Gene Expression - Transcription + Translation Flashcards
What is Diamond Blackfan anaemia?
Decreased erythrocytes progenitor cells in bone marrow»_space; anaemia
Mutation in ribosomal genes
What is a gene?
A stretch of DNA
A unit of inheritance which is transferred from parent to offspring - determines characteristics of offspring
Where does transcription occur?
In the nucleus
Describe the start and end of protein structure
N terminal at start
C terminal at end
5 to 3 - N to C
Describe the start and end of mRNA structure
5’ at start
3’ at end
5 to 3 - N to C
What are the types of RNA
mRNA
rRNA
tRNA
What are the 3 stages in DNA transcription?
1- initiation
2- elongation
3- termination
What is needed for transcription?
Enzyme - RNA polymerase
Active substrate - nucleotide triphosphates
Template - DNA
Identify 3 stop codons
UAA
UAG
UGA
Identity the start codon
AUG
Methionine
What is transcription?
DNA is copied to mRNA by RNA polymerase
Describe initiation in transcription
Transcription factors bind to promote
RNA polymerase follows + binds
Describe elongation in transcription
- DNA strand unwinds
- RNA polymerase reads nucleotide sequence of template strand > mRNA is made 5’ to 3’
Describe termination in transcription
- RNA polymerase reaches the end of the gene
- RNA polymerase stops adding nucleotides to pre mRNA
- mRNA is released
- DNA strands reform double helix
What is an intron?
Sequences in pre-mRNA that is spliced out
Not transcribed
Non coding section
What is an exon?
Coding section
Sequence in pre-mRNA that is transcribed
Outline the process of RNA splicing
Removal of introns from pre-mRNA to form mature RNA of only exons
How are mRNA molecules processed?
- nucleotide cap - 5’ cap
- poly-A-tail - at 3’ end
Provide protection against degradation
What is polydenylation?
Addition of poly A tail
How is mature mRNA released?
Exported from nucleus into cytoplasm via nuclear pores for translation to occur
What is needed for translation?
Enzyme - ribosome
Active substrates - amino acids
Template - mRNA
What is translation?
Process in which ribosomes produce polypeptides from mRNA
Describe the structure and function of ribosomes
Structure - cytoplasmic organelle with large and small subunit
Function - site of polypeptide synthesis
What are the types of ribosomes?
- Free ribosomes - float in cytoplasm
- Bound ribosomes - attached to rough ER
Explain the role of ribosomes in translation
- Large subunit contains rRNA which acts as an enzyme
- rRNA makes peptides bonds between amino acids to form a polypeptide in translation
What does tRNA do?
Brings amino acids to the mRNA ribosome complex in translation
What are the attachment sites for tRNA?
- Anticodon - pairs with complementary codon of mRNA
- Site off attachment for amino acid
Describe initiation in translation
- 5’ end of mRNA binds to small ribosomal subunit and anticodon of initiator
- tRNA brings amino acid methionine which pairs with AUG start codon
Describe elongation in translation
- tRNA bring complementary amino acids to growing peptide chain
- rRNA forms peptide bonds between amino acids
Describe termination in translation
- occurs when ribosome reaches a stop codon
- release factors binds to stop codons
- polypeptide, mRNA + tRNA released from ribosome
Distinguish between the function of DNA replication, transcription and translation
DNA replication - making DNA
DNA transcription - making RNA
DNA translation - making polypeptide
Distinguish between the enzymes used in DNA replication, transcription and translation
DNA replication- DNA polymerase
DNA transcription - RNA polymarse
DNA translation - rRNA
Distinguish between the active substrate used in DNA replication, transcription and translation
DNA replication- dNTPs
DNA transcription - NTPs
DNA translation - amino acids
Distinguish between the template needed in DNA replication, transcription and translation
DNA replication- DNA
DNA transcription - DNA
DNA translation - mRNA
What is the role of the promoter region in gene expression?
- required for initiation of transcription
- permits RNA polymerase to bind
- controls timing of transcription
