BIOL 300 - Chapter 5

what does genetic drift accumulate?

neutral mutations

what does natural selection accumulate?

positive mutations

what increases with an organisms complexity?

the minimum gene number for the organism

how many genes do humans have?

varies - between 20,000-30,000

what are some factors that correlate with genomic complexity?

cell compartments > multicellularity > development > immune systems > nervous systems

what are lethal loci?

genes that are essential for life

what is the relationship between number of genes and genome size in prokaryotes?

linear relationship -most sequences are for genes, so the more complex the organism is, the bigger its genome

what are pathogenicity islands?

DNA segments present in pathogenic bacterial genomes but absent in nonpathogenic relatives

what is horizontal gene transfer?

DNA is transferred from one cell to another through transformation, transduction, or conjugation

what is the relationship between number of genes and genome size in eukaryotes?

neither correlate with organism complexity - chart seems to plateau

what is the largest known genome?

its Tmesipteris oblanceolata - has 160 billion bp

why is predicting # of genes complicated?

interrupted gene concept - genes are split up by introns and exons

what is monocistronic mRNA?

mRNA that encodes for one polypeptide

what is polycistronic mRNA?

mRNA that encodes more than one protein

what percent of the genome encodes genes?

1%

how do complex organisms gain more genes?

de novo mutation (genetic change not inherited), existing genes are used as prototypes, or genome duplications

what happens if essential genes are lost?

organism dies or becomes sterile

how can some genes with essential function be non-essential?

redundancy - several genes have the same function

what is a gene family?

group f genes that evolved from the same ancestor gene

what happens to the resulting genes when gene duplication events occur?

the genes share sequence homology

how does number of members in a gene family relate to complexity?

increases as organisms are more complex

what determines the frequency of a mutation occuring?

likelihood that the error will occur (replication accuracy) and likelihood that it will be repaired

what does lost mean as an allele frequency?

0% frequency - wiped out due to decreased fitness

what does fixed mean as an allele frequency?

100% frequency - rare to occur in natural selection unless we would die without it

what is evolution in genetics?

the change in the inherited traits of a population of organisms through successive generations

what is genetic drift?

change in allele frequencies in a population due to random sampling of organisms - occurs rapidly in smaller populations

what determines speed of allele frequency change in non neutral mutations?

how advantageous/disadvantageous the mutation is, and whether the allele is dominant or recessive

what can cause gene duplication?

errors in replication, recombination (chromosome cross over), and repair (so incorrect recombination)

what does divergence mean in genome evolution and duplication?

as long as one copy of the genome is functional, mutations can accumulate in the other

what are pseudogenes?

genes that used to encode something but were inactivate

what is a gene cluster?

when duplications occur physically close to the original copy, and multiple duplications occur

what are homologs?

biological entities that are similar due to descent from a common ancestral source - different genes, NOT different alleles of the same gene

what are paralogs?

homologous genes within the same familythat arose from a gene duplication event and subsequently diverged in function - separated due to duplication

what are orthologs?

genes in different species that evolved from a single gene in a last common ancestor through speciation