Inheritance, Variation & Evolution Flashcards
What is mitosis?
A type of nuclear division that gives rise to cells that are genetically identical.
It is used for growth, repair of damaged tissues, replacement of cells, and asexual reproduction.
What is meiosis?
A type of nuclear division that gives rise to cells that are genetically different, used to produce gametes (sex cells).
It results in genetically diverse offspring.
Define sexual reproduction.
A process involving the fusion of the nuclei of two gametes to form a zygote, producing genetically different offspring.
What are the gametes of animals?
Sperm cells and egg cells.
What is fertilisation?
The fusion of gamete nuclei, leading to genetic variation in offspring.
Define asexual reproduction.
A process resulting in genetically identical offspring from one parent without the involvement of gametes or fertilisation.
What type of cell division is involved in asexual reproduction?
Mitosis.
What is a haploid cell?
A cell that has half the normal number of chromosomes.
What is the importance of meiosis?
Produces gametes and increases genetic variation of offspring.
What happens when male and female gametes fuse?
They form a zygote, restoring the normal number of chromosomes.
What is cell differentiation?
The process of cells becoming specialised to perform particular functions.
List advantages of sexual reproduction.
- Increases genetic variation
- Species can adapt to new environments
- Disease less likely to affect the population
- Allows for selective breeding.
List disadvantages of sexual reproduction.
- Takes time and energy to find mates
- Difficult for isolated members to reproduce.
List advantages of asexual reproduction.
- Rapid population increase when conditions are right
- Exploits suitable environments quickly
- More time and energy-efficient.
List disadvantages of asexual reproduction.
- Limited genetic variation
- Vulnerable to changes in conditions
- Disease affects the whole population.
What is the genome?
The entire set of genetic material of an organism.
What is DNA?
Deoxyribonucleic acid, the molecule containing instructions for the growth and development of all organisms.
What are genes?
Short lengths of DNA found on chromosomes that code for proteins.
What is the Human Genome Project?
An international collaborative effort to determine the DNA sequence of the entire human genome.
What are nucleotides?
The individual subunits of DNA, each consisting of a sugar, phosphate group, and one of four bases.
What are the four bases of DNA?
- Adenine (A)
- Cytosine (C)
- Thymine (T)
- Guanine (G)
What is complementary base pairing?
The pairing of bases in DNA: Adenine with Thymine (A-T) and Cytosine with Guanine (C-G).
What does a sequence of three bases in DNA code for?
A particular amino acid.
What is the role of ribosomes in protein synthesis?
Ribosomes read the mRNA code and assemble amino acids into proteins.
What is the function of enzymes?
Proteins that act as biological catalysts to speed up chemical reactions.
What is a structural protein?
Proteins that provide structure, such as collagen found in skin cells.
Fill in the blank: The process of cells becoming specialised is known as _______.
cell differentiation.
True or False: Asexual reproduction results in offspring that are genetically different from the parent.
False.
What is the function of enzymes?
Enzymes are proteins that act as biological catalysts to speed up chemical reactions occurring in the body
Example: maltase is an enzyme that breaks down maltose into glucose.
What role do hormones play in the body?
Hormones are proteins that carry messages around the body
Example: testosterone plays an important role in male reproductive system development.
What are structural proteins?
Structural proteins provide structure and are physically strong
Example: collagen strengthens connective tissues like ligaments and cartilage.
Define mutations.
Mutations are random changes that occur in the sequence of DNA bases in a gene or a chromosome.
How often do mutations occur?
Mutations occur continuously.
What is the effect of mutations on proteins?
Mutations in a gene can sometimes lead to a change in the protein that the gene codes for.
What are insertion mutations?
Insertion mutations involve a new base being randomly inserted into the DNA sequence.
What is the effect of insertion mutations?
They change the amino acid coded for by the group of three bases in which the mutation occurs.
What are deletion mutations?
Deletion mutations involve a base being randomly deleted from the DNA sequence.
