Human Genome Flashcards
What are the two main strategies for determining the linear order of nucleotides in the human genome?
Clone-by-Clone Sequencing and Whole-Genome Shotgun Sequencing.
How does the Clone-by-Clone sequencing method work?
The genome is divided into large fragments, mapped to specific locations using markers, then sequenced individually and assembled.
What is Whole-Genome Shotgun Sequencing?
A method where the genome is broken into small, random fragments, sequenced in parallel, and assembled computationally.
What are microsatellites, and why are they useful?
Microsatellites are short, tandemly repeated DNA sequences that are highly polymorphic and evenly distributed, making them excellent markers for mapping.
How are microsatellites typed from DNA samples?
By PCR amplification followed by gel or capillary electrophoresis to determine the size of the repeat regions.
Why is there only one “truly independent” human genome sequence?
The reference genome serves as a baseline for research, representing a consensus sequence that accounts for the 99.9% similarity among human genomes.
How many protein-coding genes does the human genome contain, and what percentage of the genome do they occupy?
About 20,000–25,000 genes, which account for 1.5% of the genome.
What are the main components of the non-coding human genome?
Introns, repetitive sequences (e.g., transposons), regulatory elements, and pseudogenes.
Why is human gene density lower than in organisms like D. melanogaster and S. cerevisiae?
Due to larger introns, more repetitive DNA, and non-coding functional elements like regulatory sequences and non-coding RNAs.
What is the gene density in humans, fruit flies, and yeast?
Humans: ~6 genes/Mbp.
Fruit fly (D. melanogaster): ~170 genes/Mbp.
Yeast (S. cerevisiae): ~500 genes/Mbp
What is the C-value paradox?
The observation that genome size (C-value) does not correlate with gene number or organismal complexity.
How does alternative splicing contribute to human genome complexity?
It allows a single gene to produce multiple proteins, increasing functional diversity.
What role do repetitive DNA elements play in the human genome?
They increase genome size without adding functional genes and include LINEs, SINEs, and satellite DNA.
Why does S. cerevisiae have a higher gene density than humans?
It has a compact genome with very few introns and minimal non-coding DNA.
