L4: Genetic diversity in bacteria

Question 1

Why are bacterial chromosomes always made up of double stranded DNA

Answer 1

Because it’s stable and protects the information in the double strand

Question 2

What are the four bases of nucleotides in bacterial chromosomes?

Answer 2

deoxy - guanine
deoxy - adenine
deoxy - thymine
deoxy - cytosine

Question 3

Why are nucelotides called deoxy?

Answer 3

They lack an oxygen on the 2’ carbon of sugar. This is what distinguishes DNA from RNA building blocks.

Question 4

how many hydrogen bonds are in dG and dC pairing in bacterial DNA?

Answer 4

3

Question 5

How many hydrogen bonds are in dA and Dt pairing in bacterial DNA?

Answer 5

2

Question 6

What is a base pair?

Answer 6

two complementary DNA nucleotides.

Question 7

In dsDNA, what is the difference between minor and major grooves?

Answer 7

Minor groove is narrower and deeper.
Major groove is wider and more accessible
Major groove is binding site for proteins and other molecules.

Question 8

In dsDNA, what is a major groove?

What is it and how is it formed?

Answer 8

binding site for proteins
binding site for other molecules that interact w. DNA.

formed by the larger separation between the sugar-phosphate backbones of the two DNA strands.

Question 9

In dsDNA, what is a major groove?

Answer 9

Deep grove in helix. Wider and more accessible that the minor groove, allowing proteins to bind more easily.

Question 10

how is the major groove formed?

Answer 10

Larger separation in sugar-phosphate backbone of DNA strands.

Question 11

How many base pairs are in each turn in dsDNA structure

Answer 11

10.4

Question 11

How are major and minor grooves formed in DNA?

Answer 11

By the twisting of the two strands around each other.

Question 12

What shape are bacterial chromosomes and why?

Answer 12

Circular - so the ends don’t get damaged ie in human chromosomes we have telomeres, and their ends are lost with each round of DNA replication. With circular DNA this can’t happen.

Question 13

Circular bacterial DNA takes up a lot of space. What are the three levels of organisation that makes it possible for it to fit in the relatively small confines of baterial cells?

Answer 13

Supercoiling - positive and negative supercoiling.
Nucleoid -
DNA- binding proteins -

Question 14

How is DNA replication in bacteria different to eukarotyes?

Answer 14

OriC (Origin of replication - a specific DNA site that is a starting point for replication and is timed to coincide with cell division and passed down to each daughter cell.

Question 15

Why is DNA bacterial replication referred to as being ‘bidirectional’?

Answer 15

the replication happens in both directions.

Question 16

In DNA replication, explain what is meant by open reading frames?

Answer 16

Section of DNA containing info needed to encode for a protein in pro and eukaryotic organisms.

Question 17

What is GC content and how does it differ in bacteria vs eukarotyes?

Answer 17

The percentage of Guanine and cytosine nucleotides in DNA. Humans and E-coli have similar GC%. The percentage affects stability in replication, transcription and other cellular processes. it can also affect the binding process and binding affinity of DNA binding proteins.

Question 18

What is phylogenetic analysis?

Answer 18

Reconstructing the evolutionary history of a group of organisms. Creating a tree-like diagram that looks at evolutionary relationships between organisms.