GEN BIO 2 | Pedigree Analysis

Pedigree

a chart or diagram that shows how a trait or health condition is passed through generations of a family; helpful for analyzing the prominence of rare genetic conditions.

Genetics

the study of genes, which carry information that is passed from one generation to the next

Allele

variant form of a gene that is found in a specific location of the chromosome, known as the locus

Dominant Allele

the trait that masks the recessive allele, usually denoted by a capital letter

Recessive Allele

the trait masked by the dominant allele, usually denoted by a small letter

Law of Dominance

For a set of alleles, the dominant trait will be expressed.

Genotype

organism’s genetic information

Homozygous

possessing identical alleles of one gene, can be dominant homozygous or recessive homozygous depending on the allele present

Heterozygous

possessing different alleles of one gene, one dominant and one recessive

Phenotype

the observable physical traits

True-breeding

comes from the homozygous genotype, self-fertilization yields offspring with an identical trait.

Hybrid

comes from the heterozygous genotype, self-fertilization yields offspring with mixed genotypes and phenotypes

Pedigree Chart Parts | Square

it represents the male parent

Pedigree Chart Parts | Circle

it represents the female parent

Pedigree Chart Parts | Diamond

it represents an organisms whose sex is unknown

Pedigree Chart Parts | Shaded Shape

it represents an organism affected by the trait

Pedigree Chart Parts | Unshaded Shape

it represents a organism not affected by the shape

Pedigree Chart Parts | Marriage/mating lines

a horizontal line that connects the shapes that represent mates

Pedigree Chart Parts | Sibship Line

the lines connecting the siblings

Pedigree Chart Parts | Fraternal Twins

represented by the birthline branching out into the individual twin, diagonal lines are used

Pedigree Chart Parts | Identical Twins

it is similar to the fraternal twins but the twins are also connected by a horizontal line

Pedigree Chart Parts | Generation

these are labelled with roman numerals

Pedigree Chart Parts | Individuals

they are labelled with hindu-arabic numerals within one generation

Proband

the organism in the pedigree chart that is being studied or reported on and the first to report a certain trait in their family, usually indicated with an arrow

Propositus

a male proband

Proposita

a female proband

Law of Segregation

1. F1 parents (or the parental generation (PG)) contained two separate copies of each hereditary factor, which can be either dominant or recessive.

2. The factors separated when the gametes were formed. meaning an offspring will be carrying one allele from each parents.

3. Random fusion of all possible gametes occurred upon fertilization.

4. Two alleles for a heritable trait will split into segregate into different gametes

Law of Independent Assortment

• each pair of factors segregates or assorts independently of other pairs

• all possible combination of factors can occur in the gametes

Monohybrid Cross

a kind of punnett square used to test one trait

Dihybrid Cross

a kind of punnett square used to test two trait