lecture 1 : nucleic acids and chromosomes Flashcards Preview

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Flashcards in lecture 1 : nucleic acids and chromosomes Deck (21)
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1
Q

what is a nucleotide?

A

a nucleotide is a sugar + base + phosphate

2
Q

what is a nucleoside?

A

a nucleoside is a sugar + base

3
Q

what is the difference between deoxyribose and ribose?

A

ribose contains oxygen deoxyribose does not contain oxygen

4
Q

where is 1 carbon attached?

A

attached to the carbon with the base

5
Q

where is the 5’ carbon attached ?

A

to the phosphate

6
Q

what are purines?

A

adenosine and guanine

7
Q

what are pyrimidines?

A

cytosine and thymine and uracil

8
Q

* show a diagram of purines

A

insert pic

9
Q

* show a diagram of pyrimidines

A

insert pic

10
Q

*what is the overall structure of DNA ? insert pic of DNA

A
  • phosphate of one nucleotide and 3’hydroxyl group of adjacent nucleotide are linked via phosphodiester link - the phosphate is liked to the 5’OH of an adjacent sugar - the chain has 2 ends 3’ and 5’ - the first nucleotide has a free 5’ phosphate and the last nucleotide has a free 3’ hydroxyl group - therefore it is conventionally written as 5’ to 3’ - the chains are antiparallel - there is a minor and major groove
11
Q

how many hydrogen bonds between A- T? (skinny)

A

2 hydrogen bonds

12
Q

how many hydrogen bonds between C- G? (fat)

A

3 hydrogen bonds

13
Q

how to melt or denature DNA?

A

heat or use low salt

14
Q

how to re anneal or hybridise DNA

A

cool conditions and high salt

15
Q

what is a karyotype? why are karyotypes important?

A
  • the organised profile of someones chromosomes - consisting of 22 autosomal chromosomes and one pair of sex chromosomes - can be an important diagnostic tool
16
Q

what is chromatin?

A

this is when the DNA is packaged tightly forming a complex with the histone proteins

17
Q

* what is the level of packing of a nucleosome?

A
  • the lowest level of packaging - consists of DNA wrapped around histones - linker DNA present between the DNA - 200bp of DNA per nucleosome insert pic
18
Q

what level of packaging is 30nm fibre?

A
  • this is when the nucleosomes are further packed to generate a more compact structure - 40 fold condensing of DNA
19
Q

what is the structure of the nucleosome?

A
  • histones are positively charged so they interact with the negative sugar phosphate backbone - there are 8 histones around which the DNA is wrapped - histone 1 is between the nucleosomes - nucleosome causes the 7 fold condensing of DNA
20
Q

what is a further level of organisation after the 30nm fibre

A

chromatin is folded into loops and then fits into being part of the chromosome

21
Q

what are the overall levels of organisation of the DNA ?

A

short strand of DNA *

string of chromatin *

30nm chromatin fibre - nucleosomes

chromatin fibre folded into loops

chromosome