Meiosis and Sexual Life Cycles

Vocabulary flashcards covering the concepts of heredity, variation, human life cycles, and the stages/mechanisms of meiosis based on the provided lecture notes.

Heredity

The transmission of traits from one generation to the next.

Variation

The differences in appearance that offspring show from parents and siblings.

Genetics

The scientific study of heredity and variation.

Genes

The units of heredity that are made up of segments of D N A.

Gametes

Reproductive cells, such as sperm and eggs, that pass genes to the next generation.

Somatic cells

All cells of the body except for gametes and their precursors; in humans, these contain $46$ chromosomes.

Locus

A specific position of a gene on a certain chromosome.

Asexual reproduction

A process in which a single individual passes genes to its offspring without the fusion of gametes.

Clone

A group of genetically identical individuals from the same parent, produced asexually.

Sexual reproduction

A type of reproduction where two parents give rise to offspring that have unique combinations of genes inherited from the two parents.

Life cycle

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

Karyotype

An ordered display of the pairs of chromosomes from a cell.

Homologous chromosomes

Two chromosomes in a pair that are the same length and shape and carry genes controlling the same inherited characters; also called homologs.

Sex chromosomes

The chromosomes referred to as $X$ and $Y$ that determine an individual's sex.

Autosomes

The remaining $22$ pairs of chromosomes in human somatic cells that are not sex chromosomes.

Diploid cell

A cell ($2n$) that has two sets of chromosomes; for humans, the diploid number is $46$ ($2n = 46$).

Haploid cell

A cell ($n$) containing a single set of chromosomes, such as a gamete; for humans, the haploid number is $23$ ($n = 23$).

Fertilization

The union of gametes, specifically the sperm and the egg.

Zygote

The fertilized egg, which has one set of chromosomes from each parent and is diploid.

Meiosis

A type of cell division occurring in two sets, which reduces the number of chromosome sets from diploid to haploid.

Alternation of generations

A life cycle exhibited by plants and some algae that includes both a diploid and haploid multicellular stage.

Sporophyte

The multicellular diploid organism in plants that makes haploid spores by meiosis.

Gametophyte

The multicellular haploid organism in plants that makes haploid gametes by mitosis.

Allele

Different versions of a gene that may exist on homologs.

Synapsis

The process during prophase I where members of a homologous pair associate along their length, allele by allele.

Synaptonemal complex

A zipper-like structure that forms during synapsis to attach homologous chromosomes.

Crossing over

The exchange of D N A segments between nonsister chromatids during prophase I.

Chiasmata

X-shaped regions on homologous pairs where crossing over has occurred.

Independent assortment

The random orientation of homologous pairs of chromosomes at metaphase, where each pair sorts maternal and paternal homologs into daughter cells independently of other pairs.

Recombinant chromosomes

Chromosomes produced by crossing over that combine D N A inherited from each parent.