Thursday, October 30, 2008

Basis for gender identity

Regarding our discussions in class the last few days, I have done some research into gender identity and gender roles. I found a few good articles, including this one by Ghosh and Walker, which is geared toward the medical/scientific community, this one by Brown, which is more for the public, and I found the short story I had mentioned, X: A Fabulous Child's Story, which I highly recommend reading.

First, some definitions (from the first article by Ghosh and Walker), first of gender identity and gender role:

Gender identity is defined as a personal conception of oneself as male or female (or rarely, both or neither). It is intimately related to the idea of gender role, which is defined as the outward manifestations of personality that reflect the gender identity. Simply put, gender identity is a self-label; gender role is a label given by society because of behavior and appearance. For example, if a person thinks of himself as a male and identifies himself as such, then his gender identity is male. However, his gender role is male only if he demonstrates typically male characteristics in behavior, dress, and/or mannerisms.


So gender is more of a social/psychological construct than an absolute biological outcome. Biology does determine the sex of an individual, which is often confused with the term gender:

The 2 terms sex and gender are often used interchangeably in the vernacular. However, [...] these words are not synonymous. [...] Sex, from the Latin word sexus, is defined by the gonads, or potential gonads, either phenotypically or genotypically. It is generally assigned at birth by external genital appearance.

If an intersex condition is present, one sex is often chosen with the intention of making social interactions and rearing simpler. Gender comes from the Latin word genus, meaning kind or race. It is defined by one's own identification as male, female, or intersex; gender may also be based on legal status, social interactions, public persona, personal experiences, and psychologic setting. Stating that sex is biologically determined, whereas gender is culturally determined, is fair.


So obviously, sex is determined by basic biology - XX for females, XY for males. The Y chromosome is the key; it encodes a gene named SRY, or testes determining factor (TDF). During the first 8 weeks of gestation, all fetuses are female. Around the eighth week, TDF is expressed, which leads to the development of testes. The testes begin producing testosterone, which is then converted to dihydotestosterone, the key hormone in virilization (making the fetus male). In the absence of the Y chromosome,the fetus will continue along the female developmental pathway. So that explains sex, what about gender identity?

Unfortunately, much of our understanding of gender identity stems from studying gender identity disorder patients, in which the process of gender identity development is believed to have misfired. This may be a useful strategy, but it is also like trying to figure out how a car runs by visiting a junkyard.

It is thought that the intrauterine hormone exposure sets a gender bias early in fetal development, which explains why female sex most often aligns with female gender identity, and male sex with male gender identity. There are other prenatal factors:

The environment in which a baby is reared with respect to gender begins to take shape prior to birth. Prenatal ultrasonography now allows the sex of a fetus to be determined quite accurately. In families who receive this knowledge of the child's biological sex, parental planning and reactions are often tailored by it. Names, items of clothing and toys, even specific thoughts about the baby, may be different depending on the anticipated sex. Thus, a preformed idea of the child's preferences is in place even before the child is delivered.


So a mother thinking about her child as a "boy" or "girl" and buying blue or pink drapes for the nursery has an effect? Personally, I am not sure about that, it seems like a stretch.

After birth, the parents are instrumental in reinforcing gender roles: little girls are hugged and cuddled with more, little boys wrestle and play with trucks. (According to Ghosh and Walker, this is more evident with fathers than mothers.) Gender identity may come from and be reinforced by these parentally-installed gender roles, and by 3-4 years old identity may be firmly set. Interestingly, gender-variant behavior seems to be better tolerated in females ("tomboys") than in males ("sissy-boys"), at least in Western society.

Looking at some biological bases of gender identity, there are a few chromosomal abnormalities and other mutations that can lead to sex or gender issues. In Turner's syndrome, the individual has only one X chromosome (XO genotype). These individuals are anatomically female, but are often infertile. Although the gender identity is usually reported as female, the infertility may lead to questions about gender role. Klinefelter's syndrome results from an extra X chromosome (XXY). Because of the presence of the Y chromosome, the fetus will generally develop as male. However, during puberty blood testosterone levels are lower than normal (XY) males, which leads to appearance of secondary female sexual characteristics, such as gynecomastia. These can lead to psychological problems and questions about gender identity.

Non-chromosomal causes include congenital adrenal hyperplasia (CAH) and androgen insensitivity syndrome. In CAH, a genetically female (XX) fetus is exposed to high levels of the hormome cortisol while in the uterus. This leads to enlarged external female genitalia, which sometimes are mistaken for male genitalia at birth. If the diagnosis is not made until puberty, as was often the case, these children were often raised as males, which can lead to gender identity problems when the female sex is revealed.

So is there a biological basis for gender? Since gender is a social (for gender roles) or psychological (for gender identity) construct, biology cannot be the only determinant. However, as outlined above for the disorders, there may be biological factors that influence gender. It seems to me that how a child is raised, the parental influence on gender roles, is the most important factor.

Wednesday, October 29, 2008

Mitosis lab website

Follow this link for the online mitosis lab.

