Genome Organization Flashcards
- Describe the fundamental principles regarding the evolution and organization of the human genome mentioned in the outline.
3x10^9 bp= haploid human genome sequence
human genomic DNA distributed on 46 chromosomes
chromosomes are found in 23 pairs
1) 22 autosomes (1-22)
2) 1 pair of sex chromosomes (XX or XY)
Each chromosome believed to consist of a single, continuous DNA double helix
human genome is a record of revolutionary history—variations in gene size and structure
- Explain why genome variation is an essential fuel of evolution and adaptation, but it also produces human disease.
- human genome responds to selection pressure from the environment, change over time has shaped our genome
- genes and genomic features that were adaptive were retained—many maladaptive eliminated
- random variation is the fuel of evolution
- genetic disease is the price we pay of random variation; can adapt to a changing environment, but mistakes can occur
- Discuss the dynamic nature and non-random organization of the human genome as described in the outline.
- Gene rich regions/chromosomes
- —gene rich: chromosome 19
- —gene poor: Chr 13, 18, 21 (viable trisomies)
stable regions: majority of genome
unstable regions–often disease associated
- Describe how frequently a SNP is likely to occur between two individuals.
Average of 1 SNP per every 1000 bp between any two randomly chosen unrelated human genomes
-99.9% identical, 3,000,000 differences
- Describe the types of variations that occur between genomes.
30 new mutations occur in each individual
shuffling of regions at each meiosis due to recombination
can produce somatic DNA changes as well as germ-line DNA changes
there is no “one” human genome
Average of 1 SNP per every 1000 bp between any two randomly chosen unrelated human genomes
-99.9% identical, 3,000,000 differences
- Describe the following characteristics of the genome: a) gene-rich; b) gene-poor; c) stable; d) unstable; e) GC-rich; f) AT-rich; g) euchromatic; and h) heterochromatic.
gene rich: chromosome 19
gene poor: chromosome 21, 13, 18 (viable trisomies)
stable: majority of genome, few mutations are located, usually more gene containing
unstable: many are disease associated, generally gene poor
GC-rich: 38% of genome
AT-rich: 54% of genome
Euchromatic: more relaxed (sequenced)
heterochromatic: (not used in sequencing efforts) more condensed, more repeat-rich
- Describe how in genome sequencing focused on euchromatic regions, there is no completely sequenced & assembled human genome.
no human genome is completely sequenced and assembled: some regions are either missed, are too complex and duplication rich to assemble correctly with current methods
allregions of the genome do not look/behave the same way
- Discuss that many gaps still remain even in euchromatic regions.
genome sequence effort is focused on this region
- Discuss that genes often exist in families and gene families arise by gene duplication.
gene family is composed of genes with high sequence similarity (>85%) that may carry out simple distinct function
–some clustered/some dispersed
gene families arise through duplication
- major mechanism behind evolutionary change
rationale: when a gene duplicates it frees up one copy to vary while the other copy continues to carry out a critical function–it facilities innovation
frequent co-localization of duplications and disease
- Discuss the advantages of gene duplication as an evolutionary mechanism.
rationale: when a gene duplicates it frees up one copy to vary while the other copy continues to carry out a critical function–it facilities innovation
- Explain how evolutionarily advantageous increases in gene copy number can produce many diseases as a side effect.
a
- Describe what the limitations are of current genome sequencing and screening methods, and how this relates to the “missing heritability” problem.
a
