meiosis study guide

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homologous chromosomes

Pair of chromosomes that are similar in length, centromere position, and carry the same types of genes.

diploid

cells containing two complete sets of chromosomes, one from each parent, the diploid \# for humans is 46

haploid

cells contains only one set of chromosomes, the haploid \# for humans is 23

gametes

sperm and egg cells (sex cells)

zygote

a diploid cell resulting from the fusion of two haploid gametes (fertilization)

Prophase I

The chromosomes condense, and the nuclear envelope breaks down. crossing-over occurs.

synapsis

Pairing of homologous chromosomes

tetrad

Each pair of homologous chromosomes.

crossing over

Process in which homologous chromosomes exchange portions of their DNA during prophase I of meiosis, this leads to increased genetic variation in the gametes that will be produced

Metaphase I

Paired homologous chromosomes line up across the center of the cell

independent orientation

Random arrangement of homologous chromosomes during metaphase I, leading to genetic variation

Anaphase I

Homologous chromosomes move to the opposite poles of the cell.

Telophase I

2 daughter cells are forming with reduced (haploid) \# of chromosomes, these cells will enter into meiosis II

prophase II

This phase is identical to mitotic prophase, except that the number of chromosomes was reduced by half during meiosis I.

metaphase II

Chromosomes line up in the middle, just like mitosis

anaphase II

sister chromatids separate, just like mitosis

telophase II

Nuclear membrane reforms, cytoplasm divides, 4 daughter cells formed. The daughter cells are genetically different from one another and are haploid.

nondisjunction

Error in cell division in which homologous chromosomes or sister chromatids fail to separate. This can occur during anaphase I or anaphase II.

chromosomal deletion

loss of a portion of a chromosome

chromosomal duplication

A segment of the chromosome is repeated.

chromosomal inversion

A segment of a chromosome breaks off and reattaches in reverse order

chromosomal translocation

When part of one chromosome breaks off and attaches to another non homologous chromosome.