Key Area 3.2 Flashcards
Describe and explain what polygenic inheritance is?
- Characteristic controlled by alleles of more than 1 gene
- It is continuous
- It’s effects are additive
- Characteristic that show polygenic inheritance are influenced by the environment
What is outbreeding and give an example
Fusion of two gametes from unrelated members of the same species
Examples:
Wild animals
Cross pollinating plants
Name an advantage and disadvantage of outbreeding
Advantage:
Promotes heterozygosity
Disadvantage:
Not all offspring will show the desired characteristic of the parents
What is inbreeding and give an example
Fusion of two gametes from close relatives of the same species
Examples:
Self pollination plants e.g. Peas, rice
Advantage and disadvantage of inbreeding
Advantage:
Ensures each generation receives the alleles for desired characteristic
Disadvantage:
Primates homozygosity
What is a test cross
Cross between:
Organism with unknown genotype for characteristic
X
Organism who is homozygous recessive for that characteristic
What is the desired and undesired effect of inbreeding
Desired:
Plant/animal bred for years until population breeds true
Undesired:
Loss of heterozygosity which causes inbreeding depression
What causes inbreeding depression
Deleterious recessive alleles becoming homozygous
What effect does inbreeding depression have?
Decline in:
- vigour
- size
- fertility
How can inbreeding depression be avoided
Selecting parent plants who are homozygous for desired characteristics while heterozygous for others
This maintains genetic diversity
What is cross breeding
And what is the purpose
Cross breeding is breeding an organism with different but desired genotypes
Allows new alleles to be introduced into plant and animals
What does cross breeding do?
Helps avoid the problems associated with inbreeding
What is a back cross
Crossing of an F1 hybrid with its parents
What is the purpose of back crossing
Used to introduce a required gene from a parent while still keeping other desired traits
How can you achieve an F1 generation
Crossing two genetically dissimilar parents
How can a hybrid with both desired characteristics be achieved
Organism with desired trait1
X
organism with desired trait2
What does crossing two homozygous parents create
Uniform F1 generation
What can be used to maintain a required breed
Selection
Back crossing
What will an F1 self cross produce
Produce a genetically diverse F2 generation
What is an advantage and disadvantage of a genetically diverse F2 generation
Advantage:
Production of new varieties
Disadvantage:
Unsuitable as a crop
What properties do F1 hybrids have and why
Increased:
- vigour
- yield
- fertility
Why?
Recessive alleles are masked
Name and describe 3 main factors in a plant
1) Selection of treatment:
To allow fair comparison
2) Number of replicates:
To take account of variability
3) randomisation of treatment:
To eliminate bias when measuring treatment affects
What is the aim of plant field trails
1) COMPARE the performance of different plant cultivars under same set of experimental conditions
2) Find out the effects of different ENVIRONMENTAL CONDITIONS of a cultivar of plants
How is genetic material passed to crop plant from a bacterial with a modified plasmid
Gene passed horizontally
Give an example of genetically modified crop
Gene for vitamin A into ride to make golden rice
Benefit:
Better nutrition for a human consumers in 3rd world countries
