What is DNA?

DNA (deoxyribonucleic acid) is the molecule that stores the genetic instructions for building, operating, and reproducing every living organism DNA is the molecule that provides energy to cells — it is found in mitochondria DNA is a type of protein that controls which genes are switched on or off DNA is only found in the nucleus of animal cells; plants use RNA instead

What is the double helix structure of DNA?

DNA consists of two strands wound around each other in a spiral (helix) — like a twisted ladder, with sugar-phosphate backbones as the rails and base pairs as the rungs DNA is a single straight chain of nucleotides, like a zipper DNA is a triple helix — three strands wound together for stability The double helix means DNA comes in two separate molecules that work as a pair

What are the four DNA bases and how do they pair?

Adenine (A), Thymine (T), Guanine (G), and Cytosine (C) — A always pairs with T, and G always pairs with C (Chargaff's rules) The four bases are Adenine, Uracil, Guanine, and Cytosine — A pairs with U, G pairs with C Any base can pair with any other base — pairing is random There are five DNA bases — the fifth, Xanthine, pairs with Adenine

What is a gene?

A gene is a specific segment of DNA that contains the instructions for making a particular protein or functional RNA molecule — it is the basic unit of heredity A gene is another word for a chromosome — humans have 46 genes A gene is a unit of energy stored in DNA and released when the cell needs it A gene is a mistake in DNA that causes a trait to change — like a mutation

What is a chromosome?

A chromosome is a tightly coiled structure of DNA and proteins (histones) — humans have 46 chromosomes (23 pairs) in most body cells, carrying about 20,000 genes in total A chromosome is a single gene — humans have 46 genes, one per chromosome Chromosomes are only found in sex cells (sperm and eggs), not in regular body cells A chromosome is a type of protein that helps DNA function properly

What is the difference between DNA and RNA?

DNA is double-stranded, uses thymine (T), and stores genetic information; RNA is single-stranded, uses uracil (U) instead of thymine, and carries messages from DNA to ribosomes RNA and DNA are identical — RNA is just a shorter version of DNA DNA is found in the cytoplasm; RNA is found in the nucleus RNA stores genetic information; DNA carries it from the nucleus to the ribosome

What is transcription in molecular biology?

Transcription is the process of copying a gene's DNA sequence into a messenger RNA (mRNA) molecule — it happens in the nucleus and is carried out by an enzyme called RNA polymerase Transcription is the process of copying DNA into a new DNA molecule during cell division Transcription is the process of assembling amino acids into a protein at the ribosome Transcription converts RNA back into DNA — it is the reverse of normal gene expression

What is translation in molecular biology?

Translation is the process where ribosomes read the mRNA sequence and assemble amino acids in the correct order to build a protein — each three-base codon specifies one amino acid Translation is the process of copying DNA from one chromosome to another Translation converts mRNA back into a DNA sequence in the nucleus Translation is how cells move proteins from the nucleus to the cytoplasm

What is DNA replication and when does it happen?

DNA replication is the process of copying the entire genome before cell division — the double helix unwinds and each strand serves as a template for building a new complementary strand, producing two identical DNA molecules DNA replication is how cells repair damaged DNA using backup copies stored in lysosomes DNA replication happens in the ribosome and produces protein instead of DNA DNA replication only happens in reproductive cells (sperm and eggs), not in body cells

Why is the sequence of DNA bases important?

The sequence of bases is the genetic code — it specifies the exact order of amino acids in every protein, and even a single base change can alter a protein's function and cause disease The sequence of bases determines how fast DNA replicates — longer sequences replicate faster The sequence of bases only matters in sex cells — body cells ignore the sequence The sequence of bases determines the color of the chromosomes under a microscope