Genetics

Question 1

What is Chlorosis

Answer 1

When the leaves of a plant look pale/yellow due to a lack of chlorophyll
Can be caused by different environmental features such as virus infections, lack of light, mineral deficiencies

Question 2

What is variation in body mass due to

Answer 2

A combination of both genetic and environmental factors.

Question 3

What is a genotype

Answer 3

The combination of alleles an organism has inherited for a particular characteristic

Question 4

What is a phenotype

Answer 4

The observable characteristics of an organism determined by both environmental and genetic factors

Question 5

What is a dominant allele

Answer 5

An allele that will always be expressed if present in an organism

Question 6

What is a recessive allele

Answer 6

An allele that will only be expressed when there are two copies of it

Question 7

What is Discontinuous variation

Answer 7

Differences between individuals that are qualitative and appear only in discreet values

Question 8

What is the cause and genetic control of discontinuous variation

Answer 8

Caused by genetic factors and includes one or two genes
Different alleles on gene locus cause large effects on phenotype

Question 9

What is Continuous variation

Answer 9

When differences between organisms are quantitative and can take any value within a range

Question 10

What is the cause of continuous variation and its genetic control

Answer 10

Genetic + environmental factors
Controlled by polygenes (multiple genes)

Question 11

What is an additive effect

Answer 11

When different genes add together to effect the phenotype
(eg. genes controlling height work together with an additive effect)

Question 12

What is monogenic inheritance

Answer 12

When the inheritance of a single gene is shown

Question 13

What is codominance

Answer 13

When two alleles occur in a gene that are both equally dominant causing both alleles to be expressed in phenotype

Question 14

What does it mean when a gene is sex-linked

Answer 14

That the characteristics expressed are determined by genes carried on the sex chromosome

Question 15

What is Haemophilia

Answer 15

A sex-linked recessive genetic disorder that causes patients to have blood that clots slowly due to the absence of a protein blood-clotting factor
It is carried on the X chromosome and so males dont have any corresponding chromosomes so it is always expressed if present in males

Question 16

What is Linkage

Answer 16

When particular genes are located on the same chromosome and so are inherited as one unit
Not effected by independent assortment

Question 17

What are recombiant offspring

Answer 17

When organisms have different combinations of alleles than either parent

Question 18

What happens when genes are close together on a chromosome

Answer 18

They are less likely to be separated during crossing-over and so there are less recombinant offspring

Question 19

What is recombination frequency

Answer 19

The measure of the amount of crossing over that has happened in meiosis
= num of recombinant offspring/total offspring

Question 20

What is Epistasis

Answer 20

The interaction of genes at different loci
Gene regulation is a form of epistasis as regulatory genes control activity of structural genes

Question 21

What is a hypostatic gene

Answer 21

When one gene is affected by another gene

Question 22

What is dominant epistasis

Answer 22

When a dominant allele results in having a gene having an effect on another gene

Question 23

What is evolution

Answer 23

The process through which the inherited characteristics of a population change over generations as a result of variations in the frequency of different alleles in population gene pool

Question 24

What key factors influence evolution

Answer 24

mutations, gene flow, genetic drift, natural selection, sexual selection

Question 25

How does mutation influence evolution

Answer 25

introduces new alleles + genetic variation

Question 26

What is gene flow

Answer 26

the transfer of alleles between populations

Question 27

What is genetic drift

Answer 27

Random changes in allele frequency due to chance event particularly influential in small isolated populations and can accelerate production of new species

Question 28

How does natural selection effect evolution

Answer 28

Enhances frequency of alleles that improve survival and the ability to reproduce

Question 29

How does sexual selection influence evolution

Answer 29

Increases frequency of alleles that enhance reproductive success

Question 30

How does size of population influence genetic variation

Answer 30

Small pop = risk of extermination when selection pressure changes Large pop = more likely to adapt effectively to changing selection pressures through natural selection

