Sexual Reproduction and Meiosis

Flashcards covering the vocabulary terms and core concepts of sexual reproduction, meiosis, chromosome structure, and genetic disorders from Chapter 9.

Asexual reproduction

A form of reproduction where one parent organism replicates its DNA and splits the contents of one cell into two, generating genetically identical offspring.

Sexual reproduction

A form of reproduction where the DNA of the offspring comes from two parents, through the fusion of an egg and a sperm, generating genetically diverse offspring.

Diploid cells

Cells that contain two sets of chromosomes, with one set inherited from the father and one from the mother, denoted as $2n$.

Karyotype

An image showing all of the chromosomes from a diploid cell, used to visualize the chromosome sets.

Autosomes

The 22 pairs of numbered chromosomes in human cells that are the same for both males and females.

Sex chromosomes

The chromosomes denoted by letters ($X$ and $Y$) that determine an individual's sex; humans have one set.

Homologous pair

Two chromosomes that are similar in size and structure and carry genes for the same traits, though their DNA sequences are not exactly the same.

Alleles

Alternative versions of the same gene found on members of a homologous pair.

Sister chromatids

Identical copies of a single chromosome produced after DNA replication, joined at a centromere.

Gametes

Haploid sex cells, such as sperm and egg cells, which contain only one set of chromosomes.

Haploid cell

A cell that has only one set of chromosomes, denoted as $n$.

Fertilization

The fusion of two haploid sex cells.

Zygote

The first diploid cell of a new organism formed when two haploid gametes fuse.

Germ cells

Specialized diploid cells, located in the testes or ovaries, that divide by meiosis to form haploid gametes.

Meiosis

A type of cell division that halves the chromosome number and produces four genetically distinct haploid gametes.

Crossing over

A process occurring during prophase I where two homologous chromosomes pair up and exchange pieces, scrambling genetic material.

Independent assortment

The random alignment of chromosome pairs during metaphase I, which scrambles the combination of chromosomes for each gamete.

Monozygotic twins

Genetically identical individuals that develop from a single zygote that splits into two embryos.

Dizygotic twins

Fraternal twins with unique DNA that result from two separate sperm cells fertilizing two separate egg cells.

Nondisjunction

The failure of chromosomes to separate properly during anaphase I or anaphase II, leading to gametes with too many or too few chromosomes.

Trisomy

A genetic condition characterized by having an extra copy of a chromosome, such as Trisomy 21 which causes Down syndrome.

Triplo-X

A sex chromosome abnormality ($XXX$) in females characterized by tall stature and menstrual irregularities.

Klinefelter syndrome

A sex chromosome abnormality ($XXY$) in males often resulting in sexual underdevelopment and long limbs.

Turner syndrome

A sex chromosome abnormality where a female is born with only one X chromosome ($XO$), leading to short stature and infertility.

Spermatogenesis

The process of producing four haploid sperm cells from one diploid germ cell.

Oogenesis

The process of producing one haploid egg cell and three polar bodies from one diploid germ cell.

Spores

Haploid cells produced by fungi, some protists, and certain plants that undergo mitosis to form haploid gametophytes.

Evolutionary fitness

The ability of an organism to survive and reproduce in its environment.