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Chapter 15 - Coggle Diagram
Chapter 15
Genetic Recombination and Linked Genes
Crossing Over
Occurs during Prophase I of meiosis
Exchange of genetic material between homologous chromosomes
Linked Genes
Genes located on the same chromosome
Tend to be inherited together
Produce parental type offspring that have the same genotypes as parents
Genetic Recombination
Offspring with new combinations of traits different from parents
Measured by recombination frequency (percentage of recombinant offspring)
Recombination frequency depends on crossing over
Genetic Map
Ordered list of gene locations on a chromosome
Map units: 1 map unit = 1% recombination frequency
The farther apart two genes, the higher the chance of crossing over
Linkage maps use recombination frequencies to determine gene order
Chromosomal Structural Changes
Deletion
Removal of a chromosome fragment
Duplication
Repeat of a chromosome segment
Inversion
Reversal of orientation of a chromosome segment
Translocation
Movement of a segment from one chromosome to another
Chromosome Abnormalities and Nondisjunction
Nondisjunction
Failure of homologous chromosomes to separate properly during meiosis
Aneuploidy
Result of fertilization involving a gamete with abnormal chromosome number due to nondisjunction
Monosomic
Zygote has one copy of a chromosome
Trisomic
Zygote has three copies of a chromosome
Polyploidy
Organism has more than two complete sets of chromosomes
Additional Concepts
X Chromosome Inactivation
One X chromosome in each cell is randomly inactivated during embryonic development
The inactive X condenses into a Barr body
Genomic Imprinting
Phenotype depends on which parent passed on the alleles for certain traits