Purple Booklet

Question 1

What is a genotype?

Answer 1

The genetic composition of an organism

Question 2

How many alleys are there for each gene?

Answer 2

Usually two

Question 3

What happens if both alleles in a gene contribute to the phenotype?

Answer 3

Co-dominance

Question 4

Dominant gene definition

Answer 4

Expresses itself, even when present with the recessive allele of the same gene

Question 5

Recessive alleledefinition

Answer 5

Expresses itself only in the presence of another identical allele

Question 6

Name for when both alleles are the same

Answer 6

Homozygous

Question 7

Name for when both alleles are different

Answer 7

Heterozygote

Question 8

What is the locus?

Answer 8

Position at which genes coding for the characteristic are found

Question 9

What is a dihybrid cross?

Answer 9

Crossing two characteristics

Question 10

Identify ways other than myotic events which gene variation is introduced

Answer 10

Random fertilisation
-Chromosome mutations
-Structure of chromosomes, inversion deletion and translocation

Question 11

What is the difference between mono hybrid and dihybrid inheritance?

Answer 11

Mono hybrid is one characteristic and dihybrid is two characteristics

Question 13

Suggest reasons why observed ratios are often not the same as expected ratios

Answer 13

• Each gamete produced through independent event
  -Even though there’s a 50% chance of having a dominant or recessive allele does not mean that there will be exactly half dominant/recessive
  -The more organisms used in the cross the closer the 3 to one ratio will be

Question 14

Define co dominance

Answer 14

When both genes are expressed equally

Question 15

What statistical test can be used to test expected results against observed results?

Answer 15

Chi squared

Question 16

Describe what happens in the first generation cross if no crossing over occurs

Answer 16

Homologous chromosomes pair in prophase one
If no crossing overtakes place all resulting chromosomes in gambits have original allele combinations and there are no recombinations

Question 17

Describe what happens in the first generation cross with crossing over occurring

Answer 17

Crossover may take place in prophase one
In this case, half of the resulting gambits will have unchanged chromosomes (non-recombinant)
And half will have recombinant chromosomes

Question 18

Suggest a factor that would increase the likelihood of crossing over ever occurring

Answer 18

The further the distance between the loci the more likelihood of crossing over there is

Question 19

epistasis definition

Answer 19

when the allele of one gene affects or masks the expression of another gene in the phenotypege

Question 20

gene pool definition

Answer 20

all of the alleles of the genes of all individuals in a population

Question 21

allelic frequency definition

Answer 21

number of times an allele occurs in a population

Question 22

what factors effect the allelic frequency

Answer 22

• natural/ artificial selection- increases beneficial alleles
• genetic bottle necks- due to drastic reduction in population size (results in reduced genetic biodiversity)
• founder effect- population decended from only a few individuals resulting in a small gene pool

Question 23

the proportions of alleles will remain the same in a population providing…

Answer 23

• no new mutation
• no net migration
• no natural selection for or against alleles
• large population
• random mating

Question 24

hardy weinburg equation

Answer 24

p^2 + 2pq + q^2 = 1.0w

Question 25

what genetic factors causing variation within a species

Answer 25

- mutations - meisosis - random fertalisation

Question 26

environmental factors causing variation within a species

Answer 26

diet, climactic condition, soil conditions, ph and food availability

Question 27

what are selection pressures

Answer 27

environmental factors that limit the population of a species

Question 28

what characteristics will follow a normal distribution curve (bell shaped curve)

Answer 28

characteristics that are effected by multiple genes (polygenes) and the environment

Question 29

what conditions must be met for natural selection to occur

Answer 29

- organisms produce more offspring that can be supported by the available supple of food and light - there is genetic variety within the population of all species - a variety of phenotypes that selection operates against

Question 30

the overproduction of offspring leads to what type of competition for limited resources

Answer 30

intraspecific competition

Question 31

Suggest why the hardy Weinberg principal cannot be applied to populations in zoos

Answer 31

Small population, controlled mating

Question 32

Describe the effect of natural selection on the allele frequency

Answer 32

-Some alleles will have the phenotype that creates a greater chance of survival -These individuals are more likely to make and pass on alleles to future generations -Variation provides the potential for a population to evolve an adapt to new circumstances

Question 33

Why is it beneficial for an individual to have offspring that are not genetically identical?

Answer 33

-The population will have jeans needed to survive in almost any new set of circumstances -Makes them more able to deal with changes in circumstance -Populations with less variation and more vulnerable to disease and climactic changes

Question 34

Conditions that produce stabilising selection

Answer 34

Tends to occur when environmental conditions are constant over a long period of time

Question 35

Affect on the phenotype of stabilising selection

Answer 35

Eliminates the extremes of the phenotype range also eliminates the capacity for evolutionary change

Question 36

Example of stabilising selection

Answer 36

Fur length shorten in years when climate is hotter and so when the climate causes the species are less able to deal with the conditions and a less insulated

Question 37

Conditions needed to produce directional selection

Answer 37

If the environmental conditions change so will the optimum value for survival and phenotypes adapt?

Question 38

Affect on the phenotype of directional selection

Answer 38

Range of genetically different individuals in respect to anyone phenotype -Continuous variation causes normal distribution curve

Question 39

Example of directional selection

Answer 39

Selection pressure favours, more favourable genes causing mean to be in those genes -If conditions are colder than selection pressure moves to longer fur

Question 40

Conditions that produce disruptive selection

Answer 40

When there are wide ranges in conditions such as cold winters and warm summers leading to 2 different forms of the species

Question 41

Effect on the phenotype of disruptive selection

Answer 41

Favours extreme phenotypes at the expense of intermediate phenotypes -Most important in bringing out evolutionary change

Question 42

Example of disruptive selection

Answer 42

Coho salmon -Large male or face competitors and small males can sneak up on females in spawning grounds meaning intermediate males are left a disadvantage

Question 43

Species definition

Answer 43

A group of organisms that can make and produce fertile offspring

Question 44

What has to happen for natural selection to result in the formation of two new species

Answer 44

There must be a factor that means that the two populations are no longer able to reproduce so they become reproductively separated

Question 45

What are possible causes to prevent members of the same species from mating?

Answer 45

Geographical barrier

Question 46

describe the process of speciation

Answer 46

- after serperation the 2 populations will become genetically different due to speciation occuring - each population will experience different selective pressures due to differences in the environment - natural selections causes favours alleles to be passed on - species adapt to their local enviroments