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LS - Entire Sections > DNA > Flashcards

DNA Flashcards

1
Q

What do nucleic acids have the capacity to do?

A
  • to store the information that controls cellular activity and the development of an entire organism
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2
Q

What do nucleic acids control in order to carry out their functions?

A
  • they control the synthesis of proteins
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3
Q

What do proteins do?

A
  • make up much of the structure of the body
  • control the chemical processes inside cells through enzymes
  • ultimately control the structure and functioning of all living organisms
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4
Q

What are the two nucleic acids found in cells called?

A
  1. deoxyribonucleic acid (DNA)
  2. ribonucleic acid (RNA)
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5
Q

Where is DNA mainly found and what does it do?

A
  • mainly in the nucleus of a cell
  • where it forms an important part of the chromosomes that make up the chromatin network
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6
Q

What is chromatin?

A
  • chromosomal material made up of DNA, RNA and histone proteins as found in a non-dividing cell
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7
Q

What is extracellular DNA?

A
  • small amounts of DNA that are found outside the nucleus
  • in mitochondria in plants
  • in chloroplasts in plants
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8
Q

What is the structure of a DNA molecule?

A
  • a long chain (polymer) made up of small units (monomers) called nucleotides
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9
Q

What is each nucleotide made up of?

A
  • sugar molecule - deoxyribose (S)
  • phosphate molecule (P)
  • nitrogenous base
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10
Q

What are the different kinds of nitrogenous bases?

A
  • adenine (A)
  • thymine (T)
  • guanine (G)
  • cytosine (C)
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11
Q

What do the four nitrogenous bases do?

A
  • foundation of the genetic code
  • instructing cells on how to synthesise enzymes and other proteins
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12
Q

How are the outer two strands of the double helix made up?

A
  • formed by a chain of alternating sugar/phosphate links
  • the bonds between the sugar and phosphate molecules are strong
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13
Q

How are the inner rungs of the ladder of the double helix made up?

A
  • formed from pairs of bases linked by weak hydrogen bonds
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14
Q

What are the base pairs attached to in the double helix?

A
  • base pairs are attached to the sugar molecules
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15
Q

What are the two groups of nitrogenous bases?

A
  • purines
  • pyrimidines
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16
Q

What are purines made up of?

A
  • two fused rings of nitrogen, carbon and hydrogen atoms
  • e.g. guanine and adenine
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17
Q

What are pyrimidines made up of?

A
  • one ring of similar atoms (therefore much smaller than purines)
  • e.g. thymine, cytosine and uracil
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18
Q

What is a base pair always made up of?

A
  • one purine and one pyrimidine
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19
Q

What makes the difference in DNA structures of different organisms?

A
  • the sequence in which the nucleotides are strung together
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20
Q

What determines the genetic code of an organism?

A
  • the sequence of the nucleotides
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21
Q

What does DNA do in terms of information?

A
  • carries hereditary information in each cell in the form of genes
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22
Q

What does DNA do in terms of protein synthesis?

A
  • provides a blueprint for an organism’s growth and development
  • by coding for protein synthesis
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23
Q

What does DNA do in terms of replication?

A
  • can replicate
  • so that a copy of the genetic information is passed on to each daughter cell formed during cell division
  • this ensures that the genetic code is passed through generations
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24
Q

How much human DNA codes for proteins?

A
  • less than 2%
  • the rest consists of non-coding DNA
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25
Q

What are the protein-coding regions of a DNA molecule called?

A
  • exons
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26
Q

What are the non-coding regions of a DNA molecule called?

A
  • introns
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27
Q

How do simple and complex organisms differ in terms of non-coding DNA?

A
  • complex organisms contain much more non-coding DNA than less complex organisms
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28
Q

What is the purpose of the non-coding regions of DNA?

A
  • they form functional RNA molecules
  • which have regulatory functions
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29
Q

What is DNA replication?

A
  • the process of making a new DNA molecule from an existing DNA molecule that is identical to the original molecule
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30
Q

When and where does DNA replication take place?

A
  • in the nucleus
  • during the interphase (in between cell divisions)
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31
Q

Why is DNA replication necessary?

A
  • to ensure that the genetic code is passed on to each new daughter cell formed during cell division
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32
Q

What catalyses the process of DNA replication?

A
  • the enzyme DNA polymerase
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33
Q

How is a new chromosome formed during DNA replication?

A
  1. the double helix unwinds
  2. the weak hydrogen bonds holding the base pairs together break, allowing the two strands to part
  3. each single chain of bases is exposed
  4. free nucleotides in the cytoplasm become attached to their matching, exposed base partners
  5. the 2 daughter DNA molecules each twist to form a double helix which then winds itself around the histones, forming a chromosome
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34
Q

What ensures that the sequence of the bases in the daughter DNA is exactly the same as in the parent DNA?

A
  • the fact that A will only bond with T
  • and C will only bond with G
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35
Q

What does one DNA double helix become after DNA replication?

A
  • one DNA double helix becomes 2 identical double helices
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36
Q

Where is RNA made and by what?

