Topic 4 - Genetic Infomation, variaton and relationships between organisms Flashcards
1
Q
Define Gene
A
a short section of DNA that codes for a polypeptide or functional RNA
2
Q
Define allele
A
a version of a gene
3
Q
Define locus
A
a position on a chromosome
4
Q
Define homologous
A
the structural features and pattern of genes are the same
5
Q
For maternal and paternal chromosomes where are same genes found
A
in the same positions on the chromosomes
6
Q
The genetic code is:
A
- Non overlapping
- A triplet code
- Universal
7
Q
What is meant by a triplet code?
A
every 3 base pairs (nucleotides) codes for 1 amino acid
8
Q
What is meant by universal?
A
the code is the same in all species, ATA codes for the same thing in every species
9
Q
What is meant by non overlapping?
A
Each base is discrete (123456 is 123, 456 and NOT 123, 234, 345, 456) so that the bases don’t get mixed up when they are being read, meaning the wrong amino acid is formed
10
Q
How many possible triplet codes are there?
A
64
11
Q
How many possible amino acids are there?
A
20
12
Q
The genetic code is degenerate, what does this mean?
A
Some amino acids are coded by more than one triplet, e.g. tyrosine is TAT or TAC
13
Q
What do some triplet codes act as?
A
Some triplet codes act as punctuation marks
Some indicate start and stop points for start/end of an amino acid chain:
- A start codon is ATG
14
Q
What is transcription?
A
formation of pre mRNA in the nucleus
15
Q
What is translation?
A
formation of polypeptides in the ribosomes
16
Q
How does transcription work?
A
.Parental DNA has its hydrogen bonds broken by DNA helicase, leaving a template strand
.Free RNA nucleotides are attracted to it and form weak hydrogen bonds with the DNA nucleotides that are complementary to their bases
.RNA polymerase comes along and resynthesizes the sugar phosphate backbone along the RNA nucleotides and breaks the hydrogen bonds, making a strand of pre mRNA
.The pre mRNA is then spliced, which removes introns and joins together exons, turning into mRNA (no longer pre)
17
Q
What are introns?
A
non-coding DNA
18
Q
What are exons?
A
coding DNA
19
Q
What is translation?
A
The process by which mRNA is used to make a specific protein
20
Q
Describe how translation happens
A
Translation is the process by which mRNA is used to make a specific protein, after mRNA has been produced through transcription and splicing it then moves through the cytoplasm to a ribosome and enters between the two sub units and attaches to it. Here a start codon (AUG) tells the ribosome to start reading the RNA on it. Each triplet of bases is called a codon, and after the initial start codon tells the ribosome to read it the ribosome then moves along the mRNA and reads the codons, attaches (with temporary hydrogen bonds) tRNA with a complementary anticodon to the mRNA’s codon. Each tRNA has a specific amino acid attached, as one tRNA binds to the mRNA so does another one next to it, then their amino acids form polypeptide bonds to join them together and the first tRNA leaves and another one joins as the ribosome moves along the mRNA and forms a polypeptide bond in a condensation reaction with the amino acid there. This continues till a stop codon is reached which has no complementary anticodon so the chain stops and the polypeptide chain formed leaves the ribosome and coils up into an amino acid which join using energy from ATP.
21
Q
What does tRNA do?
A
.Transport specific amino acids
22
Q
How many different tRNA’s are there?
A
20
23
Q
Do all tRNA’s have the same structure?
A
Yes
24
Q
What is a tRNA made up of?
A
codon, anti codon, hydrogen bonds, ester bonds, amino acids
25
Describe the structure of tRNA
.Each consists of a single polynucleotide strand of RNA
.Folded to form a clover arrangement
.Held in place by hydrogen bonds between complementary base pairs
.One end acts as an attachment site for the amino acid
.The other end is called the anti-codon
26
What is a mutation?
Any change in one or more nucleotide base or a change in the sequence of the bases in DNA
27
Characteristic of mutations
.Random
.Spontaneous
.Natural
.Positive or negative
28
Three types of mutations
.Insertion
.Deletion
.Substitution
29
Define insertion
A nucleotide is added to the DNA sequence
30
Define deletion
A nucleotide is lost from the DNA sequence
31
Define subsitution
One nucleotide is replaced by another nucleotide with a different base
32
What is a frame shift?
every amino acid after the insertion or deletion will move one place
33
What will substitution affect?
