[pic]
[pic]
STRUCTURE OF DNA
PROPOSED BY JAMES WATSON AND FRANCISCRICK
DNA stands for deoxyribose nucleic acid. This chemical substance is present in the nucleus of all living cells . DNA controls all the chemical changes which take place in cells. The famous double helical structure was proposed by James Watson and Francis Crick in the year 1953. Nine years later both received Nobel Prize for this discovery.
STRUCTURE OF DNA
DNA is a very large molecule made up of a long chain of sub-units. The sub-units are called nucleotides. Each nucleotide is made up of a sugar called deoxyribose a phosphate group -PO4 and an organic base
Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule.
Deoxyribose is almost the same but lacks one oxygen atom.
The most common organic bases are ADENINE, GUANINE ,THYMINE, AND CYTOSINE ← They are divided into two groups ← Pyrimidines and purines ← Pyrimidines (made of one 6 member ring) ← Thymine ← Cytosine ← Purines (made of a 6 member ring, fused to a 5 member ring) ← Adenine ← Guanine.
← In fact, the DNA usually consists of a double strand of nucleotides . The ‘backbones’ of DNA molecules are made of alternating sugar and phosphates ← The ‘rungs on the ladder’ are made of bases that are hydrogen bonded to each other
The bases always pair up in the same way
Adenine forms a bond with Thymine
Adenine forms a bond with Thymine
[pic][pic]
and Cytosine bonds with Guanine
[pic][pic]
The paired strands are coiled into a spiral called A DOUBLE HELIX
The strands run opposite of each other. The 5’ end always has the phosphate attached
[pic]
The sequence of bases in DNA forms the Genetic Code. A group of three bases (a triplet) controls the production of a particular amino acid in the cytoplasm of the cell. The different amino acids and the order in which they are joined up determines the sort of protein being produced.
For example
[pic] [pic] [pic] VALINE [pic]
CYTOSINE, GUANINE AND ADENINE FOR ALANINE
This is known as the triplet code
Each triplet codes for a specific amino acid
CGA - CAA - CCA - CCA - GCT - GGG - GAG – CCA
ALA VAL GLY GLY ARG PRO LEO GLY
A sequence of triplets in the DNA molecule may code for a complete protein.Such a sequence forms a gene.There may be a thousand or more bases in one gene
Conclusion
The Structure of DNA helped us to know how DNA is responsible for coding the characters of an Individual and there by responsible for Heridity and Variation.
You May Also Find These Documents Helpful
-
5. Why was the Hershey-Chase experiment performed? What was the outcome of the experiment? To determine if protein or DNA caused change DNA derermines the transfer…
- 499 Words
- 2 Pages
Satisfactory Essays -
DNA is a long, double-stranded molecule made up of A, T, G, and C bases.…
- 4298 Words
- 18 Pages
Good Essays -
Deoxyribose Nucleic Acid (DNA) is a polynucleotide molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses. Most DNA molecules are double stranded helices, consisting of two polynucleotide strands made up of simpler molecules known as nucleotides. A nucleotide is made up of an organic nitrogenous base, a deoxyribose sugar and phosphate groups. It is order of these bases which make up the genetic code; a set of rules, by which information is encoded within genetic material.…
- 1411 Words
- 6 Pages
Good Essays -
DNA stands for Deoxyribonucleic acid and looks like a spiral. The spiral is also known as a double helix. The strands are made up of our genetic information, composed of genes and chromosomes. There are four bases divided among purines and pyrimidines. On the purines there are Adenine (A) and Guanine (G). On the pyrimidines there are Cytosine (C) and Thymine (T). The base pairs are Adenine and Thymine (A-T) and Cytosine and Guanine (C-G). DNA is found in the nucleus of every human cell. Humans have 46 chromosomes. When a cell reproduces, the chromosomes get copied and distributed to each offspring.…
- 494 Words
- 2 Pages
Good Essays -
B. What makes up the “rungs” of the DNA molecule? Pairs of nitrogenous bases (AT, GC)…
- 866 Words
- 5 Pages
Satisfactory Essays -
DNA is typically has two strands running in opposite direction and is usually referred to as a double helix. Each on the individual strands consists of a backbone that is formed by sugar molecules linked together in groups. Each individual sugar molecule is covalently linked to one of the following possible bases: Adenine, Guanine, Cytosine and Thymine. These bases are typically aligned perpendicular to the axis of the strand. As previously stated the strands run in opposite directions with the bases paired up with Adenine always with Thymine and Guanine always with Cytosine. Theses pairs form hydrogen bonds with the A/T pair having 2 and the G/C pair having 3. The extra hydrogen bond makes the G/C pair stronger.…
- 380 Words
- 2 Pages
Satisfactory Essays -
