Patterns of inheritance

Hippocrates

Greek physicion who believed that pangenes travel from each part of the organism to the eggs or sperm, incorrect since reproductive cells aren’t composed of somatic cells and changes in somatic cells dont affect gametes

Blending hypothesis

Idea that the paretns genes are blended together, which was rejected since it didn’t explain how traits can reappear in later generations

Heredity

Transmission of traits from one generation to the next

Genetics

The scientific study of heredity, began with Mendel’s experiemnts of pea plants

Character

Variation among individuals

Trait

Variations in a character

Allele

Alternative version of genes that account for variations in inherited characters

Homozygous

A gene that has two identical alleles

Heterozygous

A gene that has two different alleles

Dominant allele

An allele that detemines the organisms appearance

Recessive allele

An allele that has no noticeable affect on the organism

Law of segregation

A sperm or egg carries one allele for each inherited character because of allele pair seperation, takes place during anaphase I

Genotype

The genes of an organism

Phenotype

The physical expression of the genotype

Punnett square

Diagram that shows the four possible combinations of alleles that could occur when these gametes combine

Monohybrid cross

Punnett Square that involves only one gene

Dihybird cross

Punnett square that involves two genes

Law of independent assortment

Alleles of a pair segregate independently of other allele pairs during gamete formation

Testcross

A mating between an individual of an unknown genotype and a homozygous recessive genotype, with their offspring revealing the unknown genotype

Rule of multiplication

Calculates the probability of two independent events both occuring

Rule of addition

Calculates the probability of an event that can occur in alternative ways

Peligrees

Family tree that describes the traits of parents and children, can help determine individual genotypes

Carries

People who carry a recessive allele but are phenotypically normal

Genetic and fetal testing

Testing for potential genes, leads to ethical dilemmas

Complete dominace

Situation where the dominant allele masks the recessive allele

Incomplete dominance

Situation where the phenotype is a mixture of their parents phenotype

Codominant

Situation where both parental phenotypes are expressed

ABO blood group

Phenotype that is controlled by three alleles and produces four phenotype, with two of the alleles being codominant

Pleiotrophy

One gene influences multiple characteristics

Polygenic inheritance

One characteristic is influenced by multiple genes

Chromosomal therory of inheritance

Genes occupy specific loci on chromosomes and chromosomes undergo segregation and independnet assortment during meiosis

Linked genes

Genes that are located close together and tend to be inherited together

Recombination frequency

The percentage of recombinant offspring among the total offspring

Genetic map

Ordered list of the genetic loci along a chromosome

Linkage map

Genetic map based on recombinant frequencies

Y chromosome

Chromosome that contains genes for the development of testes, provides data about recent human evolution that is passed down from father to son

Sex-linked gene

Gene located in a sex chromosome

X-linked gene

Gene carried by the X chromosome that controls traits unrelated to sex