Lecture 2 - Organisation of genetic information Flashcards
How is DNA packaged in prokaryotes?
DNA is circular, lacks a nuclear membrane, and is supercoiled to fit inside the nucleoid region.
What are the key differences between chromosomes in prokaryotes and eukaryotes?
Prokaryotic chromosomes are circular and lack introns.
Eukaryotic chromosomes are linear, paired, and contain introns.
What is DNA supercoiling, and why is it important?
Supercoiling is the overwinding or underwinding of DNA, important for compaction and facilitating processes like replication and transcription.
How is DNA packaged in eukaryotic cells?
DNA is wrapped around histone proteins, forming nucleosomes, and further compacted into chromatin within the nucleus.
What percentage of the human genome codes for proteins?
Only about 1.5% of the human genome codes for proteins.
What are plasmids, and where are they found?
Plasmids are small, circular DNA molecules found in prokaryotes, often carrying genes for antibiotic resistance or survival.
What is an operon, and where is it found?
An operon is a cluster of genes under the control of a single promoter, commonly found in prokaryotes.
What is synteny in genome organisation?
Synteny refers to the conserved arrangement of genes on chromosomes across different species.
What is the basic unit of chromatin?
The nucleosome, consisting of DNA wrapped around histone proteins.
What are copy number variations (CNVs), and why are they significant?
CNVs are variations in the number of copies of a gene between individuals or species, contributing to genetic diversity.
What is the difference in genome size and function between prokaryotes and eukaryotes?
Prokaryotic genomes are small and mostly encode proteins, while eukaryotic genomes are larger with a significant portion of non-coding DNA.
How does the human genome compare to other species?
The human genome has about 21,000 functional genes, and approximately 45% of its DNA comes from transposable elements.
What is the role of histones in DNA packaging?
Histones help organize DNA into nucleosomes, facilitating compaction and regulation.
Why is the nucleosome critical for eukaryotic chromatin structure?
It organizes DNA into a compact form while allowing regulated access for replication and transcription.
What are introns, and how do they differ between prokaryotes and eukaryotes?
Introns are non-coding regions found in eukaryotic genes but are absent in prokaryotic genes.
How does the arrangement of genes in prokaryotes differ from eukaryotes?
Prokaryotes often use operons, while eukaryotic genes typically have their own promoters and regulatory regions.
What structural features define eukaryotic chromosomes?
Linear, paired, and contain centromeres, telomeres, and introns.
How do transposable elements impact the genome?
They contribute to genome evolution and variation, making up nearly 45% of the human genome.
What is the nucleoid in prokaryotes?
The nucleoid is the region in a prokaryotic cell where the circular DNA is compacted and organized.
What is the importance of supercoiling in prokaryotic DNA?
Supercoiling reduces the space required for DNA storage and aids in processes like replication, transcription, and recombination.
What structural feature distinguishes eukaryotic chromosomes from prokaryotic chromosomes?
Eukaryotic chromosomes are linear, have multiple origins of replication, and are enclosed within a nuclear membrane.
How are histone proteins modified to regulate gene expression?
Histones can undergo modifications such as acetylation, methylation, and phosphorylation to change chromatin structure and influence transcription.
What is the significance of telomeres in eukaryotic chromosomes?
Telomeres protect the ends of chromosomes from degradation and prevent them from being recognized as DNA damage.
Why is genome size not always indicative of organism complexity?
Large portions of many genomes consist of non-coding DNA, repetitive sequences, and transposable elements, which do not directly contribute to organism complexity.
What is the role of regulatory elements in eukaryotic genomes?
Regulatory elements like promoters, enhancers, and silencers control the timing, location, and level of gene expression.
What are transposable elements, and what is their impact on the genome?
Transposable elements are DNA sequences that can move within the genome, causing mutations, altering gene expression, and contributing to genetic diversity.
What is the difference between heterochromatin and euchromatin?
Heterochromatin: Densely packed, transcriptionally inactive regions.
Euchromatin: Loosely packed, transcriptionally active regions.
What are the different levels of DNA packaging in eukaryotes?
DNA is packaged into nucleosomes, then into a 30-nm fiber, higher-order loops, and finally into condensed chromosomes.
How are genes in operons expressed in prokaryotes?
Genes in operons are transcribed together from a single promoter into one mRNA and translated into multiple proteins.
What is chromatin remodeling, and why is it necessary?
Chromatin remodeling involves rearranging nucleosomes to expose or hide DNA regions, allowing transcription, replication, or repair.
What are copy number variations (CNVs), and how are they identified?
CNVs are differences in the number of copies of particular DNA segments between individuals, detected using genomic analysis techniques.
Why is the 16S rRNA gene commonly used in prokaryotic phylogenetic’s?
The 16S rRNA gene is highly conserved and provides insights into evolutionary relationships among prokaryotes.
