Chapter 4 Flashcards
Terms
Anaphase I
Homologous chromosomes separate.
Anaphase II
Sister chromatids separate.
Asexual reproduction
A type of reproduction involving only one parent (genetically identical offspring.)
Asters
Clusters of microtubules radiating out from the poles in dividing cells. They are present in animal cells, but not in the cells of flowering plants and most gymnosperms.
Autosome
Any chromosome that is not a sex chromosome
Cell cycle
Cyclic series of events in the life of a dividing eukaryotic cell; consists of stages of interphase, mitosis and cytokinesis
Cell plate
The structure that forms during cytokinesis in plants, separating the two daughter
Centromere
Specialized constricted region of a chromatid; contains the kinetochore. In cells at prophase and metaphase, sister chromatids are joined in the vicinity of their centromeres.
Chiasmata
Points where homologous chromosomes exchange genetic material during meiosis. An X-shaped site in a tetrad marking the location where homologous chromatids previously underwent crossing over
Chromatid
is one half of a duplicated chromosome, which pairs with its sister chromatid during cell division seen in prophase and metaphase.
Chromatin
Uncoiled DNA found in interphase
Chromosomes
structures in the cell nucleus, composed of chromatin and containing the genes Condensed DNA seen in prophase and metaphase.
Clone
A population of cells descended by mitotic division from a single ancestral cell, or a population of genetically identical organisms asexually propagated from a single individual.
Crossing over
The breaking and rejoining of homologous (non sister) chromatids during early meiotic prophase I, resulting in an exchange of genetic material.
Cytokinesis
Stage of cell division in which the cytoplasm is divided to form two daughter cells. cells produced by mitosis
Diploid
a cell containing two copies of each chromosome (2n).
DNA
Deoxyribonucleic acid The molecule that carries genetic information in cells
DNA molecule components
A phosphate group, A deoxyribose sugar, A nitrogenous base (Adenine, Thymine, Cytosine, or Guanine)
Fertilization
Fusion of n gametes; results in the formation of a 2n zygote
Gamete
A sex cell; in plants and animals, an egg or sperm containing half the normal number of chromosomes.
Gene
A segment of DNA molecule that codes for a particular trait: found at a specific
location on a chromosome (from your parents)
Germ line cell
Cells that give rise to gametes.
Haploid
a cell containing half the usual complement of chromosomes (n).
Histone
Proteins around which DNA wraps to form nucleosomes.
Interphase
Stage of the cell cycle between successive mitotic divisions; Its subdivisions are the G1 (first gap), S (DNA synthesis) and G2 (second gap) phases
Homologous chromosomes
Matching pairs of chromosomes, similar in size and carrying information for the same gene, one from each parent.
Karyotype
the chromosomes of an individual that has been sorted and arranged according to size and type
Kinetochore Y
Portion of the chromosome centromere to which the mitotic spindle fibers attach.
Meiosis
Process in which a 2n cell undergoes two successive nuclear divisions, potentially producing four nuclei; leads to the formation of gametes in animals and spores in plants.
Metaphase
The stage of mitosis, and of meiosis I and II, in which the chromosomes line up on the equatorial plane of the cell.
Mitosis
Division of the cell nucleus, results in two daughter nuclei, each have the same number of chromosomes as the parent nucleus
Mutation
A change in the genetic code of an allele, the change may have a positive effect, a negative effect or no effect at all.
Nondisjunction
The failure of homologous chromosomes to move to opposite poles of the cell during meiosis resulting in an abnormal number of chromosomes in the daughter cells
Nucleosome
The basic structural unit of DNA packaging in eukaryotes, consisting of DNA wrapped around histone proteins.
Nucleotide:
The repeating unit in DNA, consisting of a deoxyribose sugar, phosphate group, and one of the four nitrogenous bases.
Prophase
The first stage of mitosis, and of meiosis I and II; chromosomes become visible as distinct structures, the nuclear envelope breaks down, and a spindle forms
Pyrimidine:
Single-ring nitrogenous bases in DNA (cytosine and thymine).
Purine
Double-ring nitrogenous bases in DNA (adenine and guanine).
S phase
Stage in interphase of the cell cycle during which DNA and other chromosomal constituents are synthesized.
Sexual reproduction
Type of reproduction in which two gametes (usually, but not necessarily, contributed by two different parents) fuse to form a zygote.
Somatic cell
Any cell in the body except reproductive cells (gametes)
Spindle
Structure consisting mainly of microtubules that provides the framework for chromosome movement during cell division. Spindle fibers help separate sister chromatids and move them to opposite poles of the cell
Synapsis
The process of physical pairing of homologous chromosomes during prophase I of meiosis, allowing for crossing over.
Tetrad
A pair of homologous chromosome structures each with 2 sister chromatids totaling four chromatids formed during meiosis.
Telomere
is a repetitive DNA sequence at the end of a chromosome that protects genetic information during cell division. Over time, telomeres shorten, leading to cellular aging and eventual cell death
Telophase
The last stage of mitosis, and of meiosis I and II, when, having reached the poles, chromosomes become decondensed, and a nuclear envelope forms around each group
Tetrad:
A pair of homologous chromosome structures each with 2 sister chromatids Chromosome complex formed by the synapsis of homologous chromosomes during meiotic prophase I.
Trait
A particular version of a characteristic that an organism inherited from its parents, determined by genes.
Trisomy
The presence of an extra chromosome, resulting in three copies instead of the normal two (e.g., Down syndrome - Trisomy 21).
Trisomy 13
Patau syndrome
Trisomy 18
Edward syndrome
Trisomy 21
Down syndrome
XXY
Klinefelter syndrome
Zygote
The 2n cell that results from the union of n gametes in sexual reproduction. Species that are not polyploidy have haploid gametes and diploid zygotes.
