Transcription-13 Flashcards
DNA vs RNA
DNA (deoxyribonucleic acid) Sugar: Deoxyribose N bases: A, C, G and T Complementary base pairing A-T Double stranded and longer in length Exists in 1 form More stable-less reactive due to C-H bond at 2nd Carbon position
RNA (Ribonucleic acid)
Sugar: ribose
N bases: A,C,G and U
Complementary base pairing A-U
Single stranded and shorter in length
Exist in several forms such as mRNA, rRNA and tRNA
Less stable-more reactivity due to C-OH bond at 2nd carbon position
Gene expression:
Every cell of the body (with a dew exceptions) contains a full set of chromosomes and identical genes
Only a fraction of these genes is turned on, however, and it is the subset that is “expressed” that confers unique properties to each cell type
[] Proper expression of a large number of genes is a critical component of normal growth and development and the maintenance of proper health
[] Disruptions or changes in gene expression are responsible for many diseases
What is gene regulation?
Gene regulation refers to the ability of cells to control their level of gene expression
Majority of genes are regulated so proteins produce at certain times and in specific amounts
Constitutive genes are unregulated and have essentially constant levels of expression
What are the benefits of gene regulation?
- Conserves energy- proteins produced only when needed
2. Ensures genes expressed in appropriate cell type and at the correct stage in development
Define Gene expression:
process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins
What is the purpose of Gene expression in the Central Dogma of Biology?
Serves as a blueprint to make RNA
DNA acts as a template for making RNA, which in turn acts as a template for the manufacture of proteins
During gene expression (protein synthesis), transcription copies DNA into RNA, and translation makes proteins from RNA
Where does transcription take place?
Nucleus
What is genomic DNA?
contains the master blueprint for all cell structures and activities
Where does Translation take place?
Ribosomes
What is mRNA?
Messenger RNA are the specific, short lived gene transcription
Translation:
From RNA nucleic acid language
3 nucleotides-genetic code) to protein amino acid language (20 amino acids
Gene expression: an Overview
Transcription and Translation
Transcription: the first step of gene expression. The sequence of nucleotides in DNA is copied to a sequence of nucleotides in mRNA (the transcript)
Translation: the second step, mRNA is translated into a sequence of amino acids
What is transcription?
process of making an RNA copy of a single gene
What is a gene?
specific regions of the DNA of a chromosome
How do cells know which gene to express?
- Ligand (first/primary messenger) aka signals to bind to specific receptors of the cells
- Trigger a series of signaling pathway (aka signal transduction) to activate the target proteins which serve as transcriptional factors
- Target proteins enter the nucleus, together with other regulatory proteins to form the transcriptional complex to activate the transcription of the genes of interest
What is the product of transcription?
RNA
What is the enzyme for performing transcription?
What are the substrates used?
RNA polymerase
RNA synthesis uses NTPs (ATP,CTP,GTP,UTP) as substrates
Overview of transcription strands:
DNA double helix has 2 strands
Only ONE of them is transcribed:
Transcribed strand: template strand or antisense strand
Non-transcribed strand: coding strand or sense strand
RNA is complementary to the template or antisense strand
The RNA has the same sequence as DNA coding or sense strand
What are the 3 stages of Transcription?
- Initiation
- Elongation
- Termination
What are transcription factors?
proteins that regulate the transcription of genes
When does transcription begin?
Transcription begins when RNA polymerase (RNAP) binds to a promoter sequence near the beginning of a gene (directly or through helper proteins)
What occurs during the initiation stage of Transcription?
- Begins with RNA polymerase binding to a promoter sequence near the beginning of a gene (directly or through helper proteins)
- After polymerase is bound to the promoter DNA, the two strands unwind and the enzyme starts transcribing the template strand
- The region of opened up DNA is called a transcription bubble
What occurs during the initiation stage of Elongation?
- RNA polymerase moves along DNA template and adds nucleotides in the 5’-3’ direction
- RNA polymerase reads the template DNA strand and adds nucleotides to the 3’ end of a growing chain
- new nucleotides are added at an estimated rate of about 42-54 nucleotides per second in bacteria
- eukaryotes proceed at a much slower pace of approximately 22-25 nucleotides per second
- produces an RNA copy that is complementary to the template
- As RNA polymerase moves long, DNA double helix reforms
What occurs in the termination stage of Transcription?
1- Transcription stops when RNA polymerase reaches DNA terminator
- RNA strand is released