DNA made up of units called nucleotides, nucleotides are made up of three molecules components, a nitrogen base, a sugar, and a phosphate (Simon, Reece, Dickey, 2010). The nucleotides are joined together by bonds between the sugar of one nucleotide and the phosphate of the next producing a long chain of nucleotides resulting in a sugar-phosphate backbone (Simon, Reece, Dickey, 2010) the base containing nitrogen is the only part that is variable represented by, A Adenine, C cytosine, G guanine, and T Thymine. The sugars and phosphates form the backbone of the molecule and are on the outside. The bases point inwards horizontally. The antipoarallel strands run in opposite directions and are held together by hydrogen bonds between the base pairs, these two long strands twisted and wrap around each other to form a double helix. Hydrogen bonds between bases hold the strands together; each base pairs with a complementary partner: A with T, and G with C (Simon, Reece, Dickey, 2010).…
- 472 Words
- 2 Pages
Good Essays -
Describe the structure of DNA.DNA is thread formed by two strands, related together to form a double helix. The double helix looks like a twisted ladder. The sides of this ladder are long unites called nucleotides and are made of three parts; a nitrogenous base, a sugar, and a phosphate group. The sides of the ladder or the nucleotides from the two separate strands of the DNA are attached by an appendage made of one of four separate bases. These appendages represent the rungs of the DNA ladder and are attached to the complimentary strand of the DNA. The bases or rungs are made of either Adenine (A) OR Thymine (T) or Cytosine (C) and Guanine (G). The attachment of the strands by the bases is specific Adenine can only join with Thymine, and Cytosine can only join with Guanine. Since this base pairing is specific, if one knows the sequence of bases a long one strand of the DNA one will also know the strand of the DNA one will also know the sequence along the complimentary strand.…
- 491 Words
- 2 Pages
Satisfactory Essays -
DNA is made up of two strands. At one end of each strand there is a phosphate group attached to the carbon atom number 5 of the deoxyribose (this indicates the 5' terminal) and at the other end of each strand is a hydroxyl group attached to the carbon atom number 3 of the deoxyribose (this indicates the 3' terminal). The strands run in opposite directions and so we say that they are antiparallel. One strand runs in a 5'-3' direction and the other runs in a 3'-5' direction. Adjacent nucleotides are attached together via a bond between the phosphate group of one nucleotide and the carbon atom number 3 of the deoxyribose of the other nucleotide.…
- 2219 Words
- 9 Pages
Powerful Essays -
DNA is a structure of specific molecules and a complex mixture of chemicals. DNA is a nucleic acid, which is a group of complex compounds that can be found in all living cells or viruses, and controls cell health and function. Nucleic acids are composed of polymers and monomers, which are referred to as nucleotides. There are four different types of nucleotides that make up the structure of DNA, which are abbreviated A, C, T, and G. Covalent bonds join together nucleotides through sugar and phosphate. Polynucleotides, or a polymer nucleotide, which tends to be longer than a monomer nucleotide, contains many variations of arrangements of A, C, T, and G.…
- 459 Words
- 2 Pages
Good Essays -
DNA: a double-stranded, helical nucleic acid molecule, consisting of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G) and thymine (T).…
- 2450 Words
- 7 Pages
Good Essays -
Watson and Crick reported that DNA consisted of two polynucleotide strands wrapped into a double helix.…
- 1097 Words
- 8 Pages
Good Essays -
A DNA molecule which is the abbreviation for deoxyribonucleic acid is made up of precise lengthy chains of polymers and monomers and they are called nucleotides. These two (2) chains specifically which are composed of DNA strain are then molded by the grouping of the nucleotides into the polynucleotides. The nucleotide is composed of a nitrogenous base, a phosphate and a group. In DNA there are four (4) nucleotides that can be found along the DNA chain. These four (4) nucleotides are (T) thyme, (A) adenine, (C) cytosine, and (G) guanine. These four (4) nucleotides are fused together by their covalent bonds. In other words the sugar and the phosphates which composes the sugar/phosphate support of the polynucleotide.…
- 388 Words
- 2 Pages
Satisfactory Essays -
At our All About Cats Veterinary Hospital, we cater to felines exclusively. Keeping cats safe and healthy is our only priority. Our mission is to help our companions by meeting their nutritional, physical and emotional needs throughout the life span.…
- 498 Words
- 2 Pages
Good Essays -
| Draw and describe the structure of DNA to include: Sugar, Phosphate, Bases and Hydrogen Bonds.…
- 341 Words
- 2 Pages
Satisfactory Essays