Gametogenesis= the formation of gametes involves Spermatogenesis in male and oogenesis in female

Spermatogenesis: formation of sperms Did you know? It may take up to 45 years for the eggs in a woman to complete meiosis, whereas in a man the whole process takes only a few hours; sperm are being produced all the time. This difference can explain why the risk for a baby to have a chromosome anomaly increases with the mother's age, whereas the chance for a new alteration in the DNA sequence of a gene may relate more to the father's age. Cytoplasm is divided equally during each division, forming 4 equal sized sperms Sperms are small in size and streamlined for maximum motility Male adult can produce 200 millions sperms/day

Oogenesis: Formation of egg cells (or ova) Of 4 daughter cells formed, one receives the most cytoplasm. The other three cells called polar bodies die The final product of oogenesis is therefore a single ovum or egg cell. All egg cells stop developing at the end of prophase I after a female mammal is born. A female human produces 400-500 eggs during her lifetime A male thus can produce 200 millions sperms a day while a woman can produce only one egg each menstrual cycle

Sex determination An excellent candidate for the master sex-determining gene on the Y chromosome of the medaka fish is not related to the mammalian SRY gene DMY is a Y-specific DM-domain gene required for male development in the medaka fish.Ref: M Matsuda, Y Nagahama, A Shinomiya, T Sato, C Matsuda, T Kobayashi, CE Morrey, N Shibata, S Asakawa, N Shimizu, et al. Nature 2002, 417:559-563 Temperature also influences sex determination system

Sex influenced by chemical pollutants Atrazine- a herbicide Proposed as the cause for the feminization of male frogs Dr. Tyrone Hayes- UC Berkeley

We’re all the same up until the 7th week of development SRY gene: specific to mammal http://scratchcradle.wordpress.com/2012/07/29/gms5-chicken-chromosomes/ http://www.nature.com/scitable/topicpage/genetic-mechanisms-of-sex-determination-314 In human embryos, the SRY gene activates a testis-forming pathway at about week seven of development.

Errors in Meiosis 1. Errors caused by changes in chromosome number (i.e. non-disjunction) 2. Errors caused by changes in chromosome structure (i.e. mutation) http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/ Predict disorder interactive quiz

1. Non-disjunction: the failure of homologous pairs or sister chromatids to separate during meiosis At which stage(s) of meiosis homologous pairs separate? Sister chromatids separate?

What are some implications of non-disjunctions? One daughter cell will have an extra chromosome while the other will be missing a chromosome Cells with extra chromosomes or missing a chromosome are not able to function normally

Errors in meiosis in most case are not inherited because it’s a random error during the separation of chromosomes during anaphase I or II Non-disjunction occurs in autosomal chromosomes seems to be more fatal than non-disjunction that affects # of sex chromosomes which only affect the sexual development rather than the livelihood of the carrier Down: The abnormality usually occurs in egg cells, but it occasionally occurs in sperm cells. Most cases of Down syndrome are not inherited. 

Karyotype shows 3 copies of chromosomes 21 Down syndrome Kenny- a result of inbreeding in captivity Karyotype shows 3 copies of chromosomes 21

Edward syndrome Patau syndrome

Errors in Meiosis 1. Errors caused by changes in chromosome number (i.e. non-disjunction) 2. Errors caused by changes in chromosome structure (i.e. mutation)

Jim Peek character of dustin hoffman in Rain Man probably have FG syndrome rather than autism.

The Secrets of the Sequence: On Down – Down Syndrome Video https://www.youtube.com/watch?v=bEVkbuooXo4  1. What is the typical number of chromosomes in a child who has Down Syndrome? 47  2. What were the key developments that made it possible for researchers to get a better understanding of Down Syndrome? Mapping of human genome Ability to grow stem cells in a dish   3. What are some common features of Down Syndrome mentioned in the video?  People with Down Syndrome have similar facial features (broad faces and upward slanted eyes). They will also have some form of mental impairment. They will develop a form of Alzeheimer’s Disease during their life. They have an accelerated aging process. They have an extra copy of chromosome 21.    4. Why is stem cell research so important to the study of Down Syndrome? Initially Down Syndrome studies were performed on mice, but mice do not even have Chromosome 21. The ability to grow stem cells from Down Syndrome fetal tissue and compare them to stem cells from non-Down Syndrome patients makes it possible to determine if replication of these cells occur in the same way. For example, it is now possible to view the development of stem cells into neuron cells, and it is clear that there are significant reduction in rates of neuron development in the Down Syndrome (DS) compared to non-DS stem cells. Mice only have 19 pairs plus XY chromosomes, whereas Humans have 22 plus XY. -  isolation of stem cells from Down fetal tissue   

Turner Syndrome – NJN News Healthwatch Report http://www.youtube.com/watch?v=ldjb-FR-PKo   1. What are the general symptoms of Turner’s Syndrome? 45 chromosomes (missing one X) short stature, puffy hands, shortened 4th and 5th toes, webbed neck, low set ears, breast underdevelopment, infertile 2. What is used to treat Turner’s Syndrome (TS)? Estrogen- female hornome 3. What would would be the genotype (genetic make-up) of someone who has TS? ______________ XO 4. Why is detection of Turner’s Syndrome so important? To repair congenital heart defects commonly seen with TS patients Also, to administer hormone in time of puberty It helps reducing emotional/psychological burden on person with TS http://www.youtube.com/watch?v=ldjb-FR-PKo Congenital birth defects: Before birth, the baby has a blood vessel that runs between the aorta (the main artery to the body) and the pulmonary artery (the main artery to the lungs), called the ductus arteriosus. This opening usually closes shortly after birth. A PDA occurs when this opening does not close after birth. In most cases, the doctor will use medicine to close off the opening. If this does not work, then other techniques are used to close the opening.

Homework Practice meiosis with provided handout Review similarities/differences b/t mitosis and meiosis Look at different types of mutation Predict disorder interactive quiz: http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/