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Biology > Genetics > Flashcards

Genetics Flashcards

1
Q

Evolution

A

The change in inherited characteristics of a group of organisms over time due to the change in alele frequency

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2
Q

The founders effect

A

A group of organisms start their own population which leads to a small initial gene pool and less variation

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3
Q

Codominance

A

Two alleles occur for a gene.

They are both expressed in the phenotype

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4
Q

Two ways that evolution occurs

A

genetic drift

natural selection

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5
Q

Dihybrid Inheritance

A

The inheritance of two characteristics which are controlled by different genes

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6
Q

Explain Allopatric Speciation (4)

A

Variation of alleles in a population,

environmental change which leads to geographical isolation,

change in allele frequency due to mutations (natural selection) and founders effect leading to genetic drift

reproductive isolation= new species formed

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7
Q

Genetic Drift

A

A certain allele that is passed on by chance

Random changes in allele frequency

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8
Q

Species

A

A group of similar organisms that can reproduce to produce fertile offspring

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9
Q

Apoptosis

A

programmed cell death

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10
Q

Gene regulation

A

its required for cells to specialise and co ordinate, rate of protein synthesis must be controlled on demand

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11
Q

Transcriptional

A

Genes can be turned on or off (promotors or repressors)

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12
Q

Operon

A

Group of genes that are under control of the same regulatory mechanism and expressed at the same time

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13
Q

post-transcriptional

A

mRNA can be modified once it has been made. This regulates translation and the types of proteins produced

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14
Q

Translational

A

Translation can be stopped/started

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15
Q

Post-translational

A

proteins can be modified after translation. this changes their function

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16
Q

Heterochromatin

A

tightly wound DNA around histones, causing chromosomes to be visible during cell division,

RNA polymerase cant access the genes

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17
Q

Euchromatin

A

loosely wound DNA making them visible during interphase,

genes can be easily transcribed

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18
Q

E coli

A

a bacterium that respires glucose but lactose when glucose is not available

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19
Q

Introns

A

sections of DNA that dont code for amino acids

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20
Q

Extrons

A

sections of DNA that do code for amino acids

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21
Q

Discontinuous Variation

A

a characteristic that can only appear in specific values, mostly genetic and few genes are involved

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22
Q

Continuous variation

A

a characteristic that can take any value within a range, polygenic

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23
Q

Types of mutation

A

Deletion

Substitution

Insertion

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24
Q

Sympatric speciation

A

speciation without geographical isolation

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25
Q

Order for allopatric speciation

A

Variation
Isolation
Natural Selection
Reproductively isolated

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26
Q

Hox genes

A

control body plan development in animals

highly conserved

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27
Q

What is allopatric speciation

A

Speciation due to geographical isolation

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28
Q

Transcription control

A

Chromatin remodelling
Lac operon
cAMP

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29
Q

Post transcriptional control

A

editing mRNA

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30
Q

Homeobox genes

A

regulatory genes and produce an activator protein

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31
Q

Process of Apoptosis

A

The enzymes break down cell components, this causes the cell to shrink and breakdown into fragments, they are then engulfed and digested by phagocytes

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32
Q

How do hox genes control development

A

homeobox sequences (regions on hox genes) code for homeodomain (part of protein)

the homeodomain binds to specific sites on DNA which enables the proteins to work as a transcription factor

these transcription factors bind to DNA at the start of developmental genes, activating or repressing transcription (altering the production of proteins)

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33
Q

Discuss ways in which genetic variation is produced, including nuclear division (4)

A

Independent assortment during metaphase of chromosomes in meiosis1 and chromatids in meiosis2 (could result in homologous chromosomes pairing up randomly and producing a random combination of alleles)

Crossing over between chromatids during prophase 1 in meiosis

random mating

mutation (substitution, deletion, insertion)

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34
Q

What factors affect the expression of regulatory genes

A

stress

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35
Q

When does the Hardy-Weinberg principal not work (4)

A

population size too small

random mating doesnt occur

natural selection

immigration/emigration

mutations

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36
Q

epistasis

A

the interaction of genes at different loci

when one gene masks the expression of another gene

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37
Q

The Hardy-Weinberg principal

A

this predicts that the frequencies of alleles in a population wont change from one generation to the next

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38
Q

why are operons efficient when saving resources

A

if certain gene products are not needed then all of the genes involved in its production can be switched off

