that translates mRNA codons by transferring the requested amino acid from the cytoplasm to the ribosome.

Anticodon

The part of the tRNA molecule that recognizes and complements a specific mRNA codon.

Transcription

The first major step of gene expression, taking place in the nucleus, in which mRNA captures the gene's code.

Translation

The second major step of gene expression, taking place in the ribosome, in which tRNAs translate mRNA codons into a polypeptide chain.

RNA Polymerase

The enzyme that binds to a gene's DNA, unwinds and unzips it, and uses the template strand and base-pairing rules to synthesize mRNA in the nucleus.

AUG

The start codon on mRNA where the ribosome attaches to begin translation.

Interphase

The period between cell divisions comprising the $G_1$, $S$, and $G_2$ phases jointly.

$G_1$ Phase

The cell cycle phase where mature, specialized cells spend approximately $90\%$ of their life doing their job, and begin replicating organelles if signaled to divide.

S Phase (Synthesis)

The eukaryotic cell cycle phase within interphase during which DNA and chromosome replication occurs in the nucleus.

$G_2$ Phase

The interphase stage following the S phase in which the cell finishes organelle replication before proceeding to mitosis.

Mitosis (M-Phase)

The stage of cell division following interphase that divides the cell to produce daughter cells.

Helicase

The replication enzyme that unwinds and unzips the chromosome's DNA strands.

DNA Polymerase

The replication enzyme that uses base-pairing rules to build complementary strands for each original DNA strand of the chromosomes.

Sister Chromatids

Identical duplicated copies of a chromosome held together by hydrogen bonds between the original and newly built complement strands following replication.