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29 terms

Biology A Ch. 11

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allele
Form of a gene
codominance
Both alleles are completely expressed.
crossing over
Homologous chromosomes exchange portions of the chromatids during meiosis
diploid
Cell with two sets of homologous chromosomes
gamete
Egg or sperm cell
genotype
Genetic makeup of a an organism
haploid
Cell with one set of homologous chromosomes
heterozygous
Having two different alleles for a particular gene
homologous
Chromosomes where one set comes from the male parent and one set comes from the female parent.
homozygous
Having two identical alleles for a particular gene.
hybrid
Offspring of crosses between parents with different traits
incomplete dominance
Situation in which one allele is not completely dominant over another.
meiosis
The number of chromosomes per cell is cut in half.
multiple alleles
Gene that has more than two alleles
phenotype
Physical characteristics of an organism
Polygenic traits
Trait controlled by two or more genes
principle of dominance
Some alleles are dominant and some are recessive
principle of independent assortment
Genes ofr different traits can segregate independently during the formation of gametes.
trait
Specific characteristic of an individual that varies.
interphase
chromosomes replicate and chromatin condenses
prophase 1
-pairing of homologous chromosomes occurs, each chromosome consists of two chromatids and crossing over occurs
metaphase 1
chromosome centromeres attach to spindle fibers and HC line up at the equator
anaphase 1
HC separate and move to opposite poles of the cell
telophase 1
the spindle fibers break down, chromosomes uncoil and form two nuclei, the cell divides
prophase 2
chromosomes condense, spindles form in the new cells and attach to chromosomes.
metaphase 2
centromeres of chromosomes line up randomly at the equator of each cell.
anaphase 2
centromeres split, sr. chromatids separate and move to opposite poles
telophase 2
four nuclei form around chromosomes, spindles break down, cells divide.
products
four new cells have formed, each nuleus contains a haploid number of chromosomes.