What is the effect of deletion mutations?
They change the amino acid coded for by the group of three bases in which the mutation occurs.
What are substitution mutations?
Substitution mutations involve a base in the DNA sequence being swapped for a different base.
How do substitution mutations differ from insertion and deletion mutations?
Substitution mutations only change the amino acid for the group of three bases in which the mutation occurs and do not have a knock-on effect.
What is the impact of most mutations on proteins?
Most mutations do not alter the protein or only alter it slightly so that its appearance or function is not changed.
What is gene switching?
Gene switching refers to non-coding parts of DNA that can switch genes on and off, controlling gene expression.
What is monohybrid inheritance?
Monohybrid inheritance is the inheritance of characteristics controlled by a single gene.
What defines the phenotype of an organism?
The phenotype is the observable characteristics of an organism.
What defines the genotype of an organism?
The genotype is the combination of alleles that control each characteristic.
What is the difference between dominant and recessive alleles?
A dominant allele only needs to be inherited from one parent to show up in the phenotype, while a recessive allele needs to be inherited from both parents.
What does homozygous mean?
Homozygous refers to having two identical alleles for a gene.
What does heterozygous mean?
Heterozygous refers to having two different alleles for a gene.
What is polygenic inheritance?
Polygenic inheritance is the inheritance of characteristics controlled by more than one gene.
Give an example of a polygenic characteristic.
Eye color is an example of a polygenic characteristic.
What is a Punnett square used for?
A Punnett square is used to show the possible combinations of alleles in the offspring.
What is the expected phenotype ratio in a monohybrid cross of two heterozygous plants?
The expected phenotype ratio is 3:1.
What is the inheritance pattern of cystic fibrosis?
Cystic fibrosis is inherited as a recessive disorder.
What is polydactyly?
Polydactyly is a genetic disorder that causes someone to be born with extra fingers or toes.
What is the inheritance pattern of polydactyly?
Polydactyly is inherited as a dominant disorder.
What is embryo screening?
Embryo screening is the process of analyzing an embryo’s genes before implantation to detect genetic disorders.
What is gene therapy?
Gene therapy is the process of inserting normal alleles into the chromosomes of individuals with defective alleles.
What is gene therapy?
The process by which normal alleles are inserted into the chromosomes of an individual who carries defective alleles
Is gene therapy always successful?
No, it is a developing technology and is not always successful
What are some concerns raised by gene therapy?
Economic, social, and ethical concerns similar to embryo screening
What do many people believe about gene alteration?
It is unnatural or a good idea to alleviate suffering from genetic disorders
How many pairs of chromosomes do ordinary human body cells contain?
23 pairs of chromosomes
What do 22 pairs of chromosomes control?
Characteristics only
What are the sex chromosomes in females?
XX
What are the sex chromosomes in males?
XY
Which cells determine the sex of offspring?
Sperm cells
What is a genetic diagram used to show the inheritance of sex?
Punnett square
In a Punnett square, what do the X and Y chromosomes represent?
The alleles usually written in the boxes
What is variation?
Differences between individuals of the same species
Variation can be phenotypic, genetic, environmental, or a combination of these.
Define phenotypic variation.
Difference in features between individuals of the same species
What are the two main causes of phenotypic variation?
- Genetic variation
- Environmental variation
Give examples of genetic variation in humans.
- Blood group
- Eye colour
- Gender
- Ability to roll tongue
- Free or fixed earlobes
What does environmental variation refer to?
Differences caused entirely by the environment in which the organism lives
List some environmental factors that can affect characteristics.
- Climate
- Diet
- Accidents
- Culture
- Lifestyle
What is genetic variation?
Variation that is controlled entirely by genes
What are mutations?
Random genetic changes that occur continuously
How can mutations affect phenotypes?
They can lead to the development of new alleles and new phenotypes, occasionally providing a survival advantage
Define evolution.
