HORT 1001 Week 14 Terms

Dominant allele

It is when one allele is expressed over the other alleles present.

Generative nucleus

It is a nucleus in the immature male gametophyte that will later divide by mitosis to produce two sperm cells.

Genes

They are hereditary units consisting of a sequence of DNA that occupies a specific location on a chromosome (locus) and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequence changes.

Genotype

It is the genetic composition of an organism, including chromosomes of the nucleus and the DNA in chloroplasts and mitochondria.

Heritability

It is the measurement of a quantitative trait that passes from parent to offspring and is measured in high and low; high being very similar between parent and offspring and low being dissimilar between parent and offspring.

Heterozygote

It is a plant with two different alleles of a particular gene and gives rise to varying offspring; offspring are generally more vigorous than offspring from homozygote.

Homozygote

It is a plant with identical alleles of a particular gene and give rise to identical, or nearly identical, offspring.

Integument

They are cells that form the ovary wall. Nucellus cells on the interior of the ovule wall develop into megaspore mother cells.

Linkage

It is when two genes are on the same chromosome.

Locus

It is the location on a chromosome where a particular gene is found.

Megaspornatium

It is the place in the ovary where the female gametophyte will be formed.

Mendel's First Law - the law of segregation

It is the principle that during gamete formation each member of the allelic pair separates from the other member to form the genetic constitution of the gamete e.g. Ss diploid produces S and s gametes.

Mendel's Second Law - the law of independent assortment

It is the principle that during gamete formation the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair.

Microsporangium

It is the place in the anther where the male gametophyte will be formed.

Phenotype

It is the physical appearance of an organism; expressed as Phenotype = Genotype + Environment

Punnett square

It is a simple database used to visualize the types of zygotes and their expected frequency that form from male and female gametes.

Qualitative differences

They are large differences that can easily be seen or measured in qualitative terms; e.g. fruit color.

Quantitative differences

They are small differences that are measured numerically; e.g. yield in kg/ha. They can be influenced by the environment.

Recessive allele

It is the allele(s) that are not expressed if a dominant allele is present; they will be expressed if there is no dominant allele.

Suspensor

It is produced by multiple mitotic cell divisions of the embryo's basal cell; the suspensor anchors the apical cell of the embryo to the ovule wall.

Synergid cells

They are cells flanking the egg cell in the mature female gametophyte.

Tube nucleus (or vegetative nucleus)

It is a nucleus in the male gametophyte that is associated with pollen tube growth.