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Biology AS > 1.5 Nucleic acids > Flashcards

1.5 Nucleic acids Flashcards

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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
Q

What does RNA stand for?

A

Ribonucleic acid

26
Q

What are the 3 forms of RNA?

A
  • mRNA (message RNA)
  • tRNA (transfer RNA)
  • rRNA (ribosomal RNA)
27
Q

What are the properties of RNA?

A
  • Single stranded
  • It has the sugar ribose
  • Bases - A,C,G,U - uracil instead of thymine (u is a pyrimidine)
28
Q

What happens before a cell divides by mitosis or meiosis?

A
  • the DNA in the nucleus is copied or replicated
29
Q

What happened before the mechanism of DNA replication was known in full?

A

Two hypotheses were put forward

30
Q

What is Conservative replication?

A

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
Q

Is conservative replication accepted today?

A

Not factual today

32
Q

Is semi-conservative replication accepted today?

A

Yes

33
Q

What is semi-conservative replication?

A

This would involve separation of the DNA strands followed by replication of each strand separately to produce DNA half parental and half new

34
Q

What is the first stage in the process of DNA replication?

A
  • DNA double helix unzips the enzyme
  • DNA helicase breaks the hydrogen bonds between complementary bases and the two polynucleotide strands separate
35
Q

What is the second stage in the process of DNA replication?

A
  • 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
Q

What is the third stage in the process of DNA replication?

A
  • 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
Q

What is the fourth stage of DNA replication?

A

DNA polymerase catalyses condensation reactions that join adjacent nucleotides on new strand
H-bonds reform

38
Q

What is the pentose sugar in RNA?

A

ribose

39
Q

State the role of DNA in living cells.

A
  • 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
Q

State the role of RNA in living cells

A

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
Q

How do polynucleotides form?

A

Condensation reactions between nucleotides form strong phosphodiester bonds

42
Q

Describe the structure of DNA

A
  • 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
Q

Relate the structure of DNA to its functions.

A

• 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
Q

Describe the structure of messenger RNA

A

• 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
Q

Relate the structure of messenger RNA to its functions

A

• 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
Q

Describe the structure of transfer RNA

A

• 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
Q

Order DNA, mRNA and tRNA according to increasing length

A

tRNA
mRNA
DNA

48
Q

Why did scientists initially doubt that DNA carried the genetic code?

A

Chemically simple molecule with few components

Biology AS (36 decks)

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