Introduction to DNA, RNA, and Chromosomes

Vocabulary flashcards covering DNA and RNA structural differences, nitrogenous base pairing rules, replication mechanisms, and chromosome packaging concepts.

Prokaryote

A simple, single-celled organism (typically bacteria) that lacks membrane-enclosed organelles and a nucleus, containing a single circular piece of DNA.

Eukaryote

A complex single- or multi-celled organism containing membrane-enclosed organelles and a nucleus that houses multiple linear DNA strands.

Nucleoid region

The unconfined inner region of a prokaryotic cell where its single circular DNA floats freely.

Deoxyribonucleic acid (DNA)

A double-stranded nucleic acid polymer composed of nucleotides containing deoxyribose sugar, a phosphate group, and nitrogenous bases (A, T, C, G).

Nucleotide

The monomer or building block of nucleic acids, consisting of a phosphate group, a pentose sugar, and a nitrogenous base.

Ribonucleic acid (RNA)

A typically single-stranded nucleic acid composed of ribose sugar, a phosphate group, and nitrogenous bases adenine, cytosine, guanine, and uracil (U) instead of thymine.

Double helix

The spiral staircase shape of DNA, consisting of two winding sugar-phosphate backbones on the outside with paired nitrogenous bases perpendicular in the center.

Antiparallel

The structural orientation of DNA where one strand runs in the $5'$ to $3'$ direction and the opposing complementary strand runs upside down from $3'$ to $5'$.

Semi-conservative replication

The replication model where parent DNA strands separate so each original strand acts as a template, producing daughter molecules made of 50% old DNA and 50% new DNA.

Helicase

An enzyme that breaks the hydrogen bonds between parent DNA strands like a zipper to open up the double helix during replication.

DNA polymerase

An enzyme that constructs new DNA strands by adding complementary nucleotides specifically to the $3'$ end of a growing strand.

Primase

An enzyme that adds single-stranded RNA primers to provide a starting $3'$ end for DNA polymerase to build upon during replication.

Ligase

An enzyme that acts like glue during DNA replication to seal and connect DNA fragments together.

Origin of replication

The specific position on a DNA strand where helicase opens the double helix and copying begins.

Karyotype

An image of an organism's full set of condensed chromosomes organized into corresponding pairs.

Somatic cell

Any body cell of an organism, excluding gametes such as sperm and egg cells.

Homologous chromosomes

A matched pair of chromosomes (one inherited from mom, one from dad) carrying genetic information for the same traits at the same locations.

Chromatin

The complex of DNA molecules wrapped around histone proteins inside eukaryotic cells.

Histone protein

A protein structure around which DNA double helix strands wrap to condense and compact into organized chromosomes.

Gene

A distinct segment of DNA along a chromosome that provides instructions for building a specific protein or determining a trait.

Diploid ($2n$)

Refers to a cell containing two full sets of chromosomes (one set from each parent), equaling 46 total chromosomes in human somatic cells.