BIOLOGICAL DIFFERENCES BETWEEN GENDERSHormones and Chromosomes

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Gender Issues In Psychology (PSY - 512)

Lesson 07

BIOLOGICAL DIFFERENCES BETWEEN GENDERS:

Biological differences between males and females are found in three ways:

· In chromosomes

· In hormones

· In structure of the nervous system

Hormones and chromosomes are the:

· Bases of masculinity and femininity

· Structural units and carriers of heredity

· Play important role in various human behaviors

Endocrine system is a network of glands that produce and secrete chemical messengers (hormones), directly

into the blood stream. This activity is controlled by hypothalamus: the important relay station and significant

brain structure.

Hormones and Chromosomes:

Hormones and chromosomes are not only bases of masculinity and femininity and structural units of heredity,

they play important role in various human behaviors. Endocrine System is a network of glands that produce

and secrete chemical messengers that are called hormones, directly into the blood stream. Theses glands are

controlled by hypothalamus that is important relay station and significant brain structure. Pituitary glands

(also called master glands) stimulate or inhibit secretion of hormones from other glands. Sex and reproduction

hormones are called, Steroid hormones. Reproductive organs ovaries (in females) and testes (in males) are

called gonads.

Sexual Differentiation and role of Chromosomes:

Sexual dimorphism is existence of two sexes (male & female) in a species, including differences in genetics,

gonads, hormones, internal genitalia and external genitalia. The process of sexual differentiation starts when

conception takes place. Chromosomes are threadlike structures that are structural carriers of heredity, play very

important role in sex differentiation. In human beings there are 23 pairs of chromosomes. At the time of

conception half amount of chromosomes is received from mother side and half from father side. 23rd pair of

chromosome is called sex chromosome in females it is XX and in males it is XY. Genes contain genetic

information carried on chromosomes. Researchers claim that XY chromosomal makeup may not be as stable

as XX and therefore play a role in higher mortality rates for men. XX chromosomal makeup and the hormone

estrogen seem to make women less vulnerable to physical problems so women live longer lives.

Sex Chromosomal Abnormalities:

Sudden structural changes in the genes are called mutations. These mutations lead to negative consequences in

individual's development. Some times deleted or duplicated number of chromosomes also causes abnormalities

in an individual. Researches have found that disorders in sex chromosomes lead to problems in gender role

development, intelligence, growth and hormone production.

Female Sex Chromosome Abnormalities:

Turner's syndrome:

This syndrome occurs when individual inherit only one X chromosome and their sex chromosomal structure is

XO.

Such cases are females in sex with abnormal growth patterns. They are short in stature, averaging 4 foot 7

inches as adults, and often have distinctive webbed necks (i.e., extra folds of skin), small jaws, and high arched

palates. They generally lack prominent female reproduction ability. They have exceptionally small, widely

spaced breasts, broad shield-shaped chests, and turned-out elbows. Their ovaries do not develop normally and

they do not ovulate.

Gender Issues In Psychology (PSY - 512)

They also have a higher than average incidence of thyroid disease. In some individuals, there is slight mental

retardation. Turner's syndrome is rare. Current estimates of its frequency range from 1 in 3,000 female infants

to 1 in 5,000.

If diagnosed in early childhood, regular injections of human growth hormones can increase their stature by a

few inches. Beginning around the normal age of puberty, estrogen replacement therapy can result in some

breast development and menstruation. These treatments allow Turner's syndrome women to appear relatively

normal.

Metafemales or triple-X females:

Such females inherit three X chromosomes. Their chromosomal structure is XXX. As adults, these "super-

females" are usually an inch or so taller than average with unusually long body structure. They have normal

development of sexual characteristics and are fertile. They may have slight learning difficulties and are usually

in the low range of normal intelligence. They tend to be emotionally immature for their size during childhood.

This type of chromosomal abnormality is less rare than Turner syndrome.

Male Sex Chromosome Abnormalities:

Klinefelter syndrome:

Individual with this syndrome inherit on extra X chromosome and their chromosomal structure is XXY. They

characteristically have relatively high-pitched voices, feminine body contours as well as breast enlargement, and

comparatively little facial and body hair.

They are sterile or nearly so, and their testes and prostate glands are small. As a result, they produce relatively

small amounts of testosterone The feminizing effects of this hormonal imbalance can be significantly

diminished if Klinefelter syndrome boys are regularly given testosterone from the age of puberty on.

Klinefelter syndrome men are an inch or so above average height. They also are likely to be overweight. They

usually have learning difficulties as children, especially with language and short-term memory.

If not given extra help in early childhood, this often leads to poor school grades and a subsequent low self

esteem. Klinefelter syndrome is not diagnosed until they are tested for infertility. Klinefelter syndrome males

with more than two X chromosomes usually have extreme symptoms and are often mentally retarded.

XYY syndrome:

The individual with this abnormality receive extra Y chromosome and their chromosomal structure is XYY. As

adults, these "super-males" are usually tall (above 6 feet) and generally appear and act normal. However, they

produce high levels of testosterone. During adolescence, they often are slim, have severe facial acne, and are

poorly coordinated. They are usually fertile and lead ordinary lives as adults. Majority remain unaware that they

have a chromosomal abnormality.