Only one triplet code
34
What will deletion and insertion affect?
the whole amino acid sequence, by causing a frame shift
35
What is a mutagen?
A physical or chemical agent that changes the genetic material of an organism
36
What do mutagenic agents do?
increase the frequency of a mutation occurring above the natural
37
Name 4 things that act as mutagenic agents
Caffeine, x-rays, mustard gas and UV radiation
38
What are chromosomal mutations?
Changes in the structure or number of whole chromosomes
39
What are the two types of chromosomal mutations?
.Polyploidy
| .Nondisjunction
40
What is polyploidy?
.Changes in whole sets of chromosomes
| .Cells have multiple sets of chromosomes
41
What form of polyploidy is very common in plants?
.3n = triploid
42
What is non-disjunction?
.Homologous pairs fail to separate
| .Changes in number of individual chromosomes per cell
43
What is down's syndrome caused by?
extra chromosome 21
44
Define meiosis
the process by which a diploid nucleus (2n) divides to produce four haploid daughter nuclei (n)
45
Name the phases in meiosis
Interphase, prophase I, Metaphase I, Anaphase I, Telophase I, cytokinesis, Prophase II, Metaphase II, Anaphase II, telophase II and cytokinesis
46
What is a homogolous pair?
one chromatid of mum and one chromatid of dad
47
What are sister chromatids?
identical chromatids together
48
What two forms of genetic variation are there?
Crossing over and independent segregation
49
What is crossing over?
Crossing over is the exchange of alleles
50
What is independent segregation?
Independent segregation is the random arrangement of chromosomes
51
State what happens in each phase of meiosis.
Interphase – The cell is synthesising DNA and checking it (2 chromatid per chromosome)
Prophase I – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks down
Metaphase I – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeres
Anaphase I – The pair of chromosomes are split as each is pulled to opposite poles in the cell by the spindle fibres contracting – the homologous chromosomes are separated from each other but the chromosome stays tgther
Telophase I & Cytokinesis – The cells form two nucleus, one for each set of new chromosomes, and pull apart while forming a membrane to produce two daughter cells
Prophase II – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks down
Metaphase II – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeres
Anaphase II – The sister chromatids are split as each chromatid is pulled to opposite poles in the cell by the spindle fibres
Telophase II & cytokinesis – The cells form two nucleus, one for each set of new chromatids, and pull apart while forming a membrane to produce two more daughter cells each (4 cells now altogether)
52
What is a genotype?
The genetic makeup of an organism, the genes and alleles that they have
53
What is a phenotype?
Observable characteristics, genotype + environment = phenotype
54
What are the causes of genetic variation?
.Mutations, sexual reproduction, meiosis
55
How does crossing over work?
Homologous pairs line up, chromatids of each pair become twisted, section of chromatid breaks off and re-joins chromatid of the other homologous chromosome, sections have different alleles, new combination of linked alleles
56
With crossing over, what happends to the amount of possible versions of allele combinations?
No crossing over = 2 versions
| With crossing over = 4 possible versions
57
Who discovered independent segregation? When?
.Gregor Mendel (19th Century)
58
What is independent segregation?
the random segregation of chromosomes during anaphase
59
What did Gregor Mendel say about independent segregation?
.Genes are inherited independently of one another
| .BUT genes close together have a high likelihood of being inherited together
60
Independent segregation key points
.Homologous pairs line up along the equator randomly
.Combination of chromosomes pulled to each pole is random
.Daughter cells produced are genetically different
61
The formula for the number of combinations of genes after independent segregation
2^n
62
The formula for the number of combinations of genes after fertilisation after independent segregation
(2^n)^2
63
Why does the formula (2^n)^2 not work for crossing over?
