Genetics review
The probability of a yellow-seed plant (YY) forming a Y gamete is_____ % because the principle of segregation - one_____ of each gene pair goes to a____ ; it only has "Y" alleles.
100,
If you have a heterozygous yellow-seed plant (Yy), the probability of forming a "Y" gamete is _____. The probability of forming a "y" gamete is _____. This follows the principle of segregation.
50 ,50
Chromosome
A "thread-like" molecule in the nucleus, composed of DNA. A chromosome possesses one allele for a given trait, therefore chromosomes occur in pairs. Each originates from the male and female gamete (parent)
Mutation
A change in the genetic information code
Crossing Over
A condition where non-sister chromatid of homologous chromosomes exchange genes
Chromatid
A double-stranded chromosome following replication attached by a centromere
Recessive
A gene or trait which is masked when a dominant allele is present
Trait
A genetic characteristic of the idividual
Punette Square
A grid system used to predict possible combinations of genes due to random fertilization
Spindle Fibers
A number of threadlike filaments formed between poles of the cell during cell division to which the centromeres of chromosomes attach; used to pull chromosomes apart and segregate them during anaphase.
Pure-bred
A phenotype (trait) resulting from homozygous genes from the offspring of true breeding
Gene
A portion of DNA which codes a specific hereditary trait
Gamete
A reproductive cell produced by the male or female parent, which contains the haploid number of chromosomes
Y Chromosome
A sex chromosome found in males; influencing the degree of maleness
X Chromosome
A sex chromosome; in human males only one is present and in females two are present
Centromere
A structure on the chromosome that holds a pair of chromatids together during replication
Meiosis
A type of cell division used to produce gametes and there is a reduction in the chromosome number from the diploid to the haploid number
Gene Pool
All of the genes present in a specific population
Allele
Alternative forms for a specific gene (either dominant or recessive)
Hybrid
An offspring from a cross between parents which has different phenotypes for a specific trait
Autosome
Any pair of chromosomes other than the sex chromosome
Diploid
Both members of a pair of chromosomes are present
Dihybrid Cross
Breeding of individuals which have two genes for two different characteristics
Tetrad
During metaphase I the two pairs of chromatids of the homologous pair of chromosomes comes together; crossing-over can occur at this time.
Nondisjunction
Failure of chromosomes to segregate during the formation of gametes, resulting in extra or a shortage of chromosomes in the gamete
Sex-linked
Genes that are located in the sex chromosome
Dominant
In a pair of genes, one may prevent the allele from being expressed
Principle of Segregation
Members of a gene pair separate during meiosis and are found in separate gametes
Haploid
One member of a pair of homologous chromosomes is present, such as in a gamete
Sex-Chromosomes
One of the chromosomes which determine the sex of the individual
Polar Body
One of three small cells produced during oogenesis, each contain the haploid number of chromosomes.
Oogenesis
Process of development of haploid female gametes.
Pedigree
The ancestral history of an individual; a chart showing the history of a trait in the family
Incomplete Dominance
The blending of two traits in a heterozygous individual
Monohybrid Cross
The breeding of two organisms which differ in a single trait
Probability
The chance that a given event will occur usually expressed between the number 0 (will not occur) and 1 (the event will occur)
Codominance
The condition in heterozygotes where both members of an allelic pair contribute to phenotype producing a mixture of phenotypic traits
Genotype
The genes present in an organism
Phenotype
The outward appearance of the organism which is the product of gene action
True-Breeding
The process of crossing two organisms, both having homozygous genes for the same trait
Spermatogenesis
The production of haploid male gametes by the male parent.
Prophase I
The stage in the first meiotic division where the doubled chromosomes become visible and nuclear membrane disappears.
Metaphase I
The stage in the first meiotic division where the homologous chromosomes line up as a pair, forming a tetrad of chromatids, at the equator of the cell
Metaphase II
The stage in the second meiotic division where the chromatid pair lines up at the equator of the cell..
Anaphase II
The stage in the second meiotic division where the sister chromatids of a chromosome split and migrate to opposite poles
Telophase I
The stage of the first meiotic division where the cell divides into two cells each containing one member of each pair of homologous chromosomes.
Telophase II
The stage of the second meiotic division when the cell divides into two cells with each being haploid; these cells become the gametes.
Anaphase I
The stage on the first meiotic division when the homologous chromosomes move to opposite poles but the sister chromatids remain together
Multiple Alleles
Where more than two alternatives for a gene exist
Heterozygous
Refers to a pair of genes from a specific trait in an organism which are different
Homozygous
Refers to a pair of genes in an organism which are identical in the way they influence a trait