Genome Structure

Question 1

describe eukaryotic nuclear genomes

Answer 1

typically large, linear, and made of many separate chromosomes; large intergenic spaces and introns (only 1.5% of human genome is protein coding)

Question 2

describe prokaryotic genomes

Answer 2

typically small (100,000 - 5 million bp), circular, often just a single chromosome; very compact, most of the genome encodes proteins, few intergenic spaces and no introns

Question 3

why are prokaryotic genomes so small compared to ours?

Answer 3

vast majority of size difference is due to non-protein coding sequences (basically just promoters and protein coding sequences - no exons in bacteria)

Question 4

why is gene regulation simpler in single-celled organisms versus multicellular organisms?

Answer 4

because they don’t have to make different types of cells

Question 5

main reason for bacteria to regulate genes

Answer 5

to respond to their environment

Question 6

what did chloroplasts and mitochondria evolve from?

Answer 6

symbiotic prokaryotes (bacteria)

Question 7

mitochondria have their own ___. it looks similar to a _______.

Answer 7

genome; bacterial genome

Question 8

describe our mitochondrial genome

Answer 8

circular, very tiny and compact, most genome encodes protein, few introns and intergenic sequences

Question 9

mitochondrial genome bp in humans vs yeast, why is there a big difference?

Answer 9

17,000 bp in humans; 78,000 bp in yeast
eukaryotic cells provide a lot for the mitochondria (give food, break things down) so the mitochondria don’t need as much of the genome

Question 10

describe the chloroplast genome

Answer 10

circular, not as small as mitochondrial genome, compact, few introns and intergenic regions

Question 11

how many bp in a chloroplast genome?

Answer 11

100,000-200,000 bp

Question 12

how many chloroplasts in a leaf cell?

Answer 12

100-10,000 chloroplasts

Question 13

how many mitochondria are in an animal cell?

Answer 13

1,000-5,000 mitochondria

Question 14

does yeast have a linear or circular genome?

Answer 14

eukaryote so linear

Question 15

size (in bp) of human nuclear genome

Answer 15

3.2 billion bp

Question 16

how many chromosomes do we have (haploid)?

Answer 16

23

Question 17

size (in bp) of each chromosome

Answer 17

57-250 million bp

Question 18

size (in protein coding genes) of each chromosome

Answer 18

200-2000 protein coding genes

Question 19

total protein-coding genes combined (on all chromosomes)

Answer 19

20,000 protein coding genes

Question 20

what percent of genome is translated?

Answer 20

1.5% translated (protein-coding)

Question 21

what percentage of the human genome consists of repetitive elements?

Answer 21

60%

Question 22

what do most of the repetitive sequences of DNA consist of?

Answer 22

transposable elements (transposons)

Question 23

what are transposons?

Answer 23

“jumping genes” that can cut, or copy, and then past themselves into new locations in the genome

Question 24

what kind of transposons encode proteins that allow them to jump?

Answer 24

autonomous transposons

Question 25

what do retrotransposons contain that allow them to be transcribed?

Answer 25

have a promoter and get transcribed

Question 26

autonomous retrotransposons are translated into?

Answer 26

2 proteins, one of which is a reverse transcriptase which creates a complementary DNA sequence that is then integrated into the genome

Question 27

what does it mean for most retrotransposons to be inactive?

Answer 27

they are mutated so that they can’t be transcribed and/or translated; they are molecular fossils

Question 28

what step allows one retrotransposon to become many?

Answer 28

the transcription step

Question 29

what % of the human genome is retrotransposons?

Answer 29

41%

Question 30

what percent of the human genome is DNA transposons?

Answer 30

3%

Question 31

are DNA transposons transcribed?

Answer 31

transcribed and translated, but there is no reverse transcriptase

Question 32

when can DNA transposons be duplicated?

Answer 32

if it “jumps” during DNA replication

Question 33

short DNA sequences over and over again in tandem

Answer 33

tandem repeat sequences

Question 34

what are tandem repeat sequences classified by?

Answer 34

size of repeated sequence

Question 35

percent of human genome that is tandem repeat sequences?

Answer 35

3%

Question 36

what are minisatellites?

Answer 36

group of tandem repeat sequences; 10-60 bp long repeated 5-50 times

Question 37

what are microsatellites?

Answer 37

group of tandem repeat sequences; 1-9 bp long and highly variable between individuals in a species

Question 38

what are microsatellites useful for?

Answer 38

DNA fingerprinting

Question 39

how might mini or micro satellites be extended or shortened?

Answer 39

by basal slippage of DNA polymerase during replication

Question 40

what kind of repetitive DNA sequences DO NOT need DNA polymerase to be duplicated? a) DNA transposons b) retrotransposons c) microsatellites d) minisatellites

Answer 40

b) retrotransposons

Question 41

define polyploidy

Answer 41

having multiple copies of the whole genome

Question 42

why do related plants and animals have very different genome sizes?

Answer 42

mostly due to polyploidy, also due to frequency of repetitive elements like retrotransposons

Question 43

genome size DOES NOT correlate to the ____ of an organism

Answer 43

complexity

Question 44

the cell doesn’t seem to care about the amount of DNA, rather _____

Answer 44

the number of genes

Question 45

most multicellular organism have _____ of protein-coding genes; which is around _____

Answer 45

the same; 20,000

Question 46

how many protein-coding genes do unicellular organisms have?

Answer 46

5000 protein-coding genes