Genetics Flashcards
Meiosis
Cell division that produces reproductive cells in sexually reproducing organisms
Prophase I
DNA coils & condenses into chromosomes which contain 2 sister chromatids
Nuclear membrane break down
Homologous chromosomes pair up together and form a tetrad (4 sister chromosomes side to side)
Homologous chromosomes can exchange sections of DNA, which we call Crossing Over.
Crossing Over
This is the process where the two homologous pairs of chromosomes mix their genes together to create a unique tetrad
Zygote
The unified cell between a sperm and egg cell after fertilization.
Metaphase I
Tetrads (paired homologous chromosomes) line up at the middle of the cell
They line up randomly which increases the genetic variation. This is called independent assortment.
Anaphase I
Homologous pairs are separated and pulled to opposite ends of the cells.
The centromere are NOT pulled apart
Telophase I and Cytokinesis
The nuclear membrane re-forms around chromosomes, which uncoil
Chromosomes are still composed of chromatids (still in an x-shape) but only half of the DNA is present in each daughter cell
Each cell has become a haploid and is not identical
The cleavage furrow forms and cytokinesis follows
Prophase II
No interphase occurs
Nuclear membrane disappears, DNA condenses
Metaphase II
spindle fibers pull chromosomes so they are lined up in the middle of the cell in single file.
Anaphase II
Centromeres divide
Chromatids come apart to migrate separately to each pole
Telophase II & cytokinesis
Daughter chromatids unwind into chromatin
Nuclear membrane reforms
Cytoplasm splits in cytokinesis
Four haploid daughter cells are formed
Deletion
a piece of a chromosome is deleted
ex: Cri du Chat
Duplication
a section of a chromosome appears two or more times in a row
ex: Charcot-Marie-Tooth disease
Inversion
a section of a chromosome is inverted
ex: FG Syndrome
Translocation
a segment of one chromosome becomes attached to a different chromosome
ex: Chronic Myelogenous
Down Syndrome
extra chromosome on 21st pair (trisomy)
- short height
- deformed face
- mental disabilities
Patau’s Syndrome
Extra chromosome on the 13th pair
- physical abnormalities
- Extra toes and fingers
- Cyclopia
Edward’s syndrome
Extra chromosome on the 18th pair
- Heart defects & kidney and CNS
- Malformed ears
- Small math
Klinefelter Syndrome
Two x chromosomes and on y chromosomes
- biological male at birth
XXX Female
Three x chromsomes
Turner’s syndrome
one x chromosome
- short height
Synapsis
Connection of homologous chromosomes to form a tetrad
Centromere
Area where the chromatids of a chromosome are attached
Chromatin
a mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms
Chromosomes
threadlike structures made of DNA molecules that contain the genes
Sister chromatid
Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.
Supercoil
A coil of coils; a circular molecule of DNA can coil upon itself to form a supercoil.
Homologous chromosomes
Chromosomes that have the same sequence of genes and the same structure
Karyotype
A display of the chromosome pairs of a cell arranged by size and shape.
Mitosis
cell division for growth and repair of cells
Interphase
Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases
G1 phase: When the cell grows
S phase: When DNA replicates
G2 phase: Synthesis occurs again
Prophase
Chromosomes become visable, nuclear membrane dissolves, spindle forms
Metaphase
Chromosomes line up in the middle of the cell
Anaphase
Phase of mitosis in which the chromosomes separate and move to opposite ends of the cell
Telophase
the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.
Cytokinesis
division of the cytoplasm
Diploid
2 sets of chromosomes
Haploid
having a single set of unpaired chromosomes
Independent assortment
Independent segregation of genes during the formation of gametes
Non disjunction
Error in meiosis in which homologous chromosomes fail to separate.
Gamete
sex cell
Tetrad
structure containing 4 chromatids that forms during meiosis
Cancer
any malignant growth or tumor caused by abnormal and uncontrolled cell division
Malignant
Cancerous
Benign
mild, not cancerous
