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Biology AS > 1.5 Nucleic acids > Flashcards

1.5 Nucleic acids Flashcards

1
Q

What is the pentose sugar found in DNA?

A

Deoxyribose

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2
Q

What is the nitrogen and carbon containing molecule comprising two ring structures?

A

Purine

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3
Q

What is the nitrogen and carbon containing molecule comprising a one ring structure?

A

Pyrimidine

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4
Q

What is the relationship between adenine and thymine, and between cytosine and guanine?

A

Complementary

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5
Q

What are the weak bonds formed between complementary bases?

A

Hydrogen bonds

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6
Q

What is the purine base complementary to thymine?

A

Adenine

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7
Q

What is the pyrimidine base complementary to adenine?

A

Thymine

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8
Q

What is the pyrimidine base complementary to guanine?

A

Cytosine

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9
Q

What is the purine base complementary to cytosine?

A

Guanine

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10
Q

What is the shape of DNA molecules?

A

Double Helix

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11
Q

What is the arrangement of complementary polynucleotides in the double helix?

A

Antiparallel

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12
Q

What are the strong bonds formed between adjacent nucleotides in a polynucleotide?

A

Sugar-phosphate bonds

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13
Q

What is the general name for a five carbon sugar?

A

Pentose

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14
Q

What is the monomer of nucleic acids?

A

Nucleotide

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15
Q

What is a chain of nucleotides called?

A

Polynucleotide

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16
Q

What is the number of hydrogen bonds between adenine and thymine?

A

2

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17
Q

What is the number of hydrogen bonds between cytosine and guanine?

A

3

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18
Q

What is the name of two complementary bases held together by hydrogen bonds, e.g. A-T and C-G?

A

Base pair

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19
Q

What are the 2 types of bases in DNA nucleotides?

A
  • Pyrimidines - single ring structures and smaller than;
  • Purines - double ring structure
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20
Q

Pyrimidines

A
  • Big name
  • Smaller molecule
  • C cYtosine
  • T thYmine
21
Q

Purines

A
  • Small name
  • Big molecule
  • G guanine
  • A adenine
22
Q

Polynucleotides

A
  • Nucleotides join together by bond formation between sugar of one and phosphate of the next to form a polynucleotide
  • Bond formed by a condensation reaction is a phosphodiester bond
23
Q

What is the structure of DNA?

A
  • DNA molecules exist as a double helix
  • 2 antiparallel polynucleotide strands held together by hydrogen bonds between complementary base pairs
  • The 4 DNA bases A,C,T and G form base pairs such that;
    > A can pair with T A=T (double bond)-2 hydrogen
    > C can pair with G C=_G (triple bond)-3 hydrogen
    > i.e. a purine with a pyrimidine
24
Q

What does DNA stand for?

A

Deoxyribonucleic acid

25
What does RNA stand for?
Ribonucleic acid
26
What are the 3 forms of RNA?
- mRNA (message RNA) - tRNA (transfer RNA) - rRNA (ribosomal RNA)
27
What are the properties of RNA?
- Single stranded - It has the sugar ribose - Bases - A,C,G,U - uracil instead of thymine (u is a pyrimidine)
28
What happens before a cell divides by mitosis or meiosis?
- the DNA in the nucleus is copied or replicated
29
What happened before the mechanism of DNA replication was known in full?
Two hypotheses were put forward
30
What is Conservative replication?
This would involve a completely new double stranded copy of DNA being made and the original or parental DNA staying the same (being conserved)
31
Is conservative replication accepted today?
Not factual today
32
Is semi-conservative replication accepted today?
Yes
33
What is semi-conservative replication?
This would involve separation of the DNA strands followed by replication of each strand separately to produce DNA half parental and half new
34
What is the first stage in the process of DNA replication?
- DNA double helix unzips the enzyme - DNA helicase breaks the hydrogen bonds between complementary bases and the two polynucleotide strands separate
35
What is the second stage in the process of DNA replication?
- With each strand acting as a template, free DNA nucleotides complementary base pair to the exposed bases on each strand, DNA polymerase forms phosphodiester bonds between nucleotides - The molecules rewind to form double helices
36
What is the third stage in the process of DNA replication?
- Now there are 2 DNA molecules, each one consists of one strand from the original parental molecule and one newly synthesised strand - They are formed by semi-conservative replication
37
What is the fourth stage of DNA replication?
DNA polymerase catalyses condensation reactions that join adjacent nucleotides on new strand H-bonds reform
38
What is the pentose sugar in RNA?
ribose
39
State the role of DNA in living cells.
- Base sequence of genes codes for functional RNA and amino acid sequence of polypeptides - Genetic information determines inherited characteristics = influences structure and function of organisms
40
State the role of RNA in living cells
mRNA: complementary sequence to 1 gene from DNA with introns spliced out. Codons can be translated into a polypeptide by ribosomes rRNA: component of ribosomes tRNA: supplies complementary amino acid to mRNA codons during translation
41
How do polynucleotides form?
Condensation reactions between nucleotides form strong phosphodiester bonds
42
Describe the structure of DNA
- double helix of 2 polynucleotide strands(deoxyribose) - H-bonds between complementary purine and pyrimidine base pairs on opposite strands - Bases are: A+T, G+C
43
Relate the structure of DNA to its functions.
• sugar phosphate backbone and many H-bonds provide stability • long molecules stores lots of information • helix is compact for storage in nucleus • base sequence of triplets codes for amino acids • double stranded for semi-conservative replication • complementary base pairing for accurate replication • weak H-bonds break so strands separate for replication
44
Describe the structure of messenger RNA
• long ribose polynucleotide • contains uracil instead of thymine • single stranded and linear • codon sequence is complementary to exons of 1 gene from 1 DNA strand
45
Relate the structure of messenger RNA to its functions
• long so breaks down quickly so no excess polypeptide forms • single stranded so ribosome can move along strand and tRNA can bind to exposed bases • complementary to exons so can be translated into a specific polypeptide by ribosomes
46
Describe the structure of transfer RNA
• single strand of about 80 nucleotides • folded into clover shape • anticodon on one end, amino acid binding site on the other a) anticodon binds to complementary mRNA codon b) amino acid corresponds to anticodon
47
Order DNA, mRNA and tRNA according to increasing length
tRNA mRNA DNA
48
Why did scientists initially doubt that DNA carried the genetic code?
Chemically simple molecule with few components

Biology AS (36 decks)

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