AP Biology: Meiosis

Oogenesis

Eggs in ovaries halted before anaphase I meiosis I completed during maturation meiosis 2 completed after fertilization

Nondisjunction

problems with meitotic spindle fibers cause Incorrect # of chromosomes because chromosomes don't separate properly

Nondisjunction in meiosis I

Homologous chromosomes do not separate properly (all cells abnormal)

Nondisjunction in meiosis 2

Half cells abnormal, sister chromatids fail to separate in meiosis 2

Trisomy disorder

2n+1, cells have 3 copies of one chromosome

Monosomy disorder

Cells have only one copy of a chromosome

Syndrome

A survivable chromosomal mutation

Down syndrome

3 copies of chromosome 21, the smallest chromosome, not least amount of genes, frequency correlates with age of mother

Prophase II

Spindle apparatus forms, chromatids still held at centromere

Telophase I and Cytokinesis

Cell has haploid set of chromosomes, cytokinesis creates cleavage furrow creating 2 cells, no replication between m I and m II

Metaphase II

Chromosomes position on metaphase plate, chromatids not genetically identical cuz of m I crossing over, kinetochores attach to spindle fibers

Anaphase II

Breakdown of proteins holding sister chromatids together, chromatids separate moving to opposite poles of cells,

Telephase II and cytokinesis

Nuclei form with haploid number of chromosomes, each 4 new cells genetically distinct

Heredity

The transmission of traits from one generation to the next

Variation

Differences between members of the same species

Genetics

The scientific study of heredity and hereditary variation

Gametes

A haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote

Somatic Cell

Any cell in a multicellular organism except a sperm or egg

Locus

A specific place along the length of a chromosome where a given gene is located

Asexual Reproduction

The generation of offspring from a single parent that occurs w/o fusion of gametes. In most cases, the offspring are genetically identical to the parent

Clone

A lineage of genetically identical individuals or cells

Sexual Reproduction

A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the parents

Life Cycle

The generation-to-generation sequence of stages in the reproductive history of an organism

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape

Homologous Chromosomes

A pair of chromosomes of the same length, centromere position, and staining pattern that possesses genes for the same characters at corresponding loci

Sex Chromosomes

A chromosome responsible for determining the sex of an individual

Autosome

A chromosome that is not directly involved in determining sex; not a sex chromosome

Diploid Cell

A cell containing two sets of chromosomes, one set inherited from each parent

Haploid Cell

A cell containing only one set of chromosomes

Fertilization

The union of haploid gametes to produce a diploid zygote

Zygote

The diploid product of the union of haploid gametes during fertilization; a fertilized egg

Meiosis

A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells w/ half the number of chromosome sets as the original cell

Meiosis I

The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with 1/2 the number of chromosome sets as the original cell

Meiosis II

The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells w/ half the number of chromosome sets as the original cell

Prophase I

Chromosomes condense, crossing over, Synapsis, centrosome, movement, chiasmata, micro tubules attach to centromeres

Synapsis

The pairing and physical connection of replicated homologous chromosomes during prophase I of meiosis

Tetrad

A set of 4 chromatids

Crossing Over

The reciprocal exchange of genetic material between non-sister chromatids during prophase I of meiosis

Metaphase I

Chromosomes line up on plate crossed over with independent assortment, chromosomes attached to micro tubule,

Anaphase I

Proteins holding chromatids together break down, chromosomes move to opposite poles of cell,

Recombinant Chromosomes

A chromosome created when crossing over combines the DNA from two parents into a single chromosome

Independent Assortment

The process of random segregation and assortment of chromosomes during anaphase I of meiosis resulting in the production of genetically unique gametes

Random Fertilization

Any possible egg can be fertilized by any possible sperm

How are karyotypes prepared?

By pairing up chromosomes based on size centromere location and staining patterns on a computer

What are the 3 steps of crossing over?

Breakage of DNA

Crossing over

Refusal of DNA

What happens to to most chromosomal mutations?

The baby will be aborted with high frequency, too disastrous, developmental problems result from biochemical imbalance, certain conditions tolerated