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Higher Biology > DNA and the genome > Flashcards

DNA and the genome Flashcards

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1
Q

What is the structure of a DNA nucleotide?

A

It is composed of deoxyribose sugar, phosphate and bases

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2
Q

What is the strong backbone of DNA called?

A

Sugar phosphate backbone

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3
Q

What bond holds the base pairs together?

A

Hydrogen bond.

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4
Q

Describe DNAs structure

A

DNA is a double-stranded, antiparallel (one strand goes from 3′ to 5′, the other from 5′ to 3′) structure with a deoxyribose and phosphate backbone held together by internal base pairs.

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5
Q

Is the DNA molecule circular or linear?

A

It can be both

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6
Q

What is a prokaryote?

A

A prokaryotes is a single celled organism that lacks a membrane bound nucleus, Mitochondria, or any other membrane bound organelles
(Bacteria and archea are prokaryotes)

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7
Q

What type of chromosomes do prokaryotes have?

A

They have single circular chromosomes and smaller circular plasmids.

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8
Q

What is a eukaryote?

A

Eukaryotes are cells that posses a nucleus bound by a double membrane
(Plants and animals are eukaryotes)

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9
Q

What type of chromosomes do eukaryotes have?

A

They have all linear chromosomes, in the nucleus, which are tightly coiled and packed with associated proteins called histones.
Circular chromosomes are in the mitochondria and chloroplasts of eukaryotes.

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10
Q

What is the sum total of genetic material in a cell called?

A

The genome

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11
Q

What are the enzymes that control DNA replication and wha do they do?

A

DNA polymerase: adds DNA nucleotides, using complementary base pairing, to the deoxyribose (3′) end of the new DNA strand which is forming.
DNA Ligase: joins fragments of DNA together

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12
Q

What are the requirements for DNA replication?

A
  • the original DNA molecule to act as a TEMPLATE
  • A supply of the 4 types of DNA NUCLEOTIDES
  • ENERGY(in the form of ATP)
  • ENZYMES(eg DNA polymerase, ligase, helicase)
  • PRIMERS
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13
Q

Where does DNA replication take place?

A

In the nucleus

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14
Q

What is a Primer?

A

A primer is a short strand of nucleotides which binds to the 3′ end of the template DNA strand allowing polymerase to add DNA nucleotides.

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15
Q

What are the steps in DNA replication?

A

1) the DNA double helix unwinds and unzips,hydrogen bonds between bases are broken (by helicase)to from 2 template strands
2) DNA polymerase adds DNA nucleotides using complementary base pairings to the 3’ end of the new DNA strand which is forming
3) DNA polymerase can only add nucleotides in one direction, so the leading strand is replicated continuously and on the lagging strand fragments of DNA are joined using ligase
4) DNA molecules rewind to form a double helix)

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16
Q

What type of process is DNA replication?

A

It is a semi conservative process

-each new DNA molecule contains one new strand and one old one

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17
Q

What is PCR and what is it used for?

A

PCR stands for Polymerase Chain Reaction and it is used to amplify small samples of DNA using complementary primers for specific target sequences.

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18
Q

Describe the stages of PCR.

A

1) when the temperature is raises to 92-98 degrees the DNA strands will separate to single strands. (Heating)
2) lowering the temperature to about 50-65 degrees to allow primers to bind to complimentary target sequences on the DNA (Annealing)
3) it is then heated to 70-80 degrees for heat tolerant DNA polymerase to replicate the region of DNA (extension)

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19
Q

What are the uses of PCR?

A

PCR can be used to amplify DNA samples to help solve crimes, settle paternity suits and diagnose genetic disorders (COVID testing)

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20
Q

Where does transcription occur?

A

The nucleus

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21
Q

Where does translation occur?

A

The cytoplasm

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22
Q

What are the differences between DNA and RNA?

A

DNA is double strands RNA is single stranded
DNA contain the sugar deoxyribose where as RNA contains ribose
DNA contains the base thymine where as RNA contains the base Uracil.

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23
Q

What is mRNA?