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39
Q

When lactose is NOT present…

A

the regulatory gene codes for the repressor protein

this blocks the operator so that RNA polymerase cannot bind to the promoter,

this prevents transcription of the genes

40
Q

When lactose IS present…

A

the regulatory gene codes for the repressor protein

lactose binds to the repressor protein altering the active site and causing it to fall off the operator

this allows RNA polymerase to bind to the promotor so transcription can take place

41
Q

protein kinases

A

these are enzymes that catalyse the addition of phosphate groups to proteins

these phosphate groups change the tertiary structure of the active site and so the function of the protein

42
Q

what are protein kinases activated by

A

cAMP

43
Q

post translational control (4)

modifying proteins

A

addition of non protein groups (carbohydrate chains, lipids or phosphates)

modifying amino acids

folding or shortening of proteins

modification by cAMP

44
Q

chlorosis

A

leaves look pale or yellow

this occurs when the plant does not produce enough chlorophyll and in turn has a reduced ability to make food by photosynthesis

45
Q

environmental factors causing chlorosis

A

lack of light (turn off chlorophyll production to save resources)

mineral deficiencies

virus infections

46
Q

factors affecting evolution (4)

A

mutation

sexual selection

genetic drift

natural selection

47
Q

stabilising selection

A

when the environment isnt changing much individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce (it reduces the range of possible phenotypes)

48
Q

directional selection

A

when there is a change in the environment individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce

49
Q

genetic drift leading to evolution

A

alleles passing on by chance to the offspring so the number of individuals with the allele increases

this leads to evolution as the allele becomes more common

50
Q

natural selection leading to evolution

A

some individuals have characteristics that make them better adapted to selection pressures

these are more likely to reproduce and survive passing on their advantageous alleles to the next generation

51
Q

Speciation

A

the formation of new species through evolution

this occurs when members of the same population become reproductively isolated

52
Q

events leading to speciation (3)

A

members of a population become isolated and no longer interbreed resulting in no gene flow

random mutation continues and those advantageous characteristics will be selected due to the different selection pressures

the members of the population become soo different due to mutations and genetic drift that they cannot reproduce to make fertile offspring

53
Q

why does reproductive isolation occur?

A

this occurs because of changes in the alleles and phenotypes of the two populations prevent them from successfully breeding together

54
Q

what changes causes a change in the alleles and phenotype of a population

A

seasonal changes- become sexually active at different times of the year (diff flowering or mating season)

mechanical changes- changed in genitalia

behavioural changes- rituals that aren’t attractive to other populations

55
Q

A factor that could cause sympatric speciation?

A

random mutations

56
Q

techniques used to study genes

A

PCR

Gel electrophoresis

Cutting out DNA fragments using restriction enzymes

57
Q

why is PCR used?

A

PCR is used to select a fragment of DNA and amplify it to produce millions of copies

58
Q

what does the reaction mixture that is set up in PCR contain?

A

the DNA sample, free nucleotides, primers and DNA polymerase (to create the new strands)

59
Q

Why are primers added to the reaction mixture at the beginning of PCR?

A

primers are short pieces of DNA complementary to the bases at the start of the selected fragment

60
Q

The process of PCR (6steps inc)

A

1) set up a reaction mixture
2) heat to 95 to break the H bonds
3) cool to between 50 and 65 to allow the primer to anneal
4) heat to 72 so DNA polymerase can work
5) two new copies are formed
6) the cycle starts again with the 2 new copies to produce 4 new copies (each cycle doubles the amount of DNA)

61
Q

define Gel electrophoresis

A

this is a procedure used to separate DNA fragments depending on their size using an electrical current

62
Q

what gel is used in electrophoresis?

A

agarose gel which is poured into a gel tray and left to solidify

a row of wells is created at one end of the gel (closest to the negative electrode on the gel box)

63
Q

what solution is added to the reservoirs of the gel box during Gel electrophoresis?

A

a buffer solution (must cover the surface of the gel)

64
Q

how are the DNA samples loaded into the wells during Gel electrophoresis?

A

using a micropipette (the bottom of the well could be pierced if the micropipette is in too deep)

add the same volume of loading dye to each well

65
Q

why is loading dye added to each well in Gel electrophoresis?

A

this helps the DNA samples to sink to the bottom making them easier to see

66
Q

what steps must be followed when loading the DNA samples into the wells during Gel electrophoresis? (3)

A

make sure the tip of the micropipette is under the solution but above the opening of the wells

use a clean micropipette each time

add the same volume of DNA into each well and record which DNA sample is in each well

67
Q

how is electrophoresis carried out?

A

turn on the gel box to a required voltage so an electrical current can be passed through the gel

the dna fragments would move towards the +ve end (smaller ones would move faster and travel further)

68
Q

approximately how long should the gel run for in electrophoresis?

