3.4.1-3.4.4 - Genetic information, variation and relationships Flashcards
1
Q
Why is DNA described as a polymer?
A
Because a polymer is made from a molecule made up of lots smaller repeating monomers and DNA is made up of monomers called nucleotides.
2
Q
Why is DNA referred to as a double helix?
A
the backbone structure consists of 2 helices twisted around each other
3
Q
Explain how prokaryotic DNA differs to eukaryotic DNA
A
P is shorter and smaller.
Contains less non-coding DNA.
Not found in the nucleus- free floating
Not associated with histones
4
Q
What are chromosomes?
A
Long strands of DNA. 23 pairs of chromosomes in a cell
5
Q
Gene
A
A short section of DNA that code for one polypeptide
6
Q
Allele
A
An alternative form of a gene.
7
Q
Locus
A
Location of a gene on a chromosome
8
Q
What are homologous chromosomes?
A
Two genetically similar chromosomes, one from each parent. Same structure but are not identical.
9
Q
What are the 3 things that genetic code is?
A
Series of triplet codes
Universal
Non-overlapping
10
Q
Degenerate DNA
A
A single amino acid can be coded for by more than one DNA triplet/codon.
11
Q
What does genetic code provide the instructions for?
A
Protein synthesis
12
Q
What is Protein synthesis a result of?
A
2 processes:
Transcription
Translation
13
Q
Process of transcription
A
DNA helicase breaks the hydrogen bonds between 2 strands of DNA leaving 1 template strand. Free RNA nucleotides join up to exposed bases on DNA template strand. Weak hydrogen bonds form between them. RNA polymerase resynthesises backbone of mRNA by causing strong chemical bonds to form. mRNA is spliced. Hydrogen bonds between pre-mRNA and DNA are broken and DNA strands join together again.
14
Q
What is splicing?
A
Pre-mRNA must be spliced before leaving the nucleus. Non-coding pieces of mRNA (introns) are removed. Only coding mRNA (exons) are left
15
Q
What is specific about a ribosome?
A
Have 2 subunits.
Larger top is tRNA binding site.
Smaller bottom is the mRNA binding site
The mRNA moves through the ribosome subunits
16
Q
Describe how translation leads to the production of a polypeptide (5 marks)
A
mRNA leaves the nucleus via the nuclear pores and enters the cytoplasm- it joins in between the 2 subunits of the ribosome
tRNA comes along with an amino acid and anti-codon. Anti-codon binds to complementary mRNA codon
Ribosome moves along to the next codon
Process of tRNA joining to mRNA repeats and amino acids join together using a peptide bonds
tRNA molecule moves away.
Process continues until a stop codon is reached
17
Q
Mutations
A
a random error in gene replication that leads to a change. Spontaneous
18
Q
Insertion
A
A base is inserted into the code and nucleotide added to the sequence
19
Q
Deletion
A
A nucleotide is lost from the DNA sequence
20
Q
Substitution
A
When one base is swapped for another
21
Q
effects of mutations on transcription?
A
The triplet codes are transcribed into mRNA so a change in triplet code changes the mRNA sequence
22
Q
Effects of mutation on translation?
A
Changes in mRNA changes amino acid order which changes the protein produced
23
Q
Effects of mutation on genetic diversity?
A
More mutation=increased variation
Can decrease if an advantageous allele is favoured
24
Q
Frame Shift
A
Every AA after the insertion or deletion will move one place
25
Mutagenic agent
A physical or chemical factor that changes genetic material and increases the frequency of a mutation occurring above natural rate
26
chromosomal mutation
Changes in the structure and number of whole chromosomes
27
2 types of chromosomal mutations
Polyploidy and non-disjunction
28
Polyploidy
Changes in number of whole chromosome. Cells have multiple sets of chromosomes
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Non-disjunction
Homologous pairs fail to separate during meiosis so chromosome distribution is unequal
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Mitosis Vs Meiosis- Role
Mitosis - growth/repair
Meiosis - gametes for sexual reproduction
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Mitosis Vs Meiosis- amount of cell division
Mitosis- 1
Meiosis- 2
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Mitosis Vs Meiosis- number of daughter cells
Mitosis: 2
Meiosis: 4
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Mitosis Vs Meiosis- genetic composition
Mitosis- diploid
Meiosis- haploid
34
Mitosis Vs Meiosis- similarity to parent cells
Mitosis- identical
Meiosis- not identical
35
What is meiosis?
a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
36
What happens during meiosis?
