Chapter 10 Inheritance Flashcards
Heredity
Study of inheritance (mendelian genetics)
Homozygous
genotype with two identical alleles; pure breeding
Heterozygous
Genotype with 2 different alleles
codominance
both are shown
-both traits are expressed
e.g. red + white = red + white spots
incomplete dominance
Mix of both
-Offspring is intermediate
e.g. red + white = pink
hemizygous
since males have one x allele, all daughters of a father with the trait will be carriers
- cant be sons as Y never carrier a trait only X
continuous variation
variation in characteristics caused by two or more genes
-the range of phenotypes is wide with small, smooth graduations between differences.
e.g height, eye colour
Discontinuous variation
variation in a characteristic caused by a single gene
-shows two or just a few clearly distinct phenotypes
e.g. gender, blood type
Sex-linked inheritance
-Gene located on sex chromosome
-Results in different phenotypic frequencies
Sex linked (X-linked) dominant
-Trait never passed from father to son
-Male with trait passes it onto all daughters
-Female with trait may pass it onto both daughters and sons
-if trait disappears, it does not reappear
X-linked recessive
-All sons of a female trait are affected
-All daughters of males affected will be carriers of the trait and can appear in their sons
Autosomal dominant
-Males and females are affected
-Affected individuals have at least 1 affected parent
-trait disappears, does not reappear
Autosomal recessive
-males and females can be affected
-2 unaffected parents can have an affected child
-trait may disappear, but reappear in later generation
Assigning genotypes for dominant pedigrees -> autosomal or X-linked
-If affected male has an affected son, then disease is not X-linked
-All of his daughters must also be affected if the disease is X-linked
Polygenic inheritance
-Transmission of characteristics controlled by two or more genes
e.g height, skin colour
