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Lecture 11

Biology 1201A Lecture Notes - Lecture 11: Progeria, Mendelian Inheritance, Wild Type

Course Code
BIOL 1201A
Jennifer Waugh

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Family Level Inheritance Linkage- Chapter 11
Genes, Chromosomes and Human Genetics
-Progeria: premature aging
oCaused by a genetic error that occurs once in every 8 million human births
oThe error is preserved each time cells of the embryo of the child duplicate their
chromosomes and divide
Genetic Linkage and Recombination
-Chromosomes behave independently from one another
-Genes located on the same chromosome may be inherited together in genetic crosses
oThey do not assort independently because the chromosome is inherited as a single
physical entity in meiosis
-Linked genes: genes on the same chromosome
Principles of Linkage and Recombination
-Wild type: An individual having the normal phenotype; that is, the phenotype generally
found in a natural population of organisms.
-Mutant: An individual having a phenotype that differs from the normal phenotype
-The farther genes lie apart from one another, the more likely it is that they will be
separated during meiotic crossing-over than genes lying close to each other
-Geneticists working with fruit flies have determined a “normal” or “wild-type” genotype
oAny change from wild-type is a mutant
-Mutant alleles are named based on the altered phenotype of the organism that expresses
-The names for dominant mutant alleles are written with the first letter in uppercase
-The names for recessive mutant alleles are written with the first letter in lowercase
-The notation for a wild type allele always includes a superscripted plus sign
-Behaviour of linked genes is explained by chromosome recombination during meiosis
-Frequency of recombination is a function of the distance between linked genes
-Parental offspring are the ones that inherit chromosomes that were NOT involved in
recombination in the dihybrid parent
oParental offspring do not always resemble the parents of the cross
Recombination Frequency
-The percentage of offspring frequency is the percentage of gametes that contain
recombined chromosomes
-Recombinant offspring frequencies can be used to make a linkage map of a chromosome
showing the relative locations of genes
-Genes father apart on a chromosome are more likely to have more than one crossover
occur between them
-A single crossover between two genes gives recombinant chromatids
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