Nucleic Acids & DNA/RNA Basics

Vocabulary flashcards covering DNA/RNA concepts, nucleotides, DNA structure, transcription/translation, and RNA types.

DNA

Deoxyribonucleic acid; the molecule that stores genetic information in organisms; typically a double-stranded, right-handed helix made of nucleotides linked by phosphodiester bonds; bases A–T and G–C.

RNA

Ribonucleic acid; carries genetic information and helps synthesize proteins; usually single-stranded; contains ribose and uracil instead of thymine.

Phenotype

Observable traits of an organism, including morphology, anatomy, physiology, and behavior.

Genotype

Genetic makeup of an organism—the alleles it carries.

Selective Breeding

Choosing individuals with desirable traits to reproduce, increasing those traits in the population.

Acquired Trait

Trait gained through environment or experience, not inherited genetically.

Cell Theory

All organisms are composed of cells, and cells arise from preexisting cells.

Mendel's Law of Segregation

Gene pairs separate during gamete formation; fertilization is a random joining of gametes, restoring pairs.

Fertilization

Fusion of egg and sperm forming a zygote.

Genome

The complete set of genetic material present in an organism or cell.

Nucleotide

The basic unit of nucleic acids, consisting of a phosphate group, a five‑carbon sugar, and a nitrogenous base.

Nucleoside

A five‑carbon sugar linked to a nitrogenous base; lacks the phosphate group.

Phosphodiester Bond

Covalent bond connecting nucleotides, forming the sugar–phosphate backbone of nucleic acids.

5' End

End of a nucleic acid strand bearing a free phosphate group on the 5' carbon.

3' End

End of a nucleic acid strand bearing a free hydroxyl group on the 3' carbon.

Base Pairing

In DNA: A pairs with T and G pairs with C; in RNA: A pairs with U and G with C; hydrogen bonds stabilize the helix.

Complementary Strands

Two DNA strands with sequences that enable them to pair with each other (antiparallel).

DNA Double Helix

The classic right-handed, antiparallel two-stranded structure of DNA held together by hydrogen bonds.

5' to 3' Polarity

Directionality of nucleic acid synthesis and reading; synthesis occurs on the 3' end.

B-DNA

The typical right-handed DNA form in living cells with ~10.5 base pairs per turn and major/minor grooves.

A-DNA

An alternative DNA form observed under certain conditions (often shorter/wider than B-DNA).

Z-DNA

A left-handed DNA form that can occur in particular sequences and conditions.

Transcription

Process of copying a gene's DNA sequence into messenger RNA.

Translation

Process by which ribosomes synthesize a protein using mRNA as a template.

Locus

The fixed position of a gene on a chromosome.

mRNA

Messenger RNA; conveys genetic information from DNA to the ribosome for protein synthesis.

rRNA

Ribosomal RNA; structural and functional component of ribosomes.

tRNA

Transfer RNA; carries amino acids to the ribosome and matches them to mRNA codons.

miRNA/siRNA

Small interfering RNA or microRNA; regulate gene expression by silencing or degrading target mRNA.

Nucleic Acid Polarity

Strands have distinct 5' and 3' ends; polarity determines direction of synthesis and reading.

Pyrimidine

Single-ring nitrogenous bases: cytosine (C), thymine (T), and uracil (U).

Purine

Double-ring nitrogenous bases: adenine (A) and guanine (G).

Adenine

Purine base that pairs with thymine in DNA and with uracil in RNA.

Thymine

Pyrimidine base in DNA that pairs with adenine.

Uracil

Pyrimidine base in RNA that pairs with adenine (replaces thymine).

Guanine

Purine base that pairs with cytosine.

Cytosine

Pyrimidine base that pairs with guanine.

Hydrogen Bonds

Weak bonds between complementary bases that stabilize the DNA double helix.