Chapter 21

Genomes and Their
Chapter 21
Tree of Life
 Genomics- is the study of whole sets of genes and their
 Bioinformatics-uses computers to store the large
amounts of data created by genomics
 Human Genome Project- sequencing human genome
began in 1990 and completed in 2003
3 Stage
 Cytogenetic maps
started the detailed
 Linkage maps created
the basic order and
relative distances of
 Physical maps express
distances in number of
base pairs
 The final step is
sequencing by dideoxy
chain termination
 Venter used
step 3 and
computers to
sequence whole
 Most widely
used method.
Bioinformatics Analyze Genomes
 Analyzing resources were centralized (NCBI) and houses “Genbank”
 Software is available like Blast that allows genome
 NCBI also contains 3-D protein structures
 Expressed Sequence Tags (ESTs)are used to search the
sequence for known genes
 For genes of unknown proteins biochemical and
functional studies must be preformed.
 Proteomics is the study of
the whole proteome and its
 A study of 10,000 RNA
transcripts yeieded 4700
proteins and over 4000
 Global protein interaction
maps show the interactions
Systems Biology
 Systematic approach has
proved valuable in cancer
 Gene Chips can hold
microarrays for most of the
human genes.
Genome Size, Number, & Density
 Prokaryote genomes are much smaller than eukaryotes
ranging from 1-6 Mb (million base pairs)
 Most animals and plants are at least 100 Mb
 In eukaryotes the size of the genome has no affect on
 Bacteria and archaea have fewer genes 1,500-1,700
compared to 5,000 to 40,000 for eukaryotes
 Humans have 3,200 Mb and 20,488 genes because of
alternative splicing of genes
 Mammals have the lowest gene densities because of the
inclusion of introns and non-coding regions.
Noncoding DNA & Multigene
 Noncoding regions have yet unknown functions but are
highly conserved among related species.
 1.5% of Human DNA is coding and only 24% has a
regulatory function.
 Pseudogenes have acquired mutations and are
nonfuntional account for 15%
 Repetitive DNA 44% sequences in multiple copies, these
include transposable elements.
Transposable Elements
 Transposable elements
can move from one
location to another in the
 Move by a recombination
 Transposons move cut
and paste mechanisms
 Retrotransposons
(common) move using a
RNA intermediate
 Barbara McClintock proposed
mobile genetic elements
 Alu elements 10% are
transcribed into RNA
but function is
 Line 1 (L1) is a
retrotransposon that
may regulate gene
Other Repetitive DNA
 Most repetitive DNA occurred from mistakes in
replication or recombination 15%
 Long duplications 5% are copied from chromosomal
location to chomosome.
 Simple Sequence DNA 3% contains multiple copies of
tandemly repeated short sequences.
 Short Tandem Repeats (STRs) consist of 2-5 nucleotides
 Simple Sequence DNA is located in telomeres and
centromeres suggestion chromosome formation function
Gene Families
 Human coding DNA occurs in identical or nonidentical
gene families
 Identical Families usually make RNAs or histones. Eg.
rRNA gene families. 3 rRNAs are made from one family
 Nonidentical families code for related proteins but have
different locations. See Hemoglobin proteins.
DNA Evolution by Duplication,
Rearrangement, & Mutation
 Polyploidy could facilitate gene evolution by one copy
providing essential function and the other evolving new
 Chromosome alterations can create new species by
altering the chromosome number
 Duplication or divergence of gene sized DNA is
evidenced in the existence of multigene families
Genes of Related Functions
 Hemoglobin а & β share a common ancestor and have
evolved from duplication and divergence about 450
million years ago.
 Sometime the duplication and divergence leads to genes
with new and different functions
Exon Duplication & Exon Shuffling
Clues to Evolution & Development
 The more similar the genome the more closely related
the two organisms
 Comparison of distantly related species provide
information about highly conserved and the origins of
early life
 Closely related analysis shows the fundamental genes
necessary to belong to a group.
 Comparison of closely related species can provide info
about how organisms genomes are evolving.
Transcription Factor Evolution
 FOXP2 is a transcription factor evolving in humans that
functions in vocalizations
 The changes in FOXP2 are being studied to see if these
are the reasons for human and chimp vocalization
 The detection of SNPs and other genetic markers can
lead to a trail of human evolution and migration.
Homeotic Genes
 Evo-devo is the study of
developmental biology
 Changes in development
genes can help trace
 The homeobox is included
in every homeotic gene
Hox Gene Expression
 Homeotic genes in animals are called Hox genes
 Hox genes initiate transcription but require more specific
proteins to turn on specific genes.
 Variations in Hox genes can have profound affect on the
development of the phenotype of organisms
Related flashcards
Peptide hormones

65 Cards

Rose cultivars

52 Cards

Molecular biology

64 Cards

Peptide hormones

66 Cards

Molecular biology

92 Cards

Create flashcards