Single Gene Inheritance and Beyond Mendel's Laws

Flashcards covering key vocabulary related to single gene inheritance, Mendel's Laws, complex inheritance patterns, mitochondrial genetics, sex-linked inheritance, and epigenetics.

Homozygous

Having two identical alleles for a particular gene.

Heterozygous

Having two different alleles for a particular gene.

Dominant allele

An allele whose phenotypic effect is expressed in a heterozygote.

Recessive allele

An allele whose phenotypic effect is not observed in a heterozygote.

Genotype

The genetic makeup, or set of alleles, of an organism (e.g., RR, Bb).

Phenotype

The observable physical and physiological traits of an organism (e.g., Red roses, white roses).

Wild type

The most common trait or allele in a population.

Mutant

An organism of a new genetic character arising from a change in DNA.

Monohybrid cross

A cross between two organisms that are heterozygous for the single character being followed.

Dihybrid cross

A cross between two organisms that are heterozygous for two different characters being followed.

Independent assortment

Mendel's law stating that each pair of alleles segregates independently of each other pair of alleles during gamete formation.

Pedigree

A family tree that describes the interrelationships of parents and children across generations, showing the inheritance patterns of a particular trait.

Punnett square

A diagram used in the study of inheritance to show the predicted results of random fertilization in genetic crosses between individuals of known genotype.

Gregor Mendel

Figured out how genetics are passed down from one generation to the next, notably from his studies of pea plants.

Law of Segregation

Mendel's law stating that the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes.

9:3:3:1 Phenotypic Ratio

The classical phenotypic ratio expected from a dihybrid cross of two heterozygotes where alleles show complete dominance.

Pedigree Analysis

Tracing phenotypes through a family to determine which individuals carry certain alleles and explain inheritance patterns.

Complete dominance

A situation in which the phenotypes of the heterozygote and dominant homozygote are identical.

Codominance

A condition in which both alleles for a gene are fully expressed in the phenotype, but in different parts of the organism (e.g., AB blood type).

Incomplete dominance

A situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele (e.g., red and white parents produce pink offspring).

Epistasis

A type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene; one gene can mask or modify the effect of another.

Pleiotropy

The ability of a single gene to have multiple phenotypic effects; one gene influences multiple traits.

Mitochondrial genes

Genes located in the mitochondria, possessing their own genome (approx. 16,500 base pairs, 37 genes), involved in pro-apoptotic purposes and protein expression without introns or histones.

Mitochondrial DNA (mtDNA)

Genetic material found in mitochondria, which mutates faster than nuclear DNA and is primarily inherited from the mother, useful for comparing closely related groups for evolutionary relationships.

3-Parent genetic offspring

A technique to prevent the inheritance of mitochondrial diseases by removing the nucleus from an egg and placing it into a donated enucleated egg with healthy mitochondria, then fertilizing.

Linkage map

A genetic map of a chromosome based on recombination frequencies; genes located on the same chromosome are said to be linked and don't always adhere to the law of independent assortment.

Sex-linked genes

A gene located on either sex chromosome (X or Y).

Y-linked genes

Genes located on the Y chromosome, mainly involved in sex determination (found only in males).

X-linked genes

Genes located on the X chromosome, which carries genes for many characters unrelated to sex.

X-linked recessive trait expression

For a female, two copies of the allele (homozygous) are needed; for a male, only one copy of the allele (hemizygous) is sufficient because males have only one X chromosome.

X-linked recessive disorders

Disorders that are much more common in males than females, such as color blindness, Duchenne muscular dystrophy, and hemophilia.

Epigenetics

The study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence, often due to DNA structure or location changes.

Barr body

A dense object formed from the inactivation of one of the two X chromosomes in each female mammalian cell during embryonic development, controlling gene expression by condensing DNA.

DNA Methylation

A process of modifying DNA by adding methyl groups, which typically makes DNA more condensed, blocks gene expression, is inherited from the mother, and can change over time due to environmental conditions.

Methylated DNA

DNA that is more condensed with tightly packed histones, which blocks gene expression.

Unmethylated DNA

DNA with histones spread out, allowing enzymes to access genes more easily for greater gene expression.

Multifactorial trait

A trait, condition, or disease influenced by many factors, both genetic and environmental.

Polygenic inheritance

An additive effect of two or more genes on a single phenotypic character, such as skin color, height, intelligence, or body mass index.

Genome-wide association studies (GWAS)

Scientific studies that survey the entire genome to identify genetic variations (like SNPs) that are associated with a particular disease or trait by comparing two or more groups.

Single nucleotide polymorphism (SNP)

A single base-pair variation in the genome that occurs at a specific position, contributing to genetic differences between individuals.