Genetics Week 3

Mitosis

nuclear division that generates two daughter cells containing the same number and type of chromosomes as parent cells.

Anaphase

the stage of mitosis in which the connection of sister chromatids is severed (separate), allowing the chromatids to be pulled to opposite spindle poles.

Prophase

Chromosomes condense and become visible. the phase of the cell cycle marked by the emergence of the individual chromosomes from the undifferentiated mass of chromatin, indicating the beginning of mitosis

Chiasmata

observable regions in which Non sister chromatids of homologous chromosomes cross over

Gamete

sex cells (sperm and egg)

Interphase

the period in the cell cycle between divisions

Nondisjunction

failures in chromosome segregation during cell division, when either chromatids or homologs do not separate properly

Telophase

the final stage of mitosis in which the daughter chromosomes reach the opposite poles of the cell and nuclei re-form.

Autosome

the name given to all chromosomes in a set except the x and y chromosomes (sex chromosomes). 44 ____: 2 sex chromosomes

Chromosome

the self-replicating DNA/ protein complexes in the nucleus that contain genes

Haploid

cells with only a single set of chromosomes ex:gametes

Kinetochore

a specialized chromosomal structure composed of DNA and proteins that is the site at which chromosomes attach to the spindle fibers

Prometaphase

nuclear envelope breaks down, spindles form and sister chromosomes attach to the microtubules from opposite centrosomes and begin to move toward the metaphase plate

X-linked

carried by the X chromosome.

Bivalent

a pair of attached homologous chromosomes during prophase of meiosis I

Crossing Over

during meiosis, the breaking of one maternal and one paternal chromatid, resulting in the exchange of corresponding sections of DNA and the rejoining of the chromosomes. This process can result in the exchange of alleles between chromosomes

Homologous Chromosomes

a pair of chromosomes containing the same linear gene sequence, each derived from one parent.

Meiosis

Sex cell formations. In the first division, pairs of homologous chromosomes segregate into two different daughter cells; in the second division, the chromatids of each homolog segregate into two different daughter cells. A diploid (2x) cell produces four haploid (1x) gametes by meiosis

Sister Chromatid

identical copies of a replicated chromosome held together by protein complexes called cohesins.

Zygote

diploid cells containing two matching sets of chromosomes one each from egg and sperm

Centromere

a specific location where sister chromatids are attached and is important during cell division.

Cytokinesis

final stage of cell division, begins during anaphase but is completed after telophase. Cytoplasm of parent cells split into two daughter cells (cleavage) with identical nuclei

Metaphase

stage in mitosis or meiosis during which the chromosomes are aligned along the equatorial plane of the cell.

Somatic Cells

cells in an organism other than gametes and their precursors

Arcocentric

a chromosome in which the centromere is near the end

Hemizygous

describes the genotype for genes present in only one copy in an otherwise diploid organism, such as X-linked genes in a male. The organism only has 1allele for a gene

Polar Body

a cell produced by meiosis I or meiosis II during oogenesis that does not become the primary or secondary oocyte.

Sex-influenced trait

traits that can appear in both sexes but are expressed differently in each sex due to hormonal differences.

Synaptonemal complex

the structure that helps align homologous chromosomes during prophase of meiosis I.

Criss cross Inheritance

an inheritance pattern in which males inherit a trait from their mothers, while daughters inherit the trait from their fathers

Klinefelter syndrome

a chromosomal disorder where a male is born with an extra X chromosome. XXY

Pseudoautosomal regions

homologous regions at both ends of the X and Y chromosomes.

Sexually dimorphic trait

is the condition where the sexes of the same species exhibit different characteristics, particularly characteristics not directly involved in reproduction. Ex: Males bigger than females in mammals

Metacentric

a chromosome in which the centromere is in the middle

Turner syndrome

a chromosomal disorder where a female is only born with 1 X chromosomes. X_

Gametogenesis

the creation and formation of gametes

Ovum

haploid female sex cell (eggs)

Sex-linked trait

a gene which is found on the sex chromosomes rather than the autosomal chromosomes.

Spermatid

haploid cells produced at the end of meiosis that will mature into sperm

Centrosome

microtubule organizing centers at the poles of the spindle apparatus

Centrioles

core of centrosome (not found in plants) short cylindrical structures that help organize microtubules. Two centrioles at right angles to each other form the core of a centrosome. Each centrosome serves as a pole of the mitotic spindle