6.1.2 - Patterns of Inheritance

Question 1

What is intraspecific variation?

Answer 1

When organisms of the same species have different characteristics

Question 2

What are the 2 types of intraspecific variation?

Answer 2

• Genetic variation
• Phenotypic variation

Question 3

What is genetic variation?

Answer 3

The difference in DNA between organisms of the same species resulting from organisms having a different genetic makeup through mutations or different alleles

Question 4

How is genetic variation introduced?

Answer 4

• During meiosis different combinations of gamete alleles are produced through crossing over and independent assortment
• During sexual reproduction when 2 gametes randomly fuse at fertilisation

Question 5

What is phenotypic variation?

Answer 5

The difference in phenotypes between organisms of the same species

Question 6

What causes phenotypic variation?

Answer 6

Genetic factors and environmental factors

Question 7

What is an example of phenotypic variation in plants?

Answer 7

When a plant is exposed to its regular environment the genetic factors cause it to produce chlorophyll so its phenotype shows green leaves which means it is able to photosynthesise. When an environmental factor changes such as a decrease in light the plant may stop producing chlorophyll (chlorosis) so its phenotype shows yellow leaves which means it isn’t able to photosynthesise.

Question 8

What is an example of phenotypic variation in animals?

Answer 8

When a fruit fly is given its regular diet it produces its usual black phenotype. When given a diet of silver salts during its development a fruit fly produces a yellow phenotype instead.

Question 9

What is monogenic inheritance?

Answer 9

The inheritance of one gene

Question 10

What is dihybrid inheritance?

Answer 10

The inheritance of 2 genes

Question 11

What is codominance?

Answer 11

When both alleles are expressed

Question 12

What is an autosome?

Answer 12

Any chromosome that isn’t a sex chromosome

Question 13

What is autosomal linkage?

Answer 13

When 2 or more genes appear on the same autosome

Question 14

What are sex linked genes?

Answer 14

Genes located on a sex chromosome so allele expression depends on the sex of the individual

Question 15

What is epistasis?

Answer 15

When one gene affects the expression of another gene to determine some of the phenotype

Question 16

When is the chi-squared test used?

Answer 16

To compare observed results from genetic crosses with the predicted outcomes

Question 17

What is discontinuous variation?

Answer 17

Qualitative differences between phenotypes that have distinctive groups

Question 18

What is an example of discontinuous variation?

Answer 18

Blood group

Question 19

What is discontinuous variation caused by?

Answer 19

• Caused by gene mutation
• Different alleles at the same locus have a large effect

Question 20

What is continuous variation?

Answer 20

Quantitative differences between phenotypes where there is a large range of variation within a population

Question 21

What is an example of continuous variation?

Answer 21

Height

Question 22

What is continuous variation caused by?

Answer 22

• Controlled by 2 or more genes each of which contributes to the phenotype
• Different alleles at each locus have little effect

Question 23

What are the 2 types of natural selection?

Answer 23

• Stabilising selection
• Directional selection

Question 24

What is stabilising selection?

Answer 24

• Eliminates extremes within a population
• Favours the most common individuals
• Occurs with unchanging environmental conditions

Question 25

What is an example of stabilising selection?

Answer 25

Human babies with an intermediate weight are more likely to survive, reproduce and pass on their allele for intermediate birth weight which means over many generations the allele frequency shifts in favour of this allele so the frequency of intermediate weight increases.

Question 26

What is directional selection?

Answer 26

• Favours individuals at the extreme in a range of variation
• Changes characteristics of a population
• Occurs due to a change in the environment

Question 27

What is an example of directional selection?

Answer 27

Bacteria that have antibiotic resistance are more likely to survive, reproduce and pass on their allele for resistance. This means over many generations the allele frequency skews towards the extreme.

Question 28

What is genetic drift?

Answer 28

The process by which allele frequencies change over time due to chance and it has the largest impact in small populations

Question 29

What are the 2 main types of genetic drift?

Answer 29

• Genetic bottleneck
• Founder effect

Question 30

What is genetic bottleneck?

Answer 30

When a chance event causes a dramatic reduction in the size of the population and the gene pool

Question 31

What is the founder effect?

Answer 31

The loss of genetic variation due to the establishment of a new population by a very small number of individuals from a much larger population

Question 32

What does the Hardy-Weinberg principle predict?

Answer 32

Allele frequencies will remain constant from generation to generation

Question 33

What conditions must be met for the Hardy-Weinberg principle to be correct?

Answer 33

• No mutations
• Population isolation with no migration
• No natural selection
• Very large population
• Random mating

Question 34

How does speciation occur?

Answer 34

• There is reproductive isolation where parts of the original population reproduce in separate groups due to geographical separation or variation produced by random mutations
• This means the 2 new populations have separate gene pools
• Within each new population there is genetic variation caused by random mutations
• Due to natural selection different alleles are selected for and passed on which changes the allele frequencies in each population over a long period of time until the new populations become so different they cannot interbreed to produce fertile offspring

Question 35

What are the 2 types of speciation?

Answer 35

• Allopatric speciation
• Sympatric speciation

Question 36

What is allopatric speciation?

Answer 36

Speciation arising from geographical separation such as oceans, rivers, mountains and deserts.

Question 37

What is sympatric speciation?

Answer 37

Speciation arising from reproductive isolation mechanisms with no physical barrier such as courting behaviour or fertilisation

Question 38

What is artificial selection?

Answer 38

When farmers or breeders selectively breed plants or animals with desirable characteristics

Question 39

What are the 5 steps of artificial selection?

Answer 39

• Select males and females with desired characteristics
• Interbreed males and females with desired characteristic
• From offspring select males and females with desired characteristic
• Interbreed males and females with desired characteristic
• Repeat for several generations

Question 40

What are examples of artificial selection?

Answer 40

• Dairy cows for increased milk yield
• Wheat for increased yield or disease resistance

Question 41

What problems does artificial selection cause?

Answer 41

• Reduces gene pool
• Reduces genetic variation
• Increases health problems

Question 42

How are the problems with artificial selection reduced?

Answer 42

By using wild varieties which are a resource of genetic material providing new alleles

Question 43

What are the ethical considerations with using artificial selection?

Answer 43

Over many years humans have artificially selected dogs which was originally for the role that they performed. However, now they are often selected for the way they look and this often comes with severe health issues for the dog such as breathing difficulties for pugs.