14 Questions
What are the rules of base pairing in DNA according to the analysis of DNA molecules?
Adenine only bonds to Thymine and Cytosine only bonds with Guanine.
If a DNA molecule contains 20% Thymine, what is the percentage of Adenine in the molecule?
20%
How are the two strands of DNA related to each other?
They are complementary and read in opposite directions.
What is a gene in the context of DNA?
A unique sequence of bases on one strand of DNA, encoding a functional unit of information.
What is the primary reason for the variation in the number of genes and chromosomes among different species?
Different characteristics and requirements of each species.
What are the two vital functions necessary for life that the structure of DNA enables?
Making identical copies of itself and providing a code that can be used by cells to manufacture protein molecules.
What is the significance of the variation in the base code of DNA molecules?
It enables DNA to be a versatile and diverse molecule.
What are the four organic bases found in DNA nucleotides?
Adenine, cytosine, thymine, and guanine.
What is the result of the phosphate-sugar backbone structure in DNA?
One end of the DNA strand ends in a phosphate (5' end) and the other end in a sugar (3' end), giving the DNA strand directionality.
What is the advantage of the weak hydrogen bonds between complementary base pairs in DNA?
They are easy to break and reform, which is important in DNA replication.
Why is the overall negative charge of the DNA molecule helpful?
It helps separate DNA molecules.
What is the direction in which the sequence of DNA is written?
5' to 3' direction.
What is the role of the phosphate group in DNA nucleotides?
It attaches to the sugar of the next nucleotide, forming a backbone.
What is the significance of the 5' and 3' ends of the DNA strand?
They provide directionality to the DNA strand, with the 5' end having a phosphate and the 3' end having a sugar.
Study Notes
DNA Structure and Function
- DNA stores and transmits genetic information, allowing it to code for the vast variety of life on Earth.
- DNA's structure enables it to perform two vital functions: making identical copies of itself and providing a code for cells to manufacture protein molecules.
DNA Composition
- DNA nucleotides are complex molecules composed of deoxyribose (a pentose sugar), a phosphate group, and one of four organic bases: adenine, cytosine, thymine, and guanine.
DNA Backbone and Directionality
- The phosphate of one nucleotide is attached to the sugar of the next nucleotide, forming a backbone of alternating phosphates and sugars.
- This structure gives DNA directionality, with one end (5' end) terminating in a phosphate and the other end (3' end) terminating in a sugar molecule with a hydroxyl group.
- The sequence of DNA is written in the 5' to 3' direction.
Phosphate Group and Charge
- The phosphate group is negatively charged, giving the DNA molecule an overall negative charge.
- This negative charge helps separate DNA molecules.
Base Pairs and Hydrogen Bonds
- Each base forms weak hydrogen bonds with its complementary base on the other strand.
- The weak hydrogen bonds are advantageous for cells, allowing for easy breakage and reformation during DNA replication.
Base Pairing Rules
- Adenine only bonds with Thymine, while Cytosine only bonds with Guanine.
Complementary Bonding and DNA Analysis
- DNA analysis reveals that each species has identical amounts of Adenine and Thymine, and identical amounts of Guanine and Cytosine.
- This is evident in the rule that if there is 20% Thymine, there is also 20% Adenine, resulting in 30% Guanine and 30% Cytosine.
Chromosomes and Genes
- A chromosome is composed of many functional units of information called genes.
- Each gene is a unique sequence of bases on one strand of DNA (the coding strand).
- The sequence of bases in genes varies between DNA molecules, allowing DNA to be versatile and diverse.
- Different species have different numbers of genes and chromosomes, resulting in distinct characteristics.
Learn about the structure of DNA and its vital functions in storing and transmitting genetic information. Discover how DNA makes identical copies of itself and provides a code for the synthesis of proteins.
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