3.4 Genetic information, variation and relationships between organisms - Genetic Diversity and Adaptation Flashcards
What is the definition of haploid?
Haploid (n) = one copy of each chromosome
Haploid cells are produced during meiosis.
What is the definition of diploid?
Diploid (2n) = two copies of each chromosome
Diploid cells contain pairs of homologous chromosomes.
What are the two key processes that introduce genetic differences during meiosis?
- Independent segregation of homologous chromosomes
- Crossing over between homologous chromosomes
These processes occur during meiosis and contribute to genetic variation.
What is meiosis?
Meiosis is the type of cell division that creates genetically different gametes.
It involves two nuclear divisions.
How many nuclear divisions occur during meiosis?
Two nuclear divisions
This results in four haploid daughter cells.
What occurs during interphase before meiosis?
The DNA and organelles double
Interphase is a preparatory stage before cell division.
What are the stages of meiosis referred to?
Meiosis I and Meiosis II
Each stage includes prophase, metaphase, anaphase, telophase, and cytokinesis.
What is independent segregation?
The process where homologous chromosomes are distributed randomly into daughter cells during meiosis.
This contributes to genetic variation.
What is crossing over?
The exchange of genetic material between homologous chromosomes during meiosis.
This process results in new combinations of alleles.
How many haploid daughter cells are produced at the end of meiosis?
Four haploid daughter cells
Each daughter cell contains a unique set of genetic information.
True or False: Mitosis results in genetically different daughter cells.
False
Mitosis produces genetically identical daughter cells.
Fill in the blank: Genetic variation can be introduced during meiosis, _____, and the random fertilisation of gametes.
[mutations]
Mutations are changes in the DNA sequence that can lead to genetic diversity.
What is crossing over?
Crossing over occurs in meiosis I when homologous pairs line up opposite each other at the equator, causing chromatids to twist and break, leading to genetic recombination.
This process results in new combinations of alleles in the gametes.
What happens to chromatids during crossing over?
Parts of the chromatids can become twisted around each other, causing pairs to break and recombine with another chromatid.
This leads to genetic recombination.
What is independent segregation?
In meiosis I, homologous pairs of chromosomes line up randomly at the equator, leading to the random separation of paternal and maternal chromosomes into daughter cells.
This process contributes to genetic variation.
How is the number of possible combinations of chromosomes in daughter cells calculated?
The number of combinations is calculated using the formula 2^n, where n is the number of homologous pairs.
In humans, there are approximately 8,388,608 combinations of chromosomes.
What are gametes?
Gametes are reproductive cells that carry genetic information and are produced through meiosis.
They include sperm and eggs in animals.
Fill in the blank: Crossing over occurs in _______.
meiosis I
True or False: Independent segregation leads to genetic diversity.
True
What is the result of crossing over during meiosis?
New combinations of alleles in the gametes.
This enhances genetic variation among offspring.
What does the term ‘homologous pair’ refer to?
A pair of chromosomes, one from each parent, that are similar in shape, size, and genetic content.
What is a chromatid?
A chromatid is one half of a duplicated chromosome, which is connected to its sister chromatid at the centromere.
What is a mutation in a gene?
A change in the base sequence of the DNA
Gene mutations can occur randomly during DNA replication.
What increases the likelihood of gene mutations?
Exposure to mutagenic agents
Examples include high energy radiation (UV light), ionising radiation (gamma rays and X rays), and chemicals (carcinogens such as mustard gas and cigarette smoke).
What is a frameshift mutation?
A base deletion that changes all subsequent codons
This type of mutation is more harmful as multiple amino acids may be incorrectly coded for.
What is a base substitution mutation?
A mutation where one base is replaced by another
Example: TAC CCA AGT GGC changes to TAC ACA AGT GGC.
What does it mean if a base substitution is ‘silent’?
The new codon still codes for the same amino acid
This occurs because the genetic code is degenerate.
What is non-disjunction?
When chromosomes or chromatids do not split equally during anaphase
This can lead to mutations in the number of chromosomes.
What can cause chromosome mutations?
Spontaneous non-disjunction during meiosis
This occurs during the process of cell division.
Fill in the blank: A mutation caused by a change in the base sequence of DNA is known as a _______ mutation.
gene
True or False: Mutagenic agents can include UV light and cigarette smoke.