Question 31

What are density-dependent factors

Answer 31

factors that limit a population that depend on size

Question 32

What are density-independent factors

Answer 32

factors that impact a population regardless of size

Question 33

What is the bottleneck effect

Answer 33

When a population's size reduces suddenly + drastically it lasts for at least one generation

Question 34

What issues arise due to the bottleneck effect

Answer 34

Reduced gene pool + genetic diversity so leads to inbreeding and reduced fertility

Question 35

What are some benefits of the bottleneck effect

Answer 35

May allow beneficial mutations to become more prevalent

Question 36

What is the founder effect

Answer 36

When a small group splits from a larger population and forms a new smaller population

Question 37

What are some benefits of the founder effect

Answer 37

rare alleles from original population may become more common in new population

Question 38

What are some issues with the founder effect

Answer 38

Can lead to reduced gene pool and decreased genetic diversity

Question 39

What are the types of selection

Answer 39

Directional Stabilising Disruptive

Question 40

What is directional selection

Answer 40

Selects for one extreme phenotype over other phenotypes

Question 41

What is stabilising selection

Answer 41

Selects for an average phenotype over extreme phenotypes

Question 42

What is disruptive selection

Answer 42

Selects for extreme phenotypes against intermediate phenotypes - especially when an environmental factor takes 2+ distinct forms

Question 43

What is the Hardy-Weinberg principle

Answer 43

Predicts the proportion of dominant over recessive alleles

Question 44

What are the conditions needed for the Hardy-Weinberg principle to stay the same

Answer 44

No mutations arise isolated population no selection large population random mating

Question 45

What is a gene pool

Answer 45

all alleles of all genes of all individuals in a population

Question 46

What is allele frequency

Answer 46

Number of times an allele appears in a gene pool

Question 47

What are the Hardy-Weinberg equations

Answer 47

p+q = 1 p^2 + 2pq + q^2 = 1

Question 48

What is reproductive isolation

Answer 48

When populations cant interbreed to produce viable, fertile offspring

Question 49

What does reproductive isolation result from

Answer 49

prezygotic reproductive barriers postzygotic reproductive barries

Question 50

What are prezygotic reproductive barriers + examples

Answer 50

prevent fertilisation and formation of a zygote eg. habitat isolation, variations in mating rituals

Question 51

What are postzygotic reproductive barriers

Answer 51

result of hybridisation - infertile/non-viable offspring is produced

Question 52

What are the two types of speciation

Answer 52

Allopatric speciation Sympatric speciation

Question 53

What is allopatric speciation

Answer 53

Population is split by a physical geographical barrier.

Question 54

How does allopatric speciation work

Answer 54

This exposes different groups to different selection pressures Leads to reproductive isolation -> no gene flow -> speciation

Question 55

What is sympatric speciation

Answer 55

takes place in same geographical location

Question 56

How does sympatric speciation work

Answer 56

Ecological or behavioural separation mechanisms (habitat preference/mate selection) leads to reproductive isolation -> no gene flow -> speciation

Question 57

What is adaptive radiation

Answer 57

Organisms diversify rapidly from ancestral species into new forms More likely to occur when new resources are made available

Question 58

What is artificial selection

Answer 58

When organisms are bred selectively for specific genetic traits

Question 59

What problems arise because of inbreeding

Answer 59

Reduced genetic diversity Reduces heterozygosity Inbreeding depression reduces fitness + adaptability

Question 60

what is inbreeding depression

Answer 60

loss of ability to survive well

Question 61

How can inbreeding be balanced

Answer 61

By outbreeding species to increase genetic diversity

Question 62

What is a phenotype

Answer 62

The observable physical properties of an organism

Question 63

What is an allele

Answer 63

A version of a gene

Question 64

What is autosomal linkage

Answer 64

When 2+ genes are located on the same chromosome and so are more likely to be inherited together

Question 65

What does it mean to be homogametic

Answer 65

Has/produces gametes with 1 type of sex chromosome

Question 66

Name 3 genetic disorders

Answer 66

Haemophilia Colour-blindness sickle cell disease

Question 67

What is true breeding

Answer 67

Offspring that is a homozygous individual