A

30 minutes

69
Q

how can you make the DNA fragments visible towards the end of electrophoresis?

A

using gloves, cover the surface of the gel with a staining solution then rinse with water

70
Q

define palindromic sequences of nucleotides

A

these consist of antiparallel base pairs that read the same in opposite directions

71
Q

what are restriction enzymes?

A

restriction enzymes are enzymes that recognise specific palindromic sequences and cut the DNA at these places

72
Q

why do different restriction enzymes cut at different specific recognition sequences (bases)?

A

because the shape of the recognition sequence is complementary to the enzymes active site

73
Q

what reaction is used to cute the DNA fragments out of the DNA sample?

A

a hydrolysis reaction

74
Q

define ligation

A

when DNA ligase is used to join the sugar phosphate backbones of the two sticky ends (genetic engineering)

75
Q

two types of gene therapy

A

somatic cell therapy

germ line therapy

76
Q

what is gene therapy?

A

a genetic engineering technique used to cure or treat a disease (inherited or altered behaviour of cells)

it is inserting a functional allele of gene into cells

77
Q

how is gene therapy used on a genetic disorder caused by two recessive alleles?

A

the addition of a working dominant allele is used

78
Q

how is gene therapy used on a genetic disorder caused by a dominant allele?

A

‘silence’ the dominant allele by sticking a bit of DNA in the middle so that it doesn’t work

79
Q

what are used to add the new alleles inside the cell during gene therapy?

A

vectors

80
Q

somatic cell therapy

A

altering the alleles in body cells (any offspring can still inherit the gene as this does not affect our sex cells)

81
Q

germ line therapy

A

altering the alleles in the sex cells (currently illegal) offspring will not inherit the disease

82
Q

positive ethical issues surrounding gene therapy (4)

A

prolong life

improve quality of life

conceive a baby without risk

decrease the number of sufferers

83
Q

disadvantages surrounding gene therapy (5)

A

do more harm than good

expensive

the effects could be short lived

multiple treatments involved

vectors could be identified as foreign

84
Q

a method used for DNA sequencing

A

chain termination method

85
Q

what enzyme converts mRNA to cDNA in genetic engineering?

A

reverse transcriptase

86
Q

basis processes of genetic engineering? (3)

A

obtain the plasmid from bacteria

the same restriction enzymes used on the cDNA and the plasmid

DNA ligase to join them together(recombinant plasmid)

insert into bacteria (transformation into host cell)

87
Q

what problems could arise from ligation? (2)

A

the plasmid could reseal before the recombinant DNA is inserted

the bacteria may not even take up the plasmid

88
Q

DNA ligase

A

forms phosphodiester bonds between the sugar and phosphate groups on the two strands of DNA

89
Q

how do they check that the plasmid successfully contains the recombinant gene? (4)

A

a plasmid which contains a marker gene (for antibiotic resistance) is cut open using the same restriction enzymes at the resistant site

the original dna and plasmid are also cut using these restriction enzymes to expose the selected dna fragments

they are mixed together (open plasmid and dna fragments) using dna ligase

this can then be treated with antibiotics to see if the bacteria is resistant

90
Q

name the process where the plasmid and recombinant dna is transferred into the host cell?

A

transformation

91
Q

two methods used for transformation of the plasmid and recombinant DNA to the host cell?

A

electroporation - applying an electrical current to bacteria to make the membranes porous

culture the bacterial cells (to increase membrane permeability) in a calcium rich solution and increase the temperature

92
Q

electrofusion

A

tiny electrical currents are applied to the membranes of two different cells

this fuses the nuclear membranes and cells together to form a hybrid cell (containing the DNA from both cells)

93
Q

what is the purpose of genetically modifying bacteria?

A

producing useful substances such as insulin and human growth hormone

94
Q

why is genetic engineering important in animals?

A

it enables animals to produce important proteins and it could try to cure human genetic diseases (CF or Huntington disease)

95
Q

positives of GM crops (4)

A

pest resistant crops reduce the amount of and need for pesticide sprays - protects the environment and allows an increase in yield

extended shelf life can reduce food waste

crops can grow and survive in a wider range of conditions

produce human medicines (insulin)

96
Q

negatives of GM crops (3)

A

allergies may arise due to the different proteins made

transferred genes could spread to the wild and cause problems

insect pests could become resistant and the toxins produced may harm non pest insects

97
Q

reverse transcriptase

A

isolating mRNA to produce a single strand of complementary DNA

Biology (31 decks)

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