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Biology 1201A Study Guide - Midterm Guide: Transposable Element, Noncoding Dna, Genome SizePremium

2 pages108 viewsFall 2016

Course Code
Biology 1201A
Vera Tai
Study Guide

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Biology 1201 Test 2 Outcomes Part 2
Identify what type of 'information' is coded in genomes (e.g. proteins, structural sequences, etc)
- By using DNA sequencing techniques, we can identify genes, regulatory sequences, origins of
replication, repetitive sequences, transposable elements
- Genes, mRNA, rRNA, tRNA, regulatory sequences, promotor regions, non-coding DNA
- Pseudogenes, introns and exons are also included
- There are 20,500 protein coding genes with an average of 8 exons per gene; introns make up
95% of the gene and 5% exons
- Regulatory sequences are widely scattered within regions and they encompass 15-25% of the
human genome
- DNA viruses and reverse-transcribed RNA total up to 10% of the entire genome
- Also remember that in eukaryotes, each mitochondria contains a circular mitochondrial
genome (mtDNA genes for cellular respiration)) smaller than even a prokaryotic genome
- Photosynthetic eukaryotes have circular genomes in each of their chloroplasts (genes for
Understand the proportion of human genome coding for protein, the relative distribution of various
components of genome sequence ("junk" vs. essential DNA)
- There are about 20500 protein coding genes, which is about 2% of the entire genome; this
means that the protein coding genes are spread out throughout the genome (not packed
together) there are about 8 exons per gene
- Per transcription unit, there is 95% introns and 5% exons; the introns represent 20-25% of the
entire genome
- 45% of the genome has transposable elements and only a small fraction of it are functionally
- Add in the thousands of pseudogenes, introns, and non-essential repetitive sequences and
you may be surprised to realized that junk DNA approaches 75% of your entire genome
- Majority of your genome does NOT code for proteins (most is so-called junk) --> transposons,
dead genes, viruses)
- Transposons have multiplied much faster than its has been removed (removed by natural
selection is slower than the replication of the transposons) Transposons are important
because it is a DNA sequence that can change its position within a genome; sometimes even
creatig or reversig utatios ad alterig the cell’s geoe size (important for evolution)
- Junk DNA may someday be co-opted for a useful function; sections of your DNA that are just
repeated over and over again (this repetitive element depends on each individual)
- Protein coding is 2%, other important stuff 8%, Introns 10%, unknown 25% and junk is 55%
- Some genes are transcribed left to right and some right left; this all depends on how the
teplate is read! The teplate will always e read 3-5; so depedig o where that is, the
upper or lower template strand is transcribed
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