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
2
Q
What do nucleic acids control in order to carry out their functions?
A
- they control the synthesis of proteins
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
4
Q
What are the two nucleic acids found in cells called?
A
- deoxyribonucleic acid (DNA)
- ribonucleic acid (RNA)
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
6
Q
What is chromatin?
A
- chromosomal material made up of DNA, RNA and histone proteins as found in a non-dividing cell
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
8
Q
What is the structure of a DNA molecule?
A
- a long chain (polymer) made up of small units (monomers) called nucleotides
9
Q
What is each nucleotide made up of?
A
- sugar molecule - deoxyribose (S)
- phosphate molecule (P)
- nitrogenous base
10
Q
What are the different kinds of nitrogenous bases?
A
- adenine (A)
- thymine (T)
- guanine (G)
- cytosine (C)
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
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
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
14
Q
What are the base pairs attached to in the double helix?
A
- base pairs are attached to the sugar molecules
15
Q
What are the two groups of nitrogenous bases?
A
- purines
- pyrimidines
16
Q
What are purines made up of?
A
- two fused rings of nitrogen, carbon and hydrogen atoms
- e.g. guanine and adenine
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
18
Q
What is a base pair always made up of?
A
- one purine and one pyrimidine
19
Q
What makes the difference in DNA structures of different organisms?
A
- the sequence in which the nucleotides are strung together
20
Q
What determines the genetic code of an organism?
A
- the sequence of the nucleotides
21
Q
What does DNA do in terms of information?
A
- carries hereditary information in each cell in the form of genes
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
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
24
Q
How much human DNA codes for proteins?
A
- less than 2%
- the rest consists of non-coding DNA
25
What are the protein-coding regions of a DNA molecule called?
- exons
26
What are the non-coding regions of a DNA molecule called?
- introns
27
How do simple and complex organisms differ in terms of non-coding DNA?
- complex organisms contain much more non-coding DNA than less complex organisms
28
What is the purpose of the non-coding regions of DNA?
- they form functional RNA molecules
- which have regulatory functions
29
What is DNA replication?
- the process of making a new DNA molecule from an existing DNA molecule that is identical to the original molecule
30
When and where does DNA replication take place?
- in the nucleus
- during the interphase (in between cell divisions)
31
Why is DNA replication necessary?
- to ensure that the genetic code is passed on to each new daughter cell formed during cell division
32
What catalyses the process of DNA replication?
- the enzyme DNA polymerase
33
How is a new chromosome formed during DNA replication?
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
34
What ensures that the sequence of the bases in the daughter DNA is exactly the same as in the parent DNA?
- the fact that A will only bond with T
- and C will only bond with G
35
What does one DNA double helix become after DNA replication?
- one DNA double helix becomes 2 identical double helices
36
Where is RNA made and by what?
- made in the nucleus
- by DNA
37
What is RNA involved in?
- protein synthesis
38
How does the structure of RNA differ from that of DNA?
- 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
39
What is the function of RNA?
- carries instructions from DNA in the nucleus to ribosomes in the cytoplasm
- where it controls the synthesis of proteins from amino acids
40
What are the similarities between DNA and RNA in terms of structure?
- 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
41
What are the similarities between DNA and RNA in terms of functions?
- both responsible for the synthesis of proteins
42
How is mitochondrial DNA structured?
- double-stranded
- ring-shaped
43
Where does mitochondrial DNA come from?
- the egg cell (oocyte)
- so entirely inherited from the mother
44
What do the base pairs in mitochondrial DNA code for?
- proteins (enzymes)
- tRNA
- rRNA
45
What do the genes in mitochondrial DNA do?
- essential for the normal functioning of mitochondria
- they code for the enzymes that control cellular respiration
46
What comes from the sperm during fertilisation?
- only the chromosomes
47
Where do the organelles in a zygote come from?
- the cytoplasm of the egg
- ie from the mother
48
What is a marker
- a site created by the mutation of mitochondrial DNA
- e.g. where one nucleotide is replaced by another
49
What does it mean if two mtDNA profiles are very similar?
- the organisms are closely related
50
What does it mean if 2 mtDNA profiles show differences?
- the organisms will have diverged along different evolutionary pathways
51
What is the purpose of mapping markers through generations?
- enables tracing of lineages through females (matrilineage)
- used to track the ancestry of human groups/individuals back through generations
52
How can mtDNA profiles be used?
- reconstruct family maternal-linked relationships
- investigate forensic cases where the chromosomal DNA is degraded
- determine if siblings have the same mother
53
What are the different types of RNA made in the nucleus?
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomal RNA (rRNA)
54
What type of RNA is formed in the nucleus in the same way as DNA is replicated?
- mRNA
55
What is the process of mRNA formation called?
- transcription
56
What is transcription?
- the process by which DNA makes and codes mRNA
57
How does the process of transcription start?
- when a small piece of DNA, a gene, unwinds
58
What catalyses the initial unwinding of a gene in transcription?
- the enzyme RNA polymerase
59
What does RNA polymerase specifically do?
- causes the 2 strands of DNA to separate
- by breaking the hydrogen bonds between complementary DNA nucleotides
60
What happens during transcription after the gene unwinds?
- the polymerase attaches to and moves along one of the DNA strands
- causing new nucleotides to pair up with their complementary nucleotides
61
What happens during transcription after the new nucleotides pair up with their complementary nucleotides?
