Genome Organization Flashcards
How many base pairs are in the haploid human genome sequence?
3x10^9 bp
How many chromosomes are in the human genome?
46
Where are the chromosomes located?
Nucleus
How many pairs of human chromosomes are there?
Autosomes_____
Sex Chromosomes_____
22 autosome pairs
1 sex chromosome pair
so
23 pairs in total
Does each chromosome have more than one DNA strand?
No, each chromosome is believed to consist of a single continuous DNA double helix
How do we generally number the chromosomes?
Chromosome numbering is generally based on size, with smaller chromosomes being higher numbers
e.g.
Chr1: 245 million bp
Chr22: 49 million bp
In what sense is the human genome a record of human evolutionary history?
Reflects the results of different selection pressures…these pressure have shaped our genome
In terms of evolution, which gene do we retain?
Adaptive ones :)…
Thus, many that were maladaptive were not retained
A + B = phenotype
What are A and B?
Genotype (genome) + environment
What is the fuel of genomic (and thus all) evolution?
Random variation
In general, random variation in a highly ordered structure, such as the human genome, is almost always __________
Deleterious
What is the price that we pay as a species to have a genome that can evolve, i.e. adapt to changing environments
Genetic disease
Again, random variation in a highly ordered structure is almost always deleterious. Almost!
Is the human genome static?
No! it is dynamic and continues to change and evolve
Approximately how many new mutations occur in each individual?
30
What properties of meiosis allow for genetic diversity?
Independent assortment and shuffling of regions during recombination
The human genome is dynamic, constantly shuffling and changing, is this true for both germ line and somatic cells?
Yes
Germ line cells shuffle DNA during recombination
Somatic cells also produce DNA changes, but these too can be deleterious (e.g. cancer is a disease of “genome instability”)
What is cancer a disease of?
Genome instability
Is there a “human genome”
There is no “one” human genome, there are many (billions of different) human genomes
How frequent are SNPs in the human genome
Average of 1 SNP every 1000 bp between any two randomly chosen unrelated human genomes
What percentage of the human genome is identical?
Around 99.9%
Leaving about 3,000,000 differences :)
Is the human genome organized in a random manner?
No…
there are gene rich regions
there are gene poor regions
Which chromosome is a gene rich chromosome?
19
What are the smallest chromosomes (in terms of gene content)
13, 18, 21 (not counting Y)
What special potential does having limited gene on chromosomes 13, 18, and 21 confer?
Viable trisomies