Chapter 12 Flashcards
Genetics
Study of heredity (and all things relating to DNA)
Heredity
Is the transmission of biological traits from parent to offspring
What genetic principles account for the transmission of traits from parents to offspring?
“Blending” hypothesis : genetic material mix together like paint colors
“Particulate” hypothesis of inheritance : parents pass on discrete heritable units called genes that code for a particular trait
Gregor Mendel
Founded the science of genetics and discovered the basic principles of heredity
-documented inheritance through his experiments with garden peas
Character
A heritable feature, such as flower color
Trait
A variant of a character, such as purple or white flowers
True-breeding plants
-Self pollination yields offspring with the same traits as parent
-Mendel chose true-breeders to begin tracking inheritance
Monohybrid cross
Track single trait
P generation
Parent generation, Mendel crossed parents with different traits for a given character
Ex: plant with purple flowers mates with plant with white flowers
F1 generation
The hybrid offspring of the cross pollination of P generation
F2 generation
Produced when F1 individuals self-pollinate or crossed (F1xF1)
Hybrid
Parent generation was two different traits
Medel had no knowledge of chromosome or genes or the phases of meiosis
Alleles
Are alternative versions of genes account for variations of inherited traits
Dominant
Allele determines the organisms appearance
-designated by UPPERCASE letter ( ex: P for purple)
Recessive
Allele has no noticeable effect on the organisms appearance
-designated by lowercase letter (ex: p for white)
Homozygous
Organism for a particular gene if it has a pair of identical alleles for a trait (both dominant or both recessive -PP or pp)- it will exhibit true breeding
Heterozygous
Organism for a particular gene if the pair of alleles are different for that trait (one dominant and one recessive (Pp) - only the dominant gene will ‘show’)
Phenotype
Organisms physical appearance (ex:tall, purple)
Genotype
Genetic make up (homozygous/heterozygous)
Probability
Likelihood of an event occurring
Punnet square
Used to determine all possible outcomes of known genotypes
Testcross
In pea plants with purple flowers the genotype is not immediately obvious
A dominant phenotype may result from either genotype (homozygous dominant (PP) or heterozygous (Pp)
Allows us to determine the unknown genotype of an organisms with the dominant phenotype
Dihybrids
Heterozygous for both characters
Law of segregation
Meiosis separates homologous pairs of chromosome so that a gamete receives only one (during metaphase 1)
Law of independent assortment
Homologue a zygote (offspring) receives is random based on the alignment of tetrads (during metaphase 1)
Law of independent assortment
A dihybrid cross illustrates the inheritance of two characters ; the destination of one allele (on a chromosome) into a gamete is completely unrelated to the destination of any other allele.
Complete dominance
Occurs when the phenotypes of the heterozygous and dominant homozygote are identical , one allele completely dominates
Co-dominance
Two dominant alleles affect the phenotype in separate distinguishable ways
Incomplete Dominance
Phenotype of f1 hybrids is somewhere between the phenotypes of the two parental varieties
Pleiotropy
Gene has multiple phenotypic effects
Epistasis
Gene at one locus alters the phenotypic expression of a gene at a second locus
Cystic fibrosis
Abnormal chloride transport protein
Thick mucus builds up in some internal organs (digestive tract, lungs)
Abnormal absorption of nutrients, chronic bronchitis, infections
Sickle cell disease
Malformed RBC clump and clog vessels
Insufficient oxygen exchange to tissues
Incomplete and codominance
Consanguineous
Mating with the same blood line
Huntingtons disease
Degenerative disease of the nervous system (victim of reproductive age passes the disorder to offspring)
Multi factorial disorders
Many human diseases have both genetic and environment components - any character influenced by both genetic and environmental factors
Thomas hunt Morgan
First geneticist to associate a specific gene with a specific chromosome
Chromosome theory of inheritance
Chromosomes are the vehicles of genetic heredity
Sex linked gene
Gene locates on either sex chromosome
Nondisjunction
Pairs of homologous chromosome or sister chromatids (do not separate normally during meiosis)
