3-1: Microbial Genome

Question 1

What is the first step in cell division

Answer 1

DNA replication

Question 2

What part of mRNA is converted into proteins

Answer 2

Open reading frames

Question 3

Nucleotides are comprised of what three components?

Answer 3

Nucleobase (nitrogenous base), deoxyribose, phosphate at 5’

Question 4

What is the difference btw nucleoside and nucleotide?

Answer 4

Nucleosides lack P

Question 5

How are nucleotides connected

Answer 5

Phosphodiester bonds btw 5’ P and 3’ OH

Question 6

Why do C/G base pair stronger than A/T?

Answer 6

3 hydrogen bonds

Question 7

Differences between RNA and DNA?

Answer 7

RNA = 2’ OH group on ribose sugar (less chemically stable), thymine replaced by uracil, single stranded

Question 8

How are prokaryotic chromosomes structured

Answer 8

Circular with extensive supercoiling and additional structuring layered on top

Question 9

What is the nucleoid

Answer 9

Region of cell containing chromosome (not membrane bound, but similar to the concept of the nucleus)

Question 10

How many chromosomes do prokaryotes typically have?

Answer 10

One circular chromosome

Question 11

What is an example of a bacterium with two chromosomes

Answer 11

Vibrio cholerae (one 3Mbp, one 1Mbp)

Question 12

What is special about the streptomyces chromosome?

Answer 12

Linear!

Question 13

Structure of eukaryotic chromosomes?

Answer 13

Multiple linear chromosomes, larger and less compact genomes compared to prokaryotes

Question 14

What is special about eukaryotic microbial chromosomes?

Answer 14

Smaller and has more compact genes (fewer introns)

Question 15

What are genes

Answer 15

Genetic material that encodes functional protein or RNA product

Question 16

What is the typical prokaryote genome comprised of?

Answer 16

85-90% protein-coding genes, 1-2% noncoding RNA genes, 10% non-coding DNA (eg. regulatory sequences)

Question 17

What direction do genes run?

Answer 17

Both directions (they can overlap too!)

Question 18

How are genes organized

Answer 18

Functionally related clusters

Question 19

Who has the smallest genome size?

Answer 19

Endosymbionts, parasites

Question 20

What size genome does mycoplasma have?

Answer 20

0.5 Mb

Question 21

What size genome do bacteria/archaea have?

Answer 21

Around 4.5 Mb

Question 22

Why might some bacteria need really big genomes?

Answer 22

Those with complex life cycles

Question 23

How are genome size and number of genes related in prokaryotes?

Answer 23

Genome size increase, so does number of genes

Question 24

How does the genome composition change as genome size increases?

Answer 24

Higher proportion of genes responsible for regulation (eg. transcription, signal transduction)

Question 25

What is the core genome

Answer 25

Genes present in all members (conserved genes)

Question 26

What is the pan genome

Answer 26

All genes present in any member (includes rare genes)

Question 27

What is synteny

Answer 27

Homologous genes arranged in same order in genomes of closely-related lineages

Question 28

What is a genomic island vs islet

Answer 28

When unique genes of genome found in blocks
Island = large block
Islet = small block

Question 29

What is the Salmonella Pathogenicity Island-1?

Answer 29

Encodes many genes needed for type III secretion system that allows Salmonella to enter host cells. Also encodes iron acquisition genes

Question 30

What is a prophage

Answer 30

When a bacteriophage integrates into the bacterial genomes, become a part of it. Can be stable or transient

Question 31

What is a cargo gene

Answer 31

Carried by prophage, have nothing to do with phage biology, provide the bacterial host with new genes

Question 32

What is a plasmid

Answer 32

Circular DNA molecules replicated in the cytoplasm that encode “non-essential” genes (only required under certain conditions; e.g. antibiotic resistance genes)

Question 33

What is the typically size and number of plasmids?

Answer 33

1kbp to 1Mp
Can vary from 1 to >100