chapter 13 Flashcards
Nondisjunction
failure of homologous chromosomes or sister chromatids to come apart during meiosis one or meiosis two
what would normally occur of nondisjunction were to not occur
then in anaphase of meiosis one homologous chromosomes would come apart due to the destruction of the synaptonemal complex or in anaphase two of meiosis two sister chromatids come apart due to the destruction of cohesion proteins
what are the gamets that occur as a result of nondisjunction called
they are called aneuploid gamets with either one less or one more chromosome than usual
can an aneuploid gamet fuse with a normal gamet ?
yes and thats when the result is one chromosome or three chromosomes in a single diploid
what is monosomy and how does it occur
it is when one chromosome is absent and this happens when an aneuploid gamet with 22 chromosomes fuses with a gamet with 23 chromosome to produce a total of 45 (one missing) –> (n-1)
what is trisomy
it is when one extra chromosome is present and this happens when an aneuploid gamet with 24 chromosomes fuses with a gamet with 23 chromosomes to produce 47 chromosomes –> (n+1)
Klinefelter Syndrome
xx chromosomes failed to separate and paired with a y chromosome; trisomy; results in males with breast enlargement and inactive/undeveloped testes (sterile); this example has one barr body (extra x inactive chromosome)
Turner syndrome
is missing a chromosome so its only an X; no barr bodies present; example of monosomy that results in no breast growth and infertility (total of 45 chromosomes)
nonviable zygote
is missing an x chromosome but has a Y; this diploid cannot develop because the y chromosome only has 78 genes that are used for the development of male characteristics and not for the development of the male baby itself therefore its unable to survive; example of monosomy
Jacob syndrome
two y genes and one x gene ; male baby; example of trisomy but there is normal development here; there is theory that states this extra y chromosome may make the males more aggressive but the theory has yet to be proven
normal female trisomy
has three x chromosomes; two of which are barr bodies
what are some problems that can occur in autosomal chromosomes unlike the above problem that are sex linked?
in most cases, problems occuring with autosomal chromosomes are embryonically lyselled or not born but in some cases they are and result in situations such as edwards syndrome and down syndrome
edwards syndrome
have 47 chromosomes (trisomy) and have three copies of chromosome 18 ; children born with edwards syndrome die within a few months due to heart problems and kidney malfunctions
down syndrome
also have 47 chromosomes (trisomy) and have three copies of chromosome 21; can survive into adulthood but exhibit intellectual disability; mothers age can influence the risk
Amniocentesis
one method that genetic disorders are tested; where amniotic fluid (fluid that surrounds the fetus which contains fetal cells shed from the baby’s skin) is collected and is preformed between 14-20 weeks of pregnancy by isolating the fetal cells upon removal, growing the cell culture with hormones and nutrients so that they grow and divide and become tightly packed in order to observe in a kerotype analysis or for biochemical testing to analyze gene product (enzymes or other proteins - sickle cell anemia) - risks include miscarriage due to the thin long needle
