Inheritance, Variation and Evolution Flashcards
What is sexual reproduction?
Production of gametes by meiosis.
How is a zygote formed?
When a gamete from each parent fuses together.
What is a gamete?
Sex cells
Examples of gametes (3)
Sperm cells
Egg cells
Pollen
What is a haploid?
A cell with half the chromosomes.
What is meiosis?
Cell division that forms gametes.
Involves two divisions.
What must occur before meiosis?
Interphase - when copies of genetic information are made.
What happens during meiosis?
Chromosome pairs line up in the centre of the cell.
The pairs are separated and moved to opposite poles of the cell.
The chromosome number is halved.
Why are offspring from meiosis genetically different?
When the chromosome pairs are meant to be separated and moved to opposite poles of the cell it is random.
What is produced from meosis?
4 unique haploid gametes.
Why is meiosis important for sexual reproduction?
Increases genetic variation.
Ensures that the zygote formed at fertilisation is a diploid.
What is a diploid?
A cell containing two complete sets of chromosomes.
Process of fertilisation?
Gametes join together.
Normal number of chromosomes restored.
New cell divides by mitosis.
As the embryo develops, the cells differentiate.
Malaria reproduction?
Sexual reproduction for mosquito.
Asexual reproduction for the human host.
What is DNA?
Genetic material of the cell found in the nucleus.
What is a genome?
The entire genetic material of an organism.
Benefits of understanding the human genome?
Understanding and treating inherited disorders.
Tracing human migration patterns from the past.
Searching for genes that link to different types of diseases.
What is a chromosome?
A long, coiled molecule of DNA that carries genetic information in the form of genes.
What is a gene?
A small section of DNA that codes for a specific sequence of amino acids.
What are alleles?
Different versions of the same gene.
What is a dominant allele?
A version of a gene where only one copy of the gene is required for it to be expressed.
What is a recessive allele?
A version of gene where two copies are needed for it to be expressed.
Homozygous definition?
Two copies of the same allele.
Heterozygous definition?
Two different versions of the same gene.
What is a genotype?
The genes present for a trait.
What is a phenotype?
The visible characteristic.
What is an inherited disorder?
A disorder caused by the inheritance of certain alleles.
2 examples of inherited disorders/
Polydactyly - caused by a dominant allele it is having extra toes or fingers.
Cystic Fibrosis - caused by a recessive allele, a disorder of the cell membranes.
How are embryos screened for genetic disorders?
During IVF one cell is removed from an 8 cell embryo and tested for disease causing alleles.
Ethical issues for embryo screening?
Could lead to a belief in society that disabilities are unwanted and inferior.
Destruction of embryos can be seen as murder.
Designer babies - wishing for a perfect baby.
What is gene therapy?
Inserting a normal allele into the cells of a person with an inherited disorder to replace the faulty allele.
Ethical issues about gene therapy?
People think that they’re trying to play God.
The introduced cells can enter the sex genes and be passed on to future generations.
What are sex chromosomes?
A pair of chromosomes that determine sex.
What is a sex linked characteristic?
A characteristic that is coded for by an allele found on a sex chromosome.
Why are majority of genes found on the X chromosome rather than the Y chromosome?
X is bigger.
What is variation?
Differences in the characteristics of individuals in a population.
What are the two causes of variation in a species?
Genetics
Environmental
What is a genetic variation?
Variations in the genotype of organisms of the same species due to the presence of different alleles. This creates a difference in phenotypes.
What creates genetic variation in a species?
Spontaneous mutations
Sexual reproduction
What is a mutation?
A random change to the base sequence in DNA which results in genetic variants. They occur continuously.
What is evolution?
A gradual change in the inherited traits within a population over time. Occurs due to natural selection which may result in the formation of a new species over time.
Outline the theory of natural selection (6)
1.Genetic variations occur due to spontaneous mutations.
2.Selection pressures such as disease or competition exist.
3.Random mutation gives an organism a selective advantage.
4.Organism is better adapted to the environment and survives.
5.Organism reproduces passing on its beneficial alleles.
6.Frequency of advantageous alleles increases.
How do two populations become different species?
When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring.
What is selective breeding?
The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes.
Outline the main steps involved in selective breeding? (4)
1.Identify a desired characteristic
2.Breed the parents that show the desired characteristics together.
3.Select offspring with the desired traits and breed them together.
4.Process repeated until all offspring have the desired trait.
What is the theory of natural selection?
All species of living things have evolved from simple life forms that first developed more than 3 billion years ago.