A
  • made in the nucleus
  • by DNA
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37
Q

What is RNA involved in?

A
  • protein synthesis
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38
Q

How does the structure of RNA differ from that of DNA?

A
  • consists of a single strand
  • strand is much shorter than that of DNA
  • the sugar is ribose, not deoxyribose
  • has 3 bases in common with DNA, but uracil replaces thymine
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39
Q

What is the function of RNA?

A
  • carries instructions from DNA in the nucleus to ribosomes in the cytoplasm
  • where it controls the synthesis of proteins from amino acids
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40
Q

What are the similarities between DNA and RNA in terms of structure?

A
  • both made up of polymers
  • both made up of nucleotides that are made up of a sugar, phosphate and a nitrogen base
  • both involve 4 nitrogenous bases
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41
Q

What are the similarities between DNA and RNA in terms of functions?

A
  • both responsible for the synthesis of proteins
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42
Q

How is mitochondrial DNA structured?

A
  • double-stranded
  • ring-shaped
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43
Q

Where does mitochondrial DNA come from?

A
  • the egg cell (oocyte)
  • so entirely inherited from the mother
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44
Q

What do the base pairs in mitochondrial DNA code for?

A
  • proteins (enzymes)
  • tRNA
  • rRNA
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45
Q

What do the genes in mitochondrial DNA do?

A
  • essential for the normal functioning of mitochondria
  • they code for the enzymes that control cellular respiration
46
Q

What comes from the sperm during fertilisation?

A
  • only the chromosomes
47
Q

Where do the organelles in a zygote come from?

A
  • the cytoplasm of the egg
  • ie from the mother
48
Q

What is a marker

A
  • a site created by the mutation of mitochondrial DNA
  • e.g. where one nucleotide is replaced by another
49
Q

What does it mean if two mtDNA profiles are very similar?

A
  • the organisms are closely related
50
Q

What does it mean if 2 mtDNA profiles show differences?

A
  • the organisms will have diverged along different evolutionary pathways
51
Q

What is the purpose of mapping markers through generations?

A
  • enables tracing of lineages through females (matrilineage)
  • used to track the ancestry of human groups/individuals back through generations
52
Q

How can mtDNA profiles be used?

A
  • reconstruct family maternal-linked relationships
  • investigate forensic cases where the chromosomal DNA is degraded
  • determine if siblings have the same mother
53
Q

What are the different types of RNA made in the nucleus?

A
  • messenger RNA (mRNA)
  • transfer RNA (tRNA)
  • ribosomal RNA (rRNA)
54
Q

What type of RNA is formed in the nucleus in the same way as DNA is replicated?

A
  • mRNA
55
Q

What is the process of mRNA formation called?

A
  • transcription
56
Q

What is transcription?

A
  • the process by which DNA makes and codes mRNA
57
Q

How does the process of transcription start?

A
  • when a small piece of DNA, a gene, unwinds
58
Q

What catalyses the initial unwinding of a gene in transcription?

A
  • the enzyme RNA polymerase
59
Q

What does RNA polymerase specifically do?

A
  • causes the 2 strands of DNA to separate
  • by breaking the hydrogen bonds between complementary DNA nucleotides
60
Q

What happens during transcription after the gene unwinds?

A
  • the polymerase attaches to and moves along one of the DNA strands
  • causing new nucleotides to pair up with their complementary nucleotides
61
Q

What happens during transcription after the new nucleotides pair up with their complementary nucleotides?

A
  • the nucleotides join up
  • a sugar-phosphate backbone is added
  • a new strand of mRNA is formed
62
Q

What is the sequence of nucleotides in a strand of mRNA determined by?

A
  • the sequence of the template DNA nucleotides
63
Q

What happens after a completed mRNA strand is formed during transcription?

A
  • it breaks away from the DNA
    p the DNA then re-zips
64
Q

What happens to the newly formed strand of mRNA after transcription has occurred?

A
  • it moves through the pores of the nuclear membrane
  • carries the genetic code to the ribosomes
  • which are the sites of protein synthesis
65
Q

What is a protein?

A
  • a long chain (polymer) of small units (monomers) called amino acids
66
Q

How many different amino acids are there involved in protein synthesis?

A
  • 20
67
Q

What determines the kind of protein that is made?

A
  • the order in which the amino acids are linked
68
Q

What is the sequence of amino acids determined by?

A
  • the instructions from the genetic code in the DNA molecules
  • which is passed on to mRNA
69
Q

What is a genetic code?

A
  • a sequence of codons
70
Q

What is a codon?

A
  • codon is a sequence of three nucleotides in DNA that codes for an amino acid or a stop signal in protein synthesis
71
Q

How many different codons are there and how many form proteins?

A
  • 64 different codons
  • all except 3 code for one of the 20 amino acids used to form proteins
72
Q

What is the basis of the genetic code?

A
  • the triplet code of bases
73
Q

What is a gene made up of?

A
  • a group of codons that code for the synthesis of one protein
74
Q

What does the order of codons in mRNA determine?

