Genetic information, variation and relationships Flashcards
(86 cards)
1
Q
What type of DNA do eukaryotic cells contain?
A
Linear DNA molecules that exist as chromosomes
2
Q
Is linear DNA associated with proteins?
A
Yes
3
Q
What are histone proteins?
A
Histones are DNA-binding proteins. Strands of DNA wrap around histones to form a structure called a nucleosome. A chain of nucleosomes is called chromatin.
4
Q
What is a gene?
A
A sequence of DNA bases that codes for either a polypeptide or functional RNA
5
Q
What does the sequence of amino acids in a polypeptide form?
A
Primary structure of a protein
6
Q
What is a triplet/codon?
A
Three bases in a gene
7
Q
What do genes code for that don’t code for a polypeptide code?
A
Functional RNA
8
Q
What is functional RNA?
A
RNA molecules other than mRNA, which perform special tasks during protein synthesis
9
Q
What is a genome?
A
The complete set of genes in a cell
10
Q
What is a proteome?
A
The full range of proteins that a cell is able to produce
11
Q
What are introns?
A
Genes that don’t code for amino acids
12
Q
What are exons?
A
Parts of the gene that do code for amino acids
13
Q
What is an allele?
A
A gene that exists in more than one form
14
Q
What are homologous pairs?
A
Pairs of matching chromosomes
15
Q
What is a locus?
A
The specific position of the gene on the chromosome
16
Q
What are the two stages of protein synthesis?
A
Transcription - where DNA code is copied into mRNA
Translation - where mRNA joins with a ribosome and the code it carries is used to synthesise a protein
17
Q
What is mRNA?
A
Messenger RNA
Made during transcription
Carries the genetic code from the DNA to the ribosomes, where it’s used to make a protein during translation
mRNA is a single polynucleotide strand
In mRNA, groups of three adjacent bases are called codons
18
Q
What is tRNA?
A
Transfer RNA
Involved in translation
Carries the amino acids that are used to make proteins to the ribosomes
tRNA is a single polynucleotide strand that’s folded into a clover shape
Hydrogen bonds between specific base pairs hold the molecule in this shape
Every tRNA molecule has a specific sequence of three bases at one end called an anticodon
Also has an amino acid binding site at the other end
19
Q
Describe how mRNA is formed by transcription in eukaryotes?
A
Hydrogen bonds between DNA bases break
Only one DNA strand acts as a template
Free RNA nucleotides align by complementary base pairing
In RNA uracil base pairs with adenine
RNA polymerase joins adjacent RNA nucleotides
By phosphodiester bonds between adjacent nucleotides
Pre-mRNA is spliced to form mRNA
20
Q
Describe how mRNA is produced from an exposed template strand of DNA
A
Free RNA nucleotides form complementary base pairs
Phosphodiester bonds form
By action of RNA polymerase
21
Q
Describe how a polypeptide is formed by translation of mRNA
A
mRNA attaches to ribosomes
tRNA anticodons bind to complementary mRNA codons
tRNA brings a specific amino acid
Amino acids join by peptide bonds
Amino acids join together with the use of ATP
tRNA released after amino acid joined to polypeptide
The ribosome moves along the mRNA to form the polypeptide
22
Q
Describe the role of a ribosome in the production of a polypeptide
A
mRNA binds to ribosome
Two codons/binding sites
Allows tRNA with anticodons to bind
Catalyses formation of peptide bond between amino acids held by tRNA molecules
Moves along mRNA to the next codon
23
Q
Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation
A
tRNA brings specific amino acid to ribosome
Anticodon on tRNA binds to codon on mRNA
Amino acids join by condensation reaction using ATP
24
Q
What is splicing?
A
Removing introns from pre-mRNA to form mRNA
25
What is the genetic code?
Sequence of base triplets in mRNA which code for specific amino acids
26
What three things is the genetic code?
Non-overlapping
Degenerate
Universal
27
How is the genetic code non-overlapping?
Each nucleotide base pair in a DNA or RNA sequence is part of only one codon and is not shared between adjacent codons
28
How is the genetic code degenerate?
More possible combinations of triplets than there are amino acids (20 amino acids but 64 possible triplets)
Some amino acids are coded for by more than one base triplet
29
How is the genetic code universal?
The same specific base triplets code for the same amino acids in all living things
30
What is diploid formula of chromosomes?
2n
31
What is the diploid number for humans?
46
32
What is the haploid formula?
n
33
What number of chromosomes do gametes have?
Haploid
34
What does random fertilisation produce?
Zygotes with different combinations of chromosomes to both parents
35
What does the mixing of genetic material in sexual reproduction increase?
Genetic diversity
36
Describe the process of meiosis
1. DNA unravels and replicates so there are two copies of each chromosome called chromatids
2. The DNA condenses to form double-armed chromosomes, each made from two sister chromatids. The sister chromatids are joined at the centromere
3. Meiosis I - the chromosomes arrange themselves into homologous pairs
4. These homologous pairs are then separated, halving the chromosome number
5. Meiosis II - the pairs of sister chromatids that made up each chromosome are separated
6. Four haploid cells that are genetically different from each other are produced
37
What are the two main events during meiosis that lead to genetic variation?