4 examples of desired characteristics?
Disease resistance in crops.
Higher milk/meat production in animals.
Large flowers.
Gentle nature in domestic dogs.
Other than in agriculture, where else is selective breeding useful?
Medical Research
Sport - horse racing
Disadvantages of selective breeding (3)?
Reduction in gene pool
Inbreeding leads to genetic disorders
Development of physical problems e.g respiratory issues in bulldogs.
What is genetic engineering?
Introducing a gene from one organism into the genome of another organism to introduce desirable characteristics.
What is a use for genetically modified plants (2)?
Disease resistance
Produce larger fruits
What is a use for GM bacterial cells?
To produce insulin to treat diabetes.
3 benefits of genetic engineering?
Increased crop yields for growing population e.g disease resistance.
Useful in medicine - insulin production.
Production of scarce resources e.g GM golden rice which produces beta carotene (source of Vitamin A in the body)
Risks of genetic engineering (4)?
Long term effects of the consumption of GM crops are unknown.
Late onset health problems in GM animals
GM seeds are expensive
Reduction in biodiversity
Describe the process of genetic engineering (4)
1.Enzymes are used to isolate the required gene.
2.The gene is inserted into a vector which is usually a bacterial plasmid or a virus.
3.The vector inserts the gene into required cells.
4.The genes are transferred to the cells of the animals, plants or microorganisms at the early stage of development so that they develop with the desired characteristic.
What is a vector?
A structure that delivers the desired gene into the recipient cell e.g plasmids or viruses.
State two kinds of evidence used to show evolution?
Fossils
Antibiotic resistance in bacteria
How are fossils formed?
From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent.
When parts of the organism are replaced by minerals when they decay.
As preserved traces of organisms such as footprints or becoming rock.
What does soft-bodied mean?
Leaving few traces behind - this is why there are few traces of early life forms left behind.
How do fossils act as evidence for evolution?
Scientists can identify the ages of fossils and use them to show how organisms change over time.
What do branches in evolutionary trees indicate?
They show how organisms are related
What is extinction?
Where there are no individuals of a species still alive.
State 5 factors that lead to extinction?
New disease
Predators
Competition
Changes in environment
Catastrophic events
What enables bacteria to evolve quickly?
The fast rate of their reproduction.
Outline the process of antibiotic resistance bacteria evolving?
1.Mutations occur in bacteria producing genetic variation.
2.Certain strains are resistant to antibiotics and are not killed when the antibiotic is applied.
3.Resistant strains survive and reproduce.
4.Over time the population of resistant strains increase.
Why are antibiotic resistant strains of bacteria dangerous?
People have no immunity to them and there is no effective treatment.
State an example of an antibiotic strain of bacteria.
MRSA
What can be done to reduce the rate of development of antibiotic resistant bacteria?
Restrict agricultural uses of antibiotics.
Patients should complete the prescribed course of antibiotics.
Refrain from inappropriately prescribing antibiotics such as for viral infections.
Why is it so difficult to keep up with the emerging resistant strains of bacteria?
Developing antibiotics are expensive and take a long time to develop.
Classes of organisms developed by Carl Linneaus?
Kingdom
Phylum
Class
Order
Family
Genus
Species
Katie please come over for great spaghetti.
Who was Carl Linneaus?
He developed a traditional way to group living things depending on their structure and characteristics in a system.
What is the binomial system?
How organisms are named.
What is the binomial system of naming organisms?
Genus name followed by species name.
Why were classification models proposed?
Development in microscopy allowed better examination of internal structures.
Improvement in understanding the biochemical processes.
State the three domains?
Archea
Eukarya
Bacteria
Which organisms belong in the domain Archea?
Bacteria usually living in extreme environments.
Which organisms belong in the domain Bacteria?
Bacteria
Which organisms belong in the domain Eukarya?
Plants
Fungi
Animals
Protists
How are evolutionary trees created?
By examining the DNA of different species and analysing how similar the sequences are.
Who made the three domain system?
Carl Woese
Outline the theory of evolution by natural selection?
Individuals of a species show a wide range of variation for a characteristic.
Those with the characteristic most suited to the environment will survive and breed most successfully.
The desirable characteristic that has enabled the individuals to survive are then passed to their offspring.
Why was Darwin’s theory of evolution not accepted initially?
Most people believed in creationism
Insufficient evidence to prove the theory
What is a species?
A group of organisms with similar characteristics which are able to interbreed to produce fertile offspring.
