DNA STRUCTURE AND FUNCTION Flashcards
What is the structure of DNA
Double Helix
Put the following in order from smallest to largest: nucleotide, genome, nitrogenous base, gene, nucleus, cell, codon, chromosome
nitrogenous base, nucleotide, codon, gene, chromosome, genome, nucleus, cell,
Give an overview of the structure of DNA
- Sugar phosphate backbone
- Deoxyribose Sugar
- Phosphodiester Bond
- Base Pairs
- with hydrogen bonds
Explain nucleotides fully
- Building blocks of nucleic acids
- Made up of :
1. Nitrogen containing group
2. One or more phosphate containing components
3. Sugars
What is noticed about nitrogen contains groups / bases
- 2 rings that are fused together
What is a purine
Consist of a 6 membered and a 5 membered nitrogen containing ring, fused together
- eg. Adenine and Guanine
What is a pyridmidine
- Only have a 6 membered nitrogen containing ring
eg. Thyamine and Cytosine
Explain Erwin Chargaff fully
- 1949
- Determined that despite the complexity of DNA
- the amount of Adenine = amount of thymine
- amount of guanine = amount of cytosine
Explain Wilkins and Rosalind Franklin
- 1950
- Made use of X-ray crystallography to determine the structure of DNA
- X-rays were passed through a DNA fibre and the images were “ caught “ on X-ray film by analysing the photographs which showed the shape of DNA
Explain Watson and Crick
- 1953
- Put together model of DNA structure
- 2 strands ( made up sugar phosphate with nitrogen bases between ) coiled around one another to form double helix
- Sugar phosphates form the backbone of the helix and the bases are on the inside
What are the bonds found in the DNA strand
Hydrogen; Covalent and Phosphodiester
Explain hydrogen bonds fully
- Between bases
- 2 between A & T
- 3 between G&C
Explain covalent bonds fully
- Sharing electron pairs between atoms
- Covalent bonds occur within each linear strand and strongly bond the bases; sugars and phosphate group
Explain phophodiester binds fully
- Bonds between the 3’ carbon of one nucleotide and the 5’ carbon of the adjacent nucleotide
- String covalent bonds that hold sugar phosphate backbone together
How do the strands run
Opposite directions
Explain 5’ and 3’
5’ = bears a phosphate group
3’ = hydroxyl group
Explain the ends of DNA in the nucleus
- DNA molecules in eukaryotic chromosomes is linear ( have 2 ends )
- Long stretches of nucleotides = telomeres
- 2000 Repeats of the sequence of 5’ GGTTAG 3’
What is the function of telomeres
- Start of long but as cell divide they get shorter and short till critical length then that cell has to die
- indicates cell age
- Protective caps
Process that results in cell death
Apoptocis
What are histones
Proteins that help package DNA strand
Nucleosomes
Related to histones
How is DNA used
To make proteins
What do genes have
Info to make RNA which is then translated to make the protein
What is the gene
Sequence of DNA nucleotides that codes for a specific proteins or RNA molecule and each organism has many genes
What is a genome
All the genetic material in an organisms cells
What are the 3 types of RNA
- mRNA ( messenger RNA )
-rRNA ( ribosomal RNA )
-tRNA ( transfer RNA )
Explain mRNA
- Carries info that specifies a protein
- Each gap of 3 mRNA bases in a row forms a codon, which is a genetic “ code word “ that corresponds to one amino acid
Explain rRNA
- Combines with proteins to form a ribosomes, the physical location of protein synthesis
- Some rRNA help to correctly align the ribosome and mRNA and others catalyse formation of the bonds between amino acids in developing protein
Explain tRNA
- Molecules are connectors that bind an mRNA codon at 1 end and a specific amino acid at the other end
- Their roles is to carry each amino acid to the ribosome at the correct spot along the mRNA molecule
