Meiosis and Recombination Practice Flashcards

Vocabulary practice flashcards covering meiosis, recombination, chromosomal aneuploidies, and biological life cycles based on lecture notes.

Chromatin

The form in which DNA is packaged inside the cell nucleus in a relaxed, uncoiled structure.

Sister Chromatids

Two identical copies of a single replicated chromosome that are joined together by a centromere.

Homologous Chromosomes

A pair of chromosomes containing one chromosome inherited from each parent that carry genes for the same characteristics.

Crossing Over

The exchange of genetic material/DNA between non-sister chromatids of homologous chromosomes during Prophase I of meiosis.

Meiosis I

The first meiotic division where homologous chromosome pairs align as tetrads and separate into two haploid cells ($2n \rightarrow n$).

Meiosis II

The second meiotic division where sister chromatids separate, resulting in four haploid cells ($n \rightarrow n$).

Reductional Division

A cell division process, such as Meiosis I, that reduces the chromosome ploidy level from diploid ($2n$) to haploid ($n$).

Equational Division

A cell division process, such as Meiosis II or Mitosis, where the ploidy level remains the same ($n \rightarrow n$ or $2n \rightarrow 2n$).

Independent Assortment

The random and independent alignment and separation of homologous chromosome pairs at Metaphase I.

Linked Genes

Genes located close to each other on the same chromosome that are more likely to be inherited together (e.g., Gene A and B with a $93\%$ chance compared to Gene A and C with a $53\%$ chance).

Random Fertilization

The random union of a haploid sperm ($n$) and a haploid oocyte ($n$) to form a genetically unique diploid zygote ($2n$).

Aneuploidy

A condition in which a gamete or cell has an abnormal number of chromosomes due to chromosomal separation mutations.

Nondisjunction in Meiosis I

An error where homologous chromosomes fail to separate, producing two gametes with an extra chromosome ($n + 1$) and two with a missing chromosome ($n - 1$).

Nondisjunction in Meiosis II

An error where sister chromatids fail to separate, producing two normal gametes ($n$), one with an extra chromosome ($n + 1$), and one with a missing chromosome ($n - 1$).

Trisomy 21 (Down Syndrome)

A chromosomal condition resulting from an extra copy of chromosome 21, whose incidence increases with maternal age above 30.

Trisomy 13 (Patau Syndrome)

A chromosomal disorder causing serious defects of the brain, extra fingers/toes, and cleft lip/palate, leading to death within the first year of life for most infants.

Trisomy 18 (Edwards Syndrome)

A chromosomal disorder resulting in severe intellectual disability, small head, heart defects, and deafness, with most affected dying before birth or within the first month.

Turner Syndrome

A sex chromosome aneuploidy characterized by a $45,\text{X}$ karyotype, occurring in approximately 1 in 2,000 female live births.

Klinefelter Syndrome

A sex chromosome aneuploidy characterized by a $47,\text{XXY}$ karyotype, occurring in approximately 1 in 650 male live births.

Triple X Syndrome

A sex chromosome aneuploidy characterized by a $47,\text{XXX}$ karyotype, occurring in approximately 1 in 1,000 female live births.

47,XYY Syndrome

A sex chromosome aneuploidy characterized by a $47,\text{XYY}$ karyotype, occurring in approximately 1 in 1,000 male live births.

45,Y Karyotype

A sex chromosome anomaly characterized by the absence of an X chromosome that is not viable.

Animal Life Cycle

A life cycle pattern where gametes ($n$) arise by meiosis and the resulting zygote ($2n$) divides by mitosis.

Plant and Most Fungi Life Cycle

A life cycle pattern where spores ($n$) are formed by meiosis and gametes ($n$) arise by mitosis.

Fungi and Algae Life Cycle

A life cycle pattern where gametes ($n$) arise by mitosis and the zygote ($2n$) divides by meiosis.