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Flashcards in DNA Deck (97)
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1

What gene mutation is associated with xeroderma pigmentosa? How does this mutation lead to the associated disorder?

A mutation in the NER gene - this gene codes for an enzyme which is used nucleotide excision repair - a dysfunctional gene here won't recognise and replace abnormal DNA - UV induced DNA damage is not adequately repaired, so a prolonged exposure to ultraviolet light leads to a greater propensity to developing skin cancer

2

Describe 2 ways in which chemotherapy may actually be more harmful to a cancer patient.

Chemotherapy-induced damage - where the chemotherapy itself may be causing DNA damage that is beneficial to the growth and survival of the cancer cell germ line
Differential sensitivity -

3

Describe how DNA helicase functions.

DNA helicase breaks the hydrogen bonds that hold the alpha helical DNA molecule in its secondary structure, unraveling the DNA

4

What is the end-replication problem? How is this resolved?

The end-replication problem relates to the fact that no primer can be put at the end of a bit of DNA to copy the full sequence - therefore every time DNA will be lost - DNA telomerase resolves this by adding G & C repeats onto the end of DNA fragments in order to extend it, allowing primers to bind to copy the remaining bit of coding DNA

5

How may chemotherapy actually be detrimental to the patient?

The chemicals involved in chemotherapy itself may actually induce harmful mutations to a patients DNA

6

Why after continued chemotherapy treatment may a cancer begin to proliferate again?

The chemotherapy may be acting only one a specific cell within the cancer, whereas cells within the cancer itself may have mutated and formed various phenotypes which may be resistant to chemotherapy

7

How may inhibitors of DNA synthesis be used as antibiotics?

They may inhibit the enzymes responsible for the synthesis of DNA

8

What is non-homologous end joining? What is a potential problem with this repair mechanism?

Non-homologous end-joining involves the joining of the DNA flanking gap in a double stranded DNA break - this however will lead to deletion of the sequence which has been lost from the original DNA strand

9

What is an inversion?

A reversal of the order of a sequence of genes in a chromosome from their original/normal order

10

What is a translocation?

A translocation is the interchanging of genetic sequences between 2 non-homologous chromosomes

11

List 2 types of inversion. How do they differ?

Pericentric inversion - an inversion that involves reversing the order of a genetic sequence that includes the centromere
Paracentric inversion - an inversion that reverses the order of a genetic sequence that does not include the centromere

12

What is an inversion?

A reversal of the order of a sequence of genes in a chromosome from their original/normal order

13

What is a translocation?

A translocation is the interchanging of genetic sequences between 2 non-homologous chromosomes

14

List 2 types of inversion. How do they differ?

Pericentric inversion - an inversion that involves reversing the order of a genetic sequence that includes the centromere
Paracentric inversion - an inversion that reverses the order of a genetic sequence that does not include the centromere

15

How many bases are their every turn of the DNA double helix?

10

16

What is a TATA box?

A sequence of nucleotides within a promoter region specifying where transcription will begin

17

How far upstream from the actual transcription site is the TATA box located?

Around -10 base pairs upstream

18

Within a TATA box what is the sequence of bases?

TATAAA

19

What is the difference between pre-mRNA and mature mRNA?

Mature RNA exists after certain modes of protection have been added to pre-mRNA

20

List 3 ways in which pre-mRNA is transformed to mature mRNA.

- 5' cap
- addition of a polyA tail
- splicing

21

What are the non-coding parts of DNA called? What are the coding parts called?

Non-coding parts are called introns - the coding parts are called exons

22

At which ends of the pre-mRNA does capping and polyadenylation occur? What is the supposed mechanism of these processes?

Capping occurs at the 5' end (producing a 5' cap) and polyadenylation occurs at the 3' end (producing a 3' polyA tail) - these processes both act to protect the mRNA from degradation

23

What is splicing?

Splicing is the removal of non-coding sections of DNA from the mRNA sequence

24

Describe briefly the structure of the 5' cap.

A guanosine is methylated on the 7 position

25

Briefly describe the process of polyadenylation.

Endonuclease activity initially cleaves the mRNA molecule at a specific site, where polyA polymerase acts to add as many as 200 adenine bases

26

How many adenine bases may be in an mRNA polyA tail?

As many as 200

27

What is a polysome/polyribosome?

A collection of ribosomes held together by a strand of mRNA which they're all helping to translate

28

What, and how many, molecules make up the basic structure of a eukaryotic ribosome? What 2 subunits do they compose?

4 rRNA's and 82 proteins - these make up the 40s and 60s subunits

29

What, and how many, molecules make up the basic structure of a prokaryotic ribosome? What 2 subunits do they compose?

3 rRNA's and 56 proteins - these make up the 30s and 50s subunits

30

What are the seperate names for the prokaryotic and eukaryotic ribosomes?

The prokaryotic ribosome is called the 70s ribosome, while the eukaryotic ribosome is called the 80s ribosome