Chapter 8 - Structure Of DNA Flashcards Preview

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Flashcards in Chapter 8 - Structure Of DNA Deck (11):

Nucleotide structure

A sugar, deoxyribose bonds with a phosphate, and an organic base, these bonds are made via condensation reactions


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


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