A change in the inherited characteristics of a population over time
What process leads to evolution?
Natural selection
What is speciation?
The development of new species when two populations can no longer breed together to produce fertile offspring
What is selective breeding?
The process of selecting individuals with desirable characteristics and breeding them together
What is artificial selection?
Selective breeding where humans breed plants and animals for particular genetic characteristics
List some characteristics for which animals are selectively bred.
- Milk production in cows
- Egg size in chickens
- Gentle nature in dogs
- Wool quality in sheep
- Speed in horses
What are the problems associated with selective breeding?
It can lead to inbreeding, which reduces the gene pool and increases the risk of genetic defects
What is genetic engineering?
Changing the genetic material of an organism by removing, altering, or inserting genes
What is a genetically modified organism?
An organism that has had its genetic material altered
What is recombinant DNA?
DNA that contains DNA from another organism
What is an example of genetic modification in plants?
Genetically modified tomatoes that grow larger fruit
Explain the process of inserting the human insulin gene into bacteria.
The gene is isolated using restriction enzymes, inserted into a plasmid, and then introduced into bacterial cells
What are GM crops?
Crops that have been genetically modified to improve traits such as yield or resistance to pests
What is gene therapy?
A treatment that involves inserting working versions of faulty genes into people with genetic diseases
What is tissue culture?
A process in which small pieces of plants are grown using nutrient media
What are explants?
Cells scraped from the parent plant for tissue culture
List the advantages of tissue culture.
- Produces plants cheaply
- Increases yield
- Allows for year-round production
- Prevents disease importation
What is tissue culture used for in commercial applications?
To produce a variety of a plant with desirable characteristics cheaply, quickly, with greater yield, and at any time of the year.
It helps ensure diseases are not imported by producing native varieties in sufficient quantities.
What is the main advantage of using tissue culture for plant production?
It allows for the production of genetically identical plants quickly and in large quantities.
This is important for meeting demand without importing plants.
What is the purpose of taking cuttings in plant cloning?
To create genetically identical versions of a plant by cutting a section from a good parent plant.
Cuttings are taken from healthy and visually appealing plants.
What is embryo cloning?
A process of cloning animals by creating genetically identical copies from a fertilized egg.
It involves taking egg cells from the best cow and sperm from the best bull.
How are cloned embryos created in embryo cloning?
By artificially fertilizing egg cells and then splitting the developing embryo before specialization.
This results in multiple genetically identical embryos.
What is the role of host mothers in embryo cloning?
To carry and give birth to the cloned embryos, resulting in genetically identical offspring.
The calves born from host mothers are all clones.
What is adult cell cloning?
A cloning method where the nucleus from an adult body cell is inserted into an unfertilized egg cell.
This process was used to clone Dolly the sheep.
What stimulates the egg cell to divide in adult cell cloning?
A very small electric shock.
This kickstarts the process of mitosis to form an embryo.
What was the first cloned mammal and when was it created?
Dolly the sheep, created in 1996.
This was a significant milestone in cloning technology.
What does the process of adult cell cloning produce?
An embryo with the same genetic information as the adult skin cell from which the nucleus was taken.
What is Darwin’s theory of evolution by natural selection?
It states that individuals in a species show variation, those with advantageous characteristics have a higher chance of survival and reproduction, leading to those traits becoming more common over generations.
This idea is often summarized by the phrase ‘survival of the fittest’.
What are the main points of Darwin’s theory of natural selection?
- Individuals show variation due to genetic differences
- Individuals with advantageous traits survive better and reproduce more
- Advantageous alleles are passed to offspring at higher rates
- Beneficial traits become common over generations
This process leads to evolution.
What is an example of natural selection involving snails?
Variation in shell color leads to white-shelled snails being better camouflaged from predators, allowing them to survive longer and reproduce more than black or grey-shelled snails.
Over time, the population shifts towards more white-shelled snails.
