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Higher Biology > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

Description of DNA

A

Double helix made up of two antiparallel with a phosphate on the fifth carbon

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2
Q

What are prokaryotes?

A

Organisms which lack a true membrane-bound nucleus eg bacteria
Their DNA is found in the cytoplasm of the cell

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3
Q

What are Eukaryotes?

A

Organisms which have a membrane bound nucleus that stores their genetic material eg plants and animals

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4
Q

DNA in Eukaryotes

A
  • linear chromosomes with histones
  • mitochondria
  • chloroplast
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5
Q

What is needed for DNA replications and their functions?

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.
Pool of free nucleotides
Primers: allows polymerase to start replication

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6
Q

What is the difference between the leading strand and the lagging strand in replication?

A

Leading strand made continuously

Lagging strand made in fragments

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7
Q

Steps of DNA replication

A
  • DNA is unwound and hydrogen bonds between bases are broken to form two template strands.
  • two replication forks form and open the double-strand in opposite directions, exposing the bases.
  • on the leading strand, a primer binds to the DNA and DNA polymerase adds nucleotides to the 3′ end. DNA polymerase catalyses the formation of a chemical bond between nucleotides and continues to add nucleotides to the 3′ end of the growing strand.
  • on the lagging strand, a primer binds to the DNA once it is exposed and DNA polymerase adds nucleotides to the 3′ end. As more DNA is exposed, a new primer is added. DNA polymerase extends the new strand from this primer until it meets the previous fragment. The old primer is replaced by DNA and the enzyme DNA ligase joins the fragments together.
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8
Q

Benefits to PCR

A

it is highly specific;
it is easily automated;
it is capable of amplifying minute amounts of sample

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9
Q

What is needed to amplify DNA in PCR

A 
buffer;
nucleotides;
primers;
Taq polymerase;
template DNA.
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10
Q

Why are buffers added to pcr?

A

The buffer keeps the reaction mixture at the correct pH to ensure the reaction will proceed

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11
Q

What is Taq polymerase and what is special about it?

A

Taq polymerase, an enzyme which adds nucleotides to DNA It is special type of polymerase which is stable at high temperatures, having an optimum temperature of 70°C

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12
Q

What are primers in pcr?

A

primers are short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified

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13
Q

What is the pcr process?

A
  • the DNA molecule which is to be amplified is denatured by heating to between 92 and 98°C, breaking the hydrogen bonds between base pairs to separate the strands;
  • the solution is cooled to between 50 and 65°C to allow the primers to bind to target sequences;
  • the solution is heated to between 70 and 80°C for heat-tolerant DNA polymerase to replicate the region of DNA.
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14
Q

PCR allows DNA to be amplified in … ?

A

vitro

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15
Q

Uses of PCR?

A
  • Forensic applications, allowing minute quantities of DNA from a crime scene to be amplified, sequenced, and compared to DNA sequences from suspects
  • Diagnose HIV
  • Settle paternity dispute
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16
Q

What are the components of RNA?

A

phosphate, ribose sugar and a base

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17
Q

How does RNA differ from DNA?

A

RNA nucleotides contain the sugar ribose;
RNA has the base (U) uracil rather than (T) thymine (as found in DNA);
RNA molecules are usually single-stranded

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18
Q

What are the 3 types of RNA and their functions?

A

mRNA (messenger RNA), which carries a copy of the DNA code from the nucleus to the ribosome;

tRNA (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;

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

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19
Q

What is a codon and what does it do?

A

a triplet of bases on mRNA which codes for an amino acid

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20
Q

What is at the bottom of tRNA and what does it do?

A

anticodon which is complementary base sequence to the base sequence on mRNA coding for a particular amino acid

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21
Q

What is transcription and where does it happen?

A

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

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22
Q

Steps of transcription?

A
  • The RNA polymerase enzyme moves along the DNA, unwinding the double helix and breaking the hydrogen bonds that hold the base pairs together.
  • Free RNA nucleotides bond with the complementary base pairs on the DNA. (A binds to U, T binds to A and C binds to G)
  • The RNA nucleotides are held in place by hydrogen bonds while strong bonds form between the phosphate of one nucleotide and the ribose sugar of the adjacent nucleotide
  • When transcription is complete, the RNA polymerase enzyme and the mRNA strand that has been constructed are released. The mRNA that has been produced at this stage is known as the primary transcript
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23
Q

Where does RNA splicing take place?

A

in the nucleus

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24
Q

Where does translation take place and what does it require?

A

Ribosome in the cytoplasm

tRNA

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25
Q

What is tRNA made out of and where is the amino acid attachment site?

