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Biology - Module 2 > 2.3 DNA > Flashcards

2.3 DNA Flashcards

1
Q

What are histone proteins?

A

A protein which DNA wraps around to form chromosomes.

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2
Q

What are the four bases and state whether they are purine or pyrimidine

A

Adenine (purine) base
Thymine (pyrimidine) base
Guanine (purine) base
Cytosine (pyrimidine) base

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3
Q

What is a purine and what bases are purines?

A

It is a type of nitrogen base found in DNA that consists of 2 nitrogen-carbon rings.
-Adenine and guanine

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4
Q

What is a pyrimidine and what bases are pyrimidines?

A

It is a type of nitrogen base found in DNA which consists of only one nitrogen-carbon ring.
-Thymine
-cytosine
(both contain a Y like pyrimidine does)

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5
Q

What type of bonds join together nitrogenous bases?

A

Hydrogen bonds

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6
Q

What are the rules behind drawing the skeletal formula of a base?

A 
Corner = carbon
carbon = 4 bonds
nitrogen = 3 bonds
hydrogen = 1 bond
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7
Q

How many bonds does guanine and cytosine have when joined?

A

three

G C Three

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8
Q

How many bonds do adenine and thymine have when joined?

A

two

A T Two

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9
Q

What is an ester bond?

A

A bond found in lipids such as triglycerides

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10
Q

What is a glyosidic bond?

A

A bond that joins the pentose sugar to its base within the nucleotide

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11
Q

Outline the stages of DNA replication

A

1) DNA unwinds, catalysed by the gyrase enzyme.
2) The DNA is then unzipped bonds broken. Catalysed by DNA Helicase.
3) Free phophorylated nucleotide’s bond to the exposed complementary bases, catalysed by DNA Polymerase.
4) The leading strand is synthesised continuously whereas the lagging strand is in fragments which is later joined by ligase enzymes.

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12
Q

What is a phosphorylated nucleotide?

A

A nucleotide with three phosphate groups attached.

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13
Q

What is a gene?

A

A length of DNA that codes for a polypeptide or a length of RNA that is involved in regulating gene expression.

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14
Q

What is a polypeptide?

A

A polymer made of many amino acid units joined together by peptide bonds.

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15
Q

What was the conservative DNA replication theory?

A

The original molecule acts as a template and a new molecule is made.

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16
Q

What is the dispersion DNA replication theory?

A

The original molecule breaks up into nucleotide’s, each one joins to a complementary nucleotide and new ones join up again

17
Q

What is the semi-conservative DNA replication theory?

A

This is the accepted theory. The new molecule consists of one original strand and one newly formed strand.

18
Q

What Is RNA?

A

A similar molecule to DNA and is used to in protein synthesis as a messenger of genetic information to the ribosomes.

19
Q

What is different between RNA and DNA?

A
  • replaces the base thymine with uracil
  • is only a single strand helix (can fit through nuclear pores)
  • the pentose sugar in DNA is DEOXYRIBOSE but in RNA it is just RIBOSE.
20
Q

What is mRNA?

A

Messenger RNA
It encodes the amino acid sequence of a polypeptide.
It is the chain created when the RNA nucleotides join together.

21
Q

What is tRNA?

A

Transfer RNA

It brings the amino acid to the ribosomes during translation.

22
Q

What is rRNA

A

Ribosomal RNA

Along with ribosomal proteins, it makes up the ribosomes.

23
Q

What is snRNA?

A

Small nuclear RNA

Used to make things which process RNA (only in eukaryotes)

24
Q

What does ‘anti-parallel strands’ refer to?

A

How one strand is going in the forward direction (3’ -5’) and one in the opposite direction (5’ -3’)

25
Q

What is the nucleoplasm?

A

The cytoplasm of the nucleus. It serves as a suspension medium for all of the organelles inside the nucleus, and it also helps maintain the shape and structure of the nucleus.

26
Q

What happens during the transcription stage of protein synthesis?

A

1) DNA gyrase causes the double helix to unwind
2) DNA helicase unzips the DNA by breaking the hydrogen bonds
3) RNA polymerase catalyses the formation of hydrogen bonds between free RNA nucleotides with their complementary bases on the template strand
4) The formation of phosphodiester bonds creates an mRNA coding strand which passes out of the nucleus through the nuclear pore

27
Q

What happens during the translation stage of protein synthesis?

A

1) tRNA molecules with an amino acid binds to the mRNA strand with hydrogen bonds forming between the anitcodon and its complementary mRNA codon
2) the tRNA leaves the amino acid, which forms peptide bonds to the neighbouring amino acid
3) The order of amino acids in the polypeptide chain therefore depends on the sequence of codons in the mRNA.
4) The mRNA is then recycled and the newly synthesis polypeptide chain is folded into its shape in order to carry out its function

28
Q

What are the different parts of an amino acid?

A

The amine group: consists of a Nitrogen bonded to Two hydrogens (this is then bonded to the middle carbon)

Variable group: a variable that is attached to the middle carbon and is usually responsible for the nature of that amino acid

carboxyl group: (-COOH) contains a carbon double bonded to an oxygen and single bonded to an OH group.

29
Q

What is a proteins primary structure?

A

The sequence of amino acids in a protein chain.

30
Q

What is a proteins secondary structure?

A

The structure made when a polypeptide chain is folded into either a a-helix or a B-pleated sheet.

31
Q

What is a proteins tertiary structure?

A

The overall 3-D shape of the protein that is twisted through both a-helix and b-pleated sheets to allow maximum stability and lowest energy state.

32
Q

What is a proteins Quaternary structure.

A

The final structure of a protein molecule, containing more than one polypeptide chain.

33
Q

What bonds provide most of the interactions in protein folding?

A

Hydrogen bonds

34
Q

What are disulfide bridges?

A

Bonds which form between two cysteine proteins (cysteine proteins are a type of amino acid).

35
Q

What is a phosphodiester bond?

A

The bond between a sugar a phosphate group in a polynucleotide or dinucleotide.

36
Q

How does a phosphodiester bond join together two nucleotides to create a dinucleotide?

A

A condensation reaction occurs between the phosphate group and the sugar.

This involves the hydrogen being removed from the hydroxyl (OH) group on the carbon 3 of the ribose sugar. And the other hydroxyl group being removed from the phosphate group.

https://goo.gl/images/yixX71

This leaves a covalent (phosphodiester) bond between carbon 3 of the ribose sugar and the oxygen of the phosphate group.

H20 is left as a waste product.

Biology - Module 2 (7 decks)

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