Flashcards
patterns of inheritance
Cards in this deck (45)
- 1what is continuous variationWhen the individuals in ta population vary within a range - there are no distinct categories
- 2what is discontinuous variationwhen there are two or more distinct categories - each individual falls into only one of these categories, there are no intermediates
- 3If the characteristics are said to be 'polygenic" what does this meanInherited characteristics that show continuous variation are usually influenced by many genes
E.g human skin colour - it comes in loads different shades of colours - 4if the characteristics are said to be "monogenic" what does this meanInherited characteristics that show discontinuous variation are usually influenced by only one gene (or a small number of genes)
E.g Violet flower colour is monogenic - can either be coloured or white - 5what are the two maples given when variation can be caused by differences in the environment1. Etiolation
- This is when plants grow abnormally long and spindly because ether's not getting enough light
2. Chlorosis
- This is when plants don't produce enough chlorophyll and turn yellow, caused by lack of magnesium in the soil - 6what are some examples of phenotypic variation caused by both genotype and environmental factors1. Height of pea plants
- Being tall/dwarf is determined by the genotype
- But the exact height of the plant is influenced by the environmental factors such as water availability
2. Body mass in animals
- Partly genetic, however strongly influenced by environmental factors like your diet - 7define GeneA sequence of bases on a DNA molecule that codes for a protein which results in a characteristic
- 8define AlleleA different version of a gene
- 9define Genotypegenetic makeup of an organism
- 10define Phenotypevisible characteristic of an organism
- 11define Dominant alleleAn allele whose characteristics appears in the phenotype even when theres only one copy
- 12define Recessive alleleAn allele whose characteristics appears in the phenotype if two copies are present
- 13CodominantAlleles that are both expressed in the phenotype - neither one is recessive
- 14what is a Locusthe fixed position of a gene on a chromosome. Al
- 15Homozygote organisman organism that carries two copies of the same allele
- 16Heterozygotean organism that carries two different alleles
- 17CarrierA person carrying an allele which is not expressed in the phenotype but that can be passed on to offspring
- 18what is Monogenetic inheritanceIt is the inheritance of a characteristic controlled by single gene.
One characteristic with one pair of contracting traits - 19what is Dihybrid inheritanceIt is the inheritance of two characteristics which are controlled by different genes
Involves 2 gene loci - 20what are sex linked genesgene present on the sex chromosomes
- 21why are males more likely to show recessive phenotypes for genes that are sex linked- Most hens on the sex chromosome are only carries on the chromosome (called X-linked)
- Males only have one X chromosome, they often only have one allele for sex-linked genes. So because they only have one copy, they express the characteristics of this allele even if it is recessive. - 22what are Autosomal linkagegene loci present on the same autosome (non-sex chromosome) that are often inherited together
- 23what s Epistasisinteraction of non-linked gene loci where one masks the expression of the other
- 24what is EvolutionChanges of the allele frequency over time
- 25describe how Natural Selection works- Individuals within a population will vary because the have different alleles
- Selection pressure creates a struggle for survival
- Some are better adapted than others
- Ones better adapted survive and pass in the advantageous allele to the next generation
- so over time more of the population has the advantageous allele
- So the frequency of the advantageous allele increases - 26what is Stabilising selectionType of natural selection
- When the environment isn't changing much, individuals with alleles for the characteristics towards the middle of the range are more likely to survive and reproduce.
