The Structure of DNA Flashcards

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1
Q

The nucleic acid DNA is a

A

polynucleotide – it is made up of many nucleotides bonded together in a long chain

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2
Q

DNA molecules are made up of …… polynucleotide strands lying side by side, running in …….. directions – the strands are said to be?

A

2

opposite

antiparallel

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3
Q

Each DNA polynucleotide strand is made up of

A

alternating deoxyribose sugars and phosphate groups bonded together to form the sugar-phosphate backbone.

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4
Q

These bonds are covalent bonds known as phosphodiester bonds

The phosphodiester bonds link the

A

5-carbon of one deoxyribose sugar molecule to the phosphate group from the same nucleotide, which is itself linked by another phosphodiester bond to the 3-carbon of the deoxyribose sugar molecule of the next nucleotide in the strand

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5
Q

Each DNA polynucleotide strand is said to have a …’ end and a ..’ end (these numbers relate to which carbon ……

A

3’ end 5’ end

on the pentose sugar could be bonded with another nucleotide)

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6
Q

As the strands run in opposite directions (they are……..), one is known as the .’ to .’ strand and the other is known as the .’ to .’ strand

A

antiparallel

5’ 3’

3’ 5’

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7
Q

The nitrogenous bases of each nucleotide project out ………….towards the interior of the ………….

A

from the backbone

double-stranded DNA molecule

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8
Q

The two antiparallel DNA polynucleotide strands that make up the DNA molecule are held together by

A

hydrogen bonds between the nitrogenous bases

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9
Q

These hydrogen bonds always occur between the same pairs of bases:
Which base pair has 2 hydrogen bonds

A

The purine adenine (A) always pairs with the pyrimidine thymine (T) – two hydrogen bonds are formed between these bases

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10
Q

These hydrogen bonds always occur between the same pairs of bases:
Which base pair has 3 hydrogen bonds

A

These hydrogen bonds always occur between the same pairs of bases:
Which base pair has 2 hydrogen bonds

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11
Q

This is known as complementary base pairing
These pairs are known as DNA base pairs

A
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12
Q

DNA is described as a double helix
This refers to the

A

spiral shape, where two complementary strands of nucleotides run in opposite directions and are held together by hydrogen bonds.

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13
Q

Make sure you can name the different components of a DNA molecule (sugar-phosphate backbone, nucleotide, complementary base pairs, phosphodiester bonds, hydrogen bonds) and make sure you are able to locate these on a diagram. Remember that phosphodiester bonds join the nucleotides in the sugar-phosphate backbone, and hydrogen bonds join the bases of the two complementary strands together. Remember that the bases are complementary, so the number of A = T and C = G. You could be asked to determine how many bases are present in a DNA molecule if given the number of just one of the bases. Note that knowledge of purines and pyrimidines is not required

A
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