Crossing over is completely random
64
What is the 'n' in the formula (2^n)^2?
number of chromosomes
65
What is the first '2' in the formula (2^n)^2?
possible number of routes the chromosomes could go to (pulled to two poles)
66
Define genetic diversity
The total number of different alleles in a population
67
What must happen for a genetic mutation to occur?
.There must be a change in the DNA
.A random mutation
.Resulting in:
.Polyploidy, non-disjunction, substitution, insertion, deletion
68
High genetic diversity within a species =
large number of different alleles
69
Low genetic diversity within a species =
small number of different alleles
70
Advantages of High Genetic DIversity
.Higher survival rate, we might have some people with genes to survive in certain climates and some who don’t, if we had LGD and all had the other climates genes we would all die
.Higher resistance to disease, as it won’t spread as easily
.Low chance of inbreeding
.Less competition for same habitat
.Larger food web, not solely reliant on one food
71
Disadvantages of High Genetic DIversity
.Fewer organisms with characteristics for human’s
| .Fewer organisms adapted to an environment at a specific time or place
72
What is natural selection?
The differential survival and reproduction of individuals due to differences in their phenotype
73
Define phenotype
Observable physical characteristics that an organism has
74
Define genotype
Genetic makeup of an organism
75
Define allele frequency
The number of times an allele occurs within in the gene pool
76
Define genepool
The total number of alleles in a particular population at a specific time
77
Why does allele frequency change?
Not all alleles are equally likely to be passed to the next generation
Those better adapted to their environment tend to survive and breed, at the expense of those less well adapted
78
Key points of a normal distribution curve
.No bias
.Data surrounds a central point
.Curve is symmetrical
.Curve is bell shaped
79
Mode
The most frequent value
80
Mean
the average, every value added together divided by the amount of values
81
Median
the value in the middle when the in ascending order
82
Describe the shape of a normal distribution curve
The curve is shaped like a bell, near 0 on the y axis at the extremes of the x axis and increasing like a curve to a maximum in the middle
83
In a normal distribution curve, what is the mean the same as?
The mode and the median
84
Why does the mean of a distribution curve change?
Most characteristics area a result of multiple genes (poly genes)
Each gene is affected by the environment
Changes in environment = changes in the mean
85
How does directional selection occur?
1. Mutation occurs
2. Change in the environment occurs
3. Selection favours individuals that vary in one direction from the mean
4. One extreme is favoured for
5. Allele frequency changes
86
Define selection
The process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted.
87
Essentially, what is directional selection?
.Phenotypes of one extreme in the population is selected for
.The other phenotype is selected against
.Change in allele frequency
88
In stabilising selection, what happens?
```
.Selection acts against both extremes in a range of phenotypes
.Mean is favoured
.Phenotypic variation is reduced
.Both extremes are selected against
.Environment has remained stable
```
89
Why is birth rate an example of stabilising selection?
.The extremes are favoured against since too low or too high birth weights can result in death of the child
.Too low, going to die
.Too high, going to take lots of resources and energy from the mother when alive or could kill the mother in birth so a low survival rate for the baby
90
What is aseptic technique?
‘Method designed to prevents contamination form microorganisms’
91
When is aseptic technique important?
.Handling surgical equipment
.Surgery
.During labour
.Inserting catheters or IV drips
92
Phenotype selected, directional selection
The one best suited to the changing environment, one of the extremes
93
Phenotype selected, Stabilising selection
The mean/medium/mode
94
Effect on the characteristics of a population, directional selection
Changes the overall characteristics to make it advantageous in the given environment
95
Effect on the characteristics of a population, stabilising selection
Increases the frequency of the mean/medium/mode allele at the expense of the extreme alleles to make the population as a whole better suited to their stable environment
96
Shape of the distribution curve, directional selection
Shifts the normal curve to one extreme or the other
97
Shape of the stabilising curve, directional selection
Narrows the normal curve and increases its height (frequency) for the mean/medium/mode
98
Example, directional selection
Moths in the industrial revolution or antibiotic resistance
99
Example, stabilising selection
Weight of babies after birth
100
What is a species?
A species is a group of individuals that area capable of breeding to produce living and fertile offspring.
101
What happens to a species genes in sexual reproduction?
