Cell division

Two types of cell division: Mitosis and meiosis

**MITOSIS for growth, repair and asexual reproduction

— end result is two cells identical as well as to the cell they came from

**MEIOSIS used to form sex cells during sexual reproduction

—result is four cells that are all different from each other as well as from the og

DIPLOID

Means that our things exist in pairs

Questions they could ask:

Draw/sketch cell or set of chromosomes, or given drawing and identify, or give drawing and draw the next one or previous one, Significance of meiosis, what can go wrong, why do we have it

Crossing over can be bad but also sometimes beneficial bus it can introduce a new gene that helps the species to adapt and evolve more

2-3 crossing over events per chromosome

Anaphase 1 crossing over

Other 2 random assortment 4 different combos of chromosomes in the gamet

Gene aberration- segments of chromosome (block of genes) can be lost or added

Chromosomal aberration-cell may be missing a chromosome or have an extra chromosome

Nondisjunction

Leads to a condition known as and uploads (incorrect number of chromosomes) one more or one less

Causes various physical and mental disorders

Down syndrome 3× 21 trisomy

Turner’s syndrome female has 1x chromosome monosomy

Klinefelters syndrome 3 sex chromosome XXY

Down syndrome caused during anaphase I oogenesis

Flattened facial features with slanted eyes, ears low on the head and different sizes, short stubby fingers and a wide gap between the big toe and the other

Very often accompanied by heart problems

A very happy loving nature

Varying degrees of mental retardation

Children w ds

Develop and grow slower than other children

Need special education and cannot attend mainstream school

What is a karyotype

Computerized diagram of all the chromosomes in a cell during metaphase that shows their size and shape

If they ask how many chromosomes are in the cell-4 not 23