Chapter 8 - Structure Of DNA Flashcards
Pairing of bases
Each organic base can only pair with one other type of base:
Adenine always pairs with thymine, via two hydrogen bonds
Guanine always pairs with cytosine, via three hydrogen bonds
As a result these pairings are complimentary
Nucleotide structure
A sugar, deoxyribose bonds with a phosphate, and an organic base, these bonds are made via condensation reactions
How is the DNA molecule adapted to carry out its functions?
Very stable (pass from generation to generation without change)
Two separate strands are joined with only hydrogen bonds, which allow them to separate during DNA replication and protein synthesis
Large molecule, carries vast amounts of genetic information
By having the base pairs within the cylinder of deoxyribose-phosphate backbone the genetic information is somewhat protected
Why is it beleived that there must be a minimum number of 3 bases to code for each amino acid
Only 20 amino acids occur regularly in proteins
Each amino acid must have its own code of bases
Using pair bases only 16 amino acids could be made
Using triplet bases 64 amino acids can be made- this suggests that each amino acid has more that one code for itself.
Chromosome structure
DNA combined with proteins is coiled
Coils fold to form loops
The loops are then further coiled, making the strands supecoil, and pack together to form the chromosome
Homologous chromosome pair
A chromosome pair that determine the same genetic characteristics
What is mitosis
Produces two daughter nuclei with the same number of chromosomes as the parent cell and as each other
What is meiosis?
Produces four daughter cells each with half the number of chromosomes than the parent cells
What is an allele?
One of the different forms of a particular gene
What is a locus?
Position of a gene on a chromosome
Genetic recombination by crossing over
The chromatids of each pair become twisted around each other
Tensions are created and sections of the chromatids break off
Broken sections rejoin with the chromatids of the homologous partner
In this way new genetic combinations are produced