A
  • the sequence of the amino acids
  • which determines which protein is made
75
Q

What does each tRNA have?

A
  • 3 bases as one end called an anti-codon
76
Q

What does an anti-codon do?

A
  • picks up a specific amino acid found in the cytoplasm and transfers it to a ribosome
77
Q

What is the most important feature of tRNA?

A
  • it can bind to an amino acid at one end and to mRNA at the other
  • depositing its amino acid in the correct position
  • to form a specific protein
78
Q

What is the codon called that begins the process of protein synthesis?

A
  • the ‘start signal’ codon
79
Q

What acts as ‘stop signals’ and how?

A
  • 3 codons act as ‘stop signals’
  • that indicate that the message is over and the protein chain is complete
80
Q

What is translation?

A
  • the process by which a specific protein is formed from a chain of amino acids due to the sequence of codons in the mRNA (which was coded by the DNA)
81
Q

What are antibiotics produced to do?

A
  • counteract bacterial infections
82
Q

How do antibiotics counteract bacterial infections?

A
  • by interacting with the bacterial ribosomes
  • and inhibiting their function of protein synthesis
83
Q

Why can antibiotics specifically target the ribosomes of bacteria and not those of the host?

A
  • because the ribosomes of bacteria (prokaryotes) and eukaryotes are different enough
84
Q

Why do antibiotics help to inhibit the spread of infection?

A
  • proteins are essential for the production and growth of new cells
  • so if bacteria are prohibited from making proteins
    => they will not be able to make new cells to spread the infection
85
Q

What does the tetracycline variety of antibiotics do?

A
  • prevents the attachment of tRNAs carrying amino acids
86
Q

What does the chloramphenicol variety of antibiotics do?

A
  • prevents the formation of peptide bonds
87
Q

How can antibiotics be changed if resistance develops?

A
  • by targeting different stages of the mRNA translation
88
Q

What causes genetic aberrations?

A
  • mutations
89
Q

What is a mutation?

A
  • any alteration in the genetic makeup of an organism
90
Q

What factors can lead to genetic changes?

A
  1. one or more nucleotides being damaged or last by chance
  2. breakdown of DNA by mutagens
91
Q

How can nucleotides be damaged or lost and lead to mutations?

A
  • crossing over of paternal and maternal chromosomes in meiosis
  • replication of DNA
  • transcription of DNA to RNA
92
Q

How can DNA be broken down by mutagens and lead to mutations?

A
  • environmental factors such as sunlight, radiation, and smoking
  • mutagenic chemicals
  • viruses and micro-organisms
93
Q

What is a mutagen?

A
  • a physical or chemical agent that induces and speeds up mutations in DNA
94
Q

What are gene mutations?

A
  • small, localised changes in the structure of DNA strands
95
Q

What are mutations that involve a single nucleotide called?

A
  • point mutations
96
Q

How can point mutations occur?

A
  • substitution
  • insertions
  • deletions
97
Q

What is substitution in point mutations?

A
  • where one nucleotide is exchanged for another
98
Q

What are insertions in point mutations?

A
  • where one or more extra nucleotides are added to the DNA molecule
99
Q

What are deletions in point mutations?

A
  • where one or more nucleotides are removed from the DNA molecule
100
Q

Where do the differences in human DNA occur?

A
  • in the highly variable, non-coding part of DNA
101
Q

What does DNA profiling involve?

A
  • extracting and identifying the highly variable regions of a person’s DNA that contain repeating sequences of base pairs
102
Q

What is a short tandem repeat?

A
  • repeating sequences of base-pairs found in DNA
103
Q

How many different sites on DNA molecules are investigated to show that an individual’s profile is unique?

A
  • 13-20 different sites
104
Q

What is a DNA profile?

A
  • an individual/s unique DNA fragments, separated by electrophoresis
105
Q

What is the first step in creating a DNA profile?

A
  • the cells are treated with chemicals to extract the DNA
106
Q

What happens after the DNA is extracted during the creation of a DNA profile?

A
  • restriction enzymes are used to cut at the beginning and end of each repeated sequence
  • resulting in fragments of different lengths
107
Q

What happens after restriction enzymes are used to create fragments of DNA during the creation of a DNA profile?

A
  • through a complicated process known as Polymerase Chain Reaction (PCR) a large number of these fragments are made to provide a substantial amount of DNA to work with
108
Q

What is Polymerase Chain Reaction?

A
  • a laboratory technique used to make multiple copies of a segment of DNA
109
Q

What happens after a PCR is performed during the creation of a DNA profile?

A
  • the DNA fragments that result are then separated and detected
  • using different techniques such as electrophoresis
110
Q

What is gel electrophoresis?

A
  • a method to separate large molecules mainly on the basis of size and electrical charge
111
Q

What are the uses of DNA profiling?

A
  1. forensics
  2. diagnosing inherited disorders
  3. identifying casualties
  4. paternity testing
  5. fight illegal trading
112
Q

What are the disadvantages of DNA profiling?

A
  1. violation of privacy
  2. issues with accuracy
  3. manipulation

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