Meiosis 1- homologous pairs of chromosomes are separated. Two diploid cells are produced
Meiosis 2- sister chromatids are separated. Four haploid cells are produced
37
Genotype
genetic makeup of an organism
38
Phenotype
physical characteristics of an organism
39
Causes of genetic variation
sexual reproduction (meiosis) and mutations
40
How does meiosis result in genetic variation?
Crossing Over
Independent Assortment/Random Segregation
41
independent assortment
One of Mendel's principles that states that genes for different traits can segregate independently during the formation of gametes. When homologous pairs line up, they do so randomly so each combination is changed
42
crossing over
Process in which homologous chromosomes exchange portions of their chromatids during meiosis. Sections have different alleles
43
Genetic Diversity
The total number of different alleles in a population as a result of mutations/meiosis
44
Explain how a mutation results in a change in characteristics
mutation occurs
-> Changes the DNA/Triplet code causing mRNA change
-> Changes the amino acid brought by tRNA
->Changes the primary and therefore tertiary structure
->Changes protein formed and it's functions
->Increases genetic variation
45
Why is genetic diversity important?
Diverse gene pool gives a population more flexibility to survive in a changing environment. The more genetically diverse a population, the more ways it has to adapt. All genes may be the same but number of alleles may differ so genetic characteristics become vast
46
What does high genetic variation within a species mean?
large number of alleles
47
Advantages of high genetic diversity
Ability to adapt to a change in environment
More disease resistance within a population
Prevents extinction of wholes species
More availability of food and habitats
48
Disadvantages of high genetic diversity
Fewer organisms with characteristics suited for humans and fewer adapted organisms at a specific time
49
Natural selection
by Charles Darwin. Explanation as to why species have a wide variety of alleles- due to different reproductive successes that affect allele frequency within a gene pool
50
allele frequency
Number of times that an allele occurs in a gene pool
51
Gene pool
Combined genetic information (number of alleles) of all the members of a particular population
52
Differences between the reproductive success of individuals affect the allele frequency in a population, explain how. (6 marks)
Random allele mutation occurs.
This is advantageous for a proportion of the population.
They are more likely to reproduce because natural selection has enabled them to withstand certain conditions or environments.
They pass down the advantageous genes to offspring who will also be more likely to survive and reproduce due to adaptations.
This occurs at the expense of the less well adapted.
53
distribution curve
a graph that is constructed from the frequencies of the values of a variable
54
Normal distribution curve
a symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68 percent fall within one standard deviation of it) and fewer and fewer near the extremes.
55
Why are most traits normally selected?
most characteristics are the result of multiple genes and eacch gene is affected by the environment.
Change in environment= change in the mean
56
directional selection
Form of natural selection in which the entire curve moves; there has been a change in the environment causing mean to shift to one extreme
57
stabilising selection
a type of natural selection in which genetic diversity decreases as the population stabilises on a particular trait value. selection acts against both extremes.
58
Why is variation important?
The more variation within a species, the more likely it will survive and be able to adapt further
59
Species
A group of similar organisms that can breed/combine genes and produce fertile and living offspring.
60
Why do species become better adapted?
natural selection allows the further adaptation of species in 3 ways.
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Anatomical adaptations
Structural features of an organism's body that increase its chance of survival.
e.g. sharp teeth or certain coloured fur.
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physiological adaptations
A chemical or physical event that takes place in the body of an organism to support its ability to survive and reproduce.
e.g. a camel's hump getting hydrolysed to produce water
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behavioural adaptations
Ways an organism acts that increase its chance of survival
e.g. aggressive or protective behaviours
64
What is a courtship display?
an adaptation focused on improving an organisms reproductive successes by increasing likelihood of selection by a mate
65
examples of courtship displays
vocalisation, displays of strength or beauty, release of scents or chemicals, fighting or aggression
66
What must courtship displays do?
increase the reproductive success of an individual
67
how do courtship displays increase reproductive successes?
