Genomes: structure and organization Flashcards
What is the primary difference between prokaryotic and eukaryotic genome organization?
Prokaryotic genomes are circular and lack a nucleus, while eukaryotic genomes are linear, housed in a nucleus, and organized into chromosomes.
How are genes organized within the human genome?
Genes are organized into exons (coding regions) and introns (non-coding regions) interspersed with regulatory sequences.
What role do introns and exons play in the structure of eukaryotic genomes?
Exons code for proteins, while introns are non-coding sequences that are spliced out during mRNA processing.
Explain the significance of repetitive sequences in genome organization.
Repetitive sequences, such as satellite DNA, play roles in chromosome structure, genome stability, and evolution.
How does chromatin structure affect gene expression?
Tightly packed chromatin (heterochromatin) is transcriptionally inactive, while loosely packed chromatin (euchromatin) allows gene expression
Differentiate between coding and non-coding regions of the genome.
Coding regions (exons) encode proteins, while non-coding regions (introns, regulatory elements) control gene expression and genome structure.
What are transposable elements, and how do they contribute to genome diversity?
Transposable elements are DNA sequences that can move within the genome, causing mutations and genetic variation.
Describe the function of satellite DNA.
Satellite DNA consists of repetitive sequences found in centromeres and telomeres, involved in chromosome stability and segregation.
What are pseudogenes, and how are they formed?
Pseudogenes are non-functional gene copies formed by gene duplication or retrotransposition events.
How do regulatory elements like enhancers and promoters function in gene expression?
Promoters initiate transcription, while enhancers increase transcription levels by interacting with transcription factors.
What are the major techniques used in genome mapping?
Genetic mapping (based on recombination frequency) and physical mapping (based on DNA fragment order) are the main techniques.
Explain the difference between physical and genetic mapping.
Genetic mapping measures the distance between genes using recombination rates, while physical mapping determines the actual nucleotide sequence.
What is shotgun sequencing, and how does it work?
Shotgun sequencing fragments the genome into small pieces, sequences them, and assembles the genome using overlapping sequences.
How do next-generation sequencing (NGS) techniques differ from Sanger sequencing?
NGS allows for high-throughput parallel sequencing, while Sanger sequencing reads one DNA fragment at a time.
What are some challenges in assembling a genome from sequencing data?
Repetitive sequences, sequencing errors, and incomplete coverage make assembly difficult.
How can comparative genomics help identify gene function?
Conserved sequences across species suggest functional importance and potential gene functions.
Explain the concept of synteny and its importance in comparative genomics.
Synteny refers to conserved gene order between species, providing evidence of evolutionary relationships.
What molecular markers are commonly used in constructing phylogenetic trees?
Mitochondrial DNA, ribosomal RNA genes, and conserved protein-coding genes are commonly used.
How does horizontal gene transfer affect phylogenetic analysis?
It introduces genes from unrelated species, complicating evolutionary relationships.
What is the significance of conserved sequences in evolutionary studies?
Conserved sequences indicate functional importance and evolutionary pressure to maintain them.
