29 Questions
What direction does DNA replication proceed on the leading strand?
5' to 3'
What is the function of exonuclease in DNA replication?
To remove RNA primers from the original strands
What is the direction of DNA replication on the leading strand?
5' to 3'
What is the process of replication on the lagging strand called?
Discontinuous
What is the role of DNA primase in DNA replication?
to generate primers
What are the repeated DNA sequences at the end of chromosomes called?
Telomeres
What binds to the 3' end of the strand during DNA replication?
primer
What is the role of RNA primers in DNA replication?
To act as a starting point for DNA replication
What is the function of DNA polymerase III in E. coli?
main replication enzyme
What is the function of DNA ligase in DNA replication?
To join Okazaki fragments together
Which enzyme is responsible for unwinding and rewinding DNA strands during replication?
Topoisomerase or DNA Gyrase
What is the phosphate group attached to in DNA?
5' end
How does the lagging strand begin replication?
By binding with multiple primers
What is the first step in gene expression?
Transcription
What is the direction of the replication fork?
bi-directional
What is the final product of DNA replication?
Two DNA molecules, each with one strand from the parent molecule and one new strand
What is the process of converting a gene's DNA sequence into the structures and functions of a cell?
Gene expression
What is the term for the process of creating a copy of DNA?
DNA replication
What is required for DNA replication to occur?
A strand of DNA, substrates, DNA polymerase, and a source of chemical energy
What is the result of DNA replication?
Two new DNA molecules, each with one old and one new strand
What type of genes are not translated into protein?
Non-protein coding genes
What is the function of DNA helicase?
To unwind the double-stranded DNA molecule
What is the primary function of telomerase in DNA replication?
Catalyzing the synthesis of telomere sequences at the ends of DNA
What molecules dock on a mature mRNA transcript during translation?
Ribosomes and tRNA
What is the primary function of RNA polymerase?
To synthesize a complementary strand of RNA
In what direction does RNA polymerase build an RNA strand?
5' to 3'
What is the process of creating proteins from an mRNA template?
Translation
What is the primary function of DNA polymerases during DNA replication?
To synthesize new DNA molecules by adding nucleotides to leading and lagging DNA strands
What modifications are made to RNA molecules after transcription in eukaryotes?
Splicing and poly-A tail addition, as well as 5' cap addition
Study Notes
DNA Replication
- DNA replication is a semiconservative process, where each parent strand serves as a template for a new strand, resulting in two new DNA molecules, each with one old and one new strand.
- The process occurs in the 5' to 3' direction.
- DNA replication requires a template strand, deoxyribonucleoside triphosphates (dATP, dGTP, dCTP, dTTP), DNA polymerase, and a source of chemical energy.
Replication Fork Formation
- DNA helicase unwinds and separates double-stranded DNA, breaking hydrogen bonds between nucleotide pairs, forming a replication fork.
- The leading strand is oriented 5' to 3', while the lagging strand is oriented 3' to 5'.
Primer Binding
- A short RNA piece called a primer binds to the 3' end of the leading strand, serving as the starting point for replication.
- Primers are generated by the enzyme DNA primase.
Elongation
- DNA polymerase synthesizes new DNA molecules by adding nucleotides to the leading and lagging strands.
- In bacteria, polymerase III is the main replication enzyme, while polymerases I, II, IV, and V are responsible for error checking and repair.
- In eukaryotic cells, polymerases alpha, delta, and epsilon are the primary polymerases involved in DNA replication.
- The leading strand is replicated continuously, while the lagging strand is replicated in short, discontinuous pieces called Okazaki fragments.
Termination
- An enzyme called exonuclease removes RNA primers from the original strands, replacing them with appropriate bases.
- DNA ligase joins Okazaki fragments together, forming a single, unified strand.
- Telomeres act as protective caps at the end of chromosomes, preventing nearby chromosomes from fusing.
Gene Expression
- Gene expression is the process of converting a gene's DNA sequence into the structures and functions of a cell.
- Non-protein coding genes are not translated into protein.
- Genetic information is transferred to a daughter cell through DNA replication and expressed by transcription followed by translation.
Transcription
- Transcription is the first step in gene expression, involving the copying of a gene's DNA sequence to make an RNA molecule.
- The process involves three stages: initiation, elongation, and termination.
- In eukaryotes, RNA molecules must be processed after transcription, involving splicing, 5' capping, and poly-A tailing.
Translation
- Translation refers to the process of creating proteins from an mRNA template.
- The sequence of nucleotides on the RNA is translated into the amino acid sequence of proteins, carried out by ribosomes.
- The process requires multiple enzymes and energy from ATP and GTP.
Test your knowledge on the process of gene expression, DNA replication, and the transfer of genetic information from one generation to the next. Learn about transcription, translation, and the semiconservative nature of DNA replication.
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