3.2 pant and animal breeding Flashcards
selective breeding
the process by which individuals with desirable characteristics are breed together to produce offspring with desirable features.
what do breeders select for when breeding plants
higher yield
higher nutritional value
resistance to pest and disease
what are animals selected for when breeding together cattle
improved milk yield
butterfat content
meat production
what are sheep selected for in breeding programmes
improved wool quantity and quality
phenotype
physical appearance of an organism
genotype
set of genes an organism possesses
alleles
different forms of the same gene
homosygous
having two identical alleles
heterozygous
having two different alleles of a gene
dominant allele
allele that is always expresssed
recessive allele
allele that is only expressed when homozygous
true breeding
organism that always produces the same phenotype when crossed with itself
variation
the range of differences between the member of the same species
discrete variation
when variation of a characteristic can be divided into 2 or more distinct groups
continuous variation
within a range from one extreme to another
is being able to roll your tongue a single or poly gene inheritance
single gene
is hair colour a single or polygenic gene inheritance
poly
what happened if inbreeding is performed for long periods of time
there is a loss of heterozygosity so plants and animals become homozygous for the selected trait.
how is inbreeding depression caused
by genotypes emerging that are homozygous for an increasing number of recessive alleles of harmful genes.
what can inbreeding depression lead to
decline in vigour,
size,
fertility
yield of the plant or animal
how can inbreeding depression be prevented
by choosing a population of parent plants that are homozygous for the desired characteristics heterozygous for everything else
inbreeding depression definition
the accumulation of other homozygous alleles can cause the expression of deleterious recessive alleles.
what is cross breeding
when new alleles are introduced to plant and animal lines by crossing a cultivar or breed with an individual with a different desired genotype
why are F1 hybrids not bred together with other F1 hybrids
shows to much variation
what is a benefit of hybridisation
restore hetrerozygosity
what have increased in F1 hybrids
vigour
yield
fertility
how is genome sequencing a benefit
organisms with desirable gens can be identified and used in breeding programmes
why is there a selection of treatments in a field trial
to ensure fair comparisons
why is the number of replicates taken into account during field trials
take into account the variability within the sample
why are the treatments randomised in a field trial
to eliminate bias when measuring treatment effects
