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28 terms

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genetics
the branch of biology that studies heredity and variation in organisms
heredity
the biological process whereby genetic factors are transmitted from one generation to the next "the total of inherited attributes"
trait
a characteristic that an organism can pass on to its offspring through its genes.
gregor mendel
Augustinian monk and botanist whose experiments in breeding garden peas led to his eventual recognition as founder of the science of genetics (1822-1884)
purebred
an organism that always produces offspring with the same form of a trait as the parent
hybrid
a composite of mixed origin
what does p, f1 and f2 stand for
p gen is the parent, f1 is the generation of the children of the p gen, and f2 is the generation of children of 1 or 2 individuals of the f1 gen.
Explain how Mendel's particulate mechanism differed from the blending theory of inheritance.?
Mendel: Cross of Red and White will produce EITHER Red or White looking offspring.

Blending theory: Cross of Red and White will produce Pink ( a blend of read and white).
gene
(genetics) a segment of DNA that is involved in producing a polypeptide chain, sequence of DNA that codes for a protein and thus determines a trait
allele
one of two alternate forms of a gene that can have the same locus on homologous chromosomes and are responsible for alternative traits
locus
the specific site of a particular gene on its chromosome
dominant
trait that will show up in an organism's phenotype if gene is present
recessive
The inherited characteristic often masked by the dominant characteristic and not seen in an organism.
how many alleles from each parent?
23 from each
law of dominance
this states that some alleles are dominant and others are recessive
law of segregation
members of a pair of homologous chromosomes separate during the formation of gametes and are distributed to different gametes so that every gamete receives only one member of the pair
gamete
a mature sexual reproductive cell having a single set of unpaired chromosomes
law of independent assortment
each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random`
phenotype
what an organism looks like as a consequence of its genotype`
genotypes
its genetic makeup or allele combination
monohybrid
a hybrid produced by crossing parents that are homozygous except for a single gene locus that has two alleles (as in Mendel's experiments with garden peas)
dihybrid
a hybrid produced by parents that differ only at two gene loci that have two alleles each
homozygous dominant
Both alleles (factors) for a trait are the same and dominant (AA)
heterozygous dominant
two different genes; Aa
homozygous recessive
Both alleles (factors) for a trait are the same and recessive (aa)
incomplete dominance
one allele is not completely dominant over the other allele example: The gene for curly hair seems to be dominant to the gene for straight hair. Homozygous dominant individuals have curly hair, and homozygous recessive individuals have straight hair. However, heterozygous individuals have wavy hair; a phenotype in between curly and straight hair.
codominance
situation in which both alleles of a gene contribute to the phenotype of the organism REALLY LONG EXAMPLE: neither phenotype is recessive. Instead, the heterozygous individual expresses both phenotypes. A common example is the ABO blood group system. The gene for blood types has three alleles: A, B, and i. i causes O type and is recessive to both A and B. The A and B alleles are codominant with each other. When a person has both an A and a B allele, the person has type AB blood.

When two persons with AB blood type have children, the children can be type A, type B, or type AB. There is a 1A:2AB:1B phenotype ratio instead of the 3:1 phenotype ratio found when one allele is dominant and the other is recessive. This is the same phenotype ratio found in matings of two organisms that are heterozygous for incomplete dominant alleles.
polygenic trait
trait controlled by two or more genes