Mendal's peas Flashcards
autosome
a chromosome not involved in determining the sex of the organism
sex chromosome
a chromosome involved in determining the sex of the organism
locus
specific position on the chromsome where a gene is located
allele
alternative versions of the same gene eg: A, a
trait
a characteristic of an organism (eg: seed colour)
phenotype
the appearance of an organism
genotype
- a genetic composition of an organism (AA,Aa,aa)
homozygous
when 2 individuals carries 2 of the same allele at a locs
heterozygous
individuals carries 2 different alleles at locus
law of segregation
states that 2 copies of a gene segregate from each other during meiosis which gives rise to gametes
meiosis genetic consequences
- segregation of alleles
- independent assortment of chromosomes
- crossing over and recombination of alleles
autosomal dominant
can have both homozygous genotype or heterozygous eg: BB or Bb
autosomal recessive
Can only be homozygous recessive (bb)
Incomplete dominance
- results in intermediate phenotype (one allele isn’t completely dominant to the other
- why> alleles code for alternate forms of a protein required for pigment production one red allele is only enough to make 50% pigment hence pink phenotype
codominance
where the full effect of both alleles can be seen in the phenotype of the heterozygous individual
Variations in dominance…
don’t negate mendel’s law of segregation they reflect differences in the way gene products control the production of phenotypes
- the type of dominance is dependent on the proteins encoded by the genes and their functions within a cell
- often a gene locus has more than 2 alleles
