Chromosomal DNA

Question 1

What is a nucleosome?

Answer 1

Chromatin = DNA + histones wound 2.5x

Question 2

How are chromosomes packaged in prokaryotes ?

Answer 2

Single naked chromosomes without histones but still supercoiled.

Question 3

What does DNA polymerase III do?

Answer 3

Catalyses addition and linking of nucleotides into polynucleotide strands.

Question 4

What converts relaxed to supercoiled DNA in eukaryotes?

Answer 4

DNA gyrases

Question 5

What converts relaxed to supercoiled DNA in prokaryotes?

Answer 5

Topoisomerases

Question 6

When is DNA relaxed?

Answer 6

When genes are transcribed / DNA is being repaired/ replicated

Question 7

What is the process of isolating genomic DNA based on?

Answer 7

Length and relative inflexibility of chromosomal DNA molecules

Question 8

Why are chromosomes susceptible to physical breakage?

Answer 8

They are very long & double-stranded when makes them relatively inflexible

Question 9

What is added to chromosomal DNA to get rid of RNA?

Answer 9

Ribonuclease to digest all of the RNA into ribonucleotides

Question 10

How is DNA isolated?

Answer 10

1. larger molecules can be broken
2. Gentle cell lysis w/ detergents
3. Separate and purify by spooling, dialysis and precipitation

Question 11

What are detergents?

Answer 11

Surfactants –> lower surface tension

Question 12

What are the two common detergents used?

Answer 12

SDS: bacterial lysis
DDM: eukaryotic cell lysis

Question 13

What do detergents do?

Answer 13

-Provide a long aliphatic hydrophobic chain beginning with a methyl group + capped by a charged group.

Question 14

How does SDS denature protein?

Answer 14

• Charged polar end interrupts protein surface polar + ionic interactions
• Long aliphatic chains gain access to the interior core of the folded protein
• Can bind to inner non-polar amino acid side chains

Question 15

Which is more efficient at precipitating nucleic acids (Isopropanol vs ethanol)

Answer 15

Isopropanol (only needs 1:1 ratio)

Question 16

What is epigenetics?

Answer 16

Study of changes in organisms by modification of gene expression rather than alteration of genetic code

Question 17

What are the 3 systems which initiate epigenetic change?

Answer 17

• DNA methylation
• Histone modification
• Non-coding RNA associated gene silencing

Question 18

What are some disorders that may come from epigenetics?

Answer 18

cancer, autism, schizophrenia, mood disorders

Question 19

What is imprinting?

Answer 19

About 1% of genes escape epigenetic reprogramming

Question 20

What is reprogramming?

Answer 20

The removal of epigenetic tags on sperm and eggs

Question 21

What does epigenetic inheritance?

Answer 21

Allow an organism to continually adjust its gene expression to fit its environment without changing the code

Question 22

What can epigenetics be triggered by?

Answer 22

Diet
Exercise
Drugs, alcohol, smoking
Aging
Pollutants, toxins
Changes to sleep patterns
Severe environmental stress
Cancer

Question 23

How does environmental factors trigger epigenetic changes?

Answer 23

Changes in the methylation pattern of cytosine bases in DNA (not the sequence)