What are the bases that make up DNA?

Answer 1

DNA is composed of 4 bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Uracil (U), is rarely found in DNA except as a result of chemical degradation of Cytosine, but the DNA of some viruses (notably PBS1 phage DNA) and RNA (Ribonucleic Acid), has Uracil instead of Thymine.

Each base on one strand forms a bond with just one kind of base on another strand, called a "complementary" base: A bonds with T, and C bonds with G. Therefore, the whole double-strand sequence can be described by the sequence on one of the strands, chosen by convention. Two nucleotides paired together are called a base pair.

In a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect and pi stacking. Which strands associate depends on complementary pairing. Each base forms hydrogen bonds readily to only one other base, A to T forming two hydrogen bonds, and C to G forming three hydrogen bonds. The GC content and length of each DNA molcule dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association, characterised by the temperature required to break the hydrogen bond, its melting temperature (also called Tm value))-.

Answer 2

The unit or building block of DNA. Adenine (A), cytosine (C), guanine, (G), and thymine (T) are the four bases in DNA. The order of bases is the sequence of DNA.

Two bases bonded together and attached to one of the strands in the DNA double helix. Adenine always pairs with thymine, and guanine always pairs with cytosine.

A type of cell found in cheek tissue inside the mouth.

Answer 3

The nitrogen bases that make up the DNA are purines and pyramidines viz., adenine, guanine, cytocine and thymine which are held by double and triple hydrogen bonds. The base pairing occurs between purines and pyramidines.

Answer 4

Adenine, Cytosine, Guanine and Thyamine are the four bases which make up (different strands of) DNA .
These bases undergo a pairing between them i.e.
A & T
G & C.
by da way there are 3 types of DNAs.

Answer 5

DNA is made up of 2 types of nitrogen bases, purines and pyrimidines. Purines r of 2 types...Adenine and Guanine. Pyrimidines r of 2 types...Thaimine and Cytosine.DNA is double stranded and the strands r connected to each other by weak hydrogen bonds. Adenine has a double bond with Thaimine and Guanine has a triple bond with Cytosine.

Answer 6

DNA is made of two kinds of nitrogenous bases;

Purines include - Adenine (A) and Guanine (G)

Pyramidines include - Cytosine (C) and Thymine (T)

Answer 7

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).

The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.

DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.

An important property of DNA is that it can replicate, or make copies of itself. Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell.


Base ratio, DNA content, and quinacrine-brightness of human chromosomes

Human chromosomes were labeled with base-specific radioactive DNA precursors and examined autoradiographically to measure their DNA content and base ratio (percentage A-T base pairs). The requirement that incorporation of labeled bases be uniform during DNA synthesis was met by the use of inhibitors of de novo synthesis of DNA precursors. The genome was subdivided into 75 segments based on quinacrine banding, and the base ratio of each was calculated by a method that corrects for bias due to the scatter of grains about their source. Estimates of base ratio are shown to be sufficiently precise to detect variability among chromosomes and among segments within a chromosome. Analysis of these data and of measurements of the quinacrine fluorescence intensity of segments leads to the following conclusions. Base ratio is positively correlated with brightness, as predicted from independent in vitro studies. Larger chromosomes tend to have higher base ratios and to be brighter than smaller ones. The best prediction of the brightness of a segment must take into account not only its base ratio but also its DNA content. To explain these results, we suggest an evolutionary model in which chromosomes containing repeated sequences of A-T-rich DNA tend to grow by means of unequal sister chromatid and meiotic exchanges.

Answer 8

Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the biological development of a cellular form of life or a virus. All known cellular life and some viruses have DNAs. DNA is a long polymer of nucleotides (a polynucleotide) that encodes the sequence of amino acid residues in proteins, using the genetic code.
DNA is composed of 4 bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Uracil (U), is rarely found in DNA except as a result of chemical degradation of Cytosine, but the DNA of some viruses (notably PBS1 phage DNA) and RNA (Ribonucleic Acid), has Uracil instead of Thymine.
BASE PAIRING:-
Each base on one strand forms a bond with just one kind of base on another strand, called a "complementary" base: A bonds with T, and C bonds with G. Therefore, the whole double-strand sequence can be described by the sequence on one of the strands, chosen by convention.[2] Two nucleotides paired together are called a base pair.DNA is composed of 4 bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Uracil (U), is rarely found in DNA except as a result of chemical degradation of Cytosine, but the DNA of some viruses (notably PBS1 phage DNA) and RNA (Ribonucleic Acid), has Uracil instead of Thymine.

Each base on one strand forms a bond with just one kind of base on another strand, called a "complementary" base: A bonds with T, and C bonds with G. Therefore, the whole double-strand sequence can be described by the sequence on one of the strands, chosen by convention.[2] Two nucleotides paired together are called a base pair


In a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect and pi stacking. Which strands associate depends on complementary pairing. Each base forms hydrogen bonds readily to only one other base, A to T forming two hydrogen bonds, and C to G forming three hydrogen bonds. The GC content and length of each DNA molcule dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association, characterised by the temperature required to break the hydrogen bond, its melting temperature .The rules of base pairing (or nucleotide pairing) are:
A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T)
C with G: the pyrimidine cytosine (C) always pairs with the purine guanine This is consistent with there not being enough space (20 Å) for two purines to fit within the helix and too much space for two pyrimidines to get close enough to each other to form hydrogen bonds between themBut why not A with C and G with T?

The answer: only with A & T and with C & G are there opportunities to establish hydrogen bonds (shown here as dotted lines) between them (two between A & T; three between C & G). These relationships are often called the rules of Watson-Crick base pairing, named after the two scientists who discovered their structural basis.

The rules of base pairing tell us that if we can "read" the sequence of nucleotides on one strand of DNA, we can immediately deduce the complementary sequence on the other strand.

The rules of base pairing explain the phenomenon that whatever the amount of adenine (A) in the DNA of an organism, the amount of thymine (T) is the same (called Chargaff's rule). Similarly, whatever the amount of guanine (G), the amount of cytosine (C) is the same.
The C+G:A+T ratio varies from organism to organism (particularly among the bacteria), but within the limits of experimental error, A = T and C = G Relative Proportions (%) of Bases in DNA
Organism A T G C
Human 30.9 29.4 19.9 19.8
Chicken 28.8 29.2 20.5 21.5
Grasshopper 29.3 29.3 20.5 20.7
Sea Urchin 32.8 32.1 17.7 17.3
Wheat 27.3 27.1 22.7 22.8
Yeast 31.3 32.9 18.7 17.1
E. coli 24.7 23.6 26.0 25.7

Answer 9

purines: Adenine, guanine
pyrimidines: thymine, cytosine

Answer 10

dna is made up of two types of nitrogenous bases.
purines and pyrimidines.
purines are of two types- adenine and guanine
pyrimidines are of three types- cytosine, thymine( in case of dna), and uracil(in case of rna)