Unit 3 exam Flashcards
epistasis
when one gene locus masks or modifies the phenotype of a second gene locus
polygenic inheritance
a characteristic, such as height or skin color, that is influenced by two or more genes.
pleiotropy
a single gene affects two or more characters.
test cross
By performing a test cross, one can determine whether the individual is heterozygous or homozygous dominant.
ex. AAaa x BBbb
multiple alleles
more than two variations of a gene present.
ex. A, B and O blood type
complete dominance
A form of dominance wherein the dominant allele completely masks the effect of the recessive allele.
incomplete dominance
- neither allele is dominant
- shows a third phenotype
ex. red flower + white flower = pink
codominance
the alleles of a gene pair in a heterozygote are fully expressed. As a result, the phenotype of the offspring is a combination of the phenotype of the parents. Thus, the trait is neither dominant nor recessive.
ex. AB blood types
ex. red + white flower = red and white
how does sexual reproduction contribute to genetic variation?
- crossing over
- independent assortment
- random fertilization
- law of segregation
chromosomal theory of inheritance
genes are found at specific locations on the chromosome
nondisjunction
mistakes in meiosis 2
nondisjunction in meiosis 1
homologous pairs don’t separate.
(all gametes have either have an extra chromosome or are missing one; half and half)
nondisjunction in meiosis 2
sister chromatids don’t separate
(half of the gametes are ok)
compare sister chromatids and homologous chromosomes
sister chromatids:
- exact duplicates
homologous chromosomes:
- one maternal, one paternal (not identical)
