Chromosomes, genes and DNA Flashcards
Describe a nucleotide
C5 sugar, base and a phosphate
Describe a nucloside
-C5 sugar and a base
How are nucleotides joined together?
-Phosphodiester bonds
What are DNA/RNA
-Nucleic acids
What creates polarity across a molecule of DNA
- 5’ end had free phosphate group
- 3’ end has free -OH group
- This creates polarity
What is the difference between DNA and RNA
- RNA has ribose sugar with O2 on C2
- DNA has deoxyribose sugar with no O2 on C2
- RNA has bases A,U,G and C
- DNA has bases A, T, G and C
In which direction do DNA strands run?
-5’->3’
What is the structure of prymidines and which bases are they?
- Single ring structure
- Bases, C, U and T
What is the structure of purines and what are the bases?
-Two ring structure and bases A and G
Which bases pair together and why?
- G:C by 3 H bonds
- A:T by 2 H bonds
- Shape and constituents denotes bonding
What determines the secondary structure?
-The angle of the H bonds
Why do H bonds form between bases?
-Due to electronegativity of bases pulling electron cloud
What are stem loops and what can form them?
- RNA
- One strand folding up on itself as the two halves are complementary, eg tRNA
How is DNA packaged?
- chain of negative polynucleotides bound around a positive histone core to form a nucleosome
- Nucleosomes fold up into a selenoid
- Selenoids coil around each other and form loops
- Further folding and arranged on a scaffold
- Makes a chromosome
How is euchromatin packaged?
-beads on a string -> nucleosomes
