Lecture 7a+b: Mendelian Genetics and Chromosomal Genetics Flashcards
Genetics
is the branch of biology concerned with heredity and variation of inherited characteristics
2 concepts that used to be widely accepted
“blending” theory of inheritance
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Inheritance of acquired characteristics
“blending” theory of inheritance
the genetic materials contributed by the male and female parents mix in forming the offspring, and the progeny inherits any characteristic as the average of the parents values of that characteristics
inheritance of acquired characters
it was believed that an organism acquires some traits during its life time and they are then passed on to the offspring
phenotype
The physical appearance of an organism
Genotype
the genetic makeup of an organism (alleles or variants of a gene)
cross (hybridization)
the cross-fertilization of 2 different varieties/species
Hybrid
the offspring of parents (p generation) of 2 different varieties/species
F1 generation
the first generation resulting from a cross
F2 generation
the generation of plants from self-fertilization of the F1 offspring
Alleles
alternative forms of a gene; genes governing variation of the same character that occupy corresponding positions (loci) on homologous chromosomes
homozygous
having 2 identical alleles for a given characteristic
Heterozygous
2 different alleles for a given characteristic
Hemizygous
a condition in which only one copy of a gene or DNA sequence is present in diploid cells
Dominant allele
an allele that is always expressed when it is present, regardless of homo or heterozygous
recessive allele
an allele that is not expressed in the heterozygous state
Testcross
a cross of an individual of unknown genotype for a particular characteristic with a homozygous-recessive individual for the same characteristic
Mendel’s first law- the law of segregation
when any individual produces gametes, the alleles separate, so that each gamete receives only one member of the pair of alleles
Mendel’s second law- the law of independent assortment
alleles of 2 (or more) different genes get sorted into gametes independently of one another
incomplete dominance
a type of inheritance in which one allele for a specific trait is not completely expressed over its paired allele in F1 hybrids.
Codominance
a cross between organisms with 2 different phenotypes produces offspring with a 3rd phenotype in which both traits appear together
multiple alleles
occurrence of a gene that exists as 3 or more alleles in a population
pleiotropy
the determination of more than one character by a single gene
epistasis
occurs when 2 or more different gene loci contribute to the same phenotype
polygenic inheritance
the additive effect of 2 or more gene loci on a single phenotypic characteristic
crossing over
the exchange of segments between chromatids of homologous chromosomes during the prophase of meiosis I
autosome
any chromosome that is not a sex chromosome