Follow the link on the site in the upper left corner for Onion Root Tips.

Wednesday, October 15, 2008

Ms. Drust AP Biology Class

I am pushing back the cellular respiration test until Friday. I realized that some of the questions deal directly with the lab and I want to be sure that you guys have all the data for the lab and test. Please make sure to pass it on.

Tuesday, October 14, 2008

Nobel and IgNobel

In case you missed it, the 2008 Nobel Prizes were awarded last week. The prize for physiology and medicine was split between three researchers, one who discovered human papilloma virus (HPV) and its link to cancer. The other two researchers were among the fist to discover human immunodeficiency virus (HIV) and its link to AIDS. There is a fair bit of controversy over who should get credit for the discovery of HIV. The Nobel committee decided to reward the French group, while ignoring the American contribution. Of course, I may be a little biased, since Robert Gallo is at the University of Maryland.

The prize for chemistry went to three researchers involved in isolating, cloning and basic research on green fluorescent protein (GFP). GFP was first isolated in jellyfish, and has lead to a revolution in molecular biology. Most likely, there are few molecular research laboratories that do not use some form of GFP in research right now. And you can make cool stuff like this. Or this. Or... yeah you get the idea.

As important as the Nobel Prizes are, there is an interesting take on them here. Very interesting read; if you have time and are contemplating a career in the sciences I highly recommend reading it.

Almost as prestigious as the Nobel Prizes are the IgNobel Prizes, which
honor achievements that first make people laugh, and then make them think. The prizes are intended to celebrate the unusual, honor the imaginative -- and spur people's interest in science, medicine, and technology.


The list of 2008 (and past years) winners can be found here. Which award would you rather receive?

Chapter 9 review packet answers

To help you study for the respiration test on Thursday, here are the answers to the chapter 9 review packet handed out in class on Tuesday.

Interactive questions

9.1 C6H12O6, 6 CO2, energy (ATP + heat)
9.2 a. oxidized b. oxidizing agent c. reduced
9.3 a. oxygen b. glucose c. Some is stored as ATP and some is released as heat
9.4 a. electron acceptor or oxidizing agent b. NADH
9.5 a. glycolysis: glucose --> pyruvate b. Krebs cycle c. ETC and oxidative phosphorylation d. substate-level phosphorylation e. substrate-level phosphorylation f. oxidative phosphorylation The top two arrows show electrons carried by NADH to the ETC
9.6 a. 2 ATP b. 2 glyceraldehyde phosphate (not important for this class) c. 2 NAD+ d. 2 NADH e. 4 ATP f. 2 pyruvte
9.7 a. pyruvate (from glycolysis) b. CO2 c. NADH d. CoA e. acetyl CoA f. oxaloacetate g. citrate h. CO2 i. NADH j. CO2 k. NADH l. ATP m. FADH2 n. NADH
9.8 a. intermembrane space b. inner mitochondrial membrane c. mitochondrial matrix d. ETC e. NADH + NAD+ f. NAD+ g. H+ h. 2 H+ + 1/2 O2 i. H2O j. ATP synthase k. ADP + Pi l. ATP
9.9 a. -2 b. 4 c. Krebs cycle d. 32 or 34 e. 38 f. 2 g. 6 h. 2 i. 2 j. 2
9.10 Respiration yields up to 19 times more ATP than does fermentation. By oxidizing pyruvate to CO2 and passing electrons from NADH through the ETC, respiration can produce a maximum of 38 ATP compared to the 2 net ATP that are produced by fermentation.

Test Your Knowledge
1. a 15. c
2. a 16. c
3. c 17. b
4. d 18. d
5. e 19. c
6. d 20. e
7. c 21. c
8. e 22. b
9. b 23. d
10. b 24. e
11. a 25. a
12. e 26. e
13. c 27. c
14. e 28. d

I am not overly concerned with the Structure your Knowledge questions. You have a cellular respiration overview chart that we filled out the first day of respiration that has all the important information on it.

Sunday, October 12, 2008

Respiration PowerPoint

This is a powerpoint that covers all of chapter 9, cellular respiration.



Not all of this information was presented in class.

Friday, October 3, 2008

Additional Lab Review

Hey guys,

I just wanted to remind you that the lab bench website is a great resource. I might look it over for the test if I was an AP Biology student.

Osmosis Review PowerPoint



Make sure you know the definition of isotonic, hypotonic and hypertonic, and what happens to a plant or animal cell when placed in each type of solution. If you have questions, I will be try to be online Sunday night, though I have been having problems with my internet connection at home.

Good luck on the SATs.

Thursday, October 2, 2008

Weekend events - not science related

If you are looking for something fun to do this weekend (and maybe earn a few brownie points from Dr. H) the 31st annual John Ragone road races will be held this Sunday in East Brunswick.

I am entered in the 5K race, which starts at 1 pm. If you come out early, you can cheer on my son in the kid's Pumpkin Dash at noon.

The course map can be found here.

Hope to see you there.