DEPARTMENT OF BIOLOGY-
HEREDITY- TERMS & DEFINITIONS
INSTRUCTIONS:
STUDENTS MUST FOLLOW-L W R-(LEARN, WRITE IN C.W and REVISE.)
Amino acids
Small molecules that are the components of proteins. There are 20 different kinds of amino
acids in living things. Proteins are composed of different combinations of amino acids
assembled in chain-like molecules. Amino acids are primarily composed of carbon, oxygen,
hydrogen, and nitrogen.
Carrier
An individual who is heterozygous for a trait that only shows up in the phenotype of those who
are homozygous recessive. Carriers often do not show any signs of the trait but can pass it on
to their offspring. This is the case with hemophilia.
Chronic disease
An illness that lasts for a long period of time or indefinitely. In contrast, an acute disease is one
with a rapid onset and a short but usually severe course.
Chromosomes
Thread-like, gene-carrying bodies in the nucleus of a cell. Chromosomes are composed
primarily of DNA and protein. They are visible only under magnification during certain stages of
cell division. Humans have 46 chromosomes in each somatic cell and 23 in each sex cell.
Diabetes
An inherited metabolic disorder in which there are abnormally high blood sugar levels. In
advanced stages, this often results in blindness from cataracts, nerve damage, gangrene in the
feet and legs leading to amputation, heart disease, and kidney failure. Type 1 diabetes melitis
(juvenile onset diabetes) is due to decreased production of insulin by the pancreas. Type 2
diabetes melitis is due to increased resistance of cells in the body to insulin. The gene or genes
for diabetes are incompletely penetrant.
Dominant allele
An allele that masks the presence of a recessive allele in the phenotype. Dominant alleles for a
trait are usually expressed if an individual is homozygous dominant or heterozygous.
Recessive allele
An allele that is masked in the phenotype by the presence of a dominant allele. Recessive
alleles are expressed in the phenotype when the genotype is homozygous recessive (aa).
DNA (deoxyribonucleic acid )
A large organic molecule that stores the genetic code for the synthesis of proteins. DNA is
composed of sugars, phosphates and bases arranged in a double helix shaped molecular
structure. Segments of DNA in chromosomes correspond to specific genes.
Evolution
Genetic change in a population of organisms that occurs over time. The term is also frequently
used to refer to the appearance of a new species.
F1 generation
The first offspring (or filial) generation. The next and subsequent generations are referred to
as f2, f3, etc.
Genes
Units of inheritance usually occurring at specific locations, or loci, on a chromosome. Physically,
, The study of gene structure and action and the patterns of inheritance of traits from parent to
offspring. Genetic mechanisms are the underlying foundation for evolutionary change.
Genetics is the branch of science that deals with the inheritance of biological characteristics.
Genome
The full genetic complement of an individual (or of a species). In humans, it is estimated that
each individual possesses approximately 2.9 billion base units in his or her DNA.
Phenotype
The observable or detectable characteristics of an individual organism--the detectable
expression of a genotype.
Genotype
The genetic makeup of an individual. Genotype can refer to an organism's entire genetic
Heterozygous
A genotype consisting of two different alleles of a gene for a particular trait (Aa). Individuals
who are heterozygous for a trait are referred to as heterozygotes.
Homologous chromosomes
Chromosomes that are paired during the production of of sex cells in meiosis. Such
chromosomes are alike with regard to size and also position of the centromere. They also have
the same genes, but not necessarily the same alleles, at the same locus or location.
Homozygous
Having the same allele at the same locus on both members of a pair of homologous
chromosomes. Homozygous also refers to a genotype consisting of two identical alleles of a
gene for a particular trait. An individual may be homozygous dominant (AA) or homozygous
recessive (aa). Individuals who are homozygous for a trait are referred to as homozygotes.
Hybrids
Offspring that are the result of mating between two genetically different kinds of parents--the
opposite of purebred.
Meiosis
Cell division in specialized tissues of ovaries and testes which results in the production of sperm
or ova. Meiosis involves two divisions and results in four daughter cells, each containing only
half the original number of chromosomes--23 in the case of humans.
