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Guides
Genetics ·
How many chromosomes do different species have?
Compare chromosome counts across species, explore our analysis of 465 mammals, and check the evidence behind chromosome-number records and life-cycle exceptions.
Genetics ·
How long is DNA?
Human DNA is about 2 meters long per cell and 2 nanometers wide. See the calculations, chromosome lengths, and why whole-body estimates differ.
Genetics ·
How many genes do humans have?
Humans have 19,442 protein-coding genes in GENCODE Release 50. The broader human reference annotation contains 78,733 gene entries when non-coding genes, pseudogenes, and other categories are included.
Genetics ·
How many genes are in mitochondrial DNA?
Human mitochondrial DNA has 37 canonical genes. Compare the standard count with evidence for additional small proteins and mtDNA copy numbers across tissues.
Genetics ·
How much DNA do humans share with other animals?
Human and chimpanzee DNA is about 98.8% identical across directly aligned bases. See how animal comparisons change when studies count DNA letters, proteins, or shared genes.
Genetics ·
How much DNA do humans share with bananas?
Our analysis of OMA’s May 2026 data found banana counterparts for 18.0% of human protein-coding genes. See the counts, methods, and limits of the comparison.
Genetics ·
How big is the human genome?
Compare human genome size in base pairs, nucleotides, picograms, and gigabytes, with reference assembly totals and verified download sizes.
Genetics ·
How to use Primer3 online
Learn how to use Primer3 online to design PCR primers, set target regions and product sizes, tune Tm and GC limits, inspect secondary-structure controls, and validate specificity before ordering.
Genetics ·
How accurate is DNA sequencing?
DNA sequencing accuracy ranges from about 99% per raw base to above 99.9% for high-quality or consensus reads. The exact figure depends on the platform, chemistry, software, sample, and metric.
Genetics ·
How many genomes have been sequenced?
NCBI indexes 3.67 million current public genome assemblies. See bacterial, plant, human, species, and GenBank sequence counts for 2026.
Genetics ·
How many types of RNA are there?
There are three major RNA types: mRNA, rRNA, and tRNA. rRNA is the most abundant by mass, tRNA is the smallest of the three, and mRNA can be the longest.
Genetics ·
How many transcripts are in the human transcriptome?
The current human reference annotation contains 644,292 transcript models, including 278,455 protein-coding transcripts. Database records, expressed isoforms, translations, and RNA molecules are different counts.
Genetics ·
Which organisms have the largest and smallest genomes?
Compare 27 genome size records across animals, plants, fungi, protists, and bacteria, from a 160.45-billion-base-pair fern genome to a 50,141-base-pair bacterial symbiont genome.
Genetics ·
What are the largest and smallest human genes?
RBFOX1 is the largest human protein-coding gene by GENCODE v50 genomic span. MLDHR is the shortest under an HGNC-approved protein-coding filter, at 96 base pairs.
Drugs ·
How many druggable genes are there?
About 4,500 human genes are considered part of the druggable genome. A major analysis counted 4,479 drugged or druggable genes, equal to 22% of protein-coding genes.
Genetics ·
How long does PCR take?
Most PCR runs take about 45 minutes to 2 hours in a thermocycler. Compare conventional PCR, qPCR, and RT-qPCR times and see how cycle count and target length affect the run.
Genetics ·
How long does whole-genome sequencing take?
Human whole-genome sequencing can generate genome data in hours to about a day. Sample preparation, analysis, interpretation, and reporting can extend the full turnaround to weeks.
Genetics ·
How long does mRNA last in a cell?
Cellular mRNA has a half-life of a few minutes in bacteria, about 18 minutes in budding yeast, and several hours in cultured human cells.
Genetics ·
How many nucleosomes are in a human cell?
A typical diploid human cell contains about 30 million nucleosomes. See how that estimate is calculated and why a nucleosome can be described as containing 146, 166, or about 200 base pairs.
Genetics ·
How many RNA polymerases do eukaryotes have?
Eukaryotes have three canonical nuclear RNA polymerases, while land plants have five. DNA polymerase counts vary by species, from five in E. coli to 16 in humans.
Genetics ·
How much DNA is needed for sequencing?
Most DNA sequencing workflows start with 1 ng to 1 µg of DNA. Illumina DNA Prep recommends 100–500 ng for human DNA, while Nanopore ligation libraries use 1 µg for fragments longer than 10 kb.
Genetics ·
How many chromosomes do humans have?
Humans typically have 46 chromosomes in most nucleated body cells: 44 autosomes and 2 sex chromosomes. Egg and sperm cells have 23 each.
Genetics ·
How many codons are there?
There are 64 possible codons in the standard genetic code. Of these, 61 specify amino acids and three are stop codons.
Genetics ·
How many CpG sites are in the human genome?
The human genome contains about 28 million CpG sites. A 2023 whole-genome methylation atlas analyzed 28,217,448 CpG positions, or roughly one per 110 base pairs.