- the nucleotides join up
- a sugar-phosphate backbone is added
- a new strand of mRNA is formed
62
What is the sequence of nucleotides in a strand of mRNA determined by?
- the sequence of the template DNA nucleotides
63
What happens after a completed mRNA strand is formed during transcription?
- it breaks away from the DNA
p the DNA then re-zips
64
What happens to the newly formed strand of mRNA after transcription has occurred?
- it moves through the pores of the nuclear membrane
- carries the genetic code to the ribosomes
- which are the sites of protein synthesis
65
What is a protein?
- a long chain (polymer) of small units (monomers) called amino acids
66
How many different amino acids are there involved in protein synthesis?
- 20
67
What determines the kind of protein that is made?
- the order in which the amino acids are linked
68
What is the sequence of amino acids determined by?
- the instructions from the genetic code in the DNA molecules
- which is passed on to mRNA
69
What is a genetic code?
- a sequence of codons
70
What is a codon?
- codon is a sequence of three nucleotides in DNA that codes for an amino acid or a stop signal in protein synthesis
71
How many different codons are there and how many form proteins?
- 64 different codons
- all except 3 code for one of the 20 amino acids used to form proteins
72
What is the basis of the genetic code?
- the triplet code of bases
73
What is a gene made up of?
- a group of codons that code for the synthesis of one protein
74
What does the order of codons in mRNA determine?
- the sequence of the amino acids
- which determines which protein is made
75
What does each tRNA have?
- 3 bases as one end called an anti-codon
76
What does an anti-codon do?
- picks up a specific amino acid found in the cytoplasm and transfers it to a ribosome
77
What is the most important feature of tRNA?
- 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
What is the codon called that begins the process of protein synthesis?
- the 'start signal' codon
79
What acts as 'stop signals' and how?
- 3 codons act as 'stop signals'
- that indicate that the message is over and the protein chain is complete
80
What is translation?
- 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
What are antibiotics produced to do?
- counteract bacterial infections
82
How do antibiotics counteract bacterial infections?
- by interacting with the bacterial ribosomes
- and inhibiting their function of protein synthesis
83
Why can antibiotics specifically target the ribosomes of bacteria and not those of the host?
- because the ribosomes of bacteria (prokaryotes) and eukaryotes are different enough
84
Why do antibiotics help to inhibit the spread of infection?
- 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
What does the tetracycline variety of antibiotics do?
- prevents the attachment of tRNAs carrying amino acids
86
What does the chloramphenicol variety of antibiotics do?
- prevents the formation of peptide bonds
87
How can antibiotics be changed if resistance develops?
- by targeting different stages of the mRNA translation
88
What causes genetic aberrations?
- mutations
89
What is a mutation?
- any alteration in the genetic makeup of an organism
90
What factors can lead to genetic changes?
1. one or more nucleotides being damaged or last by chance
2. breakdown of DNA by mutagens
91
How can nucleotides be damaged or lost and lead to mutations?
- crossing over of paternal and maternal chromosomes in meiosis
- replication of DNA
- transcription of DNA to RNA
92
How can DNA be broken down by mutagens and lead to mutations?
- environmental factors such as sunlight, radiation, and smoking
- mutagenic chemicals
- viruses and micro-organisms
93
What is a mutagen?
- a physical or chemical agent that induces and speeds up mutations in DNA
94
What are gene mutations?
- small, localised changes in the structure of DNA strands
95
What are mutations that involve a single nucleotide called?
- point mutations
96
How can point mutations occur?
- substitution
- insertions
- deletions
97
What is substitution in point mutations?
- where one nucleotide is exchanged for another
98
What are insertions in point mutations?
- where one or more extra nucleotides are added to the DNA molecule
99
What are deletions in point mutations?
- where one or more nucleotides are removed from the DNA molecule
100
Where do the differences in human DNA occur?
- in the highly variable, non-coding part of DNA
101
What does DNA profiling involve?
- extracting and identifying the highly variable regions of a person's DNA that contain repeating sequences of base pairs
102
What is a short tandem repeat?
- repeating sequences of base-pairs found in DNA
103
How many different sites on DNA molecules are investigated to show that an individual's profile is unique?
- 13-20 different sites
104
What is a DNA profile?
- an individual/s unique DNA fragments, separated by electrophoresis
105
What is the first step in creating a DNA profile?
- the cells are treated with chemicals to extract the DNA
106
What happens after the DNA is extracted during the creation of a DNA profile?
- restriction enzymes are used to cut at the beginning and end of each repeated sequence
- resulting in fragments of different lengths
107
What happens after restriction enzymes are used to create fragments of DNA during the creation of a DNA profile?
- 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
What is Polymerase Chain Reaction?
- a laboratory technique used to make multiple copies of a segment of DNA
109
What happens after a PCR is performed during the creation of a DNA profile?
- the DNA fragments that result are then separated and detected
- using different techniques such as electrophoresis
110
What is gel electrophoresis?
- a method to separate large molecules mainly on the basis of size and electrical charge
111
What are the uses of DNA profiling?
1. forensics
2. diagnosing inherited disorders
3. identifying casualties
4. paternity testing
5. fight illegal trading
112
What are the disadvantages of DNA profiling?
1. violation of privacy
2. issues with accuracy
3. manipulation
