ppt 12

Genes

Heredity units that are transmitted from one generation to another. They are found on chromosomes which are located in the nucleus of the cell. (DNA & RNA)

DNA

the basic genetic code for amino acid formation

Each somatic cell has _____ chromosomes (½ mom,

½ dad)

46

Cell division is achieved by

Mitosis

The function of mitosis is to

create an exact copy of the chromosome of the original cell and give a copy to each daughter cell

Primitive germ cells have

46 chromosomes

Mature germ cells (ova and sperm) have

23 chromosomes

4 Stages of Mitosis In order

Prophase

Metaphase

Anaphase

Telophase

Prophase

First and longest stage

the chromosomes are lining up toward metaphase moving to opposite polls

Metaphase

chromosomes are symmetrical at both sides of the center of the cell

Anaphase

sister chromosome separate into individual and are pulled apart

Telophase

Chromosome gather at opposite ends, chromatids are in the process of splitting

Centromere

is the constricted portion of the chromosomes that divides the short arms from the long arms.

Germ Cells

Cells with a single set of chromosomes

a mature gamete is an example of a

Haploid

Haploid

Mature germ cells that have 23 chromosomes

Diploid

Primitive germ cells that have 46 chromosomes

Meiosis

a two-step process, a special type of cell division by which the primitive germ cells reduce their number of chromosomes by half.

Meiosis process

• Chromosomes replicate (look like X's)

• Line up next to each other

• Establish contact (chiasmata); become homologous

• Chromosomes separate from each other

• Chromosomes do not split, but remain in tact Each member goes to a new cell (each will have 23 chromosomes)

What is more common in ovum cross over from birth to ovulation?

Nondisjunction

Lyon Hypothesis

theory that states that one of the X chromosomes of a female embryo is canceled and forms a Barr body which can be microscopically detected.

This is significant for the detection of those diseases which are transmitted by female carriers on the X chromosome.

_______ are seen at the nuclear periphery in female cells

Barr bodies

Phenotype

•Physical, biochemical and physiologic traits of an individual

• Combination of genetics and environment

Karyotype

a photographic representation of a person's chromosomal constitution.

.

Gross abnormalities can be observed on a

Karyotype

GROSS ABNORMALITIES:

Caused by the alteration in chromosomal number

Molecular abnormalities occur at the DNA level and are _____ detected microscopically

NOT

Euploid

complete (2+) compliment set of chromosomes

Polyploid

more than two complete sets of chromosomes (3+)

Aneuploid

extra chromosomes with no complement

Deletion

loss of part of a chromosome

Translocation

portion of a chromosome attached to another chromosome

Inversion

portion of chromosome upside down

Duplication

large chromosome

Trisomy 21 Is due to

nondisjuction mostly associated with late maternal age at the time of conception.

Acrocentric chromosome-

cell division resulting in uneven arms

Trisomy 21 is associated with

• Slanted eyes

• Shorter than normal in height

• >30% heart abnormalities

• 90% gingival and periodontal disease

• Fissured tongue and premature loss of teeth

• Intelligence varies from near normal to retardation Down's syndrome

• Acrocentric chromosome- cell

division resulting in uneven arms