Embedded Files
RELEVANT LEARNING OUTCOME:
(a) Describe the structure and roles of DNA and RNA (tRNA, rRNA and mRNA)(knowledge of mitochondrial DNA is not required).
Watch the video from 1:08 onwards on the structure of the DNA double helix.
💡Structure of DNA
💡Structure of DNA
Two polynucleotide chains
twisted around one another to form a double helix.
sugar-phosphate backbones faces the outside of the DNA molecule.
nitrogenous base faces / occupies the inside or centre of the molecule.
Anti-parallel
one strand runs in the 5' to 3' direction.
other strand runs in the 3' to 5' direction.
One complete turn of DNA double helix
ten base pairs spanning a distance of 3.4 nm.
width between the two backbones is 2 nm.
4. Complementary base pairing between purines and pyrimidines.
Adenine pairs with thymine OR uracil - two hydrogen bonds.
cytosine pairs with guanine - three hydrogen bonds.
5. Chargaff's rule: ratio of A to T, and C to G
A : T = C : G = 1 : 1
A + G (purines) = C + T (pyrimidine)
🖊️Check Your Understanding: Lecture Notes Checkpoint
🖊️Check Your Understanding: Lecture Notes Checkpoint
Count the following for BOTH DNA strands in the figure above:
The number of adenine to thymine
The number of cytosine to guanine
The number of purines to pyrimidines
Total number of adenine to thymine is 13 : 13, which is 1 : 1.
Total number of cytosine to guanine is 11 : 11, which is 1 : 1.
Total number of purine to pyrimidine is 24 : 24, which is 1 : 1.
🖊️Check Your Understanding: Learning Goals Checkpoint
🖊️Check Your Understanding: Learning Goals Checkpoint
Attempt section 1, Qn 4-9 of this SLS lesson.
💡Role of DNA
💡Role of DNA
Role: Storage molecule for genetic information
Reasons:
Store large amount of coded information within the cell
DNA can span several meters
Stable structure (3 types of bonds)
extensive hydrogen bonding between complementary nitrogenous bases
hydrophobic interactions between stacked nitrogenous bases
covalent phosphodiester bonds between adjacent nucleotides
no OH groups at carbon atom 2 of deoxyribose
Role: Template for protein synthesis
Reasons:
Each DNA strand acts as a template, leading to:
Accurate replication
Repair of damaged strand
Passing of genetic information to mRNA for protein synthesis eventually
🖊️Check Your Understanding: Learning Goals Checkpoint
🖊️Check Your Understanding: Learning Goals Checkpoint
Attempt section 1, Qns 10-11 of this SLS lesson.
💡Central dogma of molecular biology
💡Central dogma of molecular biology
The central dogma of molecular biology is the flow of genetic information from DNA through RNA to protein.
A dogma refers to a set of rules that has been agreed to be true.
Therefore, according to the dogma, the reverse (from protein to DNA) cannot happen. Of course, there will always be exceptions in biology.
Capable of carrying a large amount of coded information
Has a stable structure so that mutations rarely occur
Able to replicate accurately
Able to repair damage
Able to pass on genetic information to messenger RNA (via transcription)
🖊️Check Your Understanding: Conceptual Check Answers
🖊️Check Your Understanding: Conceptual Check Answers
1a) one molecule of DNA is composed of two polynucleotide chains
1b) a polynucleotide chain is composed of many nucleotides, each made up of a nitrogenous base, pentose sugar, and phosphoric acid.
2a) phosphodiester bond
2b) hydrogen bond
Content
Content
Page updated
Google Sites
Report abuse