True
List three types of mutations mentioned.
- Frameshift
- Base substitution
- Non-disjunction
What is genetic variation?
Genetic variation can be introduced in a variety of ways such as: during meiosis, mutations and the random fertilisation of gametes.
Genetic variation is essential for evolution and adaptation in populations.
What is meiosis?
Meiosis is the type of cell division that creates genetically different gametes.
It involves two nuclear divisions resulting in four haploid daughter cells.
What is a haploid cell?
Haploid (n) = one copy of each chromosome.
This is in contrast to diploid cells, which have two copies of each chromosome.
What is a diploid cell?
Diploid (2n) = two copies of each chromosome.
Diploid cells are typical of somatic cells in most organisms.
What are the two key processes that introduce genetic differences during meiosis?
- Independent segregation of homologous chromosomes
- Crossing over between homologous chromosomes
These processes contribute significantly to genetic diversity.
What occurs during interphase before meiosis?
During interphase, the DNA and organelles double.
This preparation is crucial for successful cell division.
What are the stages of meiosis?
Both meiosis I and meiosis II include prophase, metaphase, anaphase, telophase and cytokinesis.
Each stage has specific events that lead to the separation of chromosomes.
Fill in the blank: Meiosis involves _______ nuclear divisions.
two
This is what distinguishes meiosis from mitosis.
True or False: Meiosis results in diploid daughter cells.
False
Meiosis results in haploid daughter cells.
What occurs during crossing over in meiosis I?
Parts of the chromatids can become twisted around each other
This process leads to genetic recombination.
What is the result of crossing over?
New combinations of alleles in the gametes
This is a key mechanism for genetic diversity.
What happens at the equator during meiosis I?
Homologous pairs of chromosomes line up opposite each other
This arrangement is crucial for independent segregation.
Define independent segregation.
Random separation of paternal and maternal chromosomes from each homologous pair
This leads to genetic variation in daughter cells.
How is the number of possible combinations of chromosomes in daughter cells calculated?
Using the formula 2^n, where n is the number of homologous pairs
This calculation shows the potential genetic diversity.
Approximately how many combinations of chromosomes are there in humans?
8,388,608 combinations
This figure illustrates the complexity of human genetic variation.
What is a homologous pair?
A pair of chromosomes that are similar in shape, size, and genetic content
Homologous pairs consist of one chromosome from each parent.
What is a chromatid?
One half of a duplicated chromosome
Chromatids are joined together at the centromere before cell division.
Fill in the blank: The process that results in new combinations of alleles is called _______.
genetic recombination
This occurs during crossing over in meiosis.
True or False: Independent assortment occurs during meiosis II.
False
Independent assortment occurs during meiosis I.
What is a gene mutation?
A change in the base sequence of the DNA.
What factors can increase the likelihood of gene mutations?
Exposure to mutagenic agents such as:
* High energy radiation (UV light)
* Ionising radiation (gamma rays and X rays)
* Chemicals (carcinogens like mustard gas and cigarette smoke)
What is a frameshift mutation?
A mutation where the removal of one base changes all of the subsequent codons.
What are the two types of base mutations?
Base deletion and base substitution.
What is a base substitution mutation?
A mutation where one base is replaced by a different one.
What is a silent mutation?
A base substitution that results in the same amino acid being coded.
What results from a base deletion mutation?
A frameshift, leading to incorrect coding of multiple amino acids.
What is non-disjunction?
When chromosomes or chromatids do not split equally during anaphase.
What can cause chromosome mutations?
Spontaneous non-disjunction during meiosis.
Fill in the blank: A mutation in the number of chromosomes can arise spontaneously by ______ during meiosis.
chromosome non-disjunction
True or False: All gene mutations are harmful.
False
What is polyploidy?
Changes in whole sets of chromosomes when organisms have three or more sets of chromosomes rather than the usual two.
What is aneuploidy?
Changes in the number of individual chromosomes.
What is non-disjunction?
A failure of chromosomes to separate equally during cell division.
What are chromosome mutations?
Changes in the number or structure of whole chromosomes.
In which organisms does polyploidy mainly occur?
Plants.
