RNA structure
Laura Armstrong
Teacher
Recall Questions
This topic requires prior knowledge of nucleic acids and DNA structure. You can test your knowledge on these below.
What are the three main types of RNA?
mRNA (messenger RNA), tRNA (transfer RNA), rRNA (ribosomal RNA)
How does the structure of RNA differ from DNA?
-
RNA is single-stranded whereas DNA is double stranded.
-
RNA contains ribose sugar instead of deoxyribose sugar.
-
RNA has uracil (U) instead of thymine (T).
-
RNA is shorter than DNA (it has fewer nucleotides).
What type of bond forms between complementary bases in DNA?
Hydrogen bonds.
Topic Explainer Videos
Check out this @LauraDoesBiology video that explains RNA structure or read the full notes below. Once you've gone through the whole note, try out the practice questions!
RNA Structure
RNA (ribonucleic acid) is a polynucleotide involved in protein synthesis. Unlike DNA, which serves as the permanent genetic blueprint, RNA acts as a temporary copy of genetic information and plays various roles in the cell.
DNA contains deoxyribose sugar with a hydrogen (H) below carbon 2. RNA contains ribose sugar with a hydroxyl group (OH) below carbon 2.
These are both pentose sugars with 5 carbons.
Types of RNA and Their Functions
1. mRNA (Messenger RNA)
-
Carries the genetic code from DNA to the ribosome.
-
Single-stranded and varies in length depending on the gene being expressed.
-
mRNA is linear so there are no complementary base pairs or hydrogen bonds within the mRNA molecule itself.
-
Has codons (sets of 3 bases which code for a specific amino acid.
2. tRNA (Transfer RNA)
-
Brings specific amino acids to the ribosome during translation.
-
Has a folded, cloverleaf shape so there are complementary base pairs and hydrogen bonds between them.
-
Has an anticodon that pairs with mRNA codons.
-
Has an amino acid binding site.
3. rRNA (Ribosomal RNA)
- Forms part of the ribosome structure (along with protein).
Key Terms
-
Polynucleotide: A long chain of nucleotides linked by phosphodiester bonds.
-
Uracil (U): A nitrogenous base found in RNA, replacing thymine.
-
Ribose: A five-carbon or pentose sugar in RNA nucleotides.
-
Anticodon: A sequence of three bases on tRNA complementary to mRNA codons.
-
Transcription: The process where mRNA is synthesised from a DNA template.
-
Translation: The process where ribosomes use mRNA to assemble proteins.
No answer provided.
Exam Tip
Make sure you can compare DNA and RNA structures concisely in an exam. A good way to remember the differences is to focus on the three key changes: RNA is single-stranded, has ribose sugar, and has uracil replacing thymine.
No answer provided.
Describe the structure and function of RNA and contrast it to that of DNA. (6 marks)
-
RNA is a single-stranded polynucleotide whereas DNA is a double stranded polynucleotide.
-
RNA is composed of ribose sugar whereas DNA has deoxyribose sugar.
-
RNA has the nitrogenous bases adenine, uracil, cytosine, and guanine, unlike DNA, which has thymine, not uracil.
-
RNA is shorter and DNA is longer.
-
mRNA carries a copy of the genetic code to the ribosome for translation.
-
tRNA carries specific amino acids to the ribosome during translation.
-
DNA primarily stores genetic material in the nucleus.
Practice Question 1
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!
Practice Question 2
If you want to try out another one, check this video out and see how you do!