Inheritance and Genetics Lecture Note

A set of vocabulary flashcards covering key terms and concepts from the genetics and inheritance notes.

Inheritance

The transmission of genetic information from parents to offspring.

Natural Selection

The process by which organisms with traits that help them adapt to the environment survive and reproduce more, increasing the frequency of those traits in the population.

Fitness (evolution)

In evolution, the relative ability of an organism to survive and reproduce.

Preformation Hypothesis

Early theory that organisms are preformed in the egg or sperm and develop from miniature versions of themselves.

Blending Inheritance

Outdated idea that offspring phenotype is a uniform blend of the parents’ phenotypes.

Pangenesis

Aristotle’s idea that particles from all parts of the body contribute to the eggs and sperm; offspring receive a mixture from both parents.

DNA

Molecule that carries genetic information; central to heredity.

Location of DNA in cells

DNA is found in the nucleus and in membrane-bound organelles such as chloroplasts (plants) and mitochondria (animals).

Nucleotide

A phosphate, sugar, and nitrogen base unit that makes up DNA; sides of the ladder are phosphates and sugars, rungs are bases.

Base pairs

Adenine pairs with thymine; guanine pairs with cytosine in DNA.

Gene

A section of DNA that codes for a particular trait.

Allele

An alternate version of a gene.

Gregor Mendel

Father of genetics; proposed laws of inheritance with discrete units (genes) and versions (alleles) including dominant and recessive.

Dominant

Allele that masks the effect of another allele in a heterozygous genotype or the trait that is expressed.

Recessive

Allele whose effects are masked by a dominant allele in a heterozygous genotype.

Genotype

The specific alleles an organism has for a trait.

Phenotype

The physical expression or observable trait resulting from a genotype.

Homozygous dominant

Two identical dominant alleles for a trait (e.g., PP).

Homozygous recessive

Two identical recessive alleles for a trait (e.g., pp).

Heterozygous

One dominant and one recessive allele (Pp).

Complete Dominance

In a heterozygous genotype, one allele completely masks the other’s effect.

Law of Segregation

Genes (alleles) separate into gametes and reunite at fertilization; discrete units are inherited.

Somatic cells

Body cells; produced by mitosis; diploid; genetically identical to each other.

Mitosis

Cell division that produces two identical daughter cells.

Gametes

Sex cells (eggs and sperm) with a haploid chromosome number.

Meiosis

Cell division that reduces the chromosome number by half to form haploid gametes.

Haploid

A cell with a single set of unpaired chromosomes.

Diploid

A cell with two sets of chromosomes.

Crossing-over

Exchange of genetic material between homologous chromosomes during meiosis.

Law of Independent Assortment

Genes for different traits are sorted independently of one another during gamete formation.

Linkage

Inheritance of genes that are close together on a chromosome; tends to be inherited together, opposing independent assortment.

Sex-Linked Traits

Traits associated with genes on sex chromosomes (e.g., X-linked color vision).

Mutation

A random change in a gene or chromosome that can introduce a new trait; effects may be advantageous, deleterious, or neutral.

Codominance

Two different alleles are both fully expressed in the heterozygote (e.g., Roan coat, ABO blood types).

ABO Blood Type system

System in which A and B alleles are codominant; O is recessive; different genotypes produce types A, B, AB, or O.

Blood type A

Phenotype produced by genotypes expressing A antigen (AA or AO).

Blood type B

Phenotype produced by genotypes expressing B antigen (BB or BO).

Blood type AB

Phenotype expressing both A and B antigens (codominance of A and B alleles).

Blood type O

Phenotype expressing neither A nor B antigens (genotype OO).

Incomplete Dominance

Heterozygote phenotype is intermediate between the two homozygous phenotypes (e.g., snapdragons).

Polygenic trait

A trait influenced by two or more genes, often showing continuous variation (e.g., height, skin color).

Autosome

Any chromosome that is not a sex chromosome; humans have 22 pairs of autosomes.

Sex chromosome

Chromosome involved in determining sex (X and Y in humans).

Sickle cell trait (example of codominance)

Heterozygotes express both normal and abnormal hemoglobin, illustrating codominance.