BIO 103: Ch. 13 Sexual Reproduction and Meiosis

Heredity

The transmission of traits from one generation to the next

Variation

Differences between members of the same species

Genetics

The scientific study of heredity and hereditary variation

Gene

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

Autosome

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

Karyotype

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

Meiosis I

The first division of a two-stage process of cell division in sexually reproducing organisms that result in cell with half the number of chromosomes sets as the original cell

Somatic Cell

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

Life Cycle

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

Mitosis

A process of nuclear division in eukaryotic cells conventionally divided into five stages:prophase, prometaphase, metaphase, anaphase, and telophase. It conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.

Zygote

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

Fertilization

The union of haploid gametes to produce a diploid zygote.

Locus

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

Sexual Reproduction

Reproduction arising from fusion of two gametes.

Clone

(1) A group of genetically identical individuals or cells.
(2) In popular usage, an individual that is genetically identical to another individual.
(3) As a verb, to make one or more genetic replicas of an individual or cell.

Gamete

A haploid reproductive cell, such as an egg or sperm, that is formed by meiosis or is the descendant of cells formed by meiosis. These cells unite during sexual reproduction to produce a diploid zygote.

Asexual Reproduction

The generation of offspring from a single parent that occurs without the fusion of gametes. In most cases, the offspring are genetically identical to the parent.

Evolution

Descent with modification; the process by which species accumulate differences from their ancestors as they adapt to different environments over time; also defined as a change in the genetic composition of a population from generation to generation.

Natural Selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

Sex Chromosome

A chromosome responsible for determining the sex of an individual... X and Y chromosomes in humans.

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. Also called a homologous pair.

Haploid Cell

A cell containing only one set of chromosomes (n).

Diploid Cell

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

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.

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.

Crossing Over

The reciprocal exchange of genetic material between non-sister chromatids during prophase I of meiosis.

Independent Assortment

Formally part of Mendel's second law.... phenomenon where each pair of alleles (=gene copies) segregates, or assorts, independently of each other pair during gamete formation (meiosis); applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes (separate due to crossing over). MORE SOON ON THIS DIFFICULT IDEA

Genetic Variation

Differences among individuals in the composition of their genes or other DNA sequences.

Recombinant Chromosome

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