Genetics Foundations: DNA, Genes, and Chromosomes
What Genetics Studies
Genetics in Context
Genetics is the study of heredity and variation in living organisms. It explains how biological information is stored, copied, transmitted, and expressed across generations.
Core Terms
A gene is a functional unit of heredity, usually a stretch of DNA that contributes to a trait or product. A genome is the complete set of genetic material in an organism. In eukaryotes, DNA is packaged into chromosomes with the help of proteins such as histones.
Key Components of Genetic Material
| Term | Meaning |
|---|---|
| DNA | The molecule that stores hereditary information in most organisms |
| Gene | A DNA sequence with a biological function |
| Chromosome | A packaged DNA molecule containing many genes |
| Genome | The full genetic complement of an organism |
Why Packaging Matters
DNA packaging is not just for storage; it also affects which genes can be accessed and expressed by the cell.
DNA Structure and Information
Molecular Structure
DNA is a double-stranded polymer made of nucleotides. Each nucleotide contains a sugar, a phosphate group, and a nitrogenous base. Base pairing is complementary: pairs with , and pairs with .
Directionality
DNA strands have polarity. One strand runs and the other runs . This directionality is essential for replication and transcription.
Which statement best describes a gene?
A gene is a DNA sequence that encodes a functional product, often a protein or functional RNA.
Correct answer: A DNA region that contributes to a functional product
What two bases pair with adenine and guanine in DNA?
Complementary base pairing is - and -.
Correct answer: Thymine pairs with adenine, and cytosine pairs with guanine.
What does the genome refer to?
The genome is the full complement of DNA in an organism.
Correct answer: All the DNA in an organism