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
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
3
Q
Codominance
A
Two alleles occur for a gene.
They are both expressed in the phenotype
4
Q
Two ways that evolution occurs
A
genetic drift
natural selection
5
Q
Dihybrid Inheritance
A
The inheritance of two characteristics which are controlled by different genes
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
7
Q
Genetic Drift
A
A certain allele that is passed on by chance
Random changes in allele frequency
8
Q
Species
A
A group of similar organisms that can reproduce to produce fertile offspring
9
Q
Apoptosis
A
programmed cell death
10
Q
Gene regulation
A
its required for cells to specialise and co ordinate, rate of protein synthesis must be controlled on demand
11
Q
Transcriptional
A
Genes can be turned on or off (promotors or repressors)
12
Q
Operon
A
Group of genes that are under control of the same regulatory mechanism and expressed at the same time
13
Q
post-transcriptional
A
mRNA can be modified once it has been made. This regulates translation and the types of proteins produced
14
Q
Translational
A
Translation can be stopped/started
15
Q
Post-translational
A
proteins can be modified after translation. this changes their function
16
Q
Heterochromatin
A
tightly wound DNA around histones, causing chromosomes to be visible during cell division,
RNA polymerase cant access the genes
17
Q
Euchromatin
A
loosely wound DNA making them visible during interphase,
genes can be easily transcribed
18
Q
E coli
A
a bacterium that respires glucose but lactose when glucose is not available
19
Q
Introns
A
sections of DNA that dont code for amino acids
20
Q
Extrons
A
sections of DNA that do code for amino acids
21
Q
Discontinuous Variation
A
a characteristic that can only appear in specific values, mostly genetic and few genes are involved
22
Q
Continuous variation
A
a characteristic that can take any value within a range, polygenic
23
Q
Types of mutation
A
Deletion
Substitution
Insertion
24
Q
Sympatric speciation
A
speciation without geographical isolation
25
Order for allopatric speciation
Variation
Isolation
Natural Selection
Reproductively isolated
26
Hox genes
control body plan development in animals
highly conserved
27
What is allopatric speciation
Speciation due to geographical isolation
28
Transcription control
Chromatin remodelling
Lac operon
cAMP
29
Post transcriptional control
editing mRNA
30
Homeobox genes
regulatory genes and produce an activator protein
31
Process of Apoptosis
The enzymes break down cell components, this causes the cell to shrink and breakdown into fragments, they are then engulfed and digested by phagocytes
32
How do hox genes control development
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)
33
Discuss ways in which genetic variation is produced, including nuclear division (4)
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)
34
What factors affect the expression of regulatory genes
stress
35
When does the Hardy-Weinberg principal not work (4)
population size too small
random mating doesnt occur
natural selection
immigration/emigration
mutations
36
epistasis
the interaction of genes at different loci
when one gene masks the expression of another gene
37
The Hardy-Weinberg principal
this predicts that the frequencies of alleles in a population wont change from one generation to the next
38
why are operons efficient when saving resources
if certain gene products are not needed then all of the genes involved in its production can be switched off
39
When lactose is NOT present...
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
When lactose IS present...
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
protein kinases
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
what are protein kinases activated by
cAMP
43
post translational control (4)
| modifying proteins
addition of non protein groups (carbohydrate chains, lipids or phosphates)
modifying amino acids
folding or shortening of proteins
modification by cAMP
44
chlorosis
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
environmental factors causing chlorosis
lack of light (turn off chlorophyll production to save resources)
mineral deficiencies
virus infections
46
factors affecting evolution (4)
mutation
sexual selection
genetic drift
natural selection
47
stabilising selection
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
directional selection
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
genetic drift leading to evolution
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
natural selection leading to evolution
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
Speciation
the formation of new species through evolution
this occurs when members of the same population become reproductively isolated
52
events leading to speciation (3)
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
why does reproductive isolation occur?
this occurs because of changes in the alleles and phenotypes of the two populations prevent them from successfully breeding together
54
what changes causes a change in the alleles and phenotype of a population
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
A factor that could cause sympatric speciation?
random mutations
56
techniques used to study genes
PCR
Gel electrophoresis
Cutting out DNA fragments using restriction enzymes
57
why is PCR used?