A

A single RNA strand that folded back on itself and at the top of the tRNA molecule

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26
Q

What bonds are between amino acids?

A

peptide bonds

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27
Q

What is a polypeptide chain?

A

chain of amino acids

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28
Q

Where are the amino acids that tRNA carry?

A

cytoplasm

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29
Q

What is alternative splicing?

A

The mRNA can be edited in different ways by assembling a different sequence of exons for translation. As a result, many different mature transcripts of mRNA can be derived from one section of DNA.

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30
Q

What are meristems?

A

Meristems are regions of unspecialised cells in plants that can divide (self-renew) and/or differentiate. These cells divide rapidly by mitosis to differentiate and form new plant tissues.

31
Q

What are stem cells?

A

Stem cells are unspecialised cells.

32
Q

What can stem cells do?

A

self renewal and differentiation to become another type of cell with a more specialised function

33
Q

How to describe embryonic stem cells and why?

A

pluripotent as they can differentiate into all the cell types that make up the organism

34
Q

How to describe tissue (adult) stem cells?

A

Multipotent as they can differentiate into all of the types of cell found in a particular tissue type

35
Q

Sources of Adult stem cells?

A

brain, bone marrow, peripheral blood, blood vessels, skeletal muscle and skin

36
Q

Therapeutic use of stem cells?

A

Skin: a rich source of tissue stem cells. Patients with serious burns can be treated using a technique which grows new skin in the lab from skin stem cells.
Blood: a type of stem cell found in the bone marrow is capable of giving rise to all of the different types of blood cells. Bone marrow transplants have been carried out for many years as a treatment for diseases such as leukaemia and other blood disorders.
Cornea: corneal stem cells are removed and cultured in a laboratory. They are then transplanted onto the diseased cornea to repair it.

37
Q

Research use of stem cells?

A

Stem cell research allows scientists to discover more information about key cell processes such as growth, differentiation and gene regulation.
Stem cells can also be used to study how diseases develop
Stem cells may be a viable alternative to animals for testing new drugs in the future

38
Q

What is the genome?

A

The genome is the sum total of all the hereditary material within an organism.

39
Q

What are the two types of regions in the genome?

A

Coding and non coding

40
Q

Function of non coding regions?

A

regulating transcription,
transcription of RNA,
no known function

41
Q

Name a section of DNA that is transcribed but not translated

A

tRNA and rRNA

42
Q

Name the 3 types of gene mutations and explain what they are?

A

Substitution: A substitution mutation means that one nucleotide is substituted for another and an incorrect amino acid may be inserted into a protein

Insertion: Insertion mutations are caused by the addition of one or more nucleotides into a section of DNA. If one or two nucleotides are inserted into a protein coding gene, this can have drastic effects on the protein which is produced because all of the subsequent triplets are read incorrectly.

Deletion: A deletion mutation refers to the removal of one or more nucleotides from the DNA. As with an insertion mutation, a deletion mutation alters the pattern of base triplets in the DNA. This means that deletions of one or two nucleotides are likely to cause drastic changes to a protein if they occur in a section of DNA containing a gene.

43
Q

What is a silent mutation?

A

A substitution mutation within a protein coding gene may not always lead to a change in the amino acid sequence of the encoded protein
eg, the amino acid leucine might be encoded in a protein by the base triplet GAT, for which the corresponding mRNA codon would be CUA. If the T in the DNA base triplet mutates to C (to give GAC), the mRNA codon becomes CUG, and this still encodes leucine

44
Q

Name the 5 types of effects a mutation can have?

A

Missense: A missense mutation results in a single incorrect amino acid being inserted into a protein.

Nonsense: A nonsense mutation results in the code for an amino acid being changed to a stop codon. This can result in an abnormally short protein which may not function properly.

Splice site: Splice-site mutations result in some introns being retained and/or some exons not being included in the mature transcript and may result in a non-functional protein. Splice site mutations such as these alter post-transcriptional processing.

Point: a mutation causes only a minor change, perhaps affecting only one amino acid

Frameshift: a mutation can cause a major change affecting the coding for many amino acids and leads to a completely different protein being produced, which cannot carry out the required function

45
Q

Name and describe the 4 chromosome structure mutations

A

Translocation: a section of a chromosome is added to another chromosome, not its homologous partner.
Deletion: a section of a chromosome is removed.
Duplication: a section of a chromosome is added from its homologous partner.
Inversion: where a section of chromosome is reversed.

46
Q

Pro of a duplicated gene?

