Patterns Of Inheritance

Question 1

What genetic factors lead to variation?

Answer 1

Many versions of alleles, the ones inherited affect genotype

Sexual reproduction -meiosis (crossing over and independent assortment)
And random fusion of gametes in fertilisation

Question 2

What are 3 examples of environmental contributions to variation?

Answer 2

Diet

Etiolation

Chlorosis

Question 3

How can diet cause variation?

Answer 3

It affects the body mass of animals

Question 4

What is chlorosis and what environmental factors cause it?

Answer 4

When a plant can’t produce normal amounts of chlorophyll making the leaves pale and yellow

Caused by
-lack of light - to conserve resources turn of chlorophyll production

• mineral difficiences- lack of iron or magnesium (cofactors for enzymes to make chlorophyll and mg found in chlorophyll molecule
• virus infections-intefere with metabolism of cells so can no longer support chlorophyll production

Question 5

What is etiolatoion?

Answer 5

When plants don’t get enough light so they grown long and week stems which are yellow in colour

Question 6

How do you perform a genetic cross?

Answer 6

State the phenotype if the parents
State the genotype of the parents 
State the gametes of the parents 
Make a punnet square 
State the proportion of each genotype and corresponding phenotype

Question 7

What is codominance?

Answer 7

When two alleles for the same gene are equally dominant

Question 8

What is the expected phenotypic ratio in a dihybrid cross?

Answer 8

9:3:3:1

Question 9

Why might the ratio of a dihybrid cross differ to what’s expected?

Answer 9

Genes are linked (same chromosome) so if no crossing over occurs they will always be inherited together

Fertilisation is a random process so in a small sample chance events can lead to skewed ratio

Question 10

What does sexlinkage mean?

Answer 10

When a gene is found on the X chromosome but not on the y so men are more likely to have recessive sex linked conditions

Question 11

When do you use the chi squared test?

Answer 11

To determine the significance of the difference between observed and expected results

Question 12

How many genes are involved in phenotypes with discontinuous verses continuous variation?

Answer 12

Very few genes involved in discontinuous variation but many genes involved in continuous

Question 13

What factors effect evolution?

Answer 13

Mutation
Gene flow
Genetic drift
Natural selection

Question 14

What is a genetic bottle neck?

Answer 14

When an event happens which causes a large reduction in a population for atleast 1 generation so alleles in new gene pool will have much bigger effect due to small gene pool and low variation

Question 15

What is the founder effect?

Answer 15

When small populations arise due to establishment of new colonies by a few isolated individuals

Small gene pool and low variation so rarer genes have much larger effect

Question 16

What is genetic drift,

Answer 16

Or by chance the allele for one genotype gets passed on more often than others
Allele increases in frequency

Question 17

What is stabilising selection?

Answer 17

When the environment isn’t changing much do individuals with characteristics towards the middle section are more likely to survive and reproduce so these alleles increase in frequency

Question 18

What is directional selection?

Answer 18

When there’s a change in the environment so individuals with more extreme characteristics are more likely to survive and reproduce so these rarer alleles increase in frequency over time

Question 19

When does genetic drift have a greater effect?

Answer 19

When there’s a genetic bottle neck

The founder effect

Question 20

What does the hardy Weinberg principle do?

Answer 20

Predicts that the frequencies of alleles in a population won’t change from one generation to the next

Used to estimate the frequency of particular alleles and geno types in a population

Question 21

What has to be true when using the Harvey Weinberg principle?

Answer 21

Large populations

No immigration emigration mutations or natural selection

Random mating

Question 22

What is allopathic speciation?

Answer 22

Speciation by geographical mechanisms

Question 23

What is sympatric speciation?

Answer 23

Speciation by reproductive mechanisms

Question 24

Give three examples of sympatric speciation

Answer 24

Seasonal changes- different mating seasons

Mechanical differences- different genitalia

Behavioural- courtship rituals that don’t attract

Question 25

What is artificial selection?

Answer 25

Breeding individuals with desirable traits

Question 26

What are the problems with artificial selection?

Answer 26

It reduces the gene pool

So less likely for population to survive a change in environment as can’t adapt quickly enough

Could’ve accidentally lost useful alleles

Important to preserve original wild type organism

Question 27

How would you use selective breeding in wheat to increase yield?

Answer 27

Cross breed high yielding wheat individuals

Measure the yield

Crossbreed selected high yielding offspring

Over generations

Prevent unwanted pollination

Question 28

What term describes the random changes in allele frequency in a small population?

Answer 28

Genetic drift

Question 29

what do you use as degrees of freedom in a chi squared test?

Answer 29

the number of phenotypes/classes minus 1