Chapter 20: Genetics and Human Inheritance (Vocabulary)

Question 1

A segment of DNA on a chromosome that directs the synthesis of a specific polypeptide that will play a structural or functional role in the cell. Some have regulatory regions of DNA within their boundaries. Also, some code for RNA molecules that are needed for the production of the polypeptide but are not part of it.

Answer 1

gene

Question 2

A phenotypically expressed characteristic.

Answer 2

trait

Question 3

An alternative form of a gene. One of two or more slightly different versions of a gene that code for different forms of the same trait.

Answer 3

allele

Question 4

The condition of having two identical alleles for a particular gene.

Answer 4

homozygous

Question 5

The condition of having two different alleles for a particular gene.

Answer 5

heterozygous

Question 6

The allele that is fully expressed in the phenotype of an individual who is heterozygous for that gene. It usually produces a functional protein, whereas the recessive allele does not.

Answer 6

dominant allele

Question 7

The allele whose effects are masked in the heterozygous condition. It often produces a nonfunctional protein.

Answer 7

recessive allele

Question 8

The genetic makeup of an individual. It refers to precise alleles that are present.

Answer 8

genotype

Question 9

The observable physical and physiological traits of an individual. It results from the inherited alleles and their interactions with the environment.

Answer 9

phenotype

Question 10

A diagram showing the genetic connections among individuals in an extended family that is often used to trace the expression of a particular trait in that family.

Answer 10

pedigree

Question 11

An individual who displays the dominant phenotype but is heterozygous for a trait and can therefore pass the recessive allele to descendants.

Answer 11

carrier

Question 12

In genetic inheritance, the dominant allele in a heterozygote completely masks the effect of the recessive allele. It often occurs because the dominant allele produces a functional protein and the recessive allele produces a less functional protein or none at all.

Answer 12

complete dominance

Question 13

The condition in which the effects of both alleles are separately expressed in a heterozygote.

Answer 13

codominance

Question 14

In genetic inheritance, expression of the trait in a heterozygous individual is somewhere in between expression of the trait in a homozygous dominant individual and homozygous recessive individual.

Answer 14

incomplete dominance

Question 15

This describes a gene on one of the non-sex chromosomes; i.e. neither on the X or the Y chromosome.

Answer 15

autosomal

Question 16

The ability to duplicate genetically identical individuals. Researchers often use genes or whole chromosomes to produce identical clones. Vegetative reproduction of plants (as in the use of cuttings of shrubs) is a type of cloning.

Answer 16

Cloning

Question 17

Having both homologous partners. A homologous pair is two chromosomes of similar size, shape, and gene location. One receives one homologue from one parent and the other from the other parent. The oddest homologous partnership is between the X and the Y chromosome because they are neither the same size nor the same shape, In meiosis, however, because of a few similar genes, they do behave as homologues.

Answer 17

Diploid

Question 18

The allele (or alternative of two genes) that will be read in the DNA. For example, if you had on one homologue the gene for freckles and on the other homologue the gene for the non-freckled condition, you would have freckles. The freckle characteristic is dominant.

Answer 18

Dominant

Question 19

The places on the chromosome. For example the locus (the singular of loci) for hemophilia A is a certain place on the X chromosome. You can go the the Human Genome web site and find the specific locus for hemophilia. Finding these specific locations is called genen mapping. There is a great deal of interest in gene mapping because this allows genetic councilors to determine if a person is carrying a deleterious or lethal gene. Such a person may then choose not to reproduce and thus spread that gene to future generations. As Volpe notes, this has been an extremely useful method for limiting the incidence of Tay-Sachs disease.

Answer 19

Loci

Question 20

Genetic testing for more than one characteristic at the same time.

Answer 20

Multiplex testing

Question 21

The sex determining chromosome. With some minor exceptions, mammals (including people) with no Y’s are female (as in XX) and people with at least one Y (as in XY) are male.

Answer 21

Sex chromosomes

Question 22

The alternative gene that the cell will not read.

Answer 22

Recessive

Question 23

A gene that is on either the X or Y chromosome. There are very few proven structural genes on the Y chromosome so the term sex-linked mostly refers to genes on the X chromosome such as color blindness and hemophilia A and B.

Answer 23

Sex-linked

Question 24

A gene that has the information to make a single portion of a protein. The information from structural genes is used to make the messenger RNA.

Answer 24

Structural Gene

Question 25

A type of nuclear division occurring in somatic cells in which two identical cells, called daughter cells, are generated from a single cell. The original cell first repllicates its genetic material and then distributes a complete set of genetic information to each of its daughter cells. Usuallu divided into prophase, metaphase, anaphase, and telophase. It is esential to cell division.

Answer 25

Mitosis

Question 26

A type of cell division that occurs in the gonads and gives rise to gametes. As a result of two divisions, haploid gametes are produced from diploid germ cells.

Answer 26

Meiosis

Question 27

A pair of chromosomes that bear genes for the same traits. One member of each pair came from each parent. They are the same size and shape and line up with one another during meiosis I.

Answer 27

Homologous chromosomes