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DNA structure
DNA structure
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DNA Structure

  1. 1. Submitted by: Mahnoor Shabbir Submitted to: Ma’am Guldasta khan Subject: Microbiology-ΙΙ Department: Microbiology
  2. 2. Contents:  DNA structure Base pairing The molecular structure of DNA DNA molecules are polymers DNA monomers are called nucleotides
  3. 3.  DNA is the molecule that holds the instructions for all living things. DNA achieves this feat of storing, coding and transferring biological information though its unique structure.
  4. 4. DNA structure DNA is the molecule that holds the instructions for growth and development in every living thing. Its structure is described as a double-stranded helix held together by complementary base pairs.
  5. 5.  The basic units of DNA are nucleotides. These nucleotides consist of a deoxyribose sugar, phosphate and base.
  6. 6. • Base pairing: The nucleotides are identical except for the base, which can be an adenine, thymine, guanine or cytosine. There are chemical cross-links between the two strands in DNA, formed by pairs of bases held together by hydrogen bonds. They always pair up in a particular way, called complementary base pairing: thymine pairs with adenine (T-A) guanine pairs with cytosine (G-C)
  7. 7. Base pairing
  8. 8. • These basic units are linked together to form strands by strong bonds between the deoxyribose sugar of one nucleotide and the phosphate of the next nucleotide. These strong bonds form a sugar-phosphate backbone. The ends of the DNA strand are called the 5' end (said as "5 prime end") at the phosphate end, and the 3' end at the deoxyribose end. The two strands of DNA are antiparallel which means that one strand runs in a 5’ to 3’ direction and the other runs in a 3’ to 5’ direction. This creates the twisting double helix structure of DNA.
  9. 9. • All cells store their genetic information in the base sequence of DNA, and it is this base sequence which forms the genetic code. The genotype is determined by the sequence of bases.
  10. 10. The molecular structure of DNA
  11. 11. DNA molecules are polymers • Polymers are large molecules that are built up by repeatedly linking together smaller molecules, called monomers. Think of how a freight train is built by linking lots of individual boxcars together, or how this sentence is built by sticking together a specific sequence of individual letters (plus spaces and punctuation). In all three cases, the large structure—a train, a sentence, a DNA molecule—is composed of smaller structures that are linked together in non-random sequences— boxcars, letters, and, in the biological case, DNA monomers.
  12. 12. • DNA monomers are called nucleotides • Just like a sentence “polymer” is composed of letter “monomers,” A DNA polymer is composed of monomers called nucleotides. A molecule of DNA is a bunch of nucleotide monomers, joined one after another into a very long chain.
  13. 13. • Reference: https://www.bbc.co.uk/bitesize/guides/z36mmp3/revision/3 https://www.ncbi.nlm.nih.gov/books/NBK26821/ https://www.google.com/search?q=nucleotide+structure&sxsrf=ALeKk03X_rRbft TaOHFFFzP2_putR- • I5jA:1595262279630&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiix4CMn9zq AhVHzIUKHdMxBKYQ_AUoAXoECA4QAw&biw=1024&bih=608#imgrc=Vu_P Y8xJVWcBoM • https://www.google.com/search?q=dna+structure&sxsrf=ALeKk01bxNtkItOy621sve rWmUyclGWz_g:1595262520475&source=lnms&tbm=isch&sa=X&ved=2ahUKEw jwsez- n9zqAhUvyoUKHY3cDMAQ_AUoAXoECBIQAw&biw=1024&bih=608 https://www.google.com/search?q=base+pairing&sxsrf=ALeKk03FiYg6b-89pEwVn- 9jNZaG3no3gA:1595262948823&source=lnms&tbm=isch&sa=X&ved=2ahUKEwi D5ozLodzqAhUqzYUKHQ6iD0EQ_AUoAXoECBQQAw&biw=1024&bih=608#im grc=C_cs1KGASUnO6M

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