Topic 7 Content

Question 1

What is the genotype?

Answer 1

• The genotype is the genetic constitution of an organism.

Question 2

What is the phenotype?

Answer 2

• The phenotype is the expression of the genetic constitution and its interaction with the environment.

Question 3

What are alleles?

Answer 3

• Alleles are different forms of the same genes.

Question 4

What is the dominant allele?

Answer 4

• The allele that if present is expressed in the phenotype, even if there is only 1 copy.

Question 5

What is the recessive allele?

Answer 5

• The allele that appears in the phenotype if 2 copies are present.

Question 6

What is the co-dominant allele?

Answer 6

• Alleles that are both sharing dominance.

Question 7

What is monohybrid inheritance?

Answer 7

• The inheritance of one single characteristic controlled by a single gene.

Question 8

What is dihybrid inheritance?

Answer 8

• The inheritance of two characteristics controlled by 2 genes.
• It involves 2 genes on 2 different characteristics.

Question 9

What is sex-linkage?

Answer 9

• Gene found on sex chromosome is said to be ‘sex linked’.

Question 10

What is the trend of sex linked genes?

Answer 10

• Most genes are found on the X chromosome, and with males being XY they only have one sex linked allele.

Question 11

What are carriers?

Answer 11

• Females who have faulty recessive alleles but are heterozygous due to the presence of a dominant allele which cancels out the recessive allele.

Question 12

What is epistasis?

Answer 12

• Where the expression of one gene is affected by the expression of one or more independently inherited genes.

Question 13

What is an example of epistasis?

Answer 13

Petal colours being controlled by the presence of different enzymes.

Question 14

Why is chi squared used?

Answer 14

• Used to compare the goodness of fit of observed phenotypic ratios with expected ratios.
• Used to see if there is dihybrid cross with linkages or no linkages.

Question 15

How do you carry out chi squared?

Answer 15

• Find the chi squared value using the equation.
• Compare with the critical value (found by doing number of samples - 1)
• If chi squared is the same or exceeds the critical value then we reject the null hypothesis.

Question 16

What is a population?

Answer 16

• A group of organisms of the same species occupying a particular space at a particular time that can breed with one another to produce fertile offspring.

Question 17

What is a gene pool?

Answer 17

• the different variety of alleles in a population

Question 18

What is allele frequency?

Answer 18

• The number of times alleles appear in the population.

Question 19

What is the Hardy-Weinberg principle?

Answer 19

• The mathematical principle which states that the frequency of alleles in a population won’t change across generations.

Question 20

What is P+Q=1 used for?

Answer 20

• Used for allele frequency.

Question 21

What is P^2+2pq+Q^2=1 used for?

Answer 21

• Used for the frequency of individuals

Question 22

What are the assumptions that Hardy Weinberg principle?

Answer 22

• No natural selection
• No gene flow ( no emigration of different genes)
• Large population
• No mutations (no new alleles in the population)
• Random mating (alleles aren’t selective)

Question 23

What is disruptive selection?

Answer 23

• Where individuals with extreme characteristics are more likely to survive and reproduce.

Question 24

What is selection pressures?

Answer 24

• The ability to avoid predators depending on your characteristic.
• Example: Squirrels with short tails are harder to be caught due to predators not being able to grasp onto their tails, and squirrels with large tails can stay more balanced on trees.

Question 25

What is evolution?

Answer 25

- Evolution is the change in allele frequency in a population.

Question 26

How do new species develop?

Answer 26

- From a common ancestor

Question 27

How does speciation process?

Answer 27

1) Part of the population becomes separated and reproductively isolated. 2) Each population finds itself in a different environment, and so experience different selection pressures. 3) Different alleles have different advantages so natural selection occurs. 4) Allele frequencies change the gene pool. 5) The populations cannot interbreed to produce fertile offspring.

Question 28

What is allopatric speciation?

Answer 28

- The physical reproductive isolation by a geographical barrier.

Question 29

What is sympatric speciation?

Answer 29

- Other reasons for reproductive isolation such as mutations and behaviour.

Question 30

What is genetic drift?

Answer 30

- The change in allele frequencies due to chance. - Not every individual will have the same number of offspring. - Greater impact on smaller populations due to individauls making up a greater proportion of the population.

Question 31

What is primary succession?

Answer 31

- The change in an ecosystem over time

Question 32

What are pioneer species?

Answer 32

- Species that are able to survive in extreme, hostile conditions.

Question 33

Why are pioneer species important?

Answer 33

- They change the environment to make abiotic conditions less hostile.

Question 34

How do pioneer species make abiotic conditions less hostile?

Answer 34

- They do this by eroding rocks, releasing minerals, adding more humus when they are killed and increasing the nitrogen oxide content.

Question 35

What happens when new species arise in the community?

Answer 35

- They change the environment, making it less hostile for them and less suitable for the previous species.

Question 36

What happens when succession occurs over a longer period of time?

Answer 36

- Different organisms that are better adapted to the improved conditions outcompete those already there. - The arrival of new species increases the biodiversity.

Question 37

What happens at the end of succession?

Answer 37

- The largest and most complex community will form called a climax community.

Question 38

What happens during secondary succession?

Answer 38

- The climax community is cleared in some way (E.G Forest fire) - Succession will have to restart but at a much greater rate as the community won't start at an extremely hostile condition.

Question 39

Why do we conserve?

Answer 39

- We conserve to prevent succession from continuing which will preserve the ecosystem in its current state. - We do this because if another species arrived and dominated, existing species would be outcompeted and would die out, and we want to keep biodiversity high.

Question 40

How do we conserve

Answer 40

- We conserve by grazing, where we remove the growing tips from plants such as tree samplings or shrubs, so that they don't develop. - We can also manage fires to wipe out all species which will force secondary succession to happen.

Question 41

What is autosomal linkage?

Answer 41

Autosomal​​ linkage is when genes that are close to one another on a chromosome are likely to be inherited together.