- Alles for extreme phenotypes may e removes from the population
- Stabilising selection reduces genetic variation within the population - 27what is Directional SelectionWhen there a change in the environment, individuals with alleles for characteristics of extreme type are more likely to survive and reproduce
- The environmental change favours a new phenotype and so results in a change in the population mean - 28what is Genetic Drift- Individuals within a population show variation in their genotypes
- By chance, the allele for one genotype is passes on to the offspring more often than others
- So the number of individuals with the allele increase
- If by chance the sam allele is passed on more often again and again, it can lead to evolution
•The allele in question did not disappear due to selection pressure but due to genetic drift - 29what is Genetic Bottleneck and how does this link in with genetic Drift- Genetic drift can have a greater effect if there is a genetic bottleneck
- Genetic Bottleneck is a sharp reduction in size of a population due to environmental catastrophes
- This reduction leads to a reduction in the gene pool - 30what is the Founder effect and how does this link with genetic drift- Genetic drift can have a greater effect if there is a Founder Effect
- The founder affect is when a small sample of an original population establishes in a new area; its gene pool is not as diverse thus leading to genetic drift - 31what is the relationship between: • Natural selection (stabilising selection and directional) • Genetic drift (genetic bottleneck and founder affect)- They usually work alongside each other to drive evolution, but one process can drive evolution more than the other depending on population size
- Evolution by genetic drift usually has a greater effect in smaller populations where chance had a greater influence. - 32what is Artificial selectionthis is when human select individuals in a population to breed together to get desirable traits
also called Selective Breeding - 33modern dairy cattleModern dairy cow produce many litres of milk a day as a result of artificial breeding
- Farmers select a female ow with very high milk yield and a male whose mother had a very high milk yield and breed these two together
- They then select the offspring with the highest milk yields and breed them together
- This is continued over several generations until a ver high milk yielding cow ins produced - 34bread wheatBread wheat is the plant from which flour is produced for bread making
1. Wheat plants with a high wheat yield are bred together
2. The offspring with the highest yields are then bred together r
3. This is continues over several generations to produce a plant that has a very high yield - 35how does artificial selection reduce gene poolArtificial selection means that only organisms with similar traits and therefore similar alleles are bred together. This leads t a reduction in the umber of alleles in the gene pool
- This causes problems in the future - if a new disease appears theres less chance of alleles being resistance to that disease
- Thats why it is important that genetic biodiversity is maintained for future use - 36what are the animal welfare problems caused by artificial breeding of dogsPedigree dogs:
- Pedigree dogs breeds has gone through many generations of artificial selection to produce the dogs we know today.
- For example pugs and french bull dogs have ben bred to have flat squashed faces. This trait has become so exaggerated that theses dogs now offer breathing problems as a result
- A reduced gene pool also tends to result in an increased incidence of genetic disease
E,g High incidence of hereditary deafness in certain dog breeds (English bull terriers) - 37what does Hybrid vigour meanwhen breeders sometimes outcross individuals belonging to two different varieties to obtain individuals that are heterozygous at many gene loci
- 38what is Interbreeding depressionLack of vigour, loss of fertility and reduction in population size, due to organisms being inbred and becoming homozygous at many gene loci.
- 39what is the point of Gene banksGene banks are sources of alleles to introduce back into the artificially bred strains and increase hybrid vigour.
- 40define SpeciationThis is the development of a new species
- 41what is Allopatric speciationThis is the formation of two different species from one original species due to geographical isolation
- 42how does Allopatric speciation come about- Geographical isolation happens where the is a physical barrier divides a population of a species ( flood,volcanic eruption )
- Condition son either side of the barriers will be slightly different
- Because the environment is different on each side, different characteristics will become more common fur to natural selection
-Because different characteristics will be advantageous on each side, the allele frequencies will change in each population
- Mutations will take place independently in each population also changing the allele frequency
- Changes in allele frequency will lead to changes in phenotype frequencies
- Eventually the individual from different populations will have changes so much they not be able to breed and produce fertile offsprings - 43what is Reproductive isolation and how does it occur1.biological and behavioural changes
- a group of individuals develop courtship rituals that aren't attractive to the main population
2. Genetic changes
- changes in genitalia may prevent successful breeding
3. mutations may mean that some organisms in a population changes their foraging behaviour - 44what is Sympatric speciationSpeciation resulting from reproductive isolation
- 45suggest how certain human activities may speed the process of evolution among other speciesFor example, habitat destruction, such as clearing forests for wood/space; climate change; pollution; agriculture; use of pesticides; antibiotics; changes may cause wildlife to migrate; may introduce a novel selection pressure.
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- A-Level Biology (module 6.2 Patterns of Inheritance ) Flashcards on patterns of inheritance , created by Hina Nagano on 25/04/2017.
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- Hina Nagano · Apr 2017
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- Apr 6, 2018
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