Microbial genetics

Question 1

What is a genome?

Answer 1

all genetic information in cell

Question 2

What is a chromosome?

Answer 2

molecule of DNA + proteins

Question 3

How are prokaryotic chromosomes organized?

Answer 3

1 circular= genome

Question 4

How are eukaryotic chromosomes organized?

Answer 4

multiple pairs=genome

Question 5

What is a gene?

Answer 5

a segment of DNA encoding a functional product (ie protein)

Question 6

What is a genotype?

Answer 6

just genes of an organism

Question 7

What are plasmids?

Answer 7

exist in prokaryotes

small circular dsDNA

Extrachromosomal (not part of genome)

not essential but often advantageous

Question 8

How are plasmids advantageous?

Answer 8

antibiotic resistance

toxins

Question 9

How can DNA be described?

Answer 9

complementary (A:T and C:G)

antiparallel (opposite directions)

Question 10

What must happen before a cell divides?

Answer 10

DNA replication

Question 11

What is semiconservative DNA replication?

Answer 11

each strand of original molecule serves as template

new DNA contains one conserved “parental” and one new strand

Question 12

What does helicase do in DNA replication?

Answer 12

unzips the DNA

Question 13

What does topoisomerase do in DNA replication?

Answer 13

relaxes

Question 14

What is the function of primase in DNA replication?

Answer 14

RNA primer

Question 15

What does DNA polymerase do in DNA replication?

Answer 15

Reads 3’ to 5’
Synthesizes 5’ to 3’

Question 16

What does ligase do in DNA replication?

Answer 16

glues lagging fragments

Question 17

What happens in prokaryotic DNA replication?

Answer 17

Circular DNA

1 replication bubble

2 forks at each origin (bidirectional forks)

Question 18

What happens in eukaryotic DNA replication?

Answer 18

many origins and bubbles

linear DNA

bidirectional forks (2 forks at each origin)

Question 19

What is a phenotype?

Answer 19

physical features/functional traits of an organism

include structures, morphology, metabolism

Question 20

How does transcription stop and start?

Answer 20

start: promoter

stop: terminator

Question 21

What happens in transcription?

Answer 21

RNA polymerase reads DNA

synthesizes complementary mRNA

Question 22

What happens in translation?

Answer 22

ribosomes read mRNA three nucleotides at a time (codon)

start codon is AUG and stop codons

Transfer RNA (tRNA) is an anticodon plus an amino acid

Question 23

What is a genetic code rule?

Answer 23

1 start codon- Met

64- other amino acids (19)

3-stop codons- no amino acids

Question 24

Why does more than one codon code for the same amino acid?

Answer 24

protects from mutations

Question 25

How does gene expression happen in prokaryotes?

Answer 25

coupled translation can begin before transcription complete

Question 26

How does gene expression happen in eukaryotes?

Answer 26

transcription completed in the nucleus before translation in cytoplasm

Question 27

What is point mutation?

Answer 27

one nucleotide is changed

Question 28

What is substitution?

Answer 28

one nucleotide replaced by another

Question 29

What is frameshift?

Answer 29

insertion/deletion of nucleotide

Question 30

What is silent mutation?

Answer 30

one result of substitution only affects genotype protein not affected

Question 31

What is missense mutation?

Answer 31

one result of substitution amino acid changed may or may not have an effect on function sickle cell disease- altered hemoglobin shape

Question 32

What is nonsense mutation?

Answer 32

one result of substitution premature stop codon often nonfunctional protein

Question 33

What do drastic missense and nonsense mutations do?

Answer 33

ribosome reading frame shifted (reads in 3's remember) non functional protein

Question 34

What do base analog chemical mutations do?

Answer 34

look like normal bases initially but base pair incorrectly once incorporated induce point mutations used in research and as drugs example is 5-bromouracil

Question 35

What do intercalating agents do in chemical mutations?

Answer 35

slip in between adjoining nucleotides bulge in backbone- polymerase makes mistakes (insertion/deletion of nucleotides frameshifts for ribosomes example is benzopyrene in smoke

Question 36

What does ionizing radiation do?

Answer 36

X-rays and gamma rays energize electrons in atoms- some electrons escape free electrons strike other atoms- ions reaction with DNA- point mutations

Question 37

What does non-ionizing radiation do?

Answer 37

UV Light induces thymine dimers- covalent bonds between adjacent T's distorts backbone improper replication- frameshift mutation

Question 38

What is vertical gene transfer?

Answer 38

passing of genes down from parent to offspring

Question 39

What is horizontal gene transfer?

Answer 39

genes passed down laterally in same generation (same recombination of transferred genes) Prokaryotes (donor and recipient (recombinant cells)

Question 40

What is transformation?

Answer 40

recipient takes up DNA fragments in environment from dead cell antibiotic resistance has spread this way

Question 41

What happens in conjugation?

Answer 41

fertility plasmid allows bacteria to form special pilus (allows plasmid transfer to recipient)

Question 42

How does antibiotic resistance spread?

Answer 42

conjugation, transformation, transduction

Question 43

What happens in transduction?

Answer 43

new assembling phage accidentally package piece bacterial chromosome (transferred to new cell when phage infects it dead end for phage but could be good for bacteria (antibiotic resistance)