A

Occasionally a mutation can result in the duplication of an entire gene. The second copy of the gene can become altered and provide new DNA sequences. This gene duplication is thought to be an important driving force in evolution.

47
Q

What is evolution?

A

Evolution describes the changes that occur to a species over time, leading to offspring that are better adapted to survive in their environment than the previous generation.

48
Q

What is needed for evolution?

A

For evolution to occur, there must be changes to the gene pool and hence changes to the frequency of genes.

49
Q

Explain mutation (alter allele frequency)

A

Creates multiple alleles for many genes in the gene pool

50
Q

Gene migration (alter allele frequency)

A

The movement of alleles between populations by individuals arriving from a different population and breeding. These individuals have a different gene pool and therefore introduce new alleles into the population.

51
Q

Genetic Drift (alter allele frequency)

A

Tends to occur in small populations and describes the change in allele frequency due to a chance event. Small populations that are isolated from each other can vary greatly due to changes in allele frequencies.

52
Q

Non-random mating (alter allele frequency)

A

Does not change the frequency of the alleles, but increases the number of homozygous individuals. Inbreeding is the most common form.

53
Q

Natural selection (alter allele frequency)

A

The frequency of an allele increases in a population if it provides a selective advantage.

54
Q

Chance (alter allele frequency)

A

Changes to the allele frequency due to random loss. For example, an individual possessing a certain allele may die or fail to reproduce so that allele is lost from the population.

55
Q

What kind of sexual reproduction can eukaryotes do?

A

sexual or asexual

56
Q

What is horizontal gene transfer?

A

genes are passed between members of the same generation, not between parents and offspring

57
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

58
Q

Effect of selection

A

Stabilising Selection
In this case, the average phenotype is selected and the extremes survive much less well, possibly even disappearing.
Disruptive Selection
In this case, it is the extreme values of phenotypes that are chosen and those with average fitness are selected against.
Directional Selection
In this final case, one extreme value or phenotype is selected over both the average and the other extreme value.

59
Q

What is a species?

A

A species is described as a population of organisms that have the same characteristics and are capable of interbreeding to produce fertile offspring.

60
Q

What is speciation?

A

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

61
Q

How does isolation cause speciation?

A

The isolated populations experience different selection pressures and adapt to their particular niche, developing different characteristics. Individuals from the different populations will eventually no longer be able to breed with each other. A new species will then have been formed.

62
Q

Name and explain the 3 types of barriers to species?

A

geographical barriers: these include mountains, deserts, oceans and rivers that physically separate organisms and prevent populations from interbreeding. Geographical isolation may also occur if a habitat is lost, such as the destruction of a forest to form an arid landscape or a river drying up.
ecological barriers: factors such as temperature, pH, salinity, humidity and altitude also act to separate populations. For example, many species have evolved to inhabit regions of different pH or salinity.
behavioural barriers: if individuals in a population become fertile at different times of the year, their sexual organs change, or their courtship behaviour is different or unattractive, then the individuals cannot mate.

63
Q

Explain allopatric speciation?

A

Allopatric speciation occurs due to populations becoming physically separated; it is brought about by geographical barriers. After separation, the now isolated populations may be subjected to different selective pressures or develop and maintain mutations which benefit that group. If, for any reason, the barriers are removed and the populations can freely intermingle but still cannot reproduce and produce fertile offspring, then speciation will have occurred and a new species will have been formed.

64
Q

Explain sympatric speciation?

A

Sympatric speciation is a form of speciation where two species arise within the same habitat. For this to happen, other isolating mechanisms must be at work. Sympatric speciation occurs as a result of behavioural or ecological barriers.

65
Q

What is sympatric speciation much more common in?

A

plants compared to animals

66
Q

What is DNA sequecning?

A

DNA sequencing is the process of determining the order of nucleotides in a section of DNA.

67
Q

What two techniques are combined to perform bioinformatics?

A

computer science and statistical analysis

68
Q

What is phylogenetics?

A

Phylogenetics has been described as the field of biology that deals with identifying and understanding the relationship between the different kinds of life on Earth

69
Q

What are the three domains of life?

A

bacteria, archaea, eukaryote

70
Q

What rate does mutation occur?

A

constant and steady

71
Q

What are molecular clocks?

A

Molecular clocks are used to show when species diverged during evolution.

72
Q

As well as sequence data, what other information is required to determine the main sequence of events in the evolution of life?

A

fossil records

73
Q

What does comparisons of genomes show?

A

Comparison of genomes reveals that many genes are highly conserved across different
organisms.

74
Q

Personalised medical care to treat or alleviate symptoms is called?

A

pharmocogenetics

Higher Biology (16 decks)

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