A

It is messenger RNA which carries a copy of the DNA code from the nucleus to the ribosome

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24
Q

What is tRNA?

A

transfer RNA, which are molecules found in the cytoplasm that become attached to specific amino acids, bringing them to the ribosomes where they are joined together

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25
Q

What is rRNA?

A

ribosomal RNA, which forms a complex with protein molecules to make the ribosome.

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26
Q

What are the steps of translation

A

1) a specific tRNA molecule (with an anticodon which matches the 1st codon on the mRNA molecule) brings a specific amino acid to the ribosome
2) a second tRNA rings the next amino acid and the 2 amino acids are held in place. The ribosome forms a peptide bond between the 2 adjacent amino acids
3) the 1st tRNA molecule is released into the cytoplasm (where it can be reused) and the ribosome moves along the mRNA strand to cover the 2nd and 3rd codons.

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27
Q

What are the requirements for translation?

A 
An mRNA template
Amino acids
Transfer RNA 
Energy (ATP)
Enzymes
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28
Q

What is translation?

A

It is when Information from DNA is copied into an RNA molecule, a process which takes place in the nucleus

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29
Q

What are the requirements for RNA synthesis?

A

energy(ATP)
A DNA template
Enzymes(RNA polymerase etc)
The 4 types of RNA nucleotide

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30
Q

Describe the stages of transcription.

A
  1. ) part of the DNA molecule unwinds and unzips exposing the sequence of bases which code for one polypeptide (a single gene)
  2. ) Free RNA nucleotides align with their complimentary bases
  3. ) sugar phosphate backbone is formed by RNA polymerase.
    4) this produces a primary transcript. RNA splicing removes the introns and joins together the exons to produce a mature transcript
  4. ) RNA molecule can leave the nucleus, used as a template in translation called mRNA
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31
Q

what is a codon?

A

a codon is a triplet of bases on the mRNA molecule and it codes for a specific amino acid.

32
Q

why can different proteins be expressed from one gene?

A

because of alternative RNA splicing. Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained. (the order of exons is unchanged during splicing)

33
Q

What is phenotype determined by?

A

Phenotype is determined by the proteins produces as the result of gene expression. environmental factors also influence phenotype eg stress, diet and pollution.)

34
Q

What is cellular differentiation?

A

Cellular differentiation is the process by which a cell expresses certain genes to produce proteins characteristic for that type of cell. This allows a cell to carry out specialised functions.

35
Q

What is a Meristem?

A

Meristems are regions of unspecialised cells in plants that can divide (self-renew) and/or differentiate.

36
Q

What is a Stem cell?

A

Stem cells are unspecialised cells in animals that can divide (self-renew) and/or differentiate.

37
Q

What does Pluripotent mean?

A

Cells that can differentiate to form any cell type. embryonic cells are pluripotent so they can form any cell type.

38
Q

What does multipotent mean?

A

Multipotent cells can differentiate to form multiple types of cells within a more limited range. Adult stem cells are multipotent, eg blood stem cells are produced in bone marrow, can only form any of the types of blood cell

39
Q

What are the uses of stem cells in research?

A

Used for Drug testing, understand how cellular processes work and used to study how diseases develop

40
Q

What are the medical uses of stem cells?

A

Use of stem cells in repair of diseased or damaged organs eg skin grafts, bone marrow transplants, corneal repair

41
Q

What is a genome made up of?

A

It is made up of genes and other DNA sequences that do not code for proteins

42
Q

What is the genome of an organism?

A

The genome of an organism is its hereditary information encoded in DNA

43
Q

What is a coding region?

A

A coding region is a section of DNA that contains a gene

44
Q

What do the non coding sections of DNA do?

A

Regulate transcription or are transcribed but never translated

45
Q

What is a mutation?

A

A mutation is any change in the DNA sequence of the genome.
Mutations can result in no protein or an altered protein being synthesised. The affected individual is known as a mutant. Mutations occur randomly but can be induced.

46
Q

what is the effect of a missense mutation?

A

Missense mutations result in one amino acid being changed for another.

