lecture 16 Flashcards
germ-line cells give rise to
germ cells (special reproductive cells that carry a copy of the genome to progeny)
somatic cells
all other cells
only mutations in – cells are passed on to offspring
germ-line cells
mutations in somatic cells are not
point mutations are
changes that affect a single nucleotide pair
neutral mutation
no effect on gene
what happens if point mutations occur in regulatory DNA
the gene expression will be affected
gene duplications
promote the emergence of new genes
gene duplication and divergence
mutation in one copy will be tolerable as long as the other copy still functions
homologous recombination can cause
gene duplication
- unequal crossing over= one long chromosome w gene duplication and one short chromosome
when do whole genome duplications occur?
occurs when cell division doesn’t happen after genome duplication
exon shuffling
exons encode for independent protein domains
duplication/movement of exons so that they are found in new genes give rise to new proteins
a mobile genetic element is
a DNA sequence that can move from one location in a chromosome to another
what can a mobile genetic element do?
can disrupt a gene if inserted somewhere important (coding sequence, regulatory DNA)
can make new genes by fusing the existing gene and the mobile genetic element
horizontal gene transfer
transfer of DNA from one organism to another
vertical gene transfer
transfer of DNA from parent to progeny
homologous genes have
similar sequences due to common ancestry
- common proteins are found between species
phylogenetic tree compares
nucleotide changes between species
genetic changes and selection
changes that benefit survival will be passed on
changes that have no consequence might be passed on
changes that are harmful will not be passed on
mutations would be found in
areas of DNA that DO NOT encode for a product/regulate a product
why would mutations be found in areas of DNA that do not encode for a product?
genes that encode for products are essential.
mutations would affect ability to reproduce.
essential genes are highly conserved (kept the same!!)
noncoding/regulatory sequences are less likely to
stay the same.
therefore more likely to have mutations
conserved synteny
preservation of gene order and location in the genome of different species
-ex. mouse and human beta-globin genes occur in the same order and location
purifying selection
individuals w mutations that impair important functions have been eliminated
vertebrate genomes size
all vertebrate genomes have roughly the same number of genes but the overall size varies A LOT
compare fugu genome and human genome
Fugu genome is 1/10 the size of human genome bc of smaller introns
but the position of introns and exons are still the same between species
why is rRNA used to show evolutionary relationships between species? (tree of life)
rRNA is essential for translation
rRNA should be HIGHLY conserved.
this makes it easy to compare between organisms
