Chromosomal Disorders What happens when meiosis goes wrong?

Karyotype

Human Chromosomes Humans have 46 chromosomes arranged in 23 pairs Two sex chromosomes- determine an individual’s sex Females have two copies of the large X chromosome Males have one X and a smaller Y chromosome

Human Chromosomes The remaining 44 chromosomes are known as autosomal chromosomes or autosomes Males and females are born in a roughly 50:50 ratio All human egg cells carry a single X Half of all sperm carry an X and the other half carry a Y

Male or Female???

Types of Mutations Mutations effects vary. One factor is the type of cell if affects… GERM CELLS- Cells that undergo meiosis to produce egg and sperm cells (in ovaries and testes) SOMATIC CELLS- All the “other” body cells that only do mitosis

How would this affect the person differently?

Types of Mutations Chromosomal mutations involve changes in the number or structure of chromosomes Can lead to diseases or disorders… or (more rarely) can be beneficial

Chromosomal Mutations Examples: Entire chromosome mutation = nondisjunction “chunk” of a chromosome mutation= listed to the right in diagram (insertion, deletion…)

Gene/DNA Mutations Gene/DNA mutations involve changes in ONE nucleotide Ex’s- Point and Frameshift Mutations

Chromosomal Mutations Entire chromosomes encounter mutations as well There are four types: Deletion Inversion Insertion Translocation A B C D E Chromosome Gene

Deletion Before mutation After mutation A B C D E A C D E Occurs when a single break causes a chromosome to lose an end piece or when two simultaneous breaks lead to loss of internal segment

Inversion Before mutation After mutation A B C D E A B C E D Occurs when a part of the chromosome breaks off and is reinserted backwards

Insertion Before mutation After mutation A B C D E After mutation B C A B C B C D E Occurs when a part of the chromosome breaks off & re-attaches to the same chromosome resulting in a duplication of genes

Translocation Before mutation After mutation A B C D E F G H After mutation F A B C D E G H Occurs when a part of one chromosome breaks off & attaches to a non-homologous chromosome F G H F G H F G H

Can you spot what is wrong with this karyotype?

Creates gametes with the wrong number of chromosomes! Nondisjunction Homologous chromosomes fail to separate during meiosis I Sister chromatids fail to separate during meiosis II OR Creates gametes with the wrong number of chromosomes!

Changes in chromosome structure Deletion Part of a chromosome is lost during cell division Chromosome is missing genes Duplication Region of chromosome is repeated Translocation Piece of a chromosome moves to another chromosome