biology

genetics

scientific study of heredity

fertilization

process in sexual reproduction, male and female reproductive cells join to form cells

trait

specific characteristics of an individual

hybrid

offspring of crosses between parents with different traits

gene

sequence of DNA that codes for a protein and that determines trait

allele

one of a number of different forms of a gene

principle of dominance

mendels second conclusion, which is that some alleles are dom and others are recessive

segregation

separation of alleles during gamete formation

gamete

sex cell

probability

likelihood that a partner even will occur

homozygous

2 identical alleles for a trait

heterozygous

2 different alleles for a particular gene

phenotype

physical characteristic of an organism

genotype

genetic make up of an organism

Punnett square diagram

showing the gene combination that might result from a genetic cross

independent assortment

one of mendels principles that states that genes for different traits can segregate

incomplete dominance

situation in which one allele is not completely dominant over another

codominance

situation in which both alleles of an gene contribute

multiple alleles

3 or more forms of a gene that code for a single trait

polygenetic traits

traits controlled by 2 or more genes

homologous chromosome

type of chromosomes inn which one set comes from the male parents and one set from the female parent

diploid

a cell that contains 2 haploid sets of chromosomes

haploid

a cell that contains one set of chromosomes instead of the normal pair

meiosis

process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid

tetrad

structure containing 4 chromatids that form during meiosis

crossing over

process in which homologous chromosomes exchange portions of their chromatids during meiosis

dominant trait geno type possibilities

TT , Tt

recessive genotype possibilities

tt

difference between incomplete dominance and codominance

incomplete - one allele is not completely dominant over the others

codominance - both alleles contribute to the phenotype

diploid numbers 2N

46

haploid numbers N

23

when do tetrads form

during cross over

how is a gene map made

based on the frequency of crossing over between genes

what does phenotype look like

short or tall

what does genotype look like

TT , Tt, or tt

what does phenotype ratio look like

D:R

what does genotype ratio look like

TT:Tt:tt