Medical biochemistry Flashcards
Explain the process of transcription
Divided into three stages i.e. Initiation, Elongation and Termination.
Initiation: With the help of transcription factors, RNA polymerase binds to the promoter, pries apart the two DNA strands, and initiates mRNA synthesis at the start point on the template strand.
Elongation: As the RNA polymerase moves along the template strand, elongating the mRNA transcript one base at a time, it unwinds the DNA double helix before it and rewinds the double helix behind it.
Termination: mRNA synthesis ends when the termination signal is reached. RNA polymerase and the completed mRNA transcript are released
Outline the similarities between transcription and Replication
Both involve enzymes that synthesis a new strand of nucleic acid complementary to DNA template strand
.5’_3’ polarity
.Adherence to Watson/Crick base pairing rules
.Large multicomponent initiation complexes
Differences between replication and Transcription
The template in Replication is double stranded while the template in transcription is single stranded.
.In Replication there is a primer, there is none in transcription.
.Enzyme initiating process in replication is DNA polymerase whilst the enzyme initiating transcription is RNA polymerase
.The product of replication is double stranded DNA whilst the product of transcription is single stranded RNA.
.In replication Adenine binds with Thymine whilst in transcription Adenine binds with Uracil
What is the structure of DNA
DNA is a double-stranded helix composed of nucleotides. The strands are antiparallel, with alternating sugar-phosphate backbones and nitrogenous bases facing inward. The base pairing rule is A = T and G ≡ C.
Describe the process of DNA replication.
DNA replication involves unwinding and separating the DNA strands, followed by complementary base pairing and the addition of nucleotides to form new DNA strands. It occurs in the 5’ to 3’ direction and is semi-conservative, meaning each daughter molecule has one parental strand and one new strand.
What enzymes are involved in DNA replication?
Helicase unwinds the DNA helix, DNA polymerase synthesizes new DNA strands, and DNA ligase joins the DNA fragments together. Primase synthesizes RNA primers to initiate DNA replication.
What is the significance of DNA replication during the S phase of the cell cycle?
DNA replication occurs during the S phase of the cell cycle to ensure that each daughter cell receives a complete set of genetic information.
How do telomeres protect chromosomal ends during DNA replication?
Telomeres are repetitive DNA sequences located at the ends of chromosomes. They protect chromosomal ends by providing a buffer against the loss of genetic material during DNA replication, as DNA polymerase cannot replicate the very ends of linear chromosomes.
What is the central dogma of molecular biology?
The central dogma states that genetic information flows from DNA to RNA to protein. DNA serves as the storage molecule for genetic information, which is transcribed into RNA and then translated into proteins.
What are the differences between DNA and RNA?
DNA is double-stranded, while RNA is typically single-stranded. DNA uses deoxyribose sugar, while RNA uses ribose sugar. Additionally, DNA contains thymine (T) as a base, while RNA contains uracil (U) instead of thymine.
Explain the process of transcription.
Transcription is the process by which RNA is synthesized from a DNA template. It involves the binding of RNA polymerase to the DNA promoter region, elongation of the RNA strand, and termination of transcription when RNA polymerase reaches a terminator sequence.
What is alternative splicing?
Alternative splicing is a process in which different exons of a pre-mRNA transcript are spliced together in different combinations, leading to the production of multiple mRNA isoforms from a single gene. This increases the diversity of proteins that can be produced from a single gene.
How is mRNA processed before it leaves the nucleus?
mRNA undergoes several processing steps, including the addition of a 5’ cap and a poly-A tail. Additionally, introns are spliced out of the pre-mRNA transcript to produce a mature mRNA molecule ready for translation.
