Flashcards in Gametogenesis, Fertilization, Implantation - Kuehl Deck (43):
Through what do stem cell populations for gametes expand?
Through what processes do gametes in each gender reduce their chromosomes to half the normal number for an individual? And how many chromosomes?
2) 46 --> 23
In what process are alleles of genes rearranged to make new unique combos?
When are errors not repaired in gametes?
errors related to pre-meiotic cell divisions for germ cell numeric expansion and during meiosis are not repaired
When can nondysjunction occur and what is it?
1) can occur in both mitosis and meiosis
2) failure of chromosomes to separate
When do errors such as inversions, deletions or duplications occur?
What is the difference between DAZy and DAZL?
1) DAZy = present in higher primates
2) DAZL = located on chromosome 3 (autosomal) and expressed in both testes and fetal ovaries
What is Y chromosome microdeletion and what are its symptoms?
An inherited disorder of gene deletions on the Y chromosome that often goes unnoticed until infertility becomes obvious (reduced sperm production)
What is the proposed mechanism for DAZ function?
1) Gamete production - augments mRNA translation to proteins
2) DAZL and DAZy bind to mRNA and poly-A binding proteins to circularize mRNA and enhance translation
What happens in a male with a DAZy deleted phenotype?
1) few or no sperm cells in the ejaculate - but some limited spermatogenesis in testes
2) fathers are genotypically normal
3) DAZy deleted males can still reproduce bc of ART - will always have DAZy deleted sons
What has helped the understanding of aneuploidy transmission?
1) ART (assisted reproductive technology)
2) polar body biopsy
What percent of women bw the ages of 19-29 donating ova had errors of mitosis, meiosis or both?
Do ova with abnormal chromosome numbers have decreased fertilization?
What kinds of errors increase with age?
errors due to meiosis
What is seen as a consequence of age with pregnancy?
1) increased chormosomal numerical errors leading to
a) lethal defects - stillbirth/abortions
b) nonlethal defects - down syndrome
Where is mitosis in the female for the germline finished?
in the fetus
Where is meiosis started and finished in the female?
1) initiated in the fetus
2) arrested at prophase I of meiosis prior to recombination
3) restarted by LH signal that triggers ovulations
4) completed after fertilization
When does mitosis begin in the male?
begins in the fetus and continues throughout life
When does meiosis begin in the male?
begins at puberty
What are the differences in stem cell populations of germ cells in the male and female?
1) males maintain stem cell populations of germ cells into adulthood
2) females lose stem cell populations as meiosis of all oogonia initiates in utero
Why do male germ cells entering into spermatogenesis maintain cell-to-cell connections?
so the development is the same for X and Y containing cells
What do haploid sperm cells express at puberty?
antigens - well after immune function is established
What hormones do follicular cells produce?
What do nongrowing (NGF) or primordial follicles represent?
the population of follicles with potential for future reproduction
What limits the duration of reproduction in females?
1) lack of oocyte stem cells
2) NGF lost to atresia or growth
3) drop below 1,000 NGF
What can increase the reduction of NGF in women?
What can you use as a reference point to estimate reproductive age?
How long does it take a primordial follicle to move through all the stages of development to an ovulatory follicle?
What is the time keeper of the cycle of primordial development?
What do sertoli cells do?
1) provide an environment for spermatogenesis
2) provide ABP to carry androgen to the rest of tubule system
Why are testes more prone to edema disruption?
lymph collection at the septa instead of interstitial spaces?
What kinds of processes can alter spermatogenesis?
1) processes impacting perfusion
a) heavy metal toxicity
b) diabetes, atherosclerosis
c) increased venous pressure
d) thick basement membranes
e) altered hormone delivery
What maintains the blood testes barrier?
tight junctions between sertoli cells
Is there any differences between X and Y carrying sperm?
What increases with age in sperm?
What kind of errors in sperm are not transmitted and what kind are?
1) errors in alleles that directly impact sperm function lead to sperm being apoptotic
2) errors in genes not expressed in sperm cells can be transmitted
What primarily determines the selection of sperm for fertilization?
barriers within the female reproductive tract
What is the risk for chromosome abnormalities with age in women?
1) 50% in women < 35
2) 75% 35-40
3) 90% > 40
What are possible male contributions to errors in the embryo?
1) sex chromosome number abnormalities
2) autosomal translocations
3) genetic mutations and size of repeats
How is the oocyte in the fastest growing follicle maintained?
negative hormonal feedback mechanisms
Probes for which chromosomes are used in FISH during ART?
11, 13, 16, 18, 21, X and Y
By what days has the embryo turned of gene expression?
hCG beta - 8 cell stage