inheritance 2.4 Flashcards
what allows for variation
sexual reproduction
what is a species
a group of organisms which reproduce to produce fertile offspring
the types of variation
discrete and continuous
discrete variation
when a characteristic can be used to divide up the members of a species into two or more distinct groups
examples of discrete variation
ear lobes, dog coat colour, hair colour and finger prints
continuous variation
when a characteristic varies in a smooth continuous way and doesn’t fall into distinct groups
examples of continuous variation
petal length, body mass, height and hand span
what type of variation does single gene show
discrete variation
when are characteristics single gene
when they are controlled by only one single gene
what type of variation does polygenetic show
continuous variation
when do characteristics involve polygenetic inheritance
when a characteristic is controlled by more than one gene
most characteristic are controlled by more that one gene
homozygous
an organism that has two identical alleles
example:BB or bb
hetrozygous
an organism that has two different alleles, one being dominant and one being recessive
example:Bb
are homozygous organisms true-breeding
yes
are heterozygous organisms true-breeding
no
phenotype
a person’s physical characteristics as a result of their gene
genotype
complete set of genes
allele
different form of the same gene
what is true-breeding
when an organism is crossed with another organism who has the same genotype and all of the offspring produced have the same phenotype as parents
dominant alleles
- written as capital letters (B)
- only one copy of dominant allele needed to display dominant phenotype
recessive alleles
- written as small letter (b)
- two copies of recessive allele is needed to display recessive phenotype
monohybrid crosses
allows us to determine the genotype and phenotype of offspring
why are family trees used
to trace through several generations of families to see passing genes
why is the genotypical ratio not always achieved
because fertilisation is a random process that involves an element of chance
