Molecular Biology, Genetics, and Cell Division

Comprehensive vocabulary flashcards covering DNA structure, replication, gene expression, mutation types, and cell division based on Chapters 7, 8, and 10 lecture notes.

DNA (Deoxyribonucleic acid)

The hereditary molecule passed from parents to offspring that serves as the instruction manual for building an individual, composed of nucleotides made of a sugar, a phosphate, and a base.

Semi-conservative Replication

The mechanism of DNA copying in which each newly synthesized DNA molecule consists of one original parental strand and one newly formed strand.

Helicase

The enzyme that unwinds and unzips the DNA double helix by breaking the hydrogen bonds holding base pairs together.

Primase

An RNA polymerase that synthesizes short RNA primers to provide the pre-existing $3'$ end required for DNA polymerase to initiate replication.

DNA Polymerase

The enzyme that reads the DNA template strand and adds complementary nucleotides exclusively to a pre-existing $3'$ end according to base-pairing rules.

Purine

A larger nitrogenous base category found in nucleic acids that consists of adenine (A) and guanine (G).

Pyrimidine

A smaller nitrogenous base category that includes thymine (T) and cytosine (C) in DNA, and cytosine (C) and uracil (U) in RNA.

Double Helix

The spiral structure formed by two anti-parallel strands of DNA nucleotides held together by hydrogen bonds between complementary base pairs.

Homozygous

The genetic state of possessing two identical alleles for a specific gene.

Heterozygous

The genetic state of possessing two different alleles for a specific gene.

Autosomes

Any chromosomes that are not sex chromosomes, represented by chromosome pairs 1 through 22 in humans.

Sex Chromosomes

The pair of chromosomes determining biological sex, designated as $\text{XX}$ for females and $\text{XY}$ for males.

Karyotype

A laboratory visual display showing the complete set of chromosomes of an individual.

Genome

The complete set of genetic instructions encoded in an organism's DNA, comprising approximately 3 billion base pairs in humans.

Polymerase Chain Reaction (PCR)

A laboratory technique used to replicate and amplify a specific segment of DNA.

Denaturation (PCR)

The first step of PCR, occurring at approximately $95^\circ\text{C}$, where high heat causes double-stranded DNA to separate into single strands.

Annealing (PCR)

The second step of PCR, occurring between $55^\circ\text{C}$ and $65^\circ\text{C}$, where single-stranded DNA primers bind to their target complementary sequences.

Extension (PCR)

The third step of PCR, occurring at approximately $72^\circ\text{C}$, where Taq DNA polymerase synthesizes new DNA strands by adding nucleotides.

Short Tandem Repeats (STRs)

Short stretches of 3 to 5 nucleotides that repeat in tandem, varying in number among different individuals.

Gel Electrophoresis

A laboratory technique that separates fragments of DNA based on size.

Coding Sequence

The region of a gene that dictates the amino acid sequence of a protein, which determines its shape and function.

Regulatory Sequence

The region of a gene that acts as an on/off switch, determining when and how much protein is produced.

Template Strand

The strand of DNA that is read and copied by RNA polymerase during transcription.

Coding Strand

The DNA strand complementary to the template strand whose sequence corresponds to the mRNA transcript produced, replacing thymine with uracil.

Transcription

The process by which a complementary mRNA strand is synthesized from a DNA template strand, occurring in the eukaryotic nucleus and bacterial cytoplasm.

Codon

A set of 3 consecutive nucleotides on an mRNA transcript that codes for a specific amino acid or stop signal.

Anticodon

A set of 3 nucleotides located on a tRNA molecule that complementary base pairs with a specific codon on mRNA.

Silent Mutation

A nucleotide-pair substitution that has no effect on the amino acid produced by a codon due to redundancy in the genetic code.

Missense Mutation

A nucleotide-pair substitution that alters a codon so that it codes for a different, incorrect amino acid.

Nonsense Mutation

A nucleotide-pair substitution that converts an amino acid codon into a premature stop codon, nearly always leading to a nonfunctional protein.

Frameshift Mutation

A mutation caused by an insertion or deletion of nucleotides that shifts the codon reading frame, producing disastrous effects on the resulting protein.

Binary Fission

A rapid form of asexual reproduction in single-celled archaea and bacteria where cytoplasmic DNA replicates and the cell divides into two.

Budding

A type of asexual reproduction where a new organism develops from an outgrowth at a single site on the parent organism.

Fragmentation

A form of asexual reproduction characterized by the regrowth of complete individual organisms from separated body fragments.

Interphase

The preparatory period of the cell cycle consisting of $G_1$, $S$, and $G_2$ phases during which the cell grows and replicates its DNA.

S Phase

The specific stage of interphase during which DNA replication occurs, producing identical sister chromatids for each chromosome.

Mitosis

The division of the cell nucleus during which duplicated chromosomes are evenly divided and sister chromatids are separated.

Cytokinesis

The stage of the cell cycle responsible for dividing the cytoplasm to form two distinct daughter cells.

Haploid

Describing a cell that contains 1 of each type of chromosome, such as human gametes containing 23 chromosomes.

Diploid

Describing a cell that contains 2 of each type of chromosome, such as human somatic cells containing 46 chromosomes (23 homologous pairs).

Prophase

The stage of mitosis where chromosomes condense and become visible, the nuclear envelope breaks down, and centrosomes move apart to form the spindle apparatus.

Metaphase

The mitotic stage where chromosomes line up individually along the center of the cell at the metaphase plate.

Anaphase

The stage of mitosis where sister chromatids separate and move toward opposite poles as kinetochore microtubules shorten and polar microtubules lengthen.

Telophase

The final stage of mitosis where chromosomes reach opposite spindle poles, return to thread-like form, and two new nuclear membranes assemble.

Cell Plate

A structure formed during cytokinesis in plant cells when Golgi-derived vesicles containing cell wall material converge and fuse between the two daughter nuclei.