battle of the sexes Flashcards

Question

what affects offspring sex ration in non human primates?

Answer 1

– Maternal condition correlates offspring sex ratio – Social structure is important • Colobine monkey high ranking females have more males • Opposite is true in baboons (matriarchal society)

Answer 2

- socioeconomic variables (famine) - environmental stressors - psychological stressors

Answer 3

Pre-conception nutrition Maternal diet high in unsaturated fats or glucose • Increasedmalesborn Maternal diet high in omega-6 polyunsaturated fatty acids (vegetable oils) • Increasedfemalesborn Recent evidence: not a consistent dietary intake that determines offspring sex, but a change in nutritional status • Females gaining condition produce sons • Females losing condition produce daughters

Answer 4

Exposure of males to endocrine disruptors skews sex ratio in offspring Dioxin exposure of males at puberty • Bi-product of chemical, steel/iron industry • Increased male offspring in adulthood Dichloroethylsulphide (Mustard gas) • Exposure of Iranian soldiers during the Iran-Iraq war • Decreased male:female ratio in offspring • Decreased testosterone:gonadotrophin ratio in males • Increased sperm DNA damage – Sperm DNA integrity linked to ability to progress through the female tract – Are Y chromosome sperm more susceptible to chemically induced DNA damage?

Answer 5

Severe life event pre-conception or early pregnancy – Death/cancer diagnosis in spouse or child – Decrease in male:female sex ratio -->Differential fertilisation – more X chromosome sperm fertilised? or Differential embryo survival–more XY embryos aborted? Kobe earthquake and 10-day war in Slovenia – Both resulted in decrease in male:female sex ratio – Reduced sperm motility • Stress induced increase in prolactin and testosterone in males • Interfereinspermatogenesis • Differential effect on X or Y bearing spermatozoa? Confounding factors with psychological stress! – Sexual abstinence – Hormone concentrations differ from the norm – Poor nutrition – All affect semen quality and embryo survival

Answer 6

Natural inseminations from the most fertile males result in increased male offspring – Sons likely to disperse – Fathers pass on genes without competitive threat Paternal influence on sex ratio related to sperm variation – Biochemical – Morphological – Ability to fertilise But, is there evidence that X and Y sperm differ?

Answer 7

As the female has a disproportionate role in production of offspring it is likely that most influence on offspring sex ratio is under maternal control Female reproductive tract might control gender bias – Sex specific sperm selection/progression? – Sex specific fertilisation? – Sex specific embryo implantation/survival? Less ‘costly’ for female to manipulate gender bias before/at fertilisation than later during pregnancy

Answer 8

Female tract is not passive – it controls sperm progression – Pig, 30 billion sperm inseminated, but only 1000-5000 reach oviduct – Human, conception falls 40% to 24% <1.5 million sperm inseminated Cervix: mucus removes DNA damaged sperm – Possibly because DNA-damage is reflected in poor motility Uterus: immunological (neutrophils) removes membrane damaged sperm ``` Utero tubal junction – Prevents 90% of sperm in uterus passing into oviduct – Restricts entry to minimise polyspermy – Opportunity to exercise choice ``` Oviductal storage/selection Controls which sperm are given access to the oocyte

Answer 9

- molecular recognition system in place - failure to express sperm surface proteins A-disintegrin and metalloprotease 3 (ADAM3) other surface proteins identified for UTJ there is evidence for sperm selection via surface proteins do these sperm serfuca proteins reflect genetic quality is the sex-specific sperm selection via molecular recognition

Answer 10

electronegative charge of sperm plasma membrane correlates with DNA integrity in sperm nucleus. - negative charge correlates with stage of epididymal maturation - chromatin fragmentation and nuclear integrity related to epididymal maturation. - negative charge on sperm attributed to CD52 (membrane anchored glycoprotein with highly charged N-linked carbohydrate moiety, CD52 added to sperm during epididymal maturation) - CD52 involved in sperm binding to oviductal epithelial cells and zona pellucida - female tract can select sperm genetic profiles via membrane bound CD52

Answer 11

- negative charge on sperm attributed to CD52 (membrane anchored glycoprotein with highly charged N-linked carbohydrate moiety, CD52 added to sperm during epididymal maturation) - CD52 involved in sperm binding to oviductal epithelial cells and zona pellucida - female tract can select sperm genetic profiles via membrane bound CD52 Sperm surface markers of genetic information • Female tract can bind/select sperm using CD52 as a marker of genetic integrity • So, we know female tract uses sperm surface molecules to identify DNA damage to maximise fertilisation • What other molecules exist? • Do molecular expression patterns differ between X and Y sperm? • Might expression patterns be manipulated by environmental stressors known to skew gender bias?

Answer 12

Nuclear content differs by 2.8-4% dependant on species • Morphology differs subtly between X and Y sperm – X sperm increased head, mid-piece and tail length – Sperm morphology reflects DNA integrity • Differentially expressed proteins – Associated with cytoskeletal structures influencing motility – Regulation of metabolism • Glycolyticenzymesandcalmodulin – Levels of expression NOT presence/absence of gene product • Individual sperm microRNAs – Adopt unique 3D shapes for sperm recognition in oviduct – Powerful modulators of gene expression

Answer 13

progressions at UTJ and oviduct | fertilisation (zona pellucida)

battle of the sexes Flashcards

(37 cards)