Chapter 5 Vocabulary

Zygote

the single cell formed from fertilization

Gamete

a specialized haploid sex cell

Haploid

(1n) – a specialized cell that contains half the chromosome number

Diploid

(2n) – the cells which contain two homologous copies of each chromosome

Crossing over

he exchange of corresponding regions on chromosomes

during meiosis

Codominance

two dominant alleles are expressed at the

same time without blending of traits

– Heterozygous individuals display both phenotypes

– Both alleles represented by capital letters

Monohybrid cross

a genetic cross involving individuals both heterozygous for one trait

Dihybrid cross

a breeding experiment between two organisms which are identical hybrids for two traits.

Dominant allele

A dominant allele produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent.

Recessive allele

For a recessive allele to produce a recessive phenotype, the individual must have two copies, one from each parent.

Phenotype

the physical and physiological traits of an organism

– Descriptive

Genotype

the genetic makeup of an organism

– Written as two letters

Heterozygous

the state of having two different alleles for a given genetic character

Homozygous dominant

the state of having two of the same alleles for a given genetic character

ex: RR

Homozygous recessive

the state of having two of the same alleles for a given genetic character

ex: rr

Incomplete dominance

a form of Gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype

Multiple alleles

the three or more different forms of a gene for the same trait, each producing a single phenotype

Polygenic inheritance

quantitative inheritance, where multiple independent genes have an additive or similar effect on a single quantitative trai

P generation

the first set of parents which are used for crossing

F1 generation

 the first filial generation seeds/plants or animal offspring resulting from a cross-mating of distinctly different parental types

F2 generation

 a group of people born as a result of inbreeding and interbreeding among members of the same family

sister chromatids

one of the two identical halves of a chromosome that has been replicated in preparation for cell division. 

tetrad

the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.