Enable an organism to recognise one of their own species- avoids crossbreeding which can create infertile offspring
Identifies if a mate is capable of breeding- prevents wasted energy and ensures a desired outcome
Forming pair bonds- ensures successful breeding and investment in raising offspring
Synchronised mating season- need to know they are in season and no energy will be wasted.
68
What is a classification?
Organising living organisms into groups through a hierarchy of specific characteristics.
69
Artificial classification
a method of classification based on analogous characteristics/what we can see
70
analogous characteristics
physical features that have the same function. could have very different ancestors
71
Phylogenetic classification
A type of classification that divides organisms into groups based on evolutionary relationships and homologous characteristics. It uses a hierarchy in which smaller groups are contained within larger groups, with no group overlap.
72
homologous structures
similar structures that related species have inherited from a common ancestor
73
Compare phylogenetic & artificial classification (4 marks)
AC: analogous characteristics, similar features, not based on evolution
PC: homologous characteristics, shared features derived from a common ancestor, based on evolutionary relationships
74
Carl Linnaeus
Father of taxonomy- proposed phylogenetic classification based on ancestry and evolutionary relationship
75
Key features of classification
arranges organisms into a hierachy, each group is called a taxon. From kingdom to species
76
hierarchy
smaller groups within larger groups, no overlap between groups
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Binomial name
Scientific name of an organism, the first part of which designates the genus and the second part of which designates the species. E.g. Homo sapiens
78
phylogenetic hierarchy
Life
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
(Let Donkey Kong Play Cards Over Four Gnomes Shirts)
79
Why do we no longer use phylogenetic classification?
Based on mostly observable characteristics, subjective and influenced by the environment. We can find more accurate results using modern technology.
80
Domains
Bacteria, Archaea, Eukarya
81
Archea
Unicellular, small, DNA and genes, no murein or membrane bound organelle
82
Bacteria
single-celled organisms that lack a nucleus; prokaryotes, free floating DNA, wall made from murein
83
Eukaryote
A cell that contains a nucleus and membrane bound organelles, DNA associated with histones,
84
What is a phylogenetic tree?
diagram that shows how species are related to each other through common ancestors/close relatives. Based on evolutionary history
85
Evaluate the use of external features when constructing phylogenetic classification (5 marks)
+: easier to observe- anyone can do it
Doesn't require any advanced equipment
-: patterns aren't always clear
Interpretations are subjective
Genes can be polygenetic
May be result of different environments not genes
86
How can genetic sequencing improve classification?
Genes can be compared and similarities can be identified. This is more accurate than observable characteristics
87
What makes up the characteristics of an organism?
DNA-> Protein Structure -> characteristics of an organism
88
Classification- DNA base sequence
Compare the order of nucleotides on the dna. Mutations lead to differences. More differences means fewer similarities so individuals are more distantly related
89
Classification- mRNA sequences
mRNA is complementary to DNA.
Differences in mRNA = dna differences
More differences means more distantly related
90
Classification- amino acid sequence in proteins
Differences in dna= diff in mRNA= differences in AA
UNLESS DEGENERATE
91
How can we study genetic diversity without sequencing a genome?
DNA hybridisation or Biochemical analysis
92
What is DNA hybridization?
Direct comparisons between the DNA sequences of different organisms based on knowledge of DNA structure
93
How does DNA hybridisation occur?
DNA is heated so double strands separates into two complementary single strands - denaturation
The DNA is labelled using radioactive markers or labels
it is cooled and the complementary bases on each strands recombine - anneal
in cooling, the strands can bind to one another if hydrogen bonds form between complementary base pairs
94
Which results of DNA hybridisation show similarities?
