AP Biology Chapter 10 Vocab

Heredity

The transmission of traits from one generation to the next.

Genetics

The scientific study of heredity and hereditary variation.

Genes

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

Gametes

A haploid reproductive cell, such as an egg or sperm. Unite during sexual reproduction to produce a diploid zygote.

Somatic cells

Any cell in a multicellular organism except a sperm or egg or their precursors.

Locus

A specific place along the length of a chromosome where a given gene is located.

Asexual reproduction

The generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). In most cases, the offspring are genetically identical (clones) to the parent.

Sexual reproduction

A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from both parents via the gametes.

Life cycle

The generation-to-generation sequence of stages in the reproductive history of an organism

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Homologous chromosomes

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother.

Sex chromosomes

A chromosome responsible for determining the sex of an individual.

Autosomes

A chromosome that is not directly involved in determining sex; not a sex chromosome.

Diploid cell

A cell containing two sets of chromosomes (2n), one set inherited from each parent.

Haploid cells

A cell containing only one set of chromosomes (n)

Fertilization

The union of haploid gametes to produce a diploid zygote.

Zygote

The diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg.

Meiosis

A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.

Alteration of generations

A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants and some algae.

Meiosis I

The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Meiosis II

The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Synaptonemal complex

A zipper-like structure composed of proteins, which connects two homologous chromosomes tightly along their lengths during part of prophase I of meiosis.

Synapsis

The pairing and physical connection of duplicated homologous chromosomes during prophase I of meiosis.

Recombinant chromosomes

A chromosome created when crossing over combines DNA from two parents into a single chromosome.

Gametophyte

In organisms (plants and some algae) that have alternation of generations, the multicellular haploid form that produces haploid gametes by mitosis. The haploid gametes unite and develop into sporophytes.

Sporophyte

In organisms (plants and some algae) that have alternation of generations, the multicellular diploid form that results from the union of gametes. The sporophyte produces haploid spores by meiosis that develop into gametophytes.

Crossing over

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

Chiasma

The X-shaped, microscopically visible region where crossing over has occurred earlier in prophase I between homologous nonsister chromatids. Become visible after synapsis ends, with the two homologs remaining associated due to sister chromatid cohesion.

Nonkinetochore microtubules

Microtubules that don't attach to chromosomes but are crucial for pushing the cell poles apart, elongating the cell during anaphase, and maintaining the overall structure and integrity of the mitotic spindle, ensuring proper cell division and genetic separation

Kinetochore microtubules

The essential link between chromosomes and the mitotic spindle, serving to attach to centromeres, generate forces for chromosome movement (pulling and pushing) through polymerization/depolymerization, align them at the metaphase plate, and ensure their equal segregation into daughter cells during cell division

Kinetochore

A structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.

Sister chromatid cohesion

The crucial process that physically links identical sister chromatids together from their creation during DNA replication (S phase) until their separation in anaphase, mediated by protein complexes called cohesins, ensuring proper chromosome alignment and segregation into daughter cells during mitosis and meiosis, and also playing roles in DNA repair.

Chromosomes condense as each chromosome pairs with its homolog and crossing over occurs, DNA molecules of nonsister chromatids are broken by proteins and are rejoined to each other, microtubules from one pole or the other attach to the kinetochores, microtubules move the homologous pairs toward the metaphase plate

4 Unique Characteristics of Prophase I 

During prophase I, duplicated homologs pair up, and crossing over occurs, at metaphase I of meiosis, pairs of homologs are positioned at the metaphase plate, rather than individual chromosomes as in metaphase of mitosis, at anaphase I, the duplicated chromosomes of each homologous pair move toward opposite poles, but the sister chromatids of each duplicated chromosome remain attached. In anaphase of mitosis, by contrast, sister chromatids separate.

3 events unique to meiosis occur during meiosis I

Pairs of homologous chromosomes are arranged at the metaphase plate with one chromosome of each pair facing each pole, both chromatids of one homolog are attached to kinetochore microtubules from one pole as the chromatids of the other homolog are attached to microtubules from the opposite pole.

2 Unique Characteristics of Metaphase I

Breakdown of proteins that are responsible for sister chromatid cohesion along chromatid arms allows homologs to separate, the homologs move toward opposite poles guided by the spindle apparatus, sister chromatid cohesion persists at the centromere causing chromatids to move as a unit toward the same pole.

3 Unique Characteristics of Anaphase I

Each half of the cell has a complete haploid set of duplicated chromosomes, each chromosome is composed of two sister chromatids, cytokinesis usually occurs simultaneously, cleavage furrow forms, chromosomes decondense and nuclear envelopes form, no chromosome duplication occurs between meiosis 1 and meiosis Il

6 Unique Characteristics of Telophase I and Cytokinesis

Independent Assortment of Chromosomes

A process unique to meiosis where homologous chromosomes pair line up randomly during Metaphase I of meiosis, ensuring that alleles for different genes segregate independently into gametes (sperm/egg), creating genetic diversity by mixing maternal and paternal chromosomes in unique combinations. This randomness in alignment, coupled with crossing over, means inheriting a specific allele for one trait doesn't predict the allele for another, generating vast combinations in offspring.