47
Q

What is the effect of a nonsense mutation?

A

Nonsense mutations result in a premature stop codon being produced which results in a shorter protein.

48
Q

What is the effect of a splice site mutation?

A

Splice-site mutations result in some introns being retained and/or some exons not being included in the mature transcript.

49
Q

What is evolution?

A

The changes in organisms over generations as a result of genomic variations

50
Q

What is speciation?

A

Speciation is the generation of new biological species by evolution as a result of isolation, mutation and selection.

51
Q

What is a point mutation?

A

Point mutations are changes at the single nucleotide level, in that one nucleotide is substituted for another or a nucleotide is inserted or deleted from the DNA sequence

52
Q

What happens if there is a change in the DNA sequence?

A

There may be a change in the amino acid sequence or the final structure of the protein.

53
Q

What is a frame shift mutation?

A

Frame-shift mutations cause all of the codons and all of the amino acids after the mutation to be changed. This has a major effect on the structure of the protein produced.

54
Q

What changes the sequences of genes on a chromosome?

A

It is changed by duplication, deletion, translocation or inversion

55
Q

What is duplication?

A

Duplication is where a section of a chromosome is added from its homologous partner.

56
Q

What is deletion?

A

Deletion is where a section of a chromosome is removed

57
Q

What is translocation?

A

Translocation is where a section of a chromosome is added to a chromosome, not its homologous partner.

58
Q

What is inversion?

A

Inversion is where a section of chromosome is reversed

59
Q

What is the effect of chromosome mutations?

A

The substantial changes in chromosome mutations often means that they are lethal.

60
Q

What is the potential effect of duplication?

A

Duplication allows potential beneficial mutations to occur in a duplicated gene whilst the original gene can still be expressed to produce its protein

61
Q

What is vertical inheritance?

A

The passing of genetic material from parent to offspring. Binary fission is a form of vertical inheritance, prokaryotes usually reproduce this way

62
Q

What is horizontal inheritance?

A

It is when genetic material can be exchanged between members of the same generation.

63
Q

What does horizontal inheritance involve?

A

The exchange of whole or parts of a plasmid. Plasmid exchange will bring about rapid evolutionary change.

64
Q

What is natural selection?

A

Natural selection is the non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences.

65
Q

What are changes in phenotype a result of?

A

They are a result of stabilising, directional or disruptive selection.

66
Q

What is stabilising selection?

A

In stabilising selection, an average phenotype is selected for and extremes of the phenotype range are selected against;

67
Q

What is disruptive selection?

A

In this case, it is the extreme values of phenotypes that are chosen and those with average fitness are selected against

68
Q

What is directional selection?

A

In this case, one extreme value or phenotype is selected over both the average and the other extreme value

69
Q

What is a species?

A

A species is a group of organisms capable of interbreeding and producing fertile offspring, and which does not normally breed with other groups

70
Q

What is allopatric speciation?

A

Allopatric speciation occurs when populations become physically separated. This may be due to geographical barriers such as oceans or mountain ranges

71
Q

What is sympatric speciation?

A

Sympatric speciation is brought about by behavioural or ecological barriers. The process will usually occur within the same habitat.

72
Q

What is Pharmacogenetics?

A

Pharmacogenetics is the use of genome information in the choice of drugs.
An individual’s personal genome sequence can be used to select the most effective drugs and dosage to treat their disease

73
Q

What is phylogenetics?

A

Phylogenetics is the study of evolutionary history and relationships.

74
Q

What is the sequence of events in evolution?

A

cells, last universal ancestor, prokaryotes, photosynthetic organisms, eukaryotes, multicellularity, animals, vertebrates, land plants.

75
Q

What is a molecular clock?

A

Molecular clocks are used to show when species diverged during evolution. They assume a constant mutation rate and show differences in DNA sequences or amino acid sequences. Therefore, differences in sequence data between species indicate the time of divergence from a common ancestor

76
Q

What is bioinformatics?

A

Bioinformatics uses computer and statistical analysis to sequence genomes

Higher Biology (2 decks)

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