Ch.7 - The Evolution of Genes & Genomes

Germ line cell

cell lineage that produces gametes (sperm or eggs)

Somatic cell

any cell that is not a germ line cell (body cell)

If mutation occurs in somatic cell

mutation may affect individual that it ocurred in

If mutation occurs in germ cell after germ line is set aside

will not affect individual but may be passed to the next gen and result in heritable trait

If mutation occurs within a gene

results in altered product

If mutation occurs in regulatory region

results in altered expression

If gene duplication occurs

results in new gene family

What is the ectopic expression of antennapedia gene in the head of drosophila an example of?

mutation in its regulatory DNA

How are adult humans able to digest lactose?

mutation in regulatory DNA of lactase gene that allows enzyme to be made beyond infancy

Gene families

groups of genes that originate from common ancestral gene

Globin gene family structure

3 exons & 2 introns

Pseudogenes

non-functional genes

T/F all version of globin gene family are expressed during whole lifetime

False; different versions are expressed during fetal, embryonic, and adult stages

What does adult version of globin gene family contain?

two α & two β subunits

T/F embryonic & fetal globins have higher affinities for oxygen than adult globins

true

How do gene families originate?

by gene duplications

How does unequal crossing over cause gene duplications?

short repeated sequences within homologous chromosomes can cause misalignments & unequal crossing over

What does unequal crossing over result in?

chromosomes with altered sizes & genetic contents

How does transposition of mobile genetic elements mediate recombination of genes or regulatory sequences?

• two similar mobile genetic elements inserted near each other in chromosome by change

  • transposition mechanisms ends up using the ends of the two different elements

    • results in movement of entire segment of chromosome btwn them

What does the transposition of regulatory sequences alter?

tissue specific pattern of expression of genes

What happens if transposed segment includes an exon?

its insertion into a second gene creates a new version of that gene

How are new proteins with multiple functional domains created?

duplication & movement of segments of DNA causes fragments of different genes to be pieced together

Vertical transfer

parent → child (through gametes)

Horizontal transfer

one organism to another

Examples of horizontal transfer

• viral infections

• conjugation: transfer of DNA from one bacterium to another through a sex pilus

What causes ALS?

HERV-K: ancient retrovirus that was incorporated into human DNA 2-5 mya

HERVs

retroviruses that infect neurons & germ cells