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What is the basic mechanism behind exon duplication?
Unequal crossing over during meiosis This process can lead to the generation of recombinant chromosomes with varying numbers of exons.
Define a gene.
The entire nucleic acid sequence necessary for the synthesis of a functional gene product This includes protein-coding, enhancer, and promoter regions.
What percentage of human DNA encodes proteins and functional RNAs?
About 1.5 percent The remainder includes regulatory sequences that control gene expression and introns.
What are the three types of gene duplication outcomes?
• Redundancy • Neofunctionalization • Subfunctionalization These outcomes can lead to evolutionary innovations.
What is a simple transcription unit?
A monocistronic region extending from the 5′ cap site to the 3′ poly(A) site with introns removed It encodes one protein and represents about 10% of human transcripts.
What is the difference between homologs, orthologs, and paralogs?
• Homologs: evolved from a common ancestor • Orthologs: same function, differ due to speciation • Paralogs: differ due to gene duplication These terms describe relationships between genes across different species.
What does the histone code represent?
Specific post-transcriptional modification combinations in different chromatin regions This influences chromatin function by creating or removing chromatin-associated protein binding sites.
What is the role of telomeres?
Protect chromosome ends from degradation They play a crucial role in maintaining genomic stability.
What is epigenetics?
Inheritance depends on factors other than DNA sequences Examples include X-chromosome inactivation and differences in disease susceptibility between genetically identical twins.
What is the packing ratio of DNA in nucleosomes?
Approximately 7:1 This ratio increases significantly with higher levels of chromatin structure.
What is heterochromatin?
Highly condensed interphase chromatin that is essentially inactive and without transcription It is concentrated around the centromere and telomeres of chromosomes.
What is the function of nucleosomes?
The lowest level of chromosome organization, consisting of DNA wrapped around histone proteins Nucleosomes help in compacting DNA and regulating access to genetic information.
What is the structure of a nucleosome core particle?
Histone octamer with 147bp of DNA coiled around it The octamer consists of two molecules each of histones H2A, H2B, H3, and H4.
What are intermediate filaments?
Structural components that provide support and shape to cells They are part of the cytoskeleton and play a role in maintaining cell integrity.
True or false: Euchromatin is transcriptionally inactive.
FALSE Euchromatin represents transcriptionally active regions of chromosomes.
What is the function of chromatin-remodeling complexes?
Regulate compaction of chromatin by sliding DNA associated with octamers They hydrolyze ATP to facilitate changes in chromatin structure.
What is the ultimate in chromatin compactness?
Mitotic chromosomes They represent a packing ratio of 10,000:1.
What does epigenetics refer to in the context of inheritance?
Inheritance depends on factors other than DNA sequences Example: X-chromosome inactivation can occur even with identical DNA sequences.
What is an example of X-chromosome inactivation?
One X chromosome is inactivated while the other is not This can occur despite identical DNA sequences.
Can an epigenetic state be reversed?
Yes, it can usually be reversed X chromosomes are reactivated prior to the formation of gametes.
What may differences in disease susceptibility and longevity between genetically identical twins be attributed to?
Epigenetic differences that appear as they age These differences can influence health outcomes.
What determines the chemical modifications found in newly synthesized histones?
Parental histones This influences the epigenetic state of the daughter cells.
What is the heterochromatin epigenetic code memory?
Histone octamers di- or trimethylated at H3 lysine 9 are distributed to daughter chromosomes This process regenerates heterochromatin in both daughter chromosomes.
What are the three types of DNA sequences required for a long linear DNA molecule to function as a chromosome?
• Telomeres • Centromeres • Origins of replication These sequences are essential for chromosome function.