Heredity
The transmission of traits from one generation to the next
Variation
Difference between numbers of the same species
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. Gametes unite during sexual reproduction to produce a diploid zygote.
Sexual reproduction
A type of reproduction in which to parents give rise to offspring that have unique combinations of genes inherited by the gametes of the parents.
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 to the pa
Somatic Cell
ANy cell in a multicellular organism except a sperm or egg.
Life Cycle
The generation-to-generation-sequence of stages in the reproductive history of an organism.
Karyotype
A display of the chromosomes pairs of a cell arranged by size and shape.
Homologous Chromosomes
A pair of chromosomes of the same length, centromere position, and staining patter that posses genes for the same characters at corresponfing loci. One homologous chromosome is inherited from the organism's father, the other from the mother. Also called h
Sex Chromosomes
A chromosome respocible for determining the sex of an individual.
Autosomes
A chromosome that is not directly involved in determining sex; not a sex chromosome.
Diploid Cells
A cell containing two sets of chromosomes (2n), one set inherited from each parent.
Haploid Cells
A cell containing only one set of chromosomes.
Fertilization
(1) The union of haploid gametes to produce a diploid zygote. (2) The addition of mineral nutrients to the soil.
Zygote
The diploid product of 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.
Sporophyte
in organisms (plants abd some algae) that have alternation of generations, the multicellular dipoid form that results from the union of gametes. The sporophyte produces haploid spores by meiosis that develop into gametopgytes.
Spores
(1) In the life cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis. A spore can divide by mitosis to develop into a multicellular haploid individual, the gametophyte, without fucing with an
Meiosis I
The first division of a two stage process of cell dicision in sexually reproducing organisms that results in cells with half the number of chromosome sets as teh original cell.
Meiosis II
The second division of a two stage process of cell division in sexual reproducing organisms that results in teh number of chromosome sets as the original cell.
Synapsis
The pairing and physical connection of replicated homologous chromosomes during prophase I of meiosis.
Crossing Over
The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.
Chiasma
The X-shaped, microscopically visible region where homologous nonsister chromatids have exchanged genetic material through crossing over during meiosis, the two homologous remaining associated due to sister chromatid cohesion.
Recombinant Chromosomes
A chromosome created when crossing over combines the DNA from two parents into a single chromosome.
Alternation of Generation
A life cycle in which there is both multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants and some algae.
How are the traits of parents (such as hair color) transmitted to their offspring?
Parents pass genes to their offspring; the genes program cells to make specific enzymes and other proteins, whose cumulative action produces an individuals inherited traits.
Explain how asexual reproducing organisms produce offspring that are genetically identical to each other and to their parents.
Such organisms reproduce by mitosis, which generates offsring whose genomes are exact copies of the parent's genome (in the ansence of mutation)
How does the karyotype of a human female differ from that of a human male?
A female has two X chromosomes; male has an X and Y.
How does the alternation of meiosis and fertilization in the life cycles of sexually reproducing organisms maintain normal chromosome count for each species?
In meiosis, the chromosomes count is reduced from diploid to haploid; the union of two haploid gametes in fertilization restores the diploid chromosome count.
How are the chromosomes in a cell at metaphase of mitosis similar to and different from those in a cell metaphase of meiosis II?
They are similar in that each is composed of two sister chromatids, and the individual chromosomes are positioned similarly on the metaphase plate. They are different in that in mitotically dividing cell, sister chromatids of each are gentically identical
What is the original source of all the different alleles of a gene?
Mutations in a gene lead to the different versions (alleles) of that gene.
A human cell containing 22 autosomes and a Y chromosome is
A sperm
What life cycle stage is found in plants but not animals?
Multicellular haploid
Homologous chromosomes move toward opposite poles of a dividing cell during...
Meiosis I
Meiosis II is similar to mitosis in ?
Sister chromatids seperate during anaphase
If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be
2x
How many different combinations of maternal and paternal chromosomes can be packaged in gametes made by an organism with a diploid number of 8(2n=8)?
16