What occurs during non-disjunction in meiosis?
All chromosomes fail to separate equally.
What is the result of normal division in meiosis II?
Chromatids separate equally.
What type of gamete is produced from a diploid organism?
2n gamete.
Fill in the blank: Changes in whole sets of chromosomes occur when organisms have _______ or more sets of chromosomes.
three.
True or False: Polyploidy is a condition that can only occur in animals.
False.
What is a triploid organism?
An organism with three sets of chromosomes (3N).
How many homologous chromosomes are present in polyploid organisms?
Three or more.
What happens to the number of chromosomes in a gamete during non-disjunction?
No chromosomes may be present in the gamete.
Fill in the blank: Polyploidy mainly occurs in _______.
plants.
What is aneuploidy?
A change in the number of individual chromosomes.
Aneuploidy can result in conditions such as Down’s syndrome.
What is non-disjunction?
The failure of homologous pairs of chromosomes to separate during meiosis.
This usually results in gametes having one more or one fewer chromosome.
What condition is caused by three copies of chromosome 21?
Down’s syndrome.
This is an example of aneuploidy.
What happens during non-disjunction in meiosis 1?
One chromosome does not separate equally.
This leads to gametes with abnormal chromosome numbers.
What is the result of fertilization involving a gamete with an extra chromosome?
The resultant zygote will have more chromosomes than normal in all their body cells.
This can lead to various genetic disorders.
What is a haploid gamete?
A gamete containing one set of chromosomes (n).
Haploid gametes are produced during meiosis.
Fill in the blank: Non-disjunction usually results in a gamete having one more or one fewer _______.
chromosome.
True or False: Normal division occurs during meiosis 2.
True.
In meiosis 2, chromatids separate equally.
What is the chromosome composition of a diploid zygote formed from a gamete with one additional chromosome?
2n + 1.
This indicates one extra chromosome in the diploid state.
What is the chromosome composition of a diploid zygote formed from a gamete missing one chromosome?
2n - 1.
This indicates one fewer chromosome in the diploid state.
What is the process of meiosis?
Meiosis involves two nuclear divisions resulting in four haploid daughter cells that are all genetically different.
How does meiosis introduce variation?
Variation is introduced via independent segregation of homologous chromosomes and crossing over between homologous chromosomes.
What are gene mutations caused by?
Gene mutations are due to random copying errors in DNA replication.
What causes chromosome mutations?
Chromosome mutations are due to non-disjunction in meiosis.
How are genetic diversity, natural selection, and evolution linked?
Genetic diversity introduced by meiosis and mutations is linked to natural selection and evolution.
What is the relationship between gene mutations and cancer?
Gene mutations link to cancer through tumor suppressor genes and oncogenes.
Gene mutations are linked to _______.
[DNA replication]
What is genetic diversity?
The number of different alleles in a population.
What enables natural selection to occur?
Genetic diversity of a population.
Define gene pool.
All the genes and alleles in a population at a particular time.
What is allele frequency?
The proportion of organisms within the population carrying a particular allele.
What is natural selection?
The process that leads to evolution in populations.
What is evolution?
The change in allele frequency over many generations in a population.
What is a result of natural selection?
Species becoming better adapted to their environment.
Give an example of antibiotic resistance.
Bacteria developing resistance to antibiotics.
What are the three types of adaptations?
- Anatomical
- Physiological
- Behavioural
Give an example of an anatomical adaptation.
Spikes on a hedgehog.
Give an example of a physiological adaptation.
Hedgehogs hibernating and slowing their metabolic reactions in winter.
Give an example of a behavioural adaptation.
Hedgehogs curl up when in danger.
What are the steps of natural selection? List them.
- Random mutations occur within the population.
- This introduces genetic variation to the population.
- Some mutations are harmful, but some provide an advantage.
- The new allele provides a reproductive selective advantage.
- Over many generations, there will be an increase in the frequency of the advantageous allele.
True or False: Natural selection can lead to species that are better adapted to their environment.
True
Fill in the blank: The change in allele frequency in a population is ______.
[evolution]
What is directional selection?
Directional selection is when one of the extreme traits has a selective advantage.
What triggers directional selection?
A change in the environment triggers directional selection.
What happens to the modal trait during directional selection?
