A closer look at chromosomes Chromosomes contain our

A closer look at chromosomes. . .

Chromosomes contain our genetic material and are our ‘blue print’ for making ourselves. Chromosomes contain our DNA (deoxyribonucleic acid)

Each of our chromosome contains different genetic information about us

Hair Colour Size of Nose Freckles? How many toes do I have? Tongue Roll Curly Hair

You receive one chromosome from your mother and one from your father. Therefore you have TWO sets of information for each trait.

Chroma. . . what? Chromatin: Uncondensed genetic material present in the nucleus during interphase.

Chroma. . . what? Chromosome: Condensed form of genetic material You have 46 chromosomes

Chroma. . . what? Chromosome: Condensed form of genetic material You have 46 chromosomes

Chroma. . . what? Chromatids: Single strand that makes up a chromosome (not a homologous chromosome) Sister chromatids are identical

Mistakes In Meiosis

Mistakes in Separation Aneuploidy: Error during meiosis Separation of chromosomes doesn’t take place properly resulting in cells have too many or too few chromosomes

Mistakes in Separation Caused by: NONDISJUNCTION Failure of homologous chromosomes to separate in meiosis I Failure of sister chromatids to separate in meiosis II

Types of Aneuploidy MONOSOMY: Sex cell missing one chromosome (in place of a homologous pair)

Example of a monosomy: Turner’s Syndrome, born only with an X

Types of Aneuploidy POLYSOMY: Condition where there are more chromosomes than required (in place of a homologous pair)

Example of trisomy Down Syndrome is a trisomy of the 21 st chromosome

Types of Aneuploidy POLYPLOIDY: Non-disjunction of all of the chromosomes in a gamete that unites with a haploid gamete to produce 3 sets of chromosomes (3 n)

NONDISJUNCTION

Crossing Over

Mistakes in Crossing Over Pieces of genetic information are exchanged but do not reattach properly

Examples of Crossing Over Mistakes Deletion: When exchanged information does not reattach to the chromosome

Example of deletion: Cru du chat is a deletion of the fifth chromosome

Examples of Crossing Over Mistakes Inversion: Segment of DNA reattaches to chromosome but in the reverse order

Examples of Crossing Over Mistakes Duplication: The exchanged information is repeated on the chromosome

Examples of Crossing Over Mistakes Example of deletion: Charcot-Marie. Tooth Disease is a duplication of a portion of chromosome 17

Examples of Crossing Over Mistakes Translocation: Movement of information from one chromosome to a non-homologous chromosome