What do nitrogen bases attach to

Electronegative O and N atoms with free lone pairs are potential hydrogen bond acceptors. Hydrogen atoms attached to very electronegative atoms like O and N have strong partial positive charge and are potential hydrogen bond donors. The dotted line in the image below represents the non-covalent attractive force between a hydrogen bond donor H atom with little 'ownership' of its valence electrons and a hydrogen bond acceptor electronegative atom with at least one lone pair of electrons.

Many of the oxygen, nitrogen, and hydrogen atoms in the nitrogenous bases are very effective hydrogen bond donors and acceptors, as illustrated in the image below. Remember: Hydrogen bond donors are only those H atoms bound to an electronegative atom such as N or O. Hydrogen bond acceptors are electronegative atoms with at least one lone pair of electrons. Also notice that potential hydrogen bond donors and acceptors close to the sugar R group are ignored in the image above.

This is because those parts of the nitrogenous base close to the sugar-phosphate backbone will be unavailable for hydrogen bonding with the other base in the pair. Let's examine a single guanine residue to identify potential hydrogen bond donors and acceptors. Guanine will be highlighted in yellow , and the attached sugar and phosphate in the backbone will blink purple.

Keeping in mind the point of sugar attachment, we can identify guanine's hydrogen bond donors and acceptors that are available to interact with a paired nitrogenous base.

Locate these parts of the molecule yourself, then click the button below to see the relevant atoms blink yellow. Which of the following statements best describes the hydrogen bonding potential in guanine? Guanine has 3 H-bond donors. Guanine has 3 H-bond acceptors.

Guanine has 2 H-bond acceptors and 1 H-bond donor. Guanine has 1 H-bond acceptor and 1 H-bond donor. Guanine has 1 H-bond acceptor and 2 H-bond donors. Can you find one H-bond donor and 2 H-bond acceptors in cytosine? Examine the molecule yourself, then click the button below to see the relevant atoms blink green. Guanine and cytosine make up a nitrogenous base pair because their available hydrogen bond donors and hydrogen bond acceptors pair with each other in space.

Guanine and cytosine are said to be complementary to each other. Lawrence C. Brody, Ph. Featured Content. Introduction to Genomics. Polygenic Risk Scores. However, it is possible to see chromosomes with a standard light microscope, as long as the chromosomes are in their most condensed form. To see chromosomes in this way, scientists must first use a chemical process that attaches the chromosomes to a glass slide and stains or "paints" them.

Staining makes the chromosomes easier to see under the microscope. In addition, the banding patterns that appear on individual chromosomes as a result of the staining process are unique to each pair of chromosomes, so they allow researchers to distinguish different chromosomes from one another. Then, after a scientist has visualized all of the chromosomes within a cell and captured images of them, he or she can arrange these images to make a composite picture called a karyotype Figure This page appears in the following eBook.

Aa Aa Aa. What components make up DNA? Figure 1: A single nucleotide contains a nitrogenous base red , a deoxyribose sugar molecule gray , and a phosphate group attached to the 5' side of the sugar indicated by light gray. Opposite to the 5' side of the sugar molecule is the 3' side dark gray , which has a free hydroxyl group attached not shown.

Figure 2: The four nitrogenous bases that compose DNA nucleotides are shown in bright colors: adenine A, green , thymine T, red , cytosine C, orange , and guanine G, blue. Although nucleotides derive their names from the nitrogenous bases they contain, they owe much of their structure and bonding capabilities to their deoxyribose molecule. The central portion of this molecule contains five carbon atoms arranged in the shape of a ring, and each carbon in the ring is referred to by a number followed by the prime symbol '.

Of these carbons, the 5' carbon atom is particularly notable, because it is the site at which the phosphate group is attached to the nucleotide.

Appropriately, the area surrounding this carbon atom is known as the 5' end of the nucleotide. Opposite the 5' carbon, on the other side of the deoxyribose ring, is the 3' carbon, which is not attached to a phosphate group.

This portion of the nucleotide is typically referred to as the 3' end Figure 1. When nucleotides join together in a series, they form a structure known as a polynucleotide. At each point of juncture within a polynucleotide, the 5' end of one nucleotide attaches to the 3' end of the adjacent nucleotide through a connection called a phosphodiester bond Figure 3. It is this alternating sugar-phosphate arrangement that forms the "backbone" of a DNA molecule.

Figure 3: All polynucleotides contain an alternating sugar-phosphate backbone. This backbone is formed when the 3' end dark gray of one nucleotide attaches to the 5' phosphate end light gray of an adjacent nucleotide by way of a phosphodiester bond.

How is the DNA strand organized? Figure 4: Double-stranded DNA consists of two polynucleotide chains whose nitrogenous bases are connected by hydrogen bonds. Within this arrangement, each strand mirrors the other as a result of the anti-parallel orientation of the sugar-phosphate backbones, as well as the complementary nature of the A-T and C-G base pairing. Figure Detail. Figure 6: The double helix looks like a twisted ladder. How is DNA packaged inside cells?

Figure 7: To better fit within the cell, long pieces of double-stranded DNA are tightly packed into structures called chromosomes.

What does real chromatin look like? Compare the relative sizes of the double helix, histones, and chromosomes. Figure 8: In eukaryotic chromatin, double-stranded DNA gray is wrapped around histone proteins red. Figure 9: Supercoiled eukaryotic DNA.

How do scientists visualize DNA?