What is the significance of the peppered moth in the context of natural selection?
The evolution of the peppered moth demonstrates how environmental changes can affect survival and reproductive success, leading to changes in the population over time.
This is a classic example often cited in discussions of natural selection.
True or False: The theory of evolution by natural selection was immediately accepted by the scientific community.
False
The acceptance was gradual due to controversy and lack of sufficient evidence at the time.
What were the two main ideas of Lamarck’s theory of evolution?
- Characteristics used frequently become stronger
- Beneficial characteristics are passed to offspring
Lamarck’s theory is now considered incorrect.
Who independently developed a theory of evolution based on natural selection alongside Darwin?
Alfred Russel Wallace
Wallace’s work included studies on warning coloration in species.
What is speciation?
It is the process that results in the formation of a new species when populations become so different that they can no longer interbreed.
This can occur due to geographic isolation and different selection pressures.
What is geographic isolation?
It is when populations of the same species become separated by physical barriers, leading to different evolutionary paths.
Examples include mountains or rivers.
What was Gregor Mendel’s contribution to genetics?
He conducted breeding experiments on plants, demonstrating that characteristics are inherited in units, which are now known as genes.
His work laid the foundation for modern genetics.
What is the relationship between chromosomes and Mendel’s hereditary units?
Mendel’s units are now understood to be located on chromosomes, which behave similarly during cell division.
These units are referred to as genes.
When was the structure of DNA discovered?
In 1953
This discovery was pivotal in understanding gene function.
What is antibiotic resistance in bacteria an example of?
It is a clear evidence of evolution through natural selection, where bacteria develop resistance to antibiotics over time.
This occurs due to mutations that provide survival advantages.
What factors contribute to the extinction of species?
- Poor adaptation to the environment
- Inability to reproduce sufficiently
- Human activities
Extinction can occur naturally or be accelerated by human actions.
Fill in the blank: Extinction occurs when there are no remaining individuals of a species still _______.
alive
This can result from various factors, including environmental changes.
What is MRSA?
A dangerous bacterial strain that is resistant to most antibiotics.
Infections caused by MRSA are challenging to treat.
What is the current challenge in antibiotic development?
The number of new antibiotics discovered has slowed significantly, making it difficult to keep up with emerging resistant strains.
Developing new antibiotics is also a costly process.
What is a species?
A group of organisms that can reproduce to produce fertile offspring.
What are the shared features of mammals?
- Bodies covered in hair
- Feed young from mammary glands
- Have external ears (pinnas)
Who developed the traditional system of classification?
Carl Linnaeus.
What is the binomial system?
A naming system where the scientific name consists of two parts: genus (capitalized) and species (lowercase).
How are binomial names formatted when typed?
They are always in italics.
What is the sequence of classification in Linnaeus’s system?
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
What mnemonic can help remember the order of classification?
KING PHILIP CAME OVER FOR GRAN’S SPAGHETTI.
What does the similarity of features among organisms indicate?
They originally descend from a common ancestor.
What two methods were originally used for classification?
- Morphology
- Anatomy
What advancement allowed for a more scientific approach to classification?
DNA sequencing.
What does similarity in DNA sequences indicate?
The more similar the base sequences, the more closely related the species are.
What is the three-domain system?
A classification system dividing organisms into three groups: Archaea, Bacteria, and Eukaryota.
Who developed the three-domain system and when?
Carl Woese in 1990.
What types of organisms are included in the Eukaryota domain?
- Protists
- Fungi
- Plants
- Animals
What do evolutionary trees represent?
The relationship between species over evolutionary time.
What does a new branch in an evolutionary tree signify?
Speciation has occurred.
How are evolutionary trees created?
Using current classification data (DNA analysis, structural similarities) and fossil data for extinct organisms.
True or False: Chimpanzees are more closely related to bonobos than to any other primate species.
True.
Fill in the blank: The more recent the common ancestor, the ______ the species are related.
closely