Crossing over of chromatids
Independent segregation of chromomsomes
38
What is crossing over of chromatids?
During meiosis I, homologous chromosomes come together and pair up
The chromatids twist around each other and bits of chromatids swap over
The chromatids still contain the same genes but now have different combinations of alleles
The crossing over of chromatids in meiosis I means that each of the four daughter cells formed from meiosis II contain chromatids with different alleles
39
What is independent segregation of chromosomes?
Each homologous pair of chromosomes in your cells is made up of one chromosome from mum and one from dad
When the homologous pairs are separated during meiosis I, it's completely random which chromosome from each pair ends up in which daughter cell
So the four daughter cells produced by meiosis have completely different combinations of those maternal and paternal chromosomes
This shuffling of chromosomes leads to genetic variation in any potential offspring
40
What is a substitution mutation?
One base is substituted with another
41
What is a deletion mutation?
One base is deleted
42
What are some types of mutagenic agents?
UV radiation
Ionising radiation
Some chemicals
Some viruses
43
What do chromosome mutations lead to?
Inherited conditions because the errors are present in the gametes
44
What is genetic diversity?
Number of different alleles of genes in a species or population
45
What does a large number of alleles in a population mean?
Large variety of different characteristics and a high genetic diversity
46
What does a low genetic diversity mean?
Might not be able to adapt to a change in the environment and the whole population could be wiped out by a single event
47
What can genetic diversity within a population be increased by?
-Mutations in the DNA forming new alleles. Some of these can be advantageous, whilst other lead to problems
-Different alleles being introduced into a population when individuals from another population migrate into it and reproduce. This is known as gene flow
48
What are genetic bottlenecks?
An event that causes a big reduction in a population, e.g. when a large number of organisms within a population die before reproducing
This reduces number of different alleles in a gene pool and so reduces genetic diversity
The survivors reproduce and a larger population is created from a few individuals
49
What is the founder effect?
Describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool
50
What can the founder effect be a result of?
Migration leading to geographical separation or if a new colony is separated from the original population for another reason, such as religion
51
What is natural selection?
Individuals with advantageous traits are more likely to survive and reproduce, leading to the increased frequency of those traits in future generations, driving evolution
52
How does natural selection work?
1. There's differential reproductive success in a population - individuals that have an allele that increases their chances of survival are more likely to survive, reproduce and pass of their genes, than individuals than the less advantageous alleles
2. This means that a greater proportion of the next generation inherits the beneficial allele
3. They, in turn, are more likely to survive, reproduce and pass on their genes
4. So the frequency of the beneficial allele in the population increases from generation to generation
5. Over generations this leads to evolution as the advantageous alleles become more common in the population
53
What is evolution?
Gradual change in species over time
54
What are the three types of adaptations?
Behavioural
Physiological
Anatomical
55
What are behavioural adaptations? Give two examples
Ways in which an organism acts that increase its chance of survival
- Possums play dead - if they're being threatened by a predator they play dead to escape attack. This increases their chance of survival
-Scorpions dance before mating - this makes sure they attract a mate of the same species, increasing the likelihood of successful mating
56
What are physiological adaptations? Give two examples
Processes inside an organism's body that increase its change of survival
-Brown bears hibernate - they lower their metabolism over winter. This conserves energy, so they don't need to look for food in the months when it's scarce - increasing their chance of survival
-Some bacteria produce antibodies - these kill other species of bacteria in the area. This means there's less competition, so they're more likely to survive
57
What are behavioural adaptations? Give two examples
Structural features of an organism's body that increase its chance of survival
-Otters have a streamlined shape - making it easier to glide through the water. This makes it easier for them to catch prey and escape predators, increasing their chances of survival
-Whales have a thick layer of blubber - this helps to keep them warm in the cold sea. This increases their chances of survival in places where their food is found
58
What is directional selection?
Where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce. This could be in response to an environmental change
59
What is stabilising selection?
Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
Occurs when the environment isn't changing, and it reduces the range of possible characteristics
60
What is the method for testing the effects of antibiotics?
1. Bacteria will have been grown in liquid broth
2. Take a wire inoculation loop that has been sterilised in a Bunsen burner flame and use it to transfer the bacteria from the broth to ana gar plate. Spread bacteria over plate using loop
3. Place sterile paper discs soaked with different antibiotics spaced apart on plate. Various concentrations of antibiotics should be used. Add negative control disc soaked only in sterile water
4. Tape a lid onto the Petri dish, invert, and incubate the plate at about 25C for 48 hours. This allows bacteria to grow. Anywhere bacteria can't grow is the inhibition zone
5. Size of inhibitions zone tells how well an antibiotic works. Larger zone = more bacteria were inhibited from growing
61
What are the aseptic techniques used to prevent contamination of cultures?