The modal trait changes.
Provide an example of directional selection.
Antibiotic resistance in bacteria.
How does antibiotic resistance illustrate directional selection?
A random mutation creates an allele that provides resistance to antibiotics. Those with the resistance allele survive when exposed to the antibiotic, leading to the allele being passed on over generations.
What is the process that leads to evolution?
Natural selection is the process that leads to evolution.
How is genetic diversity introduced?
Genetic diversity is introduced by meiosis and mutations.
What links the structure and function of DNA to natural selection?
The structure and function of DNA links to natural selection.
True or False: Directional selection occurs when there is no change in the environment.
False.
Fill in the blank: _______ is an example of directional selection in bacteria.
Antibiotic resistance
What is courtship behaviour?
The different behaviours that animals demonstrate to attract a mate.
What is a species?
A group of similar organisms that can breed to make fertile offspring.
What must species do for survival?
Reproduce and pass on advantageous alleles.
When do animals display courtship behaviours?
When they are sexually mature and fertile.
What does synchronising mating behaviour help with?
It helps animals mate when the female is releasing eggs.
How does courtship behaviour increase the likelihood of successful mating?
It enables individuals to recognise members of the same species and opposite sex.
What is one benefit of courtship behaviour for offspring?
It helps form a pair bond between the parents.
How does forming a pair bond benefit offspring survival?
Parents are more likely to stay together and raise the offspring as a team.
What can females do during courtship to ensure better offspring?
Select a strong and healthy mate.
What are some examples of courtship behaviours?
- Sequence of dance moves
- Certain sounds
- Release of pheromones
- Displays of feathers
What is the binomial system?
A universal naming system where species are named after their genus and species.
Why is the binomial system important?
It prevents errors in estimates of the number of individuals of different species.
Provide an example of a species using the binomial system.
Homo sapiens for humans.
What is phylogenetic classification?
Arranges species into groups according to their evolutionary origins and relationships.
What does phylogeny tell us?
Who’s related to whom and how closely related they are.
What is a common ancestor?
An ancestral species from which multiple species have evolved.
What is a phylogenetic tree?
A diagram that represents evolutionary relationships among species.
What are mutations?
Changes in the DNA sequence that can accumulate over time.
How does DNA base sequence help in classification?
It allows comparison of common genes to measure how closely related organisms are.
What happens to DNA similarities as species become more distantly related?
Fewer similarities are usually observed.
What is compared to determine the relatedness of species?
The sequence of amino acids in the polypeptide chain of proteins.
What is the common protein used for comparison between species?
Cytochrome C.
Where is cytochrome C found?
In the mitochondria.
What does classification based on physical and biochemical similarities represent?
An example of a hierarchy.
What is a hierarchy in classification?
Smaller groups arranged within larger groups with no overlap between groups.
List the main levels of classification.
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
True or False: Classification systems allow for overlap between groups.
False.
Fill in the blank: The accuracy of classification and phylogeny is improving due to advances in _______.
[immunology and genome sequencing].
What is the definition of a taxon?
A taxon is a level in the biological classification hierarchy.
What is the plural of taxon?
Taxa
List the levels of the classification hierarchy in order.
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Why do we need a system to organize species?
To aid in understanding relationships between organisms and track changes within species.
What ensures successful mating in organisms?
Courtship behavior
What does phylogenetic classification attempt to do?
Arrange species into groups based on their evolutionary origins and relationships.
True or False: Courtship rituals are genetically determined.
True
Fill in the blank: If there is a mutation in the gene determining the ritual, the organism’s ritual is not recognized and they cannot mate. This leads to _______.
sympatric speciation
What is the significance of mutations in courtship rituals?
They can lead to the inability to mate due to unrecognized rituals.
What is biodiversity?
Biodiversity refers to the variety of life in a particular habitat or ecosystem.
It encompasses different meanings including species diversity, genetic diversity, and ecosystem diversity.
What does species diversity measure?
The number of different species and individuals within each species in a community.
AQA focuses on species diversity as a key concept.
Define genetic diversity.
The variety of genes amongst all the individuals in a population of one species.
Genetic diversity is crucial for the adaptability and survival of species.
What is ecosystem diversity?
The range of different habitats within a particular area.