Early studies of XYY syndrome done in European prisons initially led to the erroneous conclusion that these

men were genetically predisposed to antisocial, aggressive behavior, below average intelligence, and

homosexuality. Contributing to the early view that XYY syndrome men have serious personality disorders.

However, some researchers suggest that the high testosterone levels of XYY men can make them somewhat

more prone to violence and that this may cause higher rates of wife beating.

Sex Differentiation in Reproductive System

X and Y chromosomes determine the sex of child being male of female. Both sexes have two sex-related

internal systems:

Wolffian system: The system with a capacity to develop into the male internal reproductive system .

Mullerian system: The system with a capacity to develop into the female internal reproductive system.

Sex development is almost the same for both sexes during the first six weeks of prenatal development & both

systems exist in both sexes.

External sex organ development starts after sex weeks of conception. But these organs are not differentiated at

this stage and further external sex development depends upon the amount of androgen and estrogen

Gender Issues In Psychology (PSY - 512)

hormones. Androgen & estrogen hormones are gonadal hormones. Both sexes produce these two hormones.

But in males' androgens and in females estrogens are in greater proportions. Testosterone is androgen and

estradiol is common estrogen. Progesterone is another gonadal hormone that play important role in females

during pregnancy.

The production of androgen hormone is determined by Y chromosome in males that stimulates sexual

reproductive system.

Production of Testosterone (androgen) stimulates Wolffian system and degenerates the Mullerian system

that results in development of internal reproductive organs.

In female fetus X chromosome stimulate estrogen hormone that further leads to Mullerian system

development and degeneration of Wolffian system, which results in the development of female internal

reproductive organs. During prenatal development androgen & estrogen are very important for the

development of sex characteristics in both sexes.

During infancy and childhood gonadal hormones are produce in low quantities but during puberty these

hormones secretions increased and develop sexual maturity. Growth hormones are released from Pituitary in

adolescence play important role in muscular and bones development. Pituitary glands also release follicle

stimulating hormone (FSH) and luteninizing hormone (LH) that is involve in production of androgen and

estrogen hormones. In males testosterone is released by testes that are endocrine glands. It stimulates the

maturation of sex organs, production of sperms and prepare for reproduction. In females estrogen hormones

play important role in menarche; beginning of menstruation and ovulation. Progesterone hormone secreted

in females; controls menstrual cycle and significant during pregnancy.

Hormonal influences in both sexes:

Endocrine glands are the vital glands that release chemical substances, called hormones, into the bloodstream.

Hormones thus circulate throughout the body. Different organs are sensitive to different hormones. The

impact of hormones produces different actions at different locations.

Hormones directly related to sex differences and reproduction, are known as steroid hormones.

Gonads: The reproductive organs, glands , testes in males and ovaries in females, related to the steroid

hormones. The hypothalamus and the pituitary gland are the main brain structures that regulate the production

of sex hormones.

Hypothalamus causes the production of Releasing hormones. Gonadotropin- releasing hormone is one of

these hormones.

Gonadotropin- releasing hormone has active influence on the pituitary; as a result of this action, the pituitary

releases a number of other hormone.

The release of Tropic hormones results from this action.

Gonadotropins are one of these. Circulating through the bloodstream these hormones impact the testes and

ovaries, which are subsequently stimulated to produce their respective hormones. In males' androgens, and in

females' estrogens, are in greater proportions.

Testosterone is an androgen and estradiol is a common estrogen.

Progesterone is another gonadal hormone that plays an important role in females during pregnancy

A number of hormones other than steroid hormones are also involved, directly or indirectly, in reproduction

and related processes. Smaller and larger quantities of hormones affect several behaviors. For example

testosterone levels can affect performance on some tests. Women with high levels of testosterone perform

better on spatial tasks than women with low levels do, but men with low levels outperform men with high

levels. Females exposed to more quantities of androgen are tending to have behavioral characteristic like

males. University of California at Los Angeles observed the play behavior of such females with other female

siblings. Given a choice of transportation and construction toys, dolls and kitchen supplies, or books and board

games, these females preferred the more typically masculine toys--for example, they played with cars for the

same amount of time that boys did.

Study (Dabbs, 2000) revealed that individuals with high testosterone levels are associated with lower status

professions as high testosterone levels are related to impulsiveness and antisocial behavior. Comparative study

of college students and young men delinquents revealed that they have higher levels of testosterone.

Gender Issues In Psychology (PSY - 512)

Another study of male prisoners also revealed that high testosterone levels are associated with deferent types of

violence including sex and rule violations. As female also produce testosterones so, various studies have

conducted to find out relationship between testosterone and female behaviors. Results support hypothesis that

high testosterone is related to aggressive behaviors.

The Hormonal Cycle

Hypothalamus

Stimulation of

ovaries and testes

Releasing hormone

Incl. gonadotropin

releasing hormone

Gonadal hormones

released

Impact

pituitary gland

Hormones released:

Incl. tropic hormones;

Incl. gonadotropins

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