Two individuals of a species can combine their genes during sexual reproduction but selection can act to favour different phenotypes presence within species depending on where they are found
102
What is an anatomical adaptation? Example
Anatomical – structure, how the organism is shaped – appearance, e.g. shorter ears and thicker fur in arctic foxes
103
What is an physiological adaptation? Example
inside, how the organism works internally – chemical reactions/processes internally, e.g. oxidising of fat rather than carbohydrates to produce extra water
104
What is a behavioural adaptation? Example
behaviour, how you the organism acts – actions of the organisms, e.g. migration of swallows from UK to Africa
105
Key information of binomial names
.Universal naming system
.Written in italics or underlined
.Given two names
106
What is the first name in binomial names?
Generic name
.Denotes the genus
.Upper case
107
What is the second name in binomial names?
Used to identify
.Denotes the species
.Lower case
108
Binomial names, order of Latin things
```
Kingdom
Phylum
Class
Order
Family
Genus
Species
```
109
State the difference between pre-mRNA and mRNA
mRNA has introns removed
110
Birth weight is a form of stabilizing selection, why?
Both extremes have a disadvantage, too heavy or too light and it'll die
111
Why is splicing required?
So it is small enough to leave the nuclear envelope and doesn't disrupt the formation of a polypeptide
112
Examples of courtship displays
```
.Bright colours
.Patterns
.Feathers
.Birds tweeting/songs
.Building rock piles
.Fighting
.Ritualised movements (dancing)
.Displays of beauty or strength
```
113
Stimuli to male response of a courtship display happening
Stimuli the male communicates a courtship signal this acts as a visual stimulus to the females and is detected by the eyes (a receptor) sends a message to female nervous system (CNS) effector contracts or releases a hormone effector causes a specific innate/stereotyped behaviour of her own (response) acts as a stimulus to the male the male responds
114
Why do males impress the females?
They are the ones that are needed to carry the children
115
Why are courtship displays important?
they help an organism to reproduce
116
How do courtship displays help an organism to reproduce?
- Enabling an organism to recognise one of their own species – so they can produce fertile off spring and prevent cross breeding, ensures genes are passed on, use similarities in physical characteristics and behaviours
- Identifying if a mate is capable of breeding – both partners need to be sexually mature, fertile and receptive to mating, females may only be ‘in season’ once a year
- Forming pair bonds (lifelong pairings) – ensures successful breeding (more investment), successful raising of the offspring/pass on genes
- Synchronising mating season – determines whether the female is in receptive (fertile) state, correct female response then mating will take place
117
Define classification
the organisation of living organisms into groups
118
Define taxonomy
the theory and practice of biological classification
119
Key points of classification
Carl Linnaeus
Not random
Based on accepted principles
120
Define analogous
have the same function but do not have the same evolutionary origin
121
Define homologous
similar evolutionary origins/structures regardless of their function
122
What is artificial classification? With example
Based on analogous classification
Not based on evolutionary relationship
For example, wings on a bat and a butterfly
123
What is phylogenetic classification?
Classifies species based on shared features
Characteristics derived from ancestors
Based on evolutionary relationships
Partly based on homologous characteristics
124
What is each group called in phylogenetic classification?
a taxon (taxa)
125
Who developed domains and what are they?
Carl Woese developed domains – the highest taxonomic rank
126
Name the 3 domains
Bacteria, archea and eukarya
127
Key features of bacteria
```
Unicellular
Non-membrane bound organelle
Non-membrane bound DNA
Has plasmids
Has 70S ribosomes
Small
DNA is free floating
DNA is not associated with histones
Cell wall (murein)
Some may cause disease
```
128
Key features of archea
```
Single celled prokaryotes
Similar shape and size to bacteria
DNA/genes and protein synthesis like eukaryotes
No murein in cell wall
No membrane bound organelle
```
129
Key features of eukrya
```
Multicellular
Membrane bound organelle
Membrane bound DNA
Doesn’t have plasmids
Has 70S and 80S ribosomes
Large
DNA is in the nucleus
DNA is associated with histones (proteins)
No cell wall
Split into four kingdoms (protoctista, fungi, plantas, animals)
```
130
How to read phylogenetic trees
Oldest ancestral species at base, most recent divergence at the end of branches
131
Define hierarchy
smaller groups within larger groups with no overlap
132
Advantages of classifying by observable characteristics
.Easier
.Anybody could do it
.Does not require any advanced equipment
133
Disadvantages of classifying by observable charcateristcs
.Patterns of inheritance aren’t always clear
.Differences aren’t often discrete
.Interpretation subjective
.Fossil data is hard to find
.Most genes are polygenetic
.May be a result of similar environments not similar evolutionary history
134
How can DNA Base Sequences be used to see evolutionary relationships?
