Ch 15: Chromosomal Basis of Inheritance Flashcards
Who developed the Chromosome theory of inheritance?
around 1902 Sutton and Boveri and others independently noted the parallels between chroomosme behavior and the behavior of the proposed factors and developed the theory
What is a wild type?
normal phenotypes in populations
What is a sex-linked gene?g
genes on X and Y chromosomes that code for an individuals sex
What are X-linked genes?
genes on the X chromosome, which humans contain about 1,100 genes on their X chromosme
What needs to occur for a recessive X-linked trait to be expressed?
a female needs two copies of the allele (homozygous) and a male needs only one copy of the allele (hemizygous)
What are some disorders that are caused by recessive alleles on the X chromosome in humans?
color blindness (mostly X-linked), Duchenne muscular dystrophy, and hemophilia
What is the inactivated X (in females) condensed too?
a barr body
What are linked genes?
genes that are on the same chromosome that tend to be inherited together
What is genetic recombination?
the production of offspring with combinations of traits differing from either parent
What are parental types?
offspring with a phenotype matching one of the parental phenotypes
What are recombinant types (recombinants)?
offspring with nonparental phenotypes (new combinations of traits)
What is crossing over?
when genetic material is swapped between chromosomes during prophase
What increases genetic variation?
recombinant chromosomes and random fertilization
Who constructed a genetic map?
Alfred Sturtevant, one of Morgan’s student’s
What is a genetic map?
an ordered list of the genetiv loci along a particular chromosome
What is a linkage map?
a genetic map of a chromosome based on recombination frequencies
What can distances between genes be expressed as?
map units
What is nondisjunction?
when pairs of homologous chromosomes do not separate normally during meiosis, as a result, one gamete receives two of the same type of chromosome, and another gamete recieves no copy
What is aneuploidy?
offspring with an abnormal number of a particular chromosome, resulting nondisjunction
What is a monosomic zygote?
a zygote with only one copy of a particular chromosome
What is a trisomic zygote?
a zygote has three copies of a particular chromosome
What is polyploidy?
a condition in which an organism has more than two complete sets of chromosomes
What is triploidy?
three sets of chromosomes
What is tetraploidy?
four stes of chromosomes
What are the four types of changes in chromosome structure that results from the breakage of a chromosome?
deletion, duplication, inversion, and translocation
What is deletion?
the removal of a chromosomal fragment
What is duplication?
repetition of a segment
What is inversion?
the reverse orientation of a segment within a chromosome
What is translocation?
the movement of a segment from one chromosome to another
What is down syndrome?
is an aneuploid condition that results from three copies of chromosome 21
What are the two exceptions to standard Mendelian inheritance?
genes located in the nucleus and genes located outside the nucleus
What is genomic imprinting?
the silencing of certain genes depending on which parent passes them on
