Exam 1: Lecture 11 Flashcards
inversion depends on the involvement of the _ in the inversion
centromere
paracentric inversion
does not include centromere (confined to one arm of a chromosome)
pericentric inversion
change in position of centromere; occur on both arms of a chromosome and spans the centromere
an inversion in mitosis, if balanced usually no problems in mitosis, t/f?
true
an inversion in meiosis: homozygous individuals
no problems arise during meiosis
an inversion in meiosis: heterozygous individuals
para- or peri- centric inversion often have nonfcnal gametes due to loss of large amounts of genetic material during meiosis
an indiv heterozygous for a para/pericentric inversion, what occurs?
the chromosomes form an inversion loop during pairing in prophase I
in a heterozygous indiv, a single crossover within a paracentric inversion leads to
abnormal gametes
crossing over within para inversion leads to (het)
unusual structure, one of the 4 chromatids now has 2 centromeres and 1 lacks a centromere
what happens in anaphase I of meiosis during paracentric inversions (het)
centromeres separate, stretching the dicentric chromatid (from crossing over) which breaks. The chromosome lacking a centromere is lost
what happens in anaphase II of meiosis during paracentric inversions (het)
2 gametes contain non-recombinant chromosomes: one WT (normal) and one with inversion. The other 2 contain recombinant chromosomes that are missing some genes; these gametes will not produce viable offspring
resulting recombinant gametes are nonviable bc they are missing some genes
what happens in crossing over of a peri inversion (het)
2 of the resulting chromatids have too many copies of some genes and no copies of others
what happens in anaphase I of peri inversion (het)
chromosomes separate in anaphase I
what happens in anaphase II of peri inversion (het)
sister chromatids separate in anaphase II forming 4 gametes; recombinant gametes are nonviable bc genes are either missing or present in too many copies
translocations are caused by:
rearrangement of segments between nonhomologous chromosomes
a translocation can be balanced if:
in an even exchange of material with no genetic information duplicated or lost, and usually fully functioning
a translocation can be unbalanced if:
the exchange of genetic material is unequal resulting in extra or missing genes
reciprocal translocation
an exchange of material btwn nonhomologous chromosomes
nonreciprocal translocation
transfer of genes from one chromosome to another nonhomologous chromosome
robertsonian translocation
recombining with acrocentric chromosomes that allow the short arms to be lost and the long arms creating metacentric chromosome
translocation in meiosis infertility:
gametes resulting from adjacent-I and adjacent-2 segregation are nonviable bc of the loss or gain of large amts of DNA (missing or 2 copies)
it is thought that humans and chimpanzees are more closely related than chimpanzees and gorillas or orangutans.
how can you explain that chimpanzees, gorillas and orangutans all have 2 chromosomes that contain the genes on chromosome 2 of humans?
the human chromosome combined and formed one singular stable chromosome that may be similar to the 2 chromosomes in chimpanzees, gorillas, and orangutans, but the genes on human chromosome 2 are not used the exact same way/amount they are used in the 2 chromosomes of primates
chromosome 4 differs in humans and chimpanzees due to a
pericentric inversion; genes around centromeres is rearranged differently
cen
centromere
