1.3) Gene Expression Flashcards
1
Q
- What are 2 stages of gene expression and what are the 3 types of RNA involved?
A
STAGES: 🧫
1. Transcription
2. Translation
TYPES of RNA: 🧬
1. mRNA (Messenger RNA)
2. tRNA (Transfer RNA)
3. rRNA (Ribosomal RNA)
2
Q
- What is Ribonucleic Acid (RNA)?
A
- RNA is a single-stranded molecule 🧬
- RNA is also composed of nucleotides
↳ which are made up of:
➜ Phosphate Group
(Organic) Base
Ribose Sugar - Bases in RNA:
Cytosine 🔵
Guanine 🟠
Adenine 🔴
Uracil 🟣
3
Q
- What are the differences between DNA and RNA?
A
-
Number of nucleotide strands present: 🧬
1. DNA ➞ 2 strands (double-stranded)
2. RNA ➞ 1 strand (single-stranded) -
Complementary base pair or adenine: 🔄️
1. DNA ➞ Thymine
2. RNA ➞ Uracil -
Sugar present in a nucleotide: 🍭
1. DNA ➞ Deoxyribose
2. RNA ➞ Ribose
4
Q
- What is mRNA and what is its function?
A
- Messenger RNA (mRNA) carries a copy of the DNA code from the nucleus to the ribosome ⭐
- mRNA:
- transcribed from DNA in the nuclues
- translated into proteins by ribosomes in the cytoplasm.
- Each triplet of bases on the mRNA molecule is called a ‘codon’
which codes for a specific amino acid.
5
Q
- What is tRNA and what is its function?
A
- Transfer RNA (tRNA) folds due to complementary base pairing.
- Each tRNA molecule carries its specific amino acid to the ribosome. ⭐
- A tRNA molecule has an:
- ‘anticodon’ (an exposed triplet of bases) at one end
- ‘attachment site’ (for a speicifc amino acid) at the other end.
(‘t - taxi)
6
Q
- What is rRNA and what is its function?
A
- Ribosomal RNA (rRNA) and proteins form the ribosome. ⭐
7
Q
- What is the 1st step of Transcription?
A
1st STEP:
1. RNA polymerase moves along the DNA strand
➞ causing it to unwind and unzip
↳ by breaking the hydrogen bonds between the bases.
8
Q
- What is the 2nd step of Transcription?
A
2nd STEP:
* As RNA polymerase break the bonds,
➞ it synthesises a primary transcript of mRNA 📜
↳ using RNA nucleotides.
- These form hydrogen bonds with the exposed DNA strand
➞ by complementary base pairing. - As this happens,
➞ a strong sugar-phosphate backbone is formed along the mRNA molecule
↳ and it seperates from the DNA strand.
9
Q
- What is the 3rd step of Transcription?
A
3rd STEP:
* The primary transcript
➞ contains INTRONS and EXONS
↳ - Introns:
➜ non-coding regions 🔴
Exons:
➜ coding regions 🟢
- Before leaving the nucleus,
➞ the introns are removed ❌ and the remaining exons are joined together ✅
↳ to form a ‘mature transcript’ - This process is called ‘splicing’
➞The order of the exons is unchanged during splicing.
10
Q
- What is the 4th step of Transcription?
A
- Once splicing has taken place,
➞ the mature transcript exits the nucleus and heads to the ribosome. - The template DNA strand then reforms.
- ATP is also essential for this process to occur.
11
Q
- What is the 1st step of Translation? (including its requirements)
A
-
REQUIREMENTS:
➞ mRNA strand
➞ Ribosome (rRNA & protein)
➞ tRNA
➞ Amino acids - The mature mRNA transcript
➞ travels through the cytoplasm and attaches to the ribosome
12
Q
- What is the 2nd step of Translation?
A
- The first codon of an mRNA molecule
➞ is a START codon.
↳ This signals the beginning of translation.
13
Q
- What is the 3rd step of Translation?
A
- tRNA molecules
➞ transport specific amino acids to the ribosome.
14
Q
- What is the 4th step of Translation?
A
- The tRNA anti-codons
➞ match up with mRNA codons
↳ and form complementary base pairs.
15
Q
- What is the 5th step of Translation?
A
-
Peptide bonds
➞ form between the adjacent amino acids
↳ to form the polypeptide (protein).
