Meiosis and Mendelian Genetics Flashcards

Flashcards about Meiosis and Mendelian Genetics

Meiosis

Ensures the formation of haploid gamete cells in sexually reproducing diploid organisms.

Gamete Cells

Sex cells (e.g., sperm, eggs, pollen) that are haploid, containing one set of chromosomes.

Diploid Cell (2n)

A cell containing two sets of chromosomes; in humans, somatic cells (all body cells except reproductive cells) are diploid.

Heredity

The transmission of chromosomes from one generation to the next, ensuring the continuity of life.

Prophase I (Meiosis)

Phase where chromosomes condense and the nuclear envelope breaks down; homologous chromosomes pair.

Metaphase I (Meiosis)

Phase where pairs of homologous chromosomes move to the equator of the cell.

Anaphase I (Meiosis)

Phase where homologous chromosomes separate and move to opposite poles of the cell.

Telophase I (Meiosis)

Phase where chromosomes gather at the poles of the cell and cytokinesis divides the cell.

Meiosis II

Consists of prophase II, metaphase II, anaphase II, and telophase II, resulting in four haploid daughter cells.

Fertilization

The union of sperm and egg to form a zygote.

Mitosis

Cell division resulting in two genetically identical daughter cells; involves only one division and occurs in somatic (body) cells.

Meiosis

Cell division resulting in four genetically varied daughter cells; involves two divisions and occurs in gametes (sex cells).

Crossing Over

Recombination of bits of homologous chromosomes during prophase I of meiosis, contributing to genetic diversity.

Independent Assortment

Random shuffling of homologous chromosomes during metaphase I, increasing genetic variation.

Alleles

Different versions of a gene at the same locus.

Law of Segregation

Each allele segregates into separate gametes during meiosis, ensuring each gamete carries only one allele for each gene.

Law of Independent Assortment

Genes for different traits are inherited independently of each other if they are on different chromosomes.

Pedigree

A family tree that shows the relationship between family members and indicates which individuals express or carry a trait.

Autosomal Dominant

A trait that appears in every generation; affected offspring have at least one affected parent; males and females are equally affected.

Autosomal Recessive

A trait that can skip generations; affected individuals can have unaffected parents (carriers); males and females are equally affected.

X-Linked Dominant

Traits passed from affected fathers to all daughters; does not skip generations; affected males pass it to all daughters but not to sons.

X-Linked Recessive

Traits can skip generations; more males are affected than females; affected male usually has a carrier mother; sons of affected males are not affected.

Genotype

The genetic makeup of an organism, described by the alleles it carries (e.g., PP, Pp, pp).

Phenotype

The physical expression of a genetic trait (e.g., purple flower).

Homozygous

Having identical alleles for a gene (e.g., PP, pp).

Heterozygous

Having two different alleles for a gene (e.g., Pp).

Non-Mendelian Genetics

Genetic inheritance patterns that do not follow Mendel's laws, including incomplete dominance, codominance, sex-linked traits, and polygenic inheritance.

Incomplete Dominance

A form of inheritance where neither allele is completely dominant over the other, resulting in a blended phenotype (e.g., pink flower from red and white parents).

Codominance

A form of inheritance where both alleles are equally expressed in the phenotype (e.g., red and white spots on a flower).

Sex-Linked Traits

Traits associated with genes found on the sex chromosomes (X and Y), with the X chromosome carrying more genes.

X-Inactivation

In females, one of the X chromosomes in each cell is randomly inactivated during early development, forming a Barr body.

Polygenic Traits

Traits controlled by multiple genes (e.g., skin color, hair color, eye color, height).

Linked Genes

Genes that are close together on the same chromosome and tend to be inherited together.

Environmental Effects on Phenotype

The environment can influence phenotype, resulting in multiple phenotypes from the same genotype due to different environmental conditions.

Gene Disorders

Disorders caused by one or a few genes on a single chromosome (e.g., cystic fibrosis, sickle cell anemia, Huntington's disease).

Chromosome Disorders

Disorders caused by alterations in whole chromosomes (e.g., Trisomy 21/Down Syndrome, Klinefelter Syndrome, Turner Syndrome).

Nondisjunction

Failure of chromosomes to separate properly during anaphase of meiosis, leading to gametes with abnormal chromosome numbers.

Heterozygote Advantage

Some recessive disorders persist at high rates because unaffected carriers have a hidden survival advantage (e.g., sickle cell anemia carriers are resistant to malaria).

Chromosomal Theory of Inheritance

Traits pass from parents to offspring through chromosomes.