What is DNA?
DNA stands for deoxyribonucleic acid.
It contains the molecules that make up chromosomes and genes.
So, it contains the information that passes characteristics from one generation to another.
Spiral Structure
DNA is located in the nucleus of a cell.
It is made up of two interlocked spiral strands.
Genetic information is stored on the horizontal threads that connect the two spirals.
These threads store four different types of molecules in a code.
So, in the illustration below, the blue, pink, yellow, and green segments of the threads are each different types of molecules.
Function and Instructions
The function of DNA is to embody genetic instructions.
You can think of it as being somewhat like the blueprint for a house.
Using the blueprint, the builder has to interpret the design and build the house.
In the same way, the cells have to interpret and translate the DNA into action in the cells in the body.
DNA tells the cells what proteins to make and gives the protein its particular individuality.
It also communicates with the cytoplasm in the cells.
To understand the role of cytoplasm, you may want to view our post on cell structure.
Mutations
The most important point to remember about DNA mutations for your exam is that mutations normally occur very infrequently.
If DNA fails to copy itself correctly during reproduction, mutations can occur.
Mutations can be deadly because they change the way that certain cells work.
Mutations that occur in germ cells can cause variations to the offspring of an organism.
Mutations can also be caused by environmental factors.
DNA in Cell Replication
DNA replication takes place before mitosis can occur.
Just before cell division takes place, each part of the pair of chromosomes contain a double helix of DNA, which originates from the parent cell.
This is copied so that it can be passed from cell to cell during cell division.
Because of mitosis, the replicated cells have the same DNA as the parent cells.
DNA can reproduce itself by spitting in half, in much the same way as a zipper unzips.
Each thread can copy the missing thread to regenerate the genetic code.
Other Nucleic Acids
Nucleic acids are synthesized in chemical reactions controlled by enzymes.
Nucleic acids are long chains of smaller units called nucleotides.
RNA is another type of nucleic acid.
RNA is a single stranded nucleic acid.
Chromosomes, Genes, Proteins, and RNA
You may need to compare and contrast chromosomes, genes, proteins, and RNA for your exam.
A gene is a distinct sequence of nucleotides that form part of a chromosome.
A chromosome has a long coiled strand of DNA in its nucleus, with some special proteins and some RNA.
The main role of RNA is to act as a messenger to carry instructions from DNA.
Exercises
- What is the structure of DNA?
- What is the function of DNA?
- What happens when mutations occur in germ cells?
- What are nucleic acids?
- What is RNA?
Answers
- It is made up of two joined spiral strands. There are horizontal threads that connect the two spirals. These threads store the genetic code.
- It tells the cells what individual proteins to make and communicates with the cytoplasm in the cells.
- These mutations can result in variations to the offspring of an organism.
- Nucleic acids are chains of nucleotides.
- RNA acts as a messenger to carry instructions from DNA.
Now look at our post on cell differentiation.