Molecular Biology Flashcards
What are the characteristics of genetic material?
Codes for information to generate an organism, passed to progeny, regulated decoding to suit development
What experiment identified DNA as the genetic material?
Hershey-Chase 1952
What is the composition of DNA
Pentose sugar group, phosphate group, nitrogenous group
Which carbon is the phosphate attached to in DNA
carbon 5
Which carbon is the nitrogenous group attached to
carbon 1
What is the common structure of purines?
2 rings and 9 atoms
What is the common structure of pyrimidines?
1 ring and 6 atoms
What are the purine bases?
Adenine and guanine
What are the pyrimidine bases?
Cytosine, thymine and uracil
What are the differences in groups between DNA and RNA
RNA has ribose and uracil, DNA has thymine and deoxyribose
How many hydrogen bonds bind adenine and thymine?
2
How is DNA replicated?
Semi-conservatively
What enzyme catalyses polymerisation of nucleotides
DNA polymerase
Where are incoming nucleotides added?
Free hydroxyl on 3’carbon of the terminal deoxyribose
How do DNA strands get their polarity ?
oriented antiparallel to one another
Does DNA have a polarity?
YES
How is DNA synthesis initiated
replication fork
What enzyme separates paired DNA strands?
DNA helicase
What direction does DNA synthesis occur in?
5’ prime to 3’ direction
Why can new strands not be synthesised continuously?
antiparallel orientation of parental strands and unidirectional orientation of new DNA synthesis
What are Okazaki fragments?
short fragment of DNA
Which strand synthesises Okazaki fragments?
Lagging strand
Describe the synthesis of the lagging strand
discontinuous
Describe the synthesis of the leading strand
continuous
What is the function of an RNA primer
Extension of primer initiates synthesis of each new DNA strand
What is the function of RNA polymerase (DNA primase)
initiates ALL okazaki fragments and ALL leading strands
What is the function of DNA ligase
Covalently link okazaki fragments of the lagging strand
How is transcription of a typical prokaryotic gene initiated?
by binding of RNA polymerase to DNA sequences in the promoter region
Where does the promoter region lie in reference to the transcription site?
Upstream
When is transcription terminated in prokaryotes?
when RNA polymerase encounters a terminator region
What does the terminator region promote?
Dissociation of RNA polymerase from DNA
What is transcription rate limited by?
Frequency of transcription initiation
What are the three phases in the transcription of eukaryotic genes?
Initiation, Elongation, termination
How is gene expression mainly controlled in organisms?
control of rate of transcription initiation by RNA polymerase
Where are exons present?
translated mRNA
What happens to introns?
spliced out of primary RNA transcript, DONT appear in mature mRNA
What is the function of RNA processing ?
provide control points for regulating gene expression
Describe the Hershey-Chase experiment
used viruses with radioactive DNA to infect bacteria, viruses inject genetic material in bacteria, bacteria exhibit radioactivity
