Mendelian Genetics and Modes of Inheritance

Genes

Segments of DNA that determine traits.

Alleles

Variations of a gene influencing traits.

Genotype

Combination of alleles for a trait.

Phenotype

Physical expression of a trait.

Autosomal Dominant

Trait expressed if one dominant allele is present.

Autosomal Recessive

Trait expressed only if two recessive alleles are present.

Mendel's Law of Segregation

Alleles segregate during gamete formation.

Monohybrid Cross

Cross examining one trait's inheritance.

Punnett Square

Tool for predicting offspring genotype ratios.

Test Cross

Cross to determine an unknown genotype.

Selective Breeding

Choosing parents for desired traits in offspring.

Homozygous Dominant

Genotype with two dominant alleles (BB).

Heterozygous

Genotype with one dominant and one recessive allele (Bb).

Homozygous Recessive

Genotype with two recessive alleles (bb).

Dominant Allele

Allele that masks the effect of a recessive allele.

Recessive Allele

Allele whose effect is masked by a dominant allele.

Blending Theory

Outdated theory suggesting traits blend in offspring.

F1 Generation

First filial generation from a cross.

F2 Generation

Second filial generation from F1 self-cross.

True-Breeding

Organisms that produce offspring identical to themselves.

Phenotypic Ratio

Ratio of different phenotypes in offspring.

Genotypic Ratio

Ratio of different genotypes in offspring.

Gregor Mendel

Father of genetics; studied inheritance in peas.

Predictable Ratios

Consistent ratios of traits in offspring.

Accidental Selective Breeding

Unintentional selection of traits in agriculture.

Purebred

Organisms with identical alleles for a trait.

Genotype

Genetic makeup of an organism.

Phenotype

Observable traits of an organism.

F1 Generation

First filial generation from parental cross.

F2 Generation

Second filial generation from F1 cross.

Law of Segregation

Alleles segregate randomly during gamete formation.

Autosomal Dominant

Trait expressed if at least one dominant allele present.

Autosomal Recessive

Trait expressed only with two recessive alleles.

Monohybrid Cross

Cross examining a single trait inheritance.

Dihybrid Cross

Cross examining two traits simultaneously.

Independent Assortment

Genes segregate independently during gamete formation.

Homozygous

Having two identical alleles for a trait.

Heterozygous

Having two different alleles for a trait.

Allele

Different forms of a gene.

Gamete Formation

Process of forming reproductive cells.

Meiosis

Cell division producing gametes with half chromosomes.

Mendel's Experiments

Studies on inheritance patterns using pea plants.

Phenotypic Ratio

Proportion of different phenotypes in offspring.

Incomplete Dominance

Neither allele is completely dominant.

Co-dominance

Both alleles fully expressed in phenotype.

Sex-linked Traits

Traits associated with genes on sex chromosomes.

Blood Types

Classification based on specific antigens.

Sickle-cell Anemia

Condition showing incomplete dominance in inheritance.

Heterozygote

Individual with two different alleles.

Homozygous

Individual with identical alleles for a trait.

Dominant Allele

Allele that masks the effect of another.

Recessive Allele

Allele whose effect is masked by dominant.

X-linked Recessive

Trait requiring two recessive alleles in females.

Colour Blindness

X-linked recessive trait affecting vision.

Carrier

Individual carrying one recessive allele.

Barr Bodies

Inactivated X-chromosome in female cells.

Blood Type Alleles

IA, IB, and i determine human blood types.

Blood Type A

Genotype IAIA or IAi produces A phenotype.

Blood Type B

Genotype IBIB or IBi produces B phenotype.

Blood Type AB

Genotype IAIB produces AB phenotype.

Blood Type O

Genotype ii produces O phenotype.

Dominance Order

IA = IB > i indicates allele dominance.

Polygenic Inheritance

Traits controlled by multiple genes, showing continuous variation.

Continuous Traits

Traits that vary gradually, not in discrete forms.

Pleiotropic Genes

Single gene influences multiple traits or conditions.

Phenylketonuria (PKU)

Disorder caused by mutation affecting phenylalanine levels.

PKU Symptoms

Include seizures, stunted growth, and skin conditions.

Genotype Prediction

Using pedigrees to determine an individual's genotype.

X-linked Recessive

Trait expressed in males if allele is present.

Generation Analysis

Assess traits and genotypes across family generations.

Trait Expression

Visible characteristics resulting from genotype interactions.

X-linked Dominant

Trait expressed in both genders, no father-son transmission.

Autosomal Dominant

Trait appears in every generation, affected parents can have unaffected children.

Autosomal Recessive

Trait skips generations, unaffected parents can have affected children.

X-linked Recessive

Only males affected, no father to son transmission.

X-linked Dominant Example

Females affected more than males, no father-son transmission.

Gene Linkage

Genes close together on the same chromosome, inherited together.

Parental Gametes

Gametes that retain the same allele combinations as parents.

Recombinant Gametes

Gametes with new allele combinations due to crossing over.

Independent Assortment

Mendel's law predicting separate inheritance of traits.

Epigenetics

Gene expression influenced by environmental factors and methylation.

Methylation

Chemical modification that can turn genes on or off.

Phenotypic Ratio

Proportion of different observable traits in offspring.

Genotypic Ratio

Proportion of different genetic combinations in offspring.

Trait Transmission

Inheritance patterns determining how traits are passed.

Trait Skipping Generations

When traits are not expressed in every generation.

Affected Children

Children showing a trait inherited from affected parents.

Environmental Triggers

Factors that can influence gene expression and methylation.

Gamete Production

Process of forming reproductive cells with genetic material.

Crossing Over

Exchange of DNA between homologous chromosomes during meiosis.

Linked Genes

Genes that do not assort independently due to proximity.

Example of Linked Genes

Brown eyes and brown hair genes often inherited together.

Genotype BbHh

Individual with brown eyes and brown hair.

Less than 50% Recombinants

Linked genes produce fewer recombinant gametes than independent genes.

Linked Genes

Genes on the same chromosome with reduced crossing over.

Gene Mapping

Determining relative distances between genes on chromosomes.

Crossing Over

Exchange of genetic material between homologous chromosomes.

Recombination Frequency

Percentage of recombinant gametes produced.

Map Units

Distance between genes based on recombination frequency.

Non-Linked Genes

Genes that assort independently, producing 1:1:1:1 ratio.