Mendelian Inheritance III Flashcards
What is the law of segregation?
Two alleles for a gene separate during gamete formation and end up in different gametes. There is a 50% chance that either allele will end up in either gamete.
What is the law of independent assortment?
Alleles of one gene separate independently of an allele of another gene.
When does segregation occur?
Pairs of alleles are separated when gametes are formed.
What is incomplete dominance?
This occurs when a dominant allele does not completely mask the effects of the recessive allele (“blending” effect – red and white = pink)
What is codominance?
No allele can block the expression of the other allele – think of ABO blood group or speckled chickens
How do hydrangeas reflect the phenotypic interaction between genotype and environment?
Hydrangeas grown in basic soil appear pink while those grown in acidic soil appear blue, even if their genotypes are identical.
What does the norm of reaction determine?
The way in which the environmental distribution is transformed into the phenotypic distribution for a given genotype is determined by the norm of reaction.
How is a distribution of environments reflected biologically?
A distribution of environments (eg temperature) will be reflected biologically as a distribution of phenotypes (eg size at maturity).
In what scenario is it not possible to predict the phenotypes of different genotypes in new environments?
When the norms of reaction curves of different genotypes cross each other.
What is pedigree analysis?
The study of the genetic basis of phenotypes.
What is a pedigree?
A pedigree is a family tree that describes the interrelationships of parents and children across generations.
How are pedigrees used?
Using pedigrees, inheritance patterns of particular traits can be traced and described.
What are the three pedigree rules for rare dominants (autosomal)?
- Every affected person has an affected parent.
- About half of the offspring of an affected parent are also affected.
- The phenotype usually occurs in both sexes.
What are the three pedigree rules for rare recessives (autosomal)?
- Affected people usually have two parents who are not affected.
- In affected families, about one fourth of the children of unaffected parents are affected.
- The phenotype usually occurs equally in both sexes.
About how many autosomal dominant diseases are known in humans?
About 3,700