Ecosystem diversity can be assessed from local to global scales.
Define species richness.
The number of different species in a particular area at the same time.
Species richness is a component of species diversity.
What is a habitat?
The range of physical, biological, and environmental factors in which a species can live.
Habitats can vary significantly in size and complexity.
True or False: Low biodiversity is always a cause for concern.
False.
Low biodiversity can be natural in certain ecosystems like deserts and arctic regions.
Why is a loss in biodiversity concerning?
It indicates a change causing the loss of habitats, leading to death and extinction of species.
Biodiversity loss can disrupt ecosystems and their functions.
What is species richness?
A measure of the number of different species in a community.
A community is defined as all the organisms living in a particular area at a particular time.
Does species richness account for population size?
No, it only accounts for how many different species there are.
Population size of each species is not considered in species richness.
What human activity is often a cause for concern regarding biodiversity?
Farming.
Farming is necessary for food production but can negatively impact biodiversity.
List four farming practices that reduce biodiversity.
- Destruction of hedgerows
- Selective breeding
- Monocultures
- Over-grazing
- Filling in ponds and draining wetlands
These practices improve food production efficiency but harm biodiversity.
How do farming techniques impact habitats?
They remove many habitats, which also removes food sources for animals.
This includes the removal of forests, grasslands, and hedgerows.
What is the challenge faced by ecologists regarding farming and biodiversity?
To find a balance between conservation and farming.
Conservation measures are essential but should not compromise food production.
What is the index of diversity?
A measure of species diversity that calculates the relationship between the number of species in a community and the number of individuals in each species.
This index helps assess the overall biodiversity within a community.
What is Simpson’s index of diversity formula?
D = N(N - 1) / 2 n(n - 1)
Where N is the total number of organisms of all species, n is the population size of one species, and D is the index of diversity.
What does a larger value of D indicate?
Greater species diversity
Simpson’s index of diversity typically ranges from 1 to 10.
What is the total number of organisms (N) in the given example?
25
This is the sum of the number of each species: 6 (A) + 3 (B) + 12 (C) + 4 (D).
What is the genetic diversity of a population?
Measure of how many different alleles there are for each gene
Genetic diversity can be assessed through observable characteristics or genetic sequences.
What is one method of estimating genetic diversity?
Counting observable characteristics
For example, counting different hair colors can indicate the number of different alleles for that trait.
Why are samples taken when measuring variation within a population?
It is too time-consuming and potentially impossible to record data on every individual
Sampling allows for statistical analysis of a representative subset of the population.
What is required to ensure a sample is representative of a population?
A large sample taken randomly
Random sampling helps to avoid bias in the data collected.
What can be calculated from a large sample in a population?
A mean and conduct statistical tests
This helps determine if observed differences or correlations are significant.
What does the term ‘alleles’ refer to?
Different versions of a gene
Alleles contribute to genetic diversity within a population.
What are gene technologies?
Techniques used to analyze and manipulate genetic material
These technologies provide more accurate measurements of genetic diversity.
Fill in the blank: The formula for Simpson’s index of diversity is D = N(N - 1) / _______.
2 n(n - 1)
This formula helps quantify biodiversity in a given sample.
What are the two indicators of biodiversity?
Species diversity and species richness
Species diversity refers to the variety of species within a particular area, while species richness refers to the number of different species present.
What can be used to measure biodiversity?
The index of diversity
This index takes into account the number of species and the number of individuals within each species.
What does genetic diversity measure?
The number of different alleles in a population or community
Genetic diversity is crucial for the adaptability and resilience of species.
What is a consequence of the loss of species and biodiversity?
Removal of habitat and food sources for organisms
This can lead to ecosystem instability and loss of species.
How is genetic diversity linked to DNA?
It links to DNA and chromosome structure
Genetic diversity is reflected in the variation of DNA sequences and chromosome configurations.
What biological processes are linked to genetic diversity?
Mutations, meiosis, and natural selection
These processes contribute to the variation in genetic material within populations.
How does genetic diversity relate to speciation?
It links to speciation and inheritance
Genetic diversity is essential for the evolution of new species over time.
What environmental factors influence biodiversity?
Nutrient cycles and succession
Generally, less harsh environments support greater biodiversity.