When you increase the temp, it should take a longer time to separate the 2 strands as
Higher temperature= more hydrogen bond= more similarities
95
Biodiversity
The range and variety of genes, species and habitats within a particular region
96
3 aspects of biodiversity
genetic diversity, species diversity, ecosystem diversity
97
genetic diversity
The variety of genes or alleles posed by the individuals that make up 1 species
98
species diversity
The number of different species and the number of individuals of each species within any 1 community
99
ecosystem diversity
The range of different habitats within a particular area
100
Abundance
The number of individuals of a specific species
101
Species richness
the number of species in a given area at any time
102
species diversity index
mathematical formula accounting for richness, abundance, and evenness. Suggested by Simpson
103
Simpson's Diversity Index
( N-(N-1) ) / ( total n (n-1) )
N = total number of organisms
n = number of individuals of each species
104
Ecosystem stability
The higher the biodiversity the more stable the environment. If there is low biodiversity one significant change may kill all organisms which causes the ecosystem to crash
105
Where do we study biodiversity?
In a field using quantitative methods to find abundance and distribution2 methods of studying biodiversity
106
2 methods of studying biodiversity
Random sampling
Systematic sampling
107
Quadrats
Comparison of two areas estimates a population size. A square grid. Can she frame quadrat or point quadrat
108
Describe how you would estimate the population of dandelions in a field (4 marks)
1. Random number generator=Random coordinates in a field
2.place quadrat
3.count number of organisms in sample
4.repeat at 10 coordinates
5.calc mean and times by area of field
109
Transect
Measure the species distribution
110
What is sampling bias?
Biased choices made by an investigator deliberately or unwillingly which makes the sample unrepresentative
111
What should you consider when using a quadrat?
The size, the number of sample quadrats, the position of each quadrat
112
Point quadrats
Frame containing a horizontal bar, long pins can be pushed through the bar, each species of plant that the pin touches is recorded
+:smaller organisms and smaller areas
-:tedious, hard to use and takes time
113
What is systematic sampling?
studying in an ordered sampling frame. studies distribution
studies:gradual change across a habitat, transition within communities and if zonation is present
114
types of transect
line and belt
115
Line transect
a sampling method involving counting of species that touch the transect. String or tape used
116
Belt transect
two parallel lines are marked along the ground and samples are taken of the area at specified points in between the lines.
117
Evaluation of belt transect
+more consistent and bigger sample= more represenation
+more data
+finds abundance and range
-could be more time consuming
118
Evaluation of line transect
+Quicker
+Easily shows species range along transect
+Clear view of how species change
-Harder to see range across a large range
-Less data collected
119
What are transects used for?
They show how the distribution changes across an area. Show trends or patterns
120
Using Transects - Method
1) Mark out a line in the area you want to study using a tape measure
2)Place quadrat at 0m and record species present
3)Repeat at equal intervals
4)Do the transect a few more times at similar locations and times so you can calculate the mean
121
What does scientific research entail?
Observation, Hypothesis, Experimentation, Results analysis, further research
122
Statistical testing
a mechanism for making quantitative decisions about a process
123
Hypothesis
Statistical tests can be used to prove or disprove a null hypothesis
124
Null hypothesis
the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.
125
alternative hypothesis
The hypothesis that states there is a difference between two or more sets of data.
126
Standard deviation
A statistical test. A measure of the width of the curve and indicates range. How much our data deviates from the mean
127
Why is SD useful?
Tells you how much data deviates from the mean and determines how likely the results are due to chance
128
correlation coefficient
a statistical index of the relationship between two things (from -1 to +1). Is there a significant correlation between 2 variables?
129
How do you analyse statistical tests?
use the calculated value and degrees of freedom. Compare calculated value with the critical value in the table. Must be more than critical value (at 0.05) for there to be a significant difference.
130
How do you calculate standard deviation?
Square root of the sum of measured value minus mean value squared divided by total number divided by 1
131
degrees of freedom
The number of individual scores that can vary without changing the sample mean. Statistically written as 'N-1' where N represents the number of subjects.
132
what does pearson correlation coefficient tell us?
if there is a significant difference, a relationship between 2 variables, if the correlation is positive or negative
133
When would we use a two sample t test?
when you are looking for differences between measurements from different samples
134
Steps to carry out a stats test
1. Null hypothesis
2. select appropriate stats test
3. carry out calculation
4. determine the degrees of freedom
5.Compare calculated value to critical value
6. higher= reject null hypothesis
