Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
DNA stands for Deoxyribonucleic Acid and is the molecule that carries genetic information for the development and functioning of an organism.
The basic building block of DNA is the nucleotide, which consists of three parts: a phosphate group, a deoxyribose sugar (), and one of four nitrogenous bases.
There are four nitrogenous bases categorized into Purines ( and ) and Pyrimidines ( and ).
Complementary Base Pairing: Adenine () always pairs with Thymine () via hydrogen bonds, and Cytosine () always pairs with Guanine () via hydrogen bonds.
The DNA molecule is a double helix consisting of two antiparallel strands, meaning they run in opposite directions ( to and to ).
A gene is a specific sequence of nucleotides in DNA that codes for a functional product, usually a protein. The sequence of bases determines the sequence of amino acids.
DNA is organized into structures called chromosomes. Humans typically have pairs of chromosomes ().
📐Formulae
💡Examples
Problem 1:
A sample of double-stranded DNA is analyzed and found to contain Cytosine (). Calculate the percentage of Adenine () in this DNA sample.
Solution:
If , then by Chargaff's rule, . Together, . The remaining () must be . Since , the percentage of Adenine is .
Explanation:
According to Chargaff's rules, in any double-stranded DNA, the amount of Guanine equals Cytosine, and the amount of Adenine equals Thymine.
Problem 2:
Given the following DNA template strand sequence: , determine the sequence of the complementary DNA strand.
Solution:
Explanation:
To find the complementary strand, you must apply base-pairing rules ( and ) and ensure the orientation is antiparallel ( pairs with ).