Mendelian genetics
Inheritance patterns which can be explained by simple rules of dominance and recessiveness of
genes.
Modifying gene
Agene that can alter the expression of another gene in the phenotype of an individual.
Mutation
An alteration of genetic material such that a new variation is produced. For instance, a trait
that has only one allele (A) can mutate to a new form (a). This is the only mechanism of
evolution that can produce new alleles of a gene.
Principle of independent assortment
Gregor Mendel's second principle of genetic inheritance. It states that different pairs of genes
are passed to offspring independently so that new combinations of genes, present in neither
parent, are possible. In other words, the distribution of one pair of alleles does not influence
HEREDITY- TERMS & DEFINITIONS
INSTRUCTIONS:
STUDENTS MUST FOLLOW-L W R-(LEARN, WRITE IN C.W and REVISE.)
Amino acids
Small molecules that are the components of proteins. There are 20 different kinds of amino
acids in living things. Proteins are composed of different combinations of amino acids
assembled in chain-like molecules. Amino acids are primarily composed of carbon, oxygen,
hydrogen, and nitrogen.
Carrier
An individual who is heterozygous for a trait that only shows up in the phenotype of those who
are homozygous recessive. Carriers often do not show any signs of the trait but can pass it on
to their offspring. This is the case with hemophilia.
Chronic disease
An illness that lasts for a long period of time or indefinitely. In contrast, an acute disease is one
with a rapid onset and a short but usually severe course.
Chromosomes
Thread-like, gene-carrying bodies in the nucleus of a cell. Chromosomes are composed
primarily of DNA and protein. They are visible only under magnification during certain stages of
cell division. Humans have 46 chromosomes in each somatic cell and 23 in each sex cell.
Diabetes
An inherited metabolic disorder in which there are abnormally high blood sugar levels. In
advanced stages, this often results in blindness from cataracts, nerve damage, gangrene in the
feet and legs leading to amputation, heart disease, and kidney failure. Type 1 diabetes melitis
(juvenile onset diabetes) is due to decreased production of insulin by the pancreas. Type 2
diabetes melitis is due to increased resistance of cells in the body to insulin. The gene or genes
for diabetes are incompletely penetrant.
Dominant allele
An allele that masks the presence of a recessive allele in the phenotype. Dominant alleles for a
trait are usually expressed if an individual is homozygous dominant or heterozygous.
Recessive allele
An allele that is masked in the phenotype by the presence of a dominant allele. Recessive
alleles are expressed in the phenotype when the genotype is homozygous recessive (aa).
DNA (deoxyribonucleic acid )
A large organic molecule that stores the genetic code for the synthesis of proteins. DNA is
composed of sugars, phosphates and bases arranged in a double helix shaped molecular
structure. Segments of DNA in chromosomes correspond to specific genes.
Evolution
Genetic change in a population of organisms that occurs over time. The term is also frequently
used to refer to the appearance of a new species.
F1 generation
The first offspring (or filial) generation. The next and subsequent generations are referred to
as f2, f3, etc.
Genes
Units of inheritance usually occurring at specific locations, or loci, on a chromosome. Physically,
, The study of gene structure and action and the patterns of inheritance of traits from parent to
offspring. Genetic mechanisms are the underlying foundation for evolutionary change.
Genetics is the branch of science that deals with the inheritance of biological characteristics.
Genome
The full genetic complement of an individual (or of a species). In humans, it is estimated that
each individual possesses approximately 2.9 billion base units in his or her DNA.
Phenotype
The observable or detectable characteristics of an individual organism--the detectable
expression of a genotype.
Genotype
The genetic makeup of an individual. Genotype can refer to an organism's entire genetic
Heterozygous
A genotype consisting of two different alleles of a gene for a particular trait (Aa). Individuals
who are heterozygous for a trait are referred to as heterozygotes.
Homologous chromosomes
Chromosomes that are paired during the production of of sex cells in meiosis. Such
chromosomes are alike with regard to size and also position of the centromere. They also have
the same genes, but not necessarily the same alleles, at the same locus or location.
Homozygous
Having the same allele at the same locus on both members of a pair of