Yaer 9 End Of Year Revision Flashcards
What is variation
The presence of differences in living things in the same species
What are the 3 kinds of variation
Environmental
Genetical (inheritance)
Both
What is DNA
DNA is the molecule that holds the instructions for growth and development in every living thing.
Where is DNA stored
DNA is packaged into 23 pairs of chromazones (46) which are found in the nuclease of every cell in your body.
What are Alleles
Different forms of the same gene
What is a dominant allele
An allele that will always be expressed even if pared with a recessive allele
What is a recessive allele
An allele that will only be expressed if both alleles are of this type
What happens during fertilisation
The sperm cell and the egg cell each contain 23 chromosomes and are called gametes. They both fuse together and form a zygote which has 46 chromosomes
What does homozygous mean
That both alleles are the same
What does heterozygous mean
The two alleles are different
What is the genotype
The allele pair for each characteristic
E.g. BB
What is the phenotype
The physical expression of the pair of alleles
E.g. green
What is selective breeding
Selective breeding is when animals of the same species with the same desirable traits are bread together to increase the chance of the offspring having the desired trait
Give 3 examples of selective breeding
Belgium blues are bread to have extra meat
Carrots are bread to be orange instead of purple
Dogs are bread to seem cuter e.g. fluffy coats
What is a clone
A clone is an organism with an exact genetical copy of its parent so will have the same genes and look identical
E.g. dolly the sheep
