Where is dna located

Mitochondria generate the energy the cell needs to function properly. In sexual reproduction, organisms inherit half of their nuclear DNA from the male parent and half from the female parent. However, organisms inherit all of their mitochondrial DNA from the female parent. This occurs because only egg cells, and not sperm cells, keep their mitochondria during fertilization.

DNA is made of chemical building blocks called nucleotides. These building blocks are made of three parts: a phosphate group, a sugar group and one of four types of nitrogen bases. To form a strand of DNA, nucleotides are linked into chains, with the phosphate and sugar groups alternating. The four types of nitrogen bases found in nucleotides are: adenine A , thymine T , guanine G and cytosine C. The order, or sequence, of these bases determines what biological instructions are contained in a strand of DNA.

The complete DNA instruction book, or genome, for a human contains about 3 billion bases and about 20, genes on 23 pairs of chromosomes. DNA contains the instructions needed for an organism to develop, survive and reproduce. To carry out these functions, DNA sequences must be converted into messages that can be used to produce proteins, which are the complex molecules that do most of the work in our bodies.

Each DNA sequence that contains instructions to make a protein is known as a gene. The size of a gene may vary greatly, ranging from about 1, bases to 1 million bases in humans. What is DNA? From Genetics Home Reference. DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone.

What is a gene? What is a chromosome? Module 1. Module Content. Thank you for participating in this module. Click below to download the certificate. Download Certificate of Participation. Previous Section Next Section. Follow Healio. Sign Up for Email Get the latest news and education delivered to your inbox Email address.

Account Information. Welcome to Learn Genomics. Begin your journey with Learn Genomics. Figure This karyotype depicts all 23 pairs of chromosomes in a human cell, including the sex-determining X and Y chromosomes that together make up the twenty-third set lower right.

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