Patterns Of Inheritance

Question 1

What is continuous variation

Answer 1

• polygenic / controlled by environment
  Wheee the individuals vary within a range: no distinct categories
  Data = quantitative e.g. height

Question 2

What is discontinuous variation

Answer 2

• monogenic & little environmental influence
  2 or more distinct categories (& u only fall into one)
  E.g. type A, B, AB, O

Question 3

Examples of factors influenced by genetic & environmental factors (therefore continuous?)

Answer 3

• diet
• chlorosis
• etiolation

Question 4

What is chlorosis (yellowed leaves due to less chlorophyll production) due to

Answer 4

• lack of light,therefore low chlorophyll production to conserve resources
• mineral deficiencies e.g. iron needed as enzyme cofactor to make chlorophyll
• virus infections

Question 5

How can animal diet be linked to mass and obesity etc

Answer 5

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

Question 6

What is etiolation

Answer 6

When plants are grown in the dark and may develop long stems with small, curled leaves even though genetically, should grow normally

Question 7

How sexual reproduction can lead to genetic variation

Answer 7

Question 8

5 diff types of genetic diagrams

Answer 8

• monogenic inheritance
• dihybrid inheritance
• multiple alleles
• sex linkage
• co-dominance

Question 9

What’s monogenic inheritance

Answer 9

Question 10

Dihybrid inheritance (of two genes) diagram

Answer 10

Question 11

Multiple Alleles diagram

Answer 11

Question 12

Multiple Alleles diagram

Answer 12

Question 13

Genetic diagram for sex linkage

Answer 13

Question 14

Codominance diagram

Answer 14

Question 15

Difference between Co-dominance & Incomplete dominance

Answer 15

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

Question 16

How are phenotypic ratios important

Answer 16

Question 17

What is autosomal linkage

Answer 17

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

Question 18

What is epistasis

Answer 18

Question 19

What are the factors that affect the evolution of a species

Answer 19

• founder effect
• genetic drift
• genetic bottleneck
• selection pressures

Question 20

What are the 2 types of selection pressures

Answer 20

Directional selection
Stabilising selection

Question 21

What is stabilising selection

Answer 21

Natural selection that keeps alleles frequencies = constant (unless a change in environment)

Question 22

What is directional selection

Answer 22

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

Question 23

Example of directional selection:
-> process of steps using fish size as an example, as climate change selects for a smaller body size

Answer 23

1. Warmer size = metabolism increases, more need for O2, and O2 decreases in warmer seas
2. Large fish = disadvantaged is greater metabolic needs
3. Organisms sensitive to temp changes, due to enzyme activities, therefore smaller fish = fitter = better adapted
4. So smaller fish more likely to reproduce & their alleles for smaller size down
5. Over time, inc freq of alleles for a small body size

Question 24

What is genetic drift

Answer 24

-> when chance (not environmental selection pressures) affects which individuals in a population survive therefore breed & pass on their alleles

Question 25

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

Answer 25

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

Question 26

The […] the population , the bigger the impact of genetic drift

Answer 26

Smaller

Question 27

Substantial genetic drift leads to

Answer 27

Evolution

Question 28

What is genetic bottleneck

Answer 28

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

Question 29

What is founder effect

Answer 29

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

Question 30

Hardy Weinberg principle is for what

Answer 30

Allele freq for monogenic inheritance

Question 31

What is the hardy Weinberg principle & it’s assumptions

Answer 31

That in a stable, non-evolving population, allele frequencies stay constant

• large pop size
• no mutations
• no selection pressure
• random mating

Question 32

Hardy weinberg principle equations

Answer 32

Question 33

What are the types of isolating mechanisms in the evolution of new species

Answer 33

Geographic mechanism (allopatric speciation)
Reproductive mechanisms (sympatric speciation)

Question 34

What is allopatric speciation

Answer 34

-> 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

Question 35

What is sympatric speciation

Answer 35

• 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!

Question 36

What is artificial selection

Answer 36

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

Question 37

Process generally of selective breeding

Answer 37

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

Question 38

Examples of selective breeding in animals

Answer 38

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

Question 39

Examples of selective breeding in plants

Answer 39

• 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

Question 40

Ethical considerations of artificial selection

Answer 40

Question 41

Positive effects of generic manipulation

Answer 41

• cures for fatal diseases
• can be sold e.g. economic
• creates pest resistance crops
• GM crop resistance to climate change = no famine

Question 42

Negatives of genetic manipulation

Answer 42

• farms in LIC’s can’t afford parents
• unethical due to side effects
• biowarfare potential
• research = mass disease outbreak