Lecture 4

Question 1

The basic unit of heredity is the _____, the segment of DNA that encodes for a gene product

Answer 1

gene

Question 2

The ___ is the whole genes (coding regions of DNA) and the noncoding regions constituent of an organism

Answer 2

genome

Question 3

What process is accomplished by RNA polymerase enzymes to give mRNA?

Answer 3

Transcription

Question 4

What process is performed by ribosomes (rRNA + proteins) in the cytoplasm of the cell?

Answer 4

Translation

Question 5

______ participate in the translation (polypeptide synthesis) by transferring the amino acids from the cytoplasm to the ribosomes and binding them to the peptide chain according to the mRNA codon

Answer 5

Transfer RNAs (tRNA)

Question 6

___ and _____ tend to be stable and together account for more than 95% of the total RNA in a bacterial cell

Answer 6

rRNA and tRNA

Question 7

How many chromosomes in the nucleus is the eukaryotic genome carried on?

Answer 7

Two or more linear chromosomes

Question 8

Diploid eukaryotic cells contain two homologues of each chromosome. The gene that does not achieve phenotypic expression in the presence of it’s homologue is __, and the gene that overrides the effect of its homologue is ___

Answer 8

recessive, dominant

Question 9

What are introns?

Answer 9

intervening sequences of DNA that are missing in the processed mRNA when it is translated

Question 10

Most prokaryotic genomes consist of what type of DNA?

Answer 10

Single circular DNA

Question 11

What are some examples of bacteria that have two chromosomes?

Answer 11

-Brucella melitensis
-Burkholderia pseudomallei
-Vibrio cholerae

Question 12

What are some examples of bacteria that have linear chromosomes?

Answer 12

-Actinomycetes
-Myobacteria

Question 13

Bacterial genes are:
a) diploid
b) haploid

Answer 13

Haploid

Question 14

In contrast to eukaryotic genomes, 98% of bacterial genomes are ___________

Answer 14

coding sequences

Question 15

What are housekeeping genes?

Answer 15

They are genes essential for bacterial growth and reproduction

Question 16

What are housekeeping genes carried on?

Answer 16

Bacterial chromosomes

Question 17

________
-Have double-stranded DNA that can exist and replicate independently
-Some can integrate into the host’s chromosome
-Are not required for bacterial growth

Answer 17

Plasmids

Question 18

Plasmids carry genes that give their host a selective advantage. What advantages do these hosts have?

Answer 18

-render bacteria drug-resistant
-Give them new metabolic abilities
-Make them pathogenic
-Provide them with other properties

Question 19

Plasmids mediate their transfer from one organism to another through:

Answer 19

conjugation and sex pili formation

Question 20

A cluster of genes in the chromosome (up to 200 kbp) and encodes a collection of virulence genes

Answer 20

Pathogenicity Islands (PAIs)

Question 21

What are 4 important components of PAIs?

Answer 21

1. They have different G+C Content from the rest of the genome
2. Are closely linked on the chromosome to tRNA genes
3. Are flanked by direct repeats (allow the PAIs to be copied and inserted at a different location in the genome)
4. Contain diverse genes important for pathogenesis, including antibiotic resistance, adhesions, invasions, exotoxins, and genes involved in genetic mutation

Question 22

-A class of genetic elements that can move or “jump” to different locations within a genome.
-They are always integrated into the genome (chromosomes or plasmids) and can not replicate by themselves
-Most eventually become inactive and no longer move

Answer 22

Transposons (transposable elements)

Question 23

Are the simplest transposable elements (0.72-2.0 kbp long), which are found in almost all bacteria, viruses, and some eukaryotes.
They create insertion mutations

Answer 23

Insertion sequences elements (IS)

Question 24

Are elements that could have antibiotic resistance or toxic genes

Answer 24

Composite transposons

Question 25

How does DNA replication in prokaryotes occur?

Answer 25

-Begins at one point (oriC) and moves in both directions and terminates in a region called (ter) -The two old strands of DNA are separated and used as templates to synthesize new strands (semiconservative replication) -The structure where the two strands are separated is referred to as the replication fork

Question 26

_____ is a large protein complex that carries out DNA replication and has several enzymatic activities ( DNA I, II, and III)

Answer 26

Replisome

Question 27

____ are enzymes that alter the supercoiling of ds DNA, by cutting the DNA to relax the coil and extend the DNA molecule Are targets of antibiotics

Answer 27

Topoisomerases

Question 28

What are the two mechanisms of gene transfer?

Answer 28

1. Vertical gene transfer: vertical inheritance of parental genes from the parent cells to the progeny cells 2. Horizontal gene transfer (HGT): can be transferred from one organism to another. The DNA can be stably incorporated into the recipient permanently changing its genetic composition

Question 29

What are the 3 broad mechanisms that mediate HGT?

Answer 29

Conjugation, transduction, transformation

Question 30

How does the conjugation of DNA work?

Answer 30

It requires donor cell-to-recipient cell contract to transfer only one strand of DNA The recipient completes the structure of dsDNA by synthesizing the strand that complements that strand acquired from the donor

Question 31

What part of the DNA is most frequently transferred by conjugation?

Answer 31

Plasmids

Question 32

What are fertility factors responsible for?

Answer 32

The formation of sex pilus and the extracellular multimeric proteins that attach donor cells to the recipient cells

Question 33

How does the transduction of DNA work?

Answer 33

Transduction is a phage (virus) mediated genetic recombination in bacteria The phages infect bacterial cells and propagate inside them. When they leave the cell to infect other cells, they take some bacterial genes with them.

Question 34

In nature, ________ are often transported by phages

Answer 34

pathogenicity islands

Question 35

How does the transformation of DNA work?

Answer 35

It is a direct uptake of extracellular "naked" DNA by the recipient cell.

Question 36

Can the transformation of DNA be natural, forced, or both?

Answer 36

Both

Question 37

How can forced transformation be induced?

Answer 37

In a laboratory. After treatment with high salt and temperature shock, many bacteria are rendered competent for the uptake of extracellular plasmids. The competency for transformation is varied between bacterial spaces