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Genetics Test

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locus
the particular position on homologous chromosome of a gene
homozygous
having 2 identical alleles of a gene
heterozygous
having 2 different alleles of a gene
genotype
the alleles (genes) of an organism
phenotype
the physical characteristics of an organism
dominant allele
an allele with same effect on phenotype whether it is present in homo or heterozygous state
recessive allele
an allele that only has an effect on the phenotype when present in homozygous state
codominant allele
pair of alleles that both affect the phenotype when present in heterozygote
carrier
an individual that has one copy of recessive allele that causes a genetic disease in individuals that are homozygous for this allele
test cross
testing a suspect heterozygote by crossing it with a known homozygous recessive
p generation
parent generate
f1
offspring (filial)
f2
offspring of f1, allowed to self fertilize
O blood group
ii
A blood group
IAIA or IAi
B blood group
IBIB or IBi
AB blood group
IAIB
X chromosome
relatively large; carries many genes
females have 2 copies, males have 1
Y chromosome
much smaller; carries only a few genes
Sex linked genes
genes located on X chromosome
gene linkage
combinations of genes tend to be inherited together because of their loci being close together on the same chromosome
recombination
the reassortment of genes or characteristics into different combinations from those of the parents
linkage groups
crossing over allows recombination of linked genes; all of the genes that have their loci on the same chromosome form a linkage group
polygenic inheritance
a single characteristic that is controlled by 2+ genes
9
number of possible genotypes there are for a polygenic character that is controlled by 2 genes each with 2 alleles