2.1 Evolution of Genomes & Genes
Questions with Verified Answers
genome - ANSWERSthe full set of genes plus noncoding regions of DNA (for some
viruses it is RNA)
location of genes in prokaryotes vs eukaryotes - ANSWERSin PROKARYOTES, genes
are in the nucleoid or in plasmids (outside the nucleoid) (prokaryotes lack organelles)
in EUKARYOTES, most genes are on chromosomes (in nucleus), but some are in
mitochondria & chloroplasts (eukaryotes have cells with nucleus + other organelles)
(T/F) the total genome size varies tremendously - ANSWERSTRUE!
genome size varies between organisms & within organisms
is organism complexity related to genome size? - ANSWERSNO!
many protists (single-celled organisms), plants, + some amphibians have much larger
genomes than humans (3 Gb)
viruses, bacteria, and archaea have (big / small) genomes
- viruses + prokaryotes...
- free living bacteria... - ANSWERSsmall!
in viruses + prokaryotes, most of the genome (85-90%) is non-repetitive DNA, which
means it's primarily coding DNA (so pretty compact)
free living bacteria have the larger genomes as compared to pathogens or symbionts
pathogens & symbionts - ANSWERSbacteria that need to live with/in other organisms
(jettisoned some of their genes + used some of the genes of their host)
list + explain the 3 hypotheses for why smaller genomes may be favorable -
ANSWERS1. smaller genomes are less energetically costly
- if have genome, need to replicate it, proofread it, etc. (so less energetically costly if
genome is smaller)
2. smaller genomes are smaller targets for mutation
- may have 0 deleterious mutations
3. smaller genomes allow for faster replication
, - fitness advantage: will have smaller genome more representative in next generation
than larger, slower replicating organism
(T/F) total gene number also varies among organisms, but not as much -
ANSWERSTRUE!
total gene number = number of protein coding genes
it varies, but not as much as whole genome sizes
for eukaryotes with much larger number of genes: whole genome duplicated (2x as
many genes as they would have otherwise) (e.g. pufferfish, rice, etc.)
gene size varies much more than the number of genes. how? - ANSWERSas genome
size increases, the percent of genome encoding functional genes decreases by a lot!
ex: e. coli - 100% of genome is coding for functional genes
- as genomes get bigger, fewer & fewer of the DNA bases code functional genes
- SO large genomes (lungfish, lily, human, etc.) code for protein coding genes
SO why have other bases that don't code for proteins?
why study genome size? what kinds of questions can we ask? - ANSWERSis small
genome size associated with flight?
- Compared genome size across many different organisms (including dinosaurs)
- Look at cell size of fossilized dinosaur bones; correlation between bone cell size &
genome size (used cell size in bones to estimate genome size!)
- Even in dinosaurs before could fly. there's a trend for smaller genomes
- Flying organisms: quite small (pink + purple = smaller genome sizes than blues &
greens)
- 1 branch on own - flying creature; smaller genome than nearby relatives
(see figure on slide 8 of 2.1 evo of genomes)
IMP: Suggests that small genome size is associated with flight!!
genome evolution - ANSWERSthe process by which a genome changes in structure
(sequence) or size over time
list the 7 mechanisms of gene evolution (how genomes gain + maintain functions) -
ANSWERS1. gene duplication
2. whole genome duplication
3. horizontal gene transfer
4. de Novo genes (new genes)
5. transposable elements
Questions with Verified Answers
genome - ANSWERSthe full set of genes plus noncoding regions of DNA (for some
viruses it is RNA)
location of genes in prokaryotes vs eukaryotes - ANSWERSin PROKARYOTES, genes
are in the nucleoid or in plasmids (outside the nucleoid) (prokaryotes lack organelles)
in EUKARYOTES, most genes are on chromosomes (in nucleus), but some are in
mitochondria & chloroplasts (eukaryotes have cells with nucleus + other organelles)
(T/F) the total genome size varies tremendously - ANSWERSTRUE!
genome size varies between organisms & within organisms
is organism complexity related to genome size? - ANSWERSNO!
many protists (single-celled organisms), plants, + some amphibians have much larger
genomes than humans (3 Gb)
viruses, bacteria, and archaea have (big / small) genomes
- viruses + prokaryotes...
- free living bacteria... - ANSWERSsmall!
in viruses + prokaryotes, most of the genome (85-90%) is non-repetitive DNA, which
means it's primarily coding DNA (so pretty compact)
free living bacteria have the larger genomes as compared to pathogens or symbionts
pathogens & symbionts - ANSWERSbacteria that need to live with/in other organisms
(jettisoned some of their genes + used some of the genes of their host)
list + explain the 3 hypotheses for why smaller genomes may be favorable -
ANSWERS1. smaller genomes are less energetically costly
- if have genome, need to replicate it, proofread it, etc. (so less energetically costly if
genome is smaller)
2. smaller genomes are smaller targets for mutation
- may have 0 deleterious mutations
3. smaller genomes allow for faster replication
, - fitness advantage: will have smaller genome more representative in next generation
than larger, slower replicating organism
(T/F) total gene number also varies among organisms, but not as much -
ANSWERSTRUE!
total gene number = number of protein coding genes
it varies, but not as much as whole genome sizes
for eukaryotes with much larger number of genes: whole genome duplicated (2x as
many genes as they would have otherwise) (e.g. pufferfish, rice, etc.)
gene size varies much more than the number of genes. how? - ANSWERSas genome
size increases, the percent of genome encoding functional genes decreases by a lot!
ex: e. coli - 100% of genome is coding for functional genes
- as genomes get bigger, fewer & fewer of the DNA bases code functional genes
- SO large genomes (lungfish, lily, human, etc.) code for protein coding genes
SO why have other bases that don't code for proteins?
why study genome size? what kinds of questions can we ask? - ANSWERSis small
genome size associated with flight?
- Compared genome size across many different organisms (including dinosaurs)
- Look at cell size of fossilized dinosaur bones; correlation between bone cell size &
genome size (used cell size in bones to estimate genome size!)
- Even in dinosaurs before could fly. there's a trend for smaller genomes
- Flying organisms: quite small (pink + purple = smaller genome sizes than blues &
greens)
- 1 branch on own - flying creature; smaller genome than nearby relatives
(see figure on slide 8 of 2.1 evo of genomes)
IMP: Suggests that small genome size is associated with flight!!
genome evolution - ANSWERSthe process by which a genome changes in structure
(sequence) or size over time
list the 7 mechanisms of gene evolution (how genomes gain + maintain functions) -
ANSWERS1. gene duplication
2. whole genome duplication
3. horizontal gene transfer
4. de Novo genes (new genes)
5. transposable elements
