1. DNA's Double Helix Structure:
* Two strands: DNA consists of two long strands of nucleotides, each twisted around the other to form a double helix.
* Complementary base pairing: The two strands are held together by weak hydrogen bonds between specific pairs of nitrogenous bases:
* Adenine (A) always pairs with Thymine (T)
* Guanine (G) always pairs with Cytosine (C)
* Sugar-phosphate backbone: The backbone of each strand is made of alternating sugar (deoxyribose) and phosphate molecules.
2. Replication:
* Unwinding: The double helix unwinds, separating the two strands.
* Base pairing: Each strand acts as a template for the synthesis of a new complementary strand. This is done by an enzyme called DNA polymerase, which reads the existing strand and adds the appropriate nucleotides (A, T, G, C).
* Two identical copies: The result is two identical DNA molecules, each consisting of one original strand and one newly synthesized strand.
3. Genes and Traits:
* Genes: Segments of DNA that carry the code for specific proteins. These proteins are responsible for a vast array of biological functions, which ultimately determine our traits.
* Inheritance: During sexual reproduction, each parent contributes one chromosome from each pair to their offspring. This means the offspring receives one copy of each gene from their mother and one from their father.
* Variation: Differences in the DNA sequence between parents and offspring are what cause variations in traits. These differences can arise from mutations, which are changes in the DNA sequence.
In Summary:
DNA's double helix structure allows for accurate replication, ensuring that the genetic code is passed on intact from one generation to the next. The genes contained within this code determine traits, and variations in the DNA sequence lead to the diversity we observe among individuals.
