B/B

Question 1

Hayflick Limit

Answer 1

The number of times a normal human cell type can divide until telomere length stops cell division

Question 2

What is the function of reverse transcriptase enzymes?

Answer 2

These enzymes read RNA and make DNA

Question 3

What is a telomerase?

Answer 3

It is a ribonuclease complex that contains an RNA primer and a reverse transcriptase enzyme, which allows for chromosome extension of the parental DNA strand to create telomeres that are disposable during the cell cycle.

Question 4

When is the telomerase found?

Answer 4

In most organisms, telomerase is only expressed in the germ line, embryonic stem cells, and some white blood cells.

Question 5

How can UV light damage DNA?

Answer 5

If two pyrimidines are next to each other in the DNA backbone, UV light can cause them to be covalently linked to EACH OTHER and cause a distortion in the backbone that will cause trouble for DNA replication when it is not fixed and can cause mutations.

Question 6

Missense Mutations

Answer 6

This is caused by one amino acid being replaced with a different amino acid. If the amino acids are very similar in characteristics, then it might not be detrimental.

Question 7

Nonsense Mutation

Answer 7

This is when a stop codon replaces a regular codon and prematurely shortens the protein.

Question 8

Silent Mutation

Answer 8

A codon that is changed into a new codon for the same amino acid so there is no change in the protein’s amino acid sequence

Question 9

What is an inversion of the chromosome?

Answer 9

This is when a segment of a chromosome is reversed end-to-end. The chromosome undergoes a breakage and rearrangement within itself

Question 10

What is the difference between recombination and translocation?

Answer 10

Recombination is when genetic information is exchanged between homologous chromosomes whereas translocation happens between non-homologous chromosomes. Translocation is common in many types of cancer and can be either balanced (where no gene information is lost) or unbalanced (where genetic information is lost or gained).

Question 11

Hemizygous

Answer 11

Condition in which there is only one gene copy in the diploid organism

Question 12

Hemizygosity

Answer 12

This is a situation in which there is haploid expression in a diploid organism

Question 13

Haploinsufficiency

Answer 13

A diploid organism has only a single functional copy of a gene and this single copy is not enough to support a normal state.

Question 14

What are inborn errors of metabolism?

Answer 14

They are a huge group of genetic diseases that involve disorders of metabolism; can be due to a single mutation in a ingle gene that codes for some sort of metabolic enzyme. Symptoms are caused by either the build-up of toxic compounds that can’t be broken down or by the deficiency of an essential molecule that cannot be synthesized.

Question 15

What is an oncogene?

Answer 15

An oncogene is a gene that can cause cancer when it is mutated or expressed at high levels.

Question 16

What is the direct reversal DNA repair (and give an example)?

Answer 16

Some enzymes can repair UV light induced pyrimidine photodimers using visible light. This process is called photoreactivation, and directly repairs the UV damage to DNA. If pyrimidine diners are not directly reversed, nucleotide excision repair can be used instead however this mechanism can introduce a mutation when trying to complete the repair. If the covalent cross linking between pyrimidines are left unrepaired then the dimers may lead to melanoma in humans.

Question 17

Homology-dependent repair

Answer 17

This is when the cell uses the un-damaged complementary strand to repair the damage on the other strand; this is because DNA is double stranded! Very nice!

Question 18

Excision Repair

Answer 18

This involves the removal of defective bases or nucleotides and replacing them before replication

Question 19

Post-replication repair/mismatch repair pathway

Answer 19

This targets bp that were not repaired by the DNA polymerase proofreading during replication. Methylation can be used here to identify which base pairs it needs to repair! Pg 92 of the book

Question 20

How can you repair a double-strand break (DSB)?

Answer 20

You can use homologous recombination or no homologous end joining (if not done right you can have deletions or translocations)

Question 21

Homologous recombination

Answer 21

This is a process in which one sister chromatid can help repair a DSB in the other. First, the DSB is identified and trimmed at 5’ ends to generate single-stranded DNA (done by nucleases) and helicase.Many proteins bind these ends and start a search of the genome to find a sister chromatid region that is complementary to the single strand DNA. Once found, the complementary sequences are used as a template to repair and connect the broken chromatid. This requires a “joint molecule”, where damaged and undamaged sister chromatids cross over. DNA polymerase and ligase build a corrected DNA strand.

Question 22

Heterogenous nuclear RNA (hnRNA)

Answer 22

Immature/precursor of mRNA

Question 23

What are the four types of ribosomal RNA units?

Answer 23

18S, 5.8S, 28S, 5S

Question 24

In transcription, what do you call the DNA strand that is actually being transcribed by the RNA polymerase?

Answer 24

Template, non-coding, transcribed, or antisense strand and it is complementary to the transcript.

Question 25

What do you call the DNA strand that is just sitting there and not being actively transcribed by the RNA Polymerase?

Answer 25

It is called the coding or sense strand; it has the same sequence as the RNA that is being produced (with the exception that it has a T instead of an U because it is DNA).

Question 26

What is the Pribnow box in bacteria?

Answer 26

It is like the TATA box in eukaryotes and it is at the -10 and -35 sequence (upstream of the start site). This is like the “promoter” region and can initiate the RNA polymerization in prokaryotes.