Download The Eukaryotic Genome Genomics

Eukaryotic Genomes
Demonstrate Sequence
Organization
Characterized by
Repetitive DNA
Honors Genetics
Lemon Bay High School
2013-2014
The Eukaryotic Genome
• prokaryotic and eukaryotic genomes encode
many of the same functions
• eukaryotes encode additional functions
associated with organelles
• genomes of multicellular eukaryotes encode
additional functions
• each eukaryotic kingdom encodes specialized
products
The Eukaryotic Genome
• Genomics
• analyzes and compares entire genomes of
different organisms
• sequences of many genomes are complete
• Proteomics
• analyzes and compares the functions of
the proteins in an cells, tissues, organs,
organisms
The Eukaryotic Genome
Repetitive Sequences
• Genomes contain
• Single copies of unique DNA sequences that make up genes.
• Various levels of Repetitive sequences
• The majority of repetitive sequences DO NOT
encode proteins.
• Three main types of repetitive sequences
• Heterochromatin, Centromeres, and Telomeres
• Tandem repeats
• Transposable sequences
Repetitive DNA
Highly Repetitive
Middle Repetitive
Satellite
Heterchromatin
Interspersed
retrotransposons
Tandem Repeats
Centromeric
Multiple
copy genes
Minisatellites
Microsatellites
SINEs
LINEs
rRNA
genes
VNTRs
STRs
Alu
L1
The Eukaryotic Genome
Highly Repetitive Sequences
• Highly repetitive sequences (103 - 106 each)
• Characteristic of short sequences repeated a large
number of times.
• Found flanking the centromeres in heterochromatic
regions
• Makes up a variable portion of total DNA dependent
on species.
• Prokaryotes do not contain satellite DNA
• Repetitive sequences re-anneal more rapidly and can be
used for a variety of molecular techniques.
• In situ hybridization
• Polymerase chain reaction
The Eukaryotic Genome
Centromeric DNA Sequences
• Separation of chromosomes during mitosis and meiosis
depends on separation of centromeres.
• It is believed that DNA within the centromeric region is
CRITICAL to this function.
• The DNA of this region binds to the kinetochore which
binds to the spindle fiber during cell division.
• Proper binding of this structure is what allows the
chromosome to be pulled apart during anaphase.
• Alphoid region of the centromere is a tandem
array of about 1 million base pairs that produce
instructions for the production of the kinetochore.
The Eukaryotic Genome
Telomeric DNA Sequences
• Telomeres are the “caps” of repetitive
sequences that maintain the stability of
chromosomes.
• May be as many as 100 base pair repeats in
some organisms.
• Loss of telomere sequences as we age can
result in interference with coding sequence
interruption once the telomeres have been
exhausted.
The Eukaryotic Genome
Middle Repetitive Sequences
• Multiple Copy Genes
• Present when a
large amount
of gene
product is
required.
• Generally
produces RNA
sequences for
protein
synthesis
• Mini-satellites
• Variable
Number
Tandem
Repeats
(VNTRs)
• 15 to 100 bp
long
• Found within
and between
genes
• Micro-satellites
• Short
Tandem
Repeats
• 5 to 50 bp
long
• Useful
molecular
markers.
The Eukaryotic Genome
Repetitive Transposed Sequences
• Transposable elements (transposons)
• Can be mobile and move to different locations within the
genome.
• Large portion of the human genome is transposable.
• SINEs
• Short Interspersed Elements
• About 500 bp long
• LINEs
• Long Interspersed Elements
• About 6000 bp long; some are expressed
• AKA retrotransposons: Protein produced is used by retroviruses like HIV
for infection
The Eukaryotic Genome
Majority of Genome Does NOT Encode
Functional Genes
• Pseudogenes are present and considered evolutionary
“leftovers” of once functional genes that have acquired
too many insertions or deletions.
• In sea urchins, the 20,000 to 30,000 genes occupy less
than 10 percent of the genome.
• In Drosophila, only 5 to 10% of the genome is occupied
by encoding sequences.
• In humans, the estimated 20,000 function genes occupy
only 2% of the total DNA sequence making up the
genome.