DNA Structure and Function Quiz

Study Notes

DNA Structure and Function

DNA is the molecule that determines the characteristics of living things.
It's composed of nucleotides, each containing a phosphate group, a deoxyribose sugar, and one of four nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C).
Adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C) - this is called complementary base pairing.
The arrangement of nucleotides determines the sequence of amino acids in proteins, ultimately influencing an organism's traits.

DNA Organization

DNA exists as a double helix, resembling a twisted ladder.
The sides of the ladder are made of alternating phosphate and sugar groups.
The rungs of the ladder are formed by the base pairs connected to the sugar groups.

Chromosomes

Chromosomes are long, thin, thread-like structures composed of DNA and protein.
They are found in the nucleus of cells.
Human cells typically contain 46 chromosomes arranged in 23 pairs except for red blood cells and gametes (sperm and egg cells), which have 23 chromosomes each.

Genes

Genes are segments of DNA that vary in length and base sequence along the DNA strand.
Each chromosome can contain over 1000 genes.
Genes provide instructions for building and maintaining an organism.
They determine traits by coding for specific proteins, which can be structural (e.g., keratin in skin, hair, nails), enzymatic (e.g., amylase for starch digestion), or regulatory (e.g., growth hormones).

DNA Replication

DNA replication occurs when the double helix separates, exposing the bases.
Free nucleotides in the nucleus pair with the exposed bases according to complementary base pairing.
This results in two identical DNA strands, ensuring that each new cell receives a complete copy of the genetic information during cell division.
After replication, chromosomes become double structures composed of two identical chromatids joined together. Each chromatid is a double helix of DNA.

Cell Division

Interphase: The period when the cell grows and DNA replication occurs, preparing for division.
There are two main types of cell division:
- Mitosis: Responsible for growth and repair, producing two daughter cells identical to the parent cell.
- Meiosis: Produces gametes (sperm and egg cells) with half the number of chromosomes as the parent cell.

Phases of Mitosis

Prophase: The DNA coils up, and separate chromosomes become visible.
Metaphase: The nuclear membrane breaks down, and chromosomes line up across the cell's equator. Spindle fibers extend from the poles of the cell to each chromosome.
Anaphase: Chromatids separate, becoming independent chromosomes, and are pulled to opposite poles of the cell.
Telophase: The nuclear membrane encloses the chromosomes at each pole, and the chromosomes uncoil.
Cytokinesis: The cytoplasm divides, completing the process of mitosis.

Description

Test your knowledge on the structure and function of DNA. This quiz covers the composition of nucleotides, base pairing, DNA organization as a double helix, and the role of chromosomes in cells. Challenge yourself to better understand the fundamental molecule of life!