Key Definitions in Genetics
In genetics, understanding the terms chromosome, gene, allele, and DNA is essential.
- Chromosome: A chromosome is a thread-like structure composed of DNA and proteins. It carries genetic information and is found in the nucleus of eukaryotic cells. Humans have 46 chromosomes arranged in 23 pairs.
- Gene: A gene is a specific segment of DNA that contains the instructions for making a particular protein or RNA molecule. Genes determine traits such as eye color or blood type.
- Allele: An allele is a variant form of a gene. For example, the gene for eye color may have alleles for blue, brown, or green eyes. Alleles can be dominant or recessive.
- DNA (Deoxyribonucleic Acid): DNA is the molecule that carries the genetic instructions for life. It consists of two long strands forming a double helix, composed of nucleotides that include adenine, thymine, cytosine, and guanine.
Understanding these terms helps in grasping how traits are inherited and expressed in living organisms.
Key points to remember
- Chromosomes are structures made of DNA and proteins.
- Genes are segments of DNA that encode proteins.
- Alleles are different forms of a gene.
- DNA carries genetic information in a double helix structure.
Worked example
Define a gene and an allele.
- A gene is a segment of DNA that codes for a specific trait.
- An allele is a variant form of a gene that can influence the trait.