Unit 1: KA1 Structure of DNA Flashcards
Describe the structure of DNA.
DNA consists of two strands of repeating units called NUCLEOTIDES. These strands twist together to form a double helix.
The DNA strands are anti-parallel. What does this mean?
The two strands run in opposite directions.
What makes up a nucleotide?
A deoxyribose sugar, a phosphate and one of four bases.
What are the four bases? Which bases are complementary?
Adenine & Thymine
Guanine & Cytosine
How are complementary bases held together?
Using WEAK HYDROGEN BONDS.
*This is what holds the two strands of DNA together.
DNA has a sugar-phosphate backbone.
How is the phosphate of one nucleotide joined to the deoxyribose sugar of the next?
Via STRONG CHEMICAL BONDS
Which strand of DNA is the 5’ end?
The strand that starts with the phosphate.
*Remember to hi-5 phosphate! :)
Which strand of DNA is the 3’ end?
The one that starts with the deoxyribose sugar.
The order of bases (base sequence) of DNA is very important. What does it determine?
The Genotype
What type of cells are EUKARYOTES?
*you-carry…otes ;)
- animal
- plant
- fungal
What type of cells are PROKARYOTES?
- bacteria
- archaea
- Tend to be found in extreme environments
Describe the structure of DNA in a eukaryote.
Eukaryotes have linear chromosomes which are tightly coiled and packaged with associated proteins, called histones.
Small, circular chromosomes are found in the mitochondria and chloroplasts of animal & plant cells.
Yeast is a special example of a eukaryote as it also has plasmids.
Describe the structure of DNA in a prokaryote.
Prokaryotes have a single, circular chromosome and smaller circular plasmids.
Name the differences between eukaryotes and prokaryotes.
Eukaryotes:
- have membrane-bound organelles (such as the nucleus, where linear chromosomes are).
- linear chromosomes packaged around histones
- does not have plasmids
- Exception is yeast
Prokaryotes:
- have no membrane-bound organelles
- DNA is free in the cytoplasm
- has plasmids
