Kapitel 19 Flashcards
An alternative form of a gene; for a given gene - many alleles may exist in the gene pool of the species.
allele
Mode of reproduction in which offspring arise from a single parent - producing an individual genetically identical to that parent; includes budding - binary fission - and parthenogenesis.
asexual reproduction
Structure formed when a duplicated chromosome pairs with its homolog at the beginning of meiosis; contains four sister chromatids.
bivalent
X-shaped connection between paired homologous chromosomes during meiosis; represents a site of crossing-over between two non-sister chromatids.
chiasma (plural chiasmata)
Experimental techniques used to isolate the genes responsible for an interesting phenotype.
classical genetic approach
Genetic experiment that determines whether two mutations that are associated with the same phenotype lie in the same gene or in different genes.
complementation test
Process whereby two homologous chromosomes break at corresponding sites and rejoin to produce two recombined chromosomes that have physically exchanged segments of DNA.
crossing-over
Describes a cell or organism containing two sets of homologous chromosomes - one inherited from each parent. (See alsohaploid.)
diploid
The fusion of two gametes—sperm and egg—to produce a new individual organism.
fertilization
Genetic change that increases the activity of a gene or makes it active in inappropriate circumstances; such mutations are usually dominant.
gain-of-function mutation
Cell type in a diploid organism that carries only one set of chromosomes and is specialized for sexual reproduction. A sperm or an egg; also called germ cell.
gamete
A graphic representation of the order of genes in chromosomes spaced according to the amount of recombination that occurs between them.
genetic map
Experimental technique used to search through a collection of mutants for a particular phenotype.
genetic screen
The study of genes - heredity - and the variation that gives rise to differences between one living organism and another.
genetics
The genetic makeup of a cell or organism - including which alleles (gene variants) it carries.
genotype
Describes a cell or organism with only one set of chromosomes - such as a sperm cell or a bacterium. (See alsodiploid.)
haploid
A combination of alleles or other DNA markers that has been inherited as a unit - undisturbed by genetic recombination - across many generations.
haplotype block
Possessing dissimilar alleles for a given gene.
heterozygous
A gene - chromosome - or any structure that has a close similarity to another as a result of common ancestry. (See alsohomologous chromosome.)
homolog
In a diploid cell - one of the two copies of a particular chromosome - one of which comes from the father and the other from the mother.
homologous chromosome
Possessing identical alleles for a given gene.
homozygous
Principle that - during gamete formation - the alleles for different traits segregate independently of one another; Mendel’s second law of inheritance.
law of independent assortment
Principle that the maternal and paternal alleles for a trait separate from one another during gamete formation and then reunite during fertilization; Mendel’s first law of inheritance.
law of segregation
A genetic alteration that reduces or eliminates the activity of a gene. Such mutations are usually recessive: the organism can function normally as long as it retains at least one normal copy of the affected gene.
loss-of-function mutation
Specialized type of cell division by which eggs and sperm cells are made. Two successive nuclear divisions with only one round of DNA replication generate four haploid cells from an initial diploid cell.
meiosis
In meiosis - the process by which a pair of duplicated homologous chromosomes attach to one another to form a structure containing four sister chromatids.
pairing
Chart showing the line of descent - or ancestry - of an individual organism.
pedigree
The observable characteristics of a cell or organism.
phenotype
DNA sequence for which two or more variants are present at high frequency in the general population.
polymorphism
Mode of reproduction in which the genomes of two individuals are mixed to produce an individual that is genetically distinct from its parents.
sexual reproduction
Diploid cell produced by fusion of a male and a female gamete. A fertilized egg.
zygote
A heritable characteristic whose transmission to progeny does not appear to obey Mendel’s laws. Such characteristics - for example height - usually result from the interaction of multiple genes.
complex trait
