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Summary Life Sciences (Biology) - Nucleic acids
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summary of nucleic acids
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NUCLEIC ACIDS:DEOXYRIBONUCLEIC ACID (DNA)
CHROMATIN NETWORK:
Network condenses to reveal individual chromosomes.
Long DNA strands wind around histones.
Histones = protein that prevents DNA from getting tangled.
STRUCTURE OF DNA:
Forms a double helix shape
Made up of subunits = nucleotides
Has Adenine, thymine, guanine, cytosine
Complimentary base paring means the order of the of the bases in the copy
strand is determined by the order of the bases in the template strand
Bases arranged in pairs of three called codons
A gene = a section of DNA that consists of a unique sequence to form a protein
DNA strand -> genes -> protein -> trait
NUCLEOTIDES:
Monomers of DNA = nucleotides
Each nucleotide contains
- Pentose sugar ( DNA – deoxyribose and RNA – ribose )
- Phosphate group
- Nitrogen containing base
Sugar + phosphate group = back bone of DNA
Nitrogen bases = rungs of DNA
Two types of bases
1. Pyrimidines:
- Consist of Cytosine, thymine and uracil
- Smaller bases ( only one circle)
- 3 weak hydrogen bonds
2. Purines :
- consists of adenine and guanine
- larger bases ( two circles)
- 2 weak hydrogen bonds
, DNA REPLICATION:
Takes place during interphase of mitosis
Important to transmit identical DNA to each new cell.
Step 1:
- Enzyme polymerase breaks up weak H bonds between N-Bases
- Helix uncoils
- Original strand provides code for the complimentary strand.
Step 2:
- Free nucleotides from nucleoplasm bond to complimentary bases ( A+T and
G+C)
- Deoxyribose sugar bonds with phosphates to form back bone
Step 3:
- Replication occurs along entire length of DNA
- DNA recoils into double helix
- One new DNA molecule = old strand + new strand
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