Chapter 14 Mendel and the Gene Idea

Blending hypothesis
the idea that genetic material contributed by the two parents mixes in a manner analogous to the way blue and yellow paints blend to make green

gene idea
parents pass on discrete heritable units — genes — that retain their separate identities in offspring

Gregor Mendel
abby garden, monk, documented a particulate mechanism of inheritance; discovered the basic principles of heredity by breeding garden peas in carefully planned experiments

character
name for a heritable feature, such as flower color, that varies among individuals

trait
each variant for a specific characteristic that varies from one individual to another, white vs purple

true-breeding
term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate

hybridization
(genetics) the act of mixing different species or varieties of animals or plants and thus to produce hybrids

p generation
true-breeding parents

F1 generation
the hybrid offspring of the p generation

F2 generation
the offspring of the F1 generation

allele
one of many alternate forms of a gene that can have the same locus on homologous chromosomes and are responsible for alternative traits. for each character, an organism inherits 2 of these for each character

dominant
an allele whose trait always shows up in the organism when the allele is present

recessive allele
an allele that is masked when a dominant allele is present

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 (allele)

phenotype
what an organism looks like as a consequence of its genotype

genotype
the particular alleles at specified loci present in an organism; genetic makeup

homozygous
having identical alleles at corresponding chromosomal loci

heterozygous
having dissimilar alleles at corresponding chromosomal loci

testcross
mating of an individual of unknown genotype but dominant phenotype with a homozygous recessive individual. most efficient if you cross with an individual expressing the recessive trait

monohybrids
heterozygous for one character

dihybrids
individuals heterozygous for two characters`

incomplete dominance
one allele is not completely dominant over the other allele, red+white=pink

codominance
situation in which both alleles of a gene contribute to the phenotype of the organism; red+white=red and white stripes

epistasis
A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.

pleiotropy
A single gene having multiple effects on an individuals phenotype

quantitative characters
A heritable feature in a population that varies continuously as a result of environmental influences and the additive effect of two or more genes (polygenic inheritance).

polygenic inheritance
process by which several genes interact to produce a certain trait; responsible for most important traits ex skin tone

norm of reaction
The range of phenotypes produced by a single genotype, due to environmental influences.

multifactorial
involving or depending on several factors or causes for genes it could be genetics and environment

pedigree
a diagram that shows the occurrence of a genetic trait in several generations of a family

amniocentesis
A technique of prenatal diagnosis in which amniotic fluid, obtained by aspiration from a needle inserted into the uterus, is analyzed to detect certain genetic and congenital defects in the fetus.

choronic villus sampling
placental tissue test for prenatal diagnosis of potential genetic defects done btw weeks 8-12

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