L1- Genetic Material

Question 1

What are the chemical parts of a nucleotide? A nucleoside?

Answer 1

Nucleotides contain a base, a sugar and a phosphate(s). Nucleosides contain only a base and a sugar.

Question 2

What is the chemical difference between the second carbons of RNA and DNA?

Answer 2

RNA has a 2’ OH group. DNA has an H at this position.

Question 3

What is the direction in which DNA and RNA are read and written?

Answer 3

5’ to 3’.

Question 4

The terms ‘denaturation’ and ‘annealing’ of double stranded oligos and primers refer to what physical change?

Answer 4

Strand separation (denaturation) and strand association (annealing).

Question 5

Which class of enzymes relaxes positive and negative DNA supercoils?

Answer 5

Topoisomerases.

Question 6

How many chromosomes do diploid human cells have?

Answer 6

46

Question 7

How many base pairs does the haploid human genome contain, approximately?

Answer 7

About 3 billion.

Question 8

What percent of human DNA codes for proteins?

Answer 8

1-2%

Question 9

How many proteins do human genes encode, roughly (not including splice variants)?

Answer 9

About 30,000.

Question 10

The average protein is about __ amino acids long.

Answer 10

About 400

Question 11

What process often leads to more than one form of mature RNA being formed from a given transcript?

Answer 11

Alternative RNA splicing.

Question 12

Functionally related genes that appear close to each other in the genome belong to the same ____.

Answer 12

Gene cluster (i.e. beta globin gene cluster).

Question 13

What is a pseudogene?

Answer 13

A piece of DNA homologous to a coding segment that does not code for a protein.

Question 14

Compared to pseudogenes, processed psudogenes lack ____.

Answer 14

Introns.

Question 15

What is a provirus?

Answer 15

DNA copies of ancient viruses that have integrated themselves into the genome. There are about a thousand proviruses integrated into the human genome, and they make up about 8% of our DNA.

Question 16

What is a transposable element?

Answer 16

A piece of DNA that can insert copies of itself in a new location within the genome.

Question 17

What percent of our genome is composed of short interspersed repeat elements (SINEs)?

Answer 17

About 10%. Note that SINEs are inserted into the genome via reverse transcription.

Question 18

What percent of our genome encodes long (>500 nt) interspersed repeat elements (LINEs)?

Answer 18

About 20%.

Question 19

What is a transposase?

Answer 19

An enzyme that allows movement of a transposable DNA element. Note that some elements encode their own transposase.

Question 20

Name two types of SSRs (simple sequence repeats).

Answer 20

Microsatellites (very short repeats) and minisatellites (14-500 base pair repeats).

Question 21

What is the function of telomeres?

Answer 21

They protect the end of chromosomes from degradation.

Question 22

Where are telomeres found and what is their base sequence?

Answer 22

Telomeres are found at the ends of chromosomes. They contain 1000-1700 copies of the hexameric sequence TTAGGG.

Question 23

What is meant by the term mitotic clock?

Answer 23

It refers to the loss of 50-200 nucleotides from the ends of chromosomes every time a cell divides. When the telomeres are sufficiently shortened, the cell is no longer able to divide.

Question 24

Name two drugs that inhibit topoisomerases.

Answer 24

Camptothecin and mAMSA.

Question 25

What polymerase is often activated in cancer cells?

Answer 25

Telomerase - this enzyme rejuvenates the telomeres and circumvents the mitotic clock.

Question 26

How is DNA packaged in nucleosomes?

Answer 26

DNA is wrapped around histone octomers. These are packed together to form chromatin fibers.

Question 27

Telomerase is a ____ (type of enzyme).

Answer 27

Reverse transcriptase (it uses an RNA template).

Question 28

What type of enzyme is encoded by LINEs?

Answer 28

A reverse transcriptase. This is involved in introducing additional copies of the LINE into the genome.

Question 29

What is a single nucleotide polymorphism (SNP)?

Answer 29

It is a common single base substitution between individuals. Rare single base substitutions are called mutations.

Question 30

Why are simple sequent repeats (SSRs) used as biomarkers?

Answer 30

SSRs tend to be highly polymorphic, so the number of copies varies from one individual to another. This allows them to be useful biomarkers.