Hereditary influences on development

HUMAN GROWTH AND DEVELOPMENTSSYM 1023

HEREDITERY INFLUENCES ON DEVELOPMENT

PRINCIPLES OF HEREDITERY TRANSMISSION

We must start at conception to understand the working of hereditery.

Ovum released by a women’s ovary and on its way to the uterus via the fallapion tube .

Then fertilized by a man’s sperm.

THE GENETIC MATERIAL

• Sperm cell begins to disintegrate and releasing genetic material.

• Ovum also release genetic material.• New cells nucleus (zygote) forms which

contain hereditery • Zygote is about 1/20th the size of the head

of pin.

What hereditery material is present in human zygote?

• Hereditery information provided by the father’s sperm n the mother’s ovum.

• Contains 46 elongated threadlike bodies called chromosomes.

CHROMOSOMES STRUCTURE

MALE OR FEMALE?

MALE

Genetic XY

FEMALE

M

Genetic XX

GROWTH OF THE ZYGOTE AND

PRODUCTION BODY CELLS

Zygote moves through fallopian tube

Towards uterus

Begins to replicate itself through process of mitosis

Zygote divides into two cells, then become four, become eight, become sixteen and so on.

New cells with has identical 23 pairs of chromosomes(46 in all).

Same genetic material as the original cell.

Makes up muscles, bones, organs and other bodily structures.

PRODUCTION OF GAMETES THROUGH MEIOSIS

Male germ cells in the testes produce

sperm.

Female germ cells in the ovaries produce

ova.

Undergo meiosis process.

Crossing over takes places

DOMINANT AND RECESSIVE TRAITS IN HUMAN HEREDITERY

DOMINANT TRAITS RECESSIVE TRAITSDark hair Blown hair

Full head of hair Pattern baldnessCurly hair Straight hair

Facial dimples No dimplesNormal vision Color blindness

Normal blood clotting HaemophiliaNormal blood cells Sickle-cell anemia

EXAMPLE:

HEREDITERY UNIQUENES: MULTIPLE BIRTH

• Two people share a genotype.• A zygote split into separate but identical cells.• Called as monozygotic ( or identical twins) because

developed from a single zygote and have identical genes.• Occurs in 1 of of every 125 births.

SOURCES OF CONGENITAL DEFECTSCongenital defects

Inherited defects Environmental defects

Chromosomal abnormalities

Complications of the birth process

Prenatal exposures to damaging effects

Too many 0r too few

chromosomes

Broken or damaged or

chromosomes

Genetic abnormalities

Recessive genes for a

disorder

Dominant genes for a

disorder

Genetic mutation

Four common sex chromosomes abnormalities

Female abnormalities

TURNER’S SINDROME( XO)

1 in 2500 births

POLY-X or “SUPERFEMALE”

SYNDROME( XXX, XXXX, XXXXX )

1 in 1000 births

Male abnormalities

KLINEFELTER’S SYNDROME( XXY, XXXY )

1 in 750 births

SUPERMALE SYNDROME( XYY, XYYY, XYYYY )

1 in 1000 births

DOWN SYNDROME

Once in every 800 births

Extra at 21st chromosomes

Mentally retarded-IQ average is 55

-normal children is 100

characteristicsSlopping forehead, protruding tongue,

short stubby

Congenital eye, ear and heart defects

Slightly flattened nose, and almond-shaped nose.

MAJOR RECESSIVE

HEREDITERY DISEASES

Diabetes

hemophilia

Sickle-cell anemia

Tay-Sachs disease

Phenylketonuria ( PKU )

Duchenne-type

muscular dystrophy

Cystis fibrosis (CF)