Variation in Mendelian Genetics Flashcards
inheritance patterns may not?
always be predicted by mendelian genetics. inheritance patterns are way more complex than those described by mendel.
what were mendels laws?
- each character was determined by one gene
- there was only 2 alleles for each gene
- one allele was always completely dominant over the other
however, there are?
variations
for a single gene, there may be?
degrees of dominance
one allele may not be?
completely dominant over the other.
f1 may have a phenotype that is?
intermediate with those of the parents.
what is this observed in?
this is observed in snapdragons. red snapdragon and a white snapdragon results in a pink snapdragon. the offspring has a phenotype that is intermediate to that of the parents.
what is that “intermediate” called?
incomplete dominance
what does the symbol look like for incomplete dominance?
since no allele is dominant, instead of using uppercase and lowercase. the letter C for flower color is used with subscripts.
CRCR x CWCW = CRCW
what is incomplete dominance
in incomplete dominance, neither allele is completely dominant over the other. instead, the resulting phenotype is a blend or intermediate between the two parental traits.
what is codominance?
in codominance, both alleles contribute equally to the organisms phenotype. this means that both traits from the parents are fully expressed in the offspring, rather than one allele dominating over the other.
can you give an example of codominance
human mn blood group:
EXPLAIN codominance and human mn blood group example:
the MN blood group is determined by two forms a glycoproteins found on the surface of red blood cells.
M form of glycoprotein
N form of glycoprotein
these two glycoproteins are controlled by a single gene with two alleles.
LM LN.
both alleles are expressed equally when they are present in an individual.
Genotype: LMLM: this means the individual has two LM alleles homozygous for M. The red blood cells will express M phenotype: M.
Genotype: LNLN: this means the individual has two LN alleles homozygous for N. The blood cells will express N. phenotype: N.
Genotype: LMLN: this means that this individual has one LM and one LN allele. Since the alleles are codominant, both M and N forms will be expressed on rbc. Phenotype: MN
how can incomplete dominance be distinguished from codominance?
in incomplete dominance: the offspring will show an intermediate phenotype: mix of traits. example: red flowered snapdragon x white flowered snapdragon = pink flowered snapdragon.
in codominance: both traits will be expressed clearly. like in Mn blood group example, both M and N antigens will be expressed on the red blood cells. another example. or speckled chhicken example.
unlike the genes mendel studied in the garden pea plant, most genes…?
exist in more than two allelic forms: multiple alleles.
