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MCB Genomic Organization/Pack
by Chelsea (complete)
21
Medical
Graduate
02/20/2009

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Cards

Term
DNA + proteins = ?
Definition
Chromatin
Term
What type of histone is between nucleosomes?
Definition
H1. It is the biggest and most charged type of histone.
Term
When is the amount of compaction maximal? When it is more variable?
Definition
Maximal during metaphase, variable during interphase.
Term
Where can we find genes that are being expressed?
Definition
In euchromatin, the less compacted regions that can be transcribed.
Term
What is heterochromatin?
Definition
More compact regions of DNA. This is the "archive" of information.
Term
What is the "extreme case" of heterochromatic control?
Definition
Barr bodies in human female cells. The inactivated X chromosome is packed into a very stable and compact form of heterochromatin. This process must be reversible in cells that will make oocytes.
Term
What is an "epigenetic phenomena"?
Definition
When the DNA is normal, but the packaging is not. This means the expression is also faulty.
Term
What is "C-value"?
Definition
The DNA Content (or the amount of DNA per cell). In general, more complex organisms have a higher C-value.
Term
What is the genome?
Definition
Vaguely, the collection of all the DNA in the nucleus of a eukaryotic cell.
Term
What is a chromosome? What are the three pieces?
Definition
An independently segregating DNA fragment. Chromosomes have a centromere in the middle, a telomere at each end, and at least one origin.
Term
How much DNA do humans have anyway?
Definition
3x10^9 bp per haploid genome, which comes out to 6x10^9 bp per cell (6,000,000,000)!
Term
Why is it so tricky to determine what exactly IS a gene?
Definition
A gene is definitely the protein coding region, but it can also include promoters and enhancers that can be really far away. Also, some genes don't even encode a protein (like a tRNA)!
Term
Where can we find rDNA in the genome?
Definition
All lumped together, and repeated thousands of times!
Term
What are pseudogenes?
Definition
Partial repeats, often lacking introns. Possibly from transposition attempts.
Term
What is an alpha-satellite?
Definition
A sequence that is repeated 500,000 times! They might be a functional component of the centromere. They also represent about the same amount of DNA it takes to get around a nucleosome.
Term
Why are microsatellites useful in diagnostic methods?
Definition
Because the exact number of repeats at a specific site (hypervariable region or VNTRs) varies from person to person.
Term
What are transposons?
Definition
Pieces of DNA (20% of the genome) that move around. They either "cut and paste" or move through an RNA intermediate (retrotransposons).
Term
What are LINEs closely related to?
Definition
Retroviruses! They even encode reverse transcriptase and are retroposons.
Term
What is the L1 or KpnI family?
Definition
A common LINE found in humans. Transposition may cause rare genetic disorders.
Term
What do SINEs encode? Why are they useful?
Definition
SINEs don't encode anything. But they do have different sequences across species and can be used to determine if that "mystery meat" came from a cow or a horse...
Term
What is the Alu family?
Definition
The human SINE. It is seen once every 5,000-10,000 bp in humans.
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