Genetics second test
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more than 1 gene specifying a given phenotype
the production by one particular mutant gene, of apparently unrelated multiple effects at the phenotopic level
Aa = AA
Incomplete (semi-) dominance
- not mutually related in terms of dominance-recessivity.
- Instead, their gene products occur
- independently, and both are manifest phenotypically.
- The frequency (in percent) with which a (dominant or homozygous recessive) gene or gene combination manifests itself in the phenotype of the carriers.
- It is complete when:
- homozygous recessives show one phenotype.
- homozygous dominants show another phenotype.
- All the heterozygotes are alike.
the degree of expression of a gene or mutation
a form of gene interaction whereby one gene (A) interferes with the phenotypic expression of another non allelic gene (B).
the production of a wild-type phenotype when two haploid genomes bearing different recessive mutations are united in the same cell.
Determination of whether cells with the same phenotype have the same genotype.
the members of such a group fail to complement one another, and they functionally define a “gene”
- a mutant whose viability is dependent on a set of (permissive) conditions
- ex: auxotrophs, temperature-sensitive
a list of ancestry or genealogical register
females and males are equally likely to be affected
on average, half the individuals in sibships with an affected parent are affected
the region of each chromosome with which the spindle fibers become associated during mitosis and meiosis
the particular chromosome complement of an individual or of a related group of individuals, defined both by the number and morphology of the chromosomes
having one or more whole chromosomes or chromosome segments absent form or in addition to the basic chromosome complement
contain three or more chromosome sets
Are polyploids euploid?
>2 monoploid chromosomes sets
Causes of genome duplication
- Meiotic non-reduction of gametes
- genome duplication w/o cytokinesis (after fertilization)
fertility disturbances due to unbalanced meiosis (specially in odd-numbered autopolyploids)
- contain structurally and genetically different chromosome sets
- allopolyploidy arises from hybridization, plus genome duplication
a single chromosome set that is repeated in polyploids
the chromosome complement of the gametes of a species
- chromosomal segments are missing
- even small deletions are homozygous lethal
- large ones are even heterozygous lethal
- deletion of a locus uncovers a recessive mutation when they pair with a "full-length" chromosome carrying the recessive allele at the locus
a chromosomal structural change resulting in the doubling of a section of the genome
- the duplicated segments are contained within a single chromosome
- tandem (contiguous) duplications
- non-contiguous duplications
the duplicated segment is incorporated into a non-homologous chromosome
does not include the centromere
includes the centromere
- change in the position of chromosome segments within the chromosome complement
- it can be intra-chromosomal.... but it usually involves intergchange of parts between non-homologous chromosomes
non reciprocal translocation
terminal translocations (at the telomere are not possible)
non-homologous chromosome fusion at their centromeres
any monocentric chromosome in which the material from one chromosome arm is represented twice
- two arms may join
- by attachement of the base of one to the terminus of there other to form
by attachment of both proximally to a single centromere.
the ends of compound chromosomes may join to form a ring chromosome
heterozygous symmetrical reciprocal translocations
- the four chromosomes share partial homology, but no two are identical
- they are characterized by a cross configuration of the paired chromosomes in meiosis
- they cause semi sterility
segregation of a heterozygous reciprocal translocation in which a translocated chromosome and a normal chromosome, segregate together, producing an aneuploid gamete.
homologous centromeres go to opposite poles (they disjoin as usual)
homologous centromeres go to the same pole (non disjuction)
- neighboring chromosomes will not go to the same pole
- all the gametes are euploid and half are carriers for the translocation
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