CMMB 411 Lecture Notes - Lecture 28: Eukaryotic Dna Replication, Okazaki Fragments, Reverse Transcriptase

24 views2 pages

rosefrog223

8 Dec 2018

School

University of Calgary

Department

Cellular, Molecular and Microbial Biology

Course

CMMB 411

Professor

Sui-Lam Wong

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Because a primer is needed for the lagging strand, a little bit of dna will be lost from the end of the chromosome during each replication cycle this is the end replication problem . End replication problem: with the standard mechanism of leading and lagging strands, you will always end up loosing a bit of dna with each round of replication. The 3" end of the chromosome will still have the rna primer, which, when removed, there is nothing to fill that sequence. So that sequence will be missing the next round of the cell cycle (replication) Telomerase is an enzyme that adds repeats to the end of chromosomes. Telomerase contains an rna subunit (template) and a reverse transcriptase subunit. The reverse transcriptase polymerizes telomeric repeats at the ends of the chromosome. For humans, the template sequence in the rna is 5" cuaacccuaa 3". Reverse transcriptase uses rna as the template to make dna.

Related Questions

1) What is the difference between the leading strand and the lagging strand in DNA replication? Place the following steps of DNA replication in right chronological order.

1. Primase adds an ribonucleotide primer
2. Initiator proteins bind the origin of replication and helicase breaks hydrogen bonds between complementary bases of double stranded template DNA
3. DNA polymerase III extends by complementary base pairing deoxyribonucleotides to the template strands
4. Ligase phosphodiester bonds the nucleotides to connect okazaki fragments nad connect fragments at the origin and where the "crotches or forks" collide
5. DNA polymerase I removes RNA primer and replaces with Deoxyribonucleotides

2) Given the template DNA and primer sequences below, what bases will be added to the primer as DNA replication proceeds? (The bases should appear in the order that they will be added)

5'-GTCGTCTCCCTTTTTAAAAACCCCCCC-3'
5'-UUUUUAAAAAGGG-3'

3) Given the DNA sequence below, what could be a primer sequence used in its replication?
5'-CGTACGGCCCCAAAATTGCTACTCTGCTG-3'

raspberryleopard304

Make a table that contains the names and functions of DNAreplication actors in both prokaryotes and eukaryotes (ifapplicable).

Prokaryote	Eukaryote	Function(s)
		Sliding clamp that keeps polymerase onDNA
		Protein complex that loads clamp ontoDNA, associates with polymerase and helicase to keep replication ofboth strands at the replication fork
		Removes RNA primers
		Endonuclease that cuts off the RNAprimer from new DNA strand
		seals a nick with a phosphodiesterbond in the DNA backbone
		DNA sequence capping the ends oflinear chromosomes
		Enzyme that adds new DNA to the end oflinear chromosomes
		RNA component that acts as template
		Enzyme (protein) part that adds DNA from RNA template
		Structure formed to protecttelomere-capped chromosome ends