-Disinfect work surfaces before you start work to minimise contamination. Disinfect them again once you've finished
-Work near a Bunsen flame. Hot air rises, so any microbes in the air should be drawn away from your culture
-Sterilise the wire inoculation loop before and after each use by passing it through a hot Bunsen burner flame for 5 seconds. This will kill any microbes on the loop
-Briefly flame the neck of the glass container of broth just after it's been opened and just before it's closed - this causes air to move out of the container, preventing unwanted organisms from falling in
-Sterilise all glassware before and after use, e.g. in an autoclave
62
What is phylogeny?
Study of evolutionary history of groups of organisms
Tells us who's related to whom and how closely related they are
63
What is taxonomy?
Science of classification
Involves naming organisms and organising them into groups
Makes it easier to identify and study them
64
What are taxa? What is a taxon
Taxa: the eight groups of taxonomy used to classify organisms
Taxon: Each group
65
How are the groups in taxonomy arranged?
In a hierarchy with the largest groups at the top and smallest groups at the bottom
66
What are the taxonomy groups?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Dry King Prawns Cooked On Fat Greasy Sausages
67
What is the binomial system?
The nomenclature used for classification
All organisms are given one internationally accepted scientific name in Latin that has two parts
The first part of the name is the genus name and has a capital letter
The second part is the species name and begins with a lower case letter
68
What is courtship behaviour?
Carried out by organisms to attract a mate of the right species
69
Give three examples of simple courtship behaviours?
- Releasing a chemical - e.g. male bumble bees produce chemicals called pheromones to attract female bumble bees to their territory
- Using sound - e.g. male red deer make a roaring noise to attract a mate
- Visual displays - e.g. the great tit will attract a male by puffing out its chest to show off its black stripe
70
Give three examples of complex courtship behaviours?
- Dancing - e.g. blue-footed boobies perform a complex dance which involves lifting up their feet to show off the blue colour
- Building - e.g. bowerbirds construct bowers (shelters) made of leaves, twigs, flowers, shells, stones and whatever else the male can find
71
How is courtship behaviour being species specific beneficial?
-Allows member of same species to recognise each other
-Prevents interbreeding
-Makes reproduction more successful
72
What three technologies are useful for clarifying evolutionary relationships and how?
- Genome sequencing: Advances in genome sequencing have meant that the entire base sequence of one organism's DNA can be determined. The DNA base sequence of one organism can be compared to the DNA base sequence of another organism, to see how closely related they are
- Comparing amino acid sequence: Proteins are made of amino acids. The sequence of amino acids in a protein is coded for by the base sequence in DNA. Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins
-Immunological comparisons: Similar proteins will also bind the same antibodies
73
What are the causes of variation?
- Genetic factors. Different species have different genes, which causes variation between species. Individuals of the same species have the same genes but different alleles
- Variation within a species can also be cause by differences in the environment e.g. climate, food, lifestyle
- Most variation within a species is caused by a combination of genetic and environmental factors. e.g. genes determine how tall an organism can grow, but nutrient availability affects how tall the organism actually grows
74
Why is random sampling used?
To ensure data isn't biased
75
How could you obtain random samples?
Pick random sites by diving the field into a grid and using a random number generator to select coordinates
76
What is the formula for finding the mean?
Total of all values in data / number of values in data
77
What is standard deviation?
Tells how much the values in a sample vary
It's a measure of the spread of values about the mean
78
What is biodiversity?
The variety of living organisms in an area
79
What is a habitat?
The place where an organism lives
80
What is a community?
All the populations of different species in a habitat
81
What is local diversity?
The variety of different species in a small habitat that is local
82
What is global diversity?
The variety of species on Earth
Estimates put the total number of species on Earth at about 8.7 million
83
What is species richness?
A measure of the number of different species in a community - which makes it a simple measure of biodiversity
84
How can species richness be worked out?
Taking random samples of a community and counting the number of different species
85
What is index of diversity?
d = (N(N-1))/(Σn(n-1))
N = total number of organisms of all species
n = total number of organisms of one species
86
What are the agricultural methods of reducing biodiversity?
- Woodland clearance is done to increase the area of farmland. It directly reduces the number of trees and sometimes number of different tree species. It also destroys habitats, so some species could lose their shelter and food source. This means that species will die or be forced to migrate to another suitable area, further reducing biodiversity
- Hedgerow removal is also done to increase the area of farmland by turning lots of small fields into fewer large fields. This reduces biodiversity for the same reasons as woodland clearance
- Pesticides are chemicals that kill organisms that feed on crops. This reduces diversity by directly killing the pests. Also, any species that feed on the pests will lose a food source, so their number could decrease too
- Herbicides are chemicals that kill unwanted plants (weeds). This reduces plant diversity and could reduce the number of organisms that feed on the weeds
- Monoculture is when farmers have fields containing only one type of plant. A single type of plant reduces biodiversity directly and will support fewer organisms, which further reduces biodiversity
