AP Biology Chapter 14: Mendel and the Gene Idea

character
a heritable feature that varies among individuals

trait
each variant of a character

true-breeding
organisms that, when reproducing, create offspring of all the same variety

hybridization
the crossing of two true-breeding parents

P generation
the name for the true-breeding parents

F1 Generation
the hybrid offspring of true-breeding parents

F2 Generation
after the self-polonization of the F1 generation, this is produced.

The Law of Segregation
1. alternative versions of genes account for variations in inherited characters. 2. for each character, an organism inherits two alleles, one from each parent. 3. two alleles for a heretable character separate during gamete formation and end up in different gametes.

dominant allele
determines organisms apperence

recessive allele
has no noticible affect on organisms appearence

Punnett square
a diagram for predicting the allele composition of offspring from a cross between individuals of known genetic makeup

homozygous
an organism having a pair of identical alleles for a character, either dominant or recessive

phenotype
an organisms traits

genotype
an organisms genetic makeup

testcross
the result of breeding a recessive homozygote with an organism of dominant phenotype but unknown genotype

monohybrids
parent heterozygous for one character

dihybrids
heterozygous for two characters

law of independent assortment
each pair of alleles segregates independently of other pairs of alleles during gamete formation

multiplication rule
to determine the probability, we multiply the probability of one event by the probability of another

addition rule
the probability that any one of two or more mutually exclusive events will occur is calculated by adding together their individual probabilities

complete dominance
the situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable

codominance
the situation in which the phenotypes of both alleles are exhibited in the heterozygote

incomplete dominance
the situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele

Tay-Sachs disease
inherited disorder in humans. the brain cells of a baby with this disease are unable to metabolize certain lipids because a crucial enzyme does not work properly. as these lipids accumulate in the brain cells, an infant begins to suffer seizures, blindness, and degeneration of motor and mental preformance.

pleiotropy
multiple phenotypic effects, common for most genes

epistasis
a gene at one locus alters the phenotypic expression of a gene at a second locus. the mice color, review

quantitative characters
characters that vary in the population along a continuum (in gradations)

polygenic inheritance
an additive effect of two or more genes on a single phenotypic character

norm of reaction
the range of phenotypic possibilities due to environmental influences.

multifactoral
many factors, both genetic and environmental, influence phenotype

pedigree
the assembling of information about a particular trait into a family tree describing the interrelationships of parents and children across the generations

Cystic Fibrosis
most common lethal genetic disorder in the us. normal allele for this gene codes for a membrane protein that functions in chloride ion transport between certain cells and the extracellular fluid. these chloride transport channels are defective or absent in the plasma membrane of children who inherit two recessive alleles for this disorder. results in abnormally high concentraion of extracellular chloridem which causes the mucus that coats cells to become thicker and the buildup causes many problems

sickle-cell disease
the most common inherited disease of people of african decent. caused by a substitution of an amino acid in the hemoglobin protein of red blood cells. when an individuals blood oxygen is low, the cells turn into rod shaped ones. clump and clog blood vessels.

Huntington’s disease
dominantly inherited, degenerative disease caused by dominant allele that has no obvious phenotypic effect until the individual is 35-45. leads to deterioration of the nervous system

aminocentesis
14-16 week of pregrancy. determines if fetus has taysachs. physician inserts a needle in the unterus and extracts extracellular fluid. MUST BE CULTURED. Takes awhile.

chorionic villus sampling CVS
physician inserts a narrow tube in the cervix to the uterus, takes part of placenta, tests for taysachs and others. preformed 8-10th wk of pregnancy, do not have to wait to culture.

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