BJU Biology (Fifth Edition)- Chapter 8: Basic Genetics

chromosome

A structure consisting of DNA and supporting proteins, usually found in a cell's nucleus.

gene

A segment of DNA that codes for a specific protein, resulting in a particular trait.

chromatid

One of identical halves of a chromosome formed prior to a cell division.

centromere

A cellular organelle that functions in the organization of microtubules.

sex chromosome

A chromosome that determines whether an organism is male or female.

autosome

A chromosome other than a sex chromosome.

homologous

Referring to one of a pair of chromosomes that carry the same genes in the same order on each chromosomes.

diploid

Having two complete sets of chromosomes.

haploid

Having a single set of chromosomes.

cell cycle

The series of events, including duplication of DNA, leading to the division of a cell into daughter cells.

interphase

The period of the cell cycle in between cell divisions; the time of regular growth and activity.

mitosis

The phase of the cell cycle in which a cell's duplicated DNA is divided into two identical sets.

cytokinesis

The process during cell division in which the cytoplasm of a cell is divided between two new daughter cells.

prophase

The phase of mitosis during which a cell's chromatin condenses into X-shaped chromosomes.

mitotic spindle

The cellular structure that sorts separated chromatids into daughter cells during mitosis.

metaphase

The phase of mitosis in which chromosomes are aligned on the cells equator before being separated and sorted into daughter cells.

anaphase

The phase of mitosis during which chromosomes are separated into chromatids, and the chromatids are separated and sorted into daughter cells by the mitotic spindle.

telophase

The final phase of mitosis, during which new nuclei form in the daughter cells and their chromosomes unwind.

meiosis

The process by which haploid gametes are produced form diploid cells.

tetrad

A group of four chromatids formed during meiosis by the pairing of a chromosome with its homologous partner.

crossing over

The exchange of sections of chromatids between homologous chromosomes during meiosis.

gamete

A haploid reproductive cell that can unite with another gamete to form a zygote

zygote

A diploid cell formed by the union of two gametes.

asexual reproduction

A type of reproduction in which new organisms are produced by a single parent and receive only the genes of that parent, producing, in effect, genetic clones of the original organism.

sexual reproduction

A type of reproduction in which haploid gametes are fused to produce a diploid zygote.

heredity

The passing of traits from one generation to another.

dominant trait

A characteristic that is expressed even in the presence of a recessive allele of the gene that codes for that characteristic.

recessive trait

The characteristic that is expressed only in the absence of a dominant allele of the gene that codes for that characteristic.

allele

One of the pairs of genes that have the same position on homologous chromosomes and code for the same trait, through each may code for a different form of the trait.

homozygous

Describes the condition of having the same two alleles for a gene at the same position on homologous chromosomes.

genotype

The genetic makeup of an individual organism, especially regarding its particular combination of alleles for a specific trait.

phenotype

The physical expression of a trait in an organism.

heterozygous

Describes the condition of having different alleles for a gene at the same position on homologous chromosomes.

Punnett square

A diagram that is used to visualize genetic crosses.

Monohybrid Cross

A genetic cross that tests only on set of alleles.

Dihybrid Cross

A genetic cross that tests two sets of alleles.

pedigree

A heredity chart that tracks the expression of a trait through several generations.

incomplete dominance

A type of inheritance in which different alleles of a gene are neither dominant nor recessive and are expressed simultaneously, resulting in a blended, usually intermediate phenotype

codominance

A type of inheritance in which different alleles of a gene are expressed simultaneously, producing a phenotype that exhibits contributions from both alleles.

multiple alleles

A condition in which more than two alleles for a gene are possible.

polygenic inheritance

A type of inheritance in which a trait is determined by more than one gene.

sex-linked traits

A trait coded for by a gene located on a sex chromosome.

carrier

A heterozygous organism that expressed the normal form of a trait but carries the recessive gene for an undesirable form of the trait and can pass it on to its offspring.

gene expression

The process by which the information in a gene is used to make a functional gene product, usually a protein.

promoter

A short sequence of DNA that determines where an RNA polymerase molecule is to begin the transcription of a strand of messenger RNA

TATA box

A common promoter sequence.

cell differentiation

In a multicellular organisms, the process of cells changing in order to preform specialized tasks.

homeotic gene

A gene that regulates the development of an anatomical structure in an organism.

stem cell

A generalized cell that has the potential to differentiate into cells that preform a specific function.

embryo

The early stage of development in the unborn young of a multicellular organism.