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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

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