Summary Grade 12 Genetics notes

GENETICS & INHERITANCE


HEREDITARY - tendency for the characteristics of parents to be passed to
their offspring



LOCUS - the position of gene on a chromosome



ALLELE - two or more alternative forms of a gene at the same locus on
homologous chromosomes



Homozygous recessive
Homozygous dominant
 Allele’s are the same
 Allele’s are the same
 bb
 BB -> genotype

Allele’s of a
chromosome




Heterozygous

 Allele’s are different
 Bb



Genotype:

: alleles for characteristics

: BB, Bb, bb

, Phenotype:

: description of the condition produced by the alleles

: brown hair



DOMINANT ALLELE RECESSIVE ALLELE
 Shows in the phenotype when  Not shown in the phenotype
in heterozygous or when in heterozygous
homozygous condition condition
 Capital letter  Both alleles must be recessive
for recessive gene to show
 Lowercase letter


Examples:



B - brown hair

b - blond hair


BB Bb bb

 Homozygous dominant  Heterozygous  Homozygous recessive
 Brown hair  Brown hair  Blond hair



MENDEL - THE FATHER OF GENETICS


GREGOR MENDEL - made the first break through in understanding how
characteristics were inherited



*STUDIED MONOHYBRID INHERITANCE