Chapter 15 Flashcards
which of Mendel’s laws were supported by the behavior of chromosomes during meiosis
law of segregation and law of independent assortment
describe the chromosome theory of inheritance
mendelian genes have specific loci on chromosomes, chromosomes undergo segregation and independent assortment
who provided convincing evidence that chromosomes are the location of mendel’s heritable factors
Thomas Hunt Morgan
how did Morgan provide the first solid evidence that genes are associated with a specific chromosomes
during his breeding of fruit flies he came upon a gene that was only showing up in his male flies and not the females. This led him to believe that the Y chromosome did not have a copy of the gene.
what is a sex-linked gene
a gene located on either sex chromosome
how does the production of sex-linked proteins in females compare to that of males
they are at similar rates, as one of the two x chromosomes in each female cell is randomly inactivated during embryonic development
what happens if a female is heterozygous for a particular gene located on the x chromosome
she will be a mosaic for that character
What did Morgan conclude about how linkage affects the inheritance of different characters
genes that are close together on the same chromosome are inherited together, those on different chromosomes or further apart are inherited independently
what are offspring called that show new combinations of the parental traits
recombinant offspring
what percentage of offspring are recombinants
50%
how did Morgan explain a recombination of genes that were located close together
he theorized that there was a process that occasionally broke the physical connection between the genes, this was later discovered to be the crossing over of homologous chromosomes
what is a genetic map and how is it developed
it is an ordered list of the genetic loci along a particular chromosome, developed using recombination frequencies
what is a linkage map
an illustration of the relative locations of genes along a chromosome
what often results from large-scale chromosomal alterations
spontaneous abortions (miscarriages) or a variety of developmental disorders
what is nondisjunction
when pairs of homologous chromosomes do not separate normally during meiosis, causes gametes to form with two copies or no copies of a particular chromosome
what is aneuploidy
a condition in which offspring have an abnormal number of a particular chromosome
what does it mean for a zygote to be trisomic
it has three copies of a particular chromosome
what does it mean if a zygote is monosomic
it has only one copy of a particular chromosome
what are the fours types of changes in chromosome structure
deletion, duplication, inversion, and translocation
what causes down syndrome
trisomy 21
what causes Klinefelter syndrome
extra chromosome in male (XXY)
what causes Turner Syndrome
monosomy X (X0)
what causes Cri du chat
a deletion in a chromosome
what common disease is often caused by translocations of chromosomes
cancer
Describe genomic imprinting
the silencing of certain genes that are “stamped” with an imprint during gamete production (effect of the allele depends on which parent it was inherited from)
what are extranuclear genes
genes found in organelles in the cytoplasm
which parent controls the inheritance of traits controlled by genes present in the chloroplasts or mitochondria
mother - zygotes cytoplasm comes from the egg
what types of diseases are caused by defects in mitochondrial genes
diseases that affect the muscular and nervous systems - prevent cells from making enough ATP