Compare the exact order of nucleotides on the DNA
Mutation occurs causing a difference between individuals
More differences in bases = fewer similarities
Individuals more distantly related
135
How can mRNA Base Sequences be used to see evolutionary relationships?
mRNA is complementary to DNA
Differences in mRNA = differences in DNA
Compare the exact order of nucleotides on the DNA
Mutation occurs causing a difference between individuals
More differences in bases = fewer similarities
Individuals more distantly related
136
How can amino acid sequences in proteins be used to see evolutionary relationships?
Differences in DNA = differences in mRNA
Differences in mRNA = differences in amino acids
Compare the exact order of nucleotides on the DNA
Mutation occurs causing a difference between individuals
More differences in bases = fewer similarities
Individuals more distantly related
137
Adv of using DNA and mRNA when finding evolutionary relationships
.Determine the exact order of nucleotide bases
.Determine how diverse organisms are
.Determine the time since divergence through the number of mutations present
138
Disadv of using DNA and mRNA when finding evolutionary relationships
.Can cost a lot
.Can take a long time to sequence the full genome
.Requires specialist equipment and personnel
139
Adv of using amino acids when finding evolutionary relationships
.Determines the DNA and mRNA sequence
| .Usually easier to identify amino acids present
140
Disadv of using amino acids when finding evolutionary relationships
.Can cost a lot
.Can take a long time
.DNA may be non-coding so not detected as difference
.The genetic code is degenerate so the same amino acid may be a result of very different DNA sequences
141
How can we identify genetic diversity?
.DNA Hybridisation
| .Biochemical analysis
142
What is hybrid?
combination of two different elements
143
What is DNA hybridisation?
direct comparison between the DNA sequences of different organisms
144
What is a hybrid strand?
one strand from one set of DNA and one strand from another
145
How does DNA Hybridisation work?
1. DNA from two species is heated
2. Denatures DNA and breaks the hydrogen bonds
3. Strand A given radioactive labels or fluorescent markers
4. Strand A and B are mixed
5. Strands are cooled
6. Two strands recombine and hydrogen bonds can reform between
7. Gaps are present when no complimentary base pairing has occurred
8. The higher percentage f hydrogen bonds formed = greater similarity in genetic material
146
How does biochemical analysis work?
Serum containing many human antigens is injected into another species, rabbits are commonly used. The rabbit responds by producing anti-human antibodies, anti-human antibodies from rabbit are extracted in a serum and mixed with other species. The antihuman antibodies will bind to human antigens in the serum of other species, the more human like antigens in the serum (similar in structure), the more antigen-antibody complexes formed (as they are complementary), the more precipitate seen in the serum. The more precipitate seen, then the more closely related to the human the other species are (if there is similarity in protein structure, there is similarity in DNA).
147
In biochemical analysis, the human serum first must be added to a different species, why?
so that antibodies complementary to the human antigens can be formed, and then used to test for the complementary human antigens
148
Why are species like rabbits used in biochemical analysis?
Species like rabbits are used since they are small, easy to keep, produce lots of young and cheap
149
Define biodiversity
The range and variety of genes, species and habitats within a particular region.
150
What are the 3 types of biodiversity?
Species diversity, genetic diversity and ecosystem diversity
151
What is species diversity?
the number of different species and the number of individuals of each species within any one community
152
What is genetic diversity?
the variety of genes possessed by the individuals that make up any one species
153
What is ecosystem diversity?
the range of different habitats within a particular area
154
What is species richness?
