Patterns Of Inheritance Flashcards
What is continuous variation
- polygenic / controlled by environment
Wheee the individuals vary within a range: no distinct categories
Data = quantitative e.g. height
What is discontinuous variation
- monogenic & little environmental influence
2 or more distinct categories (& u only fall into one)
E.g. type A, B, AB, O
Examples of factors influenced by genetic & environmental factors (therefore continuous?)
- diet
- chlorosis
- etiolation
What is chlorosis (yellowed leaves due to less chlorophyll production) due to
- lack of light,therefore low chlorophyll production to conserve resources
- mineral deficiencies e.g. iron needed as enzyme cofactor to make chlorophyll
- virus infections
How can animal diet be linked to mass and obesity etc
Obesity can be due to genes e.g. mutations on chromosomes = altered fat deposition
Bit mainly due to environmental factors e.g. how much u eat, workout, disease
What is etiolation
When plants are grown in the dark and may develop long stems with small, curled leaves even though genetically, should grow normally
How sexual reproduction can lead to genetic variation
5 diff types of genetic diagrams
- monogenic inheritance
- dihybrid inheritance
- multiple alleles
- sex linkage
- co-dominance
What’s monogenic inheritance
Dihybrid inheritance (of two genes) diagram
Multiple Alleles diagram
Multiple Alleles diagram
Genetic diagram for sex linkage
Codominance diagram
Difference between Co-dominance & Incomplete dominance
Co-dominance = both alleles have the effect so e.g. a red and a white coat come together to give a pink coat
Incomplete dominance = a mixture of the alleles in the genotype e.g. than the pink coat, it would be red or white stripes or spots on the coat
How are phenotypic ratios important
What is autosomal linkage
If 2 genes are found on the same (nonsex chromosome)
- the closer the two genes are, the likelier they both are of being inherited as one unit
Occurs differently depending on the gene loci / location as they affect that the two genes / alleles & how they may be inherited
What is epistasis
What are the factors that affect the evolution of a species
- founder effect
- genetic drift
- genetic bottleneck
- selection pressures
What are the 2 types of selection pressures
Directional selection
Stabilising selection
What is stabilising selection
Natural selection that keeps alleles frequencies = constant (unless a change in environment)
What is directional selection
Natural selection that produces a gradual change in allele frequencies over several generations
- usually happens when there are changes in environmental & therefore change in selection pressures, or a new allele has appeared in the population that’s advantages
Example of directional selection:
-> process of steps using fish size as an example, as climate change selects for a smaller body size
- Warmer size = metabolism increases, more need for O2, and O2 decreases in warmer seas
- Large fish = disadvantaged is greater metabolic needs
- Organisms sensitive to temp changes, due to enzyme activities, therefore smaller fish = fitter = better adapted
- So smaller fish more likely to reproduce & their alleles for smaller size down
- Over time, inc freq of alleles for a small body size
What is genetic drift
-> when chance (not environmental selection pressures) affects which individuals in a population survive therefore breed & pass on their alleles
Example of genetic drift e.g. when the population is small, & chance can affect which alleles get passed onto the next generation, & therefore how over time, some alleles can be lost of favoured purely by luck
Example: if a small population of plants are at a playground with rubber sections & the allele for blue flowers = half the plants & the allele for pink = the other half
If most the pink seeds are blown to the rubber, and blue onto fresh soil, the allele for pink may disappear from population due to chance
The […] the population , the bigger the impact of genetic drift
Smaller
Substantial genetic drift leads to
Evolution
What is genetic bottleneck
Occurs when a previously large population suffers a dramatic fall in numbers
- it can be due to major environmental effects e.g. disasters, climate change, etc, which reduce the number of individuals in a population which reduces the genetic diversity in the population as alleles are lost
- surviving individuals breed & reproduce with close relatives
What is founder effect
It only occurs when a small no. of individuals from a large parent population start a new population
-> the new population is only made up of a few, so only some of the total alleles are present (not the whole gene pool)
Therefore, change in allele frequency may occur in diff directions
Hardy Weinberg principle is for what
Allele freq for monogenic inheritance
What is the hardy Weinberg principle & it’s assumptions
That in a stable, non-evolving population, allele frequencies stay constant
- large pop size
- no mutations
- no selection pressure
- random mating
Hardy weinberg principle equations
What are the types of isolating mechanisms in the evolution of new species
Geographic mechanism (allopatric speciation)
Reproductive mechanisms (sympatric speciation)
What is allopatric speciation
-> o.g. population split into two via (e.g.) formation of mountain ranges, rivers etc
-> now they can’t reproduce due to geographical barrier
-> now each population = diff adapting (diff beneficial mutations) & therefore change
What is sympatric speciation
- due to differences in behaviour, despite being in the same condition
E.g. random mutation to impact courtship rituals, mating calls etc - therefore no reproducing & gene flow messed up!
What is artificial selection
The process by which humans choose organisms with desirable traits & selective breed them together to enhance the expression of these desirable traits over time & over many generations
AKA selective breeding
Process generally of selective breeding
Population shows phenotypic variation - there are individuals with diff phenotypes & the breeder selects the individual with a desired phenotype
-> another individual (with the desired one) = bred together
Offspring produced & those with desired phenotype are selected for further breeding, over many generations
Examples of selective breeding in animals
Usually focuses on 1 characteristic, often to an extreme e.g.
- cows / sheep / chickens etc (yield of meat & milk & wool)
- domestic dogs
Issues = selective bred individuals more prone to ailments e.g. milk fever, udder inflammation
Examples of selective breeding in plants
- for characterises e.g.
disease resistance in food crops, increased crop yield, good taste
E.g. wheat: breeding to introduce a fungus resistance allele from a different wheat species, now we have hybrid ones
Ethical considerations of artificial selection
Positive effects of generic manipulation
- cures for fatal diseases
- can be sold e.g. economic
- creates pest resistance crops
- GM crop resistance to climate change = no famine
Negatives of genetic manipulation
- farms in LIC’s can’t afford parents
- unethical due to side effects
- biowarfare potential
- research = mass disease outbreak
