PACK 18: GENETICS AND INHERITENCE Flashcards
(13 cards)
define genotype
the genetic constitution of an organism
define phenotype
the genetic expression of the genotype and its interaction with the environment
define gene
a sequence of bases on DNA that code for one polypeptide
define allele
an alternative form of a gene
what is a test cross?
an organisms that displays a dominant trait may be heterozygous or homozygous dominant, to determine the genotype it can be crossed with an organism with a a homozygous recessive phenotype
what is codominance?
both alleles are expressed in the phenotype of a heterozygous organism
what is meant by the phrase multiple alleles?
some genes may have multiple alleles, e.g. the blood group ABO
what is sex determination?
sex is determined by the combination of chromosomes in a cell/organism rather than the genes (XX is female, XY is male)
what is sex linkage?
many genes carried on the sex chromosomes are unrelated to sexual characteristics but are inherited in different ways in males and females- these are said to be sex-linked genes and characteristics
what evidence form pedigree diagrams goes against sex linkage?
look for where a female with the recessive phenotype has a son or father with the dominant phenotype, this isn’t possible if the gene is on the X chromosone
what are dihybrid crosses?
this considers how two different genes coding for two different characteristics are inherited, the cross between two heterozygous individuals should produce a 9:3:3:1 ratio
what is epistatis?
prostatic arises in a dihybrid cross when there is some form of interaction between the 2 genes, such that one gene suppresses the expression of the other in the phenotype
what is autosomal linkage
genes on the same non-sex christine’s are said to be linked, a dibybrid cross would not produce an expected ratio (9:3:3:1)