Species richness is the number of different species in a particular area at a given time (community)
155
Equation for species diversity index? With meaning for each letter
```
d = species diversity
N = total number of organisms of all species
n = total number of organisms of each species
Σ = the sum of
```
156
Human factors affecting biodiversity
.Agriculture – demand for food has more than doubled
.Increased use of herbicides and pesticides
.Use land for homes and industry
.Increased waste and land fill
.Deforestation
157
How does agriculture affect biodiversity?
1. Monoculture (growing only one species)
2. Lack of intercropping (not rotating what is grown each season)
3. Competition for space
4. Use of pesticides and herbicides
5. Cattle in the field where species may grow
6. Draining wetland and marshes
7. Removing hedgerows (replacing hedge borders with fences)
158
How do monocultures affect biodiversity?
reduction in species and genetic diversity directly and indirectly as fewer food sources and habitats
159
how does lack of intercropping affect biodiversity?
Drains the soil of nutrients, results in monoculture
160
How does competition for space affect biodiversity?
Natural species habitats cannot grow/are outcompeted by dominant
161
How does use of pesticides and herbicides affect biodiversity?
Can be toxic to species, enters water cycle, eutrophication
162
How does cattle in the field where species may grow affect biodiversity?
Over grazing, trampling, reduction in species diversity
163
How does draining wetland and marches affect biodiversity?
Removes nutrients and moisture from soil so species cannot grow
164
How does removing hedgerows affect biodiversity?
Removes habitats and food sources
165
What is deforestation?
The permanent clearing of forests and the conversion of land to other uses, such as agriculture, grazing or settlement
166
How many species are being lost each year due to deforestation?
50,000
167
How does deforestation reduce biodiversity?
by clearing the forests you are not only killing the trees (a species) and so reducing the species diversity index directly but the trees may also act as a habitat or food source to other animals so by killing the trees you are killing the animals that rely on the tree as well – thereby indirectly reducing biodiversity as well.
168
How can maintaining biodiversity bring economic benefit?
2. By maintaining biodiversity, you can keep biodiverse areas (like the coral reef or forests) which attract tourists and people for days out, thereby benefiting the economy. Also extracts of plants can be used for medicine, so you keep the biodiversity and keep the money.
169
How can you reduce human impacts of deforestation?
.Eco charges
| .Increased taxes/fines
170
Define intraspecific
variation within a species, eye colour or blood group
171
Define interspecific
variation between a species, food source or pollinator
172
State when you would use quadrats and transects with examples
1. You use quadrats to compare how common an organism is in two or more sample areas (shady and sunny spots in a playing field). You use transects to find out how organisms are distributed across an area (if an organism becomes more or less common as you move from a hedge towards the middle of a field).
173
How would you use quadrats?
Place a 1m^2 quadrat on the ground at a random point within the first sample area, count all the organisms within that quadrat, repeat as many times as possible, work out the mean number of organisms per quadrat within the first sample area. Repeat this all for the second sample area. Compare the two means.
174
How would you use trasects?
Mark out a line in the area you want to study using a tape measure, collect data along this line (this can be done by counting the amount of organisms touching the line or by placing quadrats down as you go down the line at even intervals). Interpret the data.
175
What is sampling bias and how is it avoided?
- Biased choices made by the investigator
- Deliberate or unwillingly
- Sample is unrepresentative
- Avoided using random sampling
176
What is chance variation and how is it avoided?
- Even if sampling bias is avoided, this can still occur
- Not a representative sample
- I.E. all individuals are the same
- Avoided by increasing sample size
- Repeat lots
177
Define distribution
the way in which data is spread/shared out
178
What is standard deviation a form of?
A statistical test
179
What is standard deviation and what does it do?
.A measure of the width of the curve
.Indicates of the range
.The distance from the mean until the curve goes from convex to concave
.Determines how likely it is that results are due to chance
180
With standard deviation, the closer to the mean values (less spread), the ____ reliable
more
181
__% of data lies within 1 s.d
68
182
__% of data lies within 2 s.d
95
183
Standard deviation equation
root((Σ(x-(Σx/n))^2)/(n-1))