PCR is used to select a fragment of DNA and amplify it to produce millions of copies
58
what does the reaction mixture that is set up in PCR contain?
the DNA sample, free nucleotides, primers and DNA polymerase (to create the new strands)
59
Why are primers added to the reaction mixture at the beginning of PCR?
primers are short pieces of DNA complementary to the bases at the start of the selected fragment
60
The process of PCR (6steps inc)
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
define Gel electrophoresis
this is a procedure used to separate DNA fragments depending on their size using an electrical current
62
what gel is used in electrophoresis?
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
what solution is added to the reservoirs of the gel box during Gel electrophoresis?
a buffer solution (must cover the surface of the gel)
64
how are the DNA samples loaded into the wells during Gel electrophoresis?
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
why is loading dye added to each well in Gel electrophoresis?
this helps the DNA samples to sink to the bottom making them easier to see
66
what steps must be followed when loading the DNA samples into the wells during Gel electrophoresis? (3)
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
how is electrophoresis carried out?
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
approximately how long should the gel run for in electrophoresis?
30 minutes
69
how can you make the DNA fragments visible towards the end of electrophoresis?
using gloves, cover the surface of the gel with a staining solution then rinse with water
70
define palindromic sequences of nucleotides
these consist of antiparallel base pairs that read the same in opposite directions
71
what are restriction enzymes?
restriction enzymes are enzymes that recognise specific palindromic sequences and cut the DNA at these places
72
why do different restriction enzymes cut at different specific recognition sequences (bases)?
because the shape of the recognition sequence is complementary to the enzymes active site
73
what reaction is used to cute the DNA fragments out of the DNA sample?
a hydrolysis reaction
74
define ligation
when DNA ligase is used to join the sugar phosphate backbones of the two sticky ends (genetic engineering)
75
two types of gene therapy
somatic cell therapy
germ line therapy
76
what is gene therapy?
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
how is gene therapy used on a genetic disorder caused by two recessive alleles?
the addition of a working dominant allele is used
78
how is gene therapy used on a genetic disorder caused by a dominant allele?
‘silence’ the dominant allele by sticking a bit of DNA in the middle so that it doesn’t work
79
what are used to add the new alleles inside the cell during gene therapy?
vectors
80
somatic cell therapy
altering the alleles in body cells (any offspring can still inherit the gene as this does not affect our sex cells)
81
germ line therapy
altering the alleles in the sex cells (currently illegal) offspring will not inherit the disease
82
positive ethical issues surrounding gene therapy (4)
prolong life
improve quality of life
conceive a baby without risk
decrease the number of sufferers
83
disadvantages surrounding gene therapy (5)
do more harm than good
expensive
the effects could be short lived
multiple treatments involved
vectors could be identified as foreign
84
a method used for DNA sequencing
chain termination method
85
what enzyme converts mRNA to cDNA in genetic engineering?
reverse transcriptase
86
basis processes of genetic engineering? (3)
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
what problems could arise from ligation? (2)
the plasmid could reseal before the recombinant DNA is inserted
the bacteria may not even take up the plasmid
88
DNA ligase
forms phosphodiester bonds between the sugar and phosphate groups on the two strands of DNA
89
how do they check that the plasmid successfully contains the recombinant gene? (4)
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
name the process where the plasmid and recombinant dna is transferred into the host cell?
transformation
91
two methods used for transformation of the plasmid and recombinant DNA to the host cell?
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
electrofusion
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
what is the purpose of genetically modifying bacteria?
producing useful substances such as insulin and human growth hormone
94
why is genetic engineering important in animals?
it enables animals to produce important proteins and it could try to cure human genetic diseases (CF or Huntington disease)
95
positives of GM crops (4)
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
negatives of GM crops (3)
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
reverse transcriptase
isolating mRNA to produce a single strand of complementary DNA
