Apologia Biology Module 08 Vocabulary

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bred true

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If an organism has a certain characteristic that is always passed on to its offspring, we say that this organism ______ ______ with respect to that characteristic.

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self-pollination

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the process of a plant sexually reproducing with itself

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allele

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One of a pair of genes that occupies the same position on homologous chromosomes.

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genotype

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Two-letter set that represents the alleles an organism possesses for a certain trait.

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phenotype

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The observable expression of an organism's genes. (such as height)

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homozygous

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A genotype in which both alleles are identical.

(“TT” or “tt,” for example)

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heterozygous

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A genotype with two different alleles.

(“Tt,” for example)

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dominant allele

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An allele that will determine phenotype if just one is present in the genotype.

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recessive allele

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An allele that will not determine the phenotype unless the genotype is homozygous in that allele.

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Punnett squares

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For any single, definable trait, we can predict the likelihood that an offspring will have a given genotype and phenotype. So we construct a ___________ _________.

We do this by taking the genotype of one parent and the genotype of the other and place them on the top and side of a grid. This allows us to predict all possible genotypes of the offspring.

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pedigree

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A diagram that follows a particular phenotype through several generations which helps you determine the genotype of an organism.

(such as with guinea pig coat color)

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monohybrid cross

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A cross between two individuals, concentrating on only one definable trait.

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dihybrid cross

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A cross between two individuals, concentrating on two definable traits.

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autosomes

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the first 22 pairs of chromosomes that do not determine the sex of an individual

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sex chromosomes

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the last pair of chromosomes that do determine the sex of an individual

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sex-linked genetic traits

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when a trait is much more prevalent among males than females, it is often governed by one of these recessive traits

(think: autism)

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polygenetic inheritance

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Although many traits are caused by a specific gene, many traits are also caused by the interaction of several genes. This is called:

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incomplete dominance

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Some traits are controlled by alleles where neither are dominant. This is called:

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epistasis

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In some cases, one set of alleles might affect how another set of alleles is expressed.

Stated a different way: A form of interaction between genes in which one combination of such genes has a dominant effect over other combinations.

Certain genes can be "turned off".....

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pleiotrophy

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A single gene that can affect multiple observable traits (multiple phenotypes).

(sickle-cell anemia)

All of the observable traits (phenotypes) can be caused by being homozygous in just one set of alleles.

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blood type

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Everybody has one, and it can be either A, B, AB, or O. There is also a positive or negative associated with it.

It is determined by one set of alleles, but unlike the alleles that we have been studying so far, there are three possibilities. (A, B, and O)

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codominance

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The allele for blood type O is recessive to both A and B. Thus, a person with genotype “AO” will have type A blood, while a person with genotype “BO” will have type “B” blood. However, the A and B alleles are not dominant over each other.

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antigens

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A protein that, when introduced in the blood, triggers the production of an antibody.

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Rh factor

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It refers to whether or not another particular antigen exists on the red blood cells.

(think: Rhesus monkey)

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Rh-positive

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If the Rh antigen exists on the plasma membrane of the red blood cells, the blood is called:

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Rh-negative

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If there is no Rh antigen on the red blood cells, the blood is:

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autosomal inheritance

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Inheritance of a genetic trait not on a sex chromosome.

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genetic disease carriers

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A person who is heterozygous in a recessive genetic disorder.

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Huntington's disorder

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Disease where the nervous system deteriorates rapidly once he/she hits his/her forties. He/she eventually has trouble doing even the simplest of tasks and ends up dying prematurely.

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sex-linked inheritance

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Inheritance of a genetic trait located on the sex chromosomes

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mutation

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A radical chemical change in one or more alleles which can sometimes be benign. Usually, however, the results are very bad...

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Hutchinson-Gilford progeria syndrome

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Disease that results when an allele on one of the human autosomes mutates during meiosis. A child with this allele ages rapidly. By age three or four, the child has many of the characteristics of a very old person: wrinkles, hair loss, arthritis. Because of their rapid aging, people with this disease die extremely young.

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change in chromosome structure

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A situation in which a chromosome loses or gains genes during meiosis.

When a chromosome has too many or too few genes, the body does not understand all of the genetic information. As a result, disorders occur.

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cri-du-chat

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Commonly called the “cat's-cry disease” is caused when the fifth chromosome is damaged during meiosis. The chromosome loses some of its genes, and a child produced by the damaged gamete will be mentally retarded. In addition, the child's larynx (the organ used to make sounds) is abnormal, and the infant's cry sounds like the meow of a cat.

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change in chromosome number

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A situation in which abnormal cellular events in meiosis lead to either none of a particular chromosome in the gamete or more than one chromosome in the gamete.

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Down's syndrome

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An example of a disease related to the change in chromosome number. It occurs when a person has three of chromosome number 21. This happens because either the father's sperm or the mother's egg has two of that chromosome rather than just one.

The children are mentally retarded. Their skeletons also develop more slowly than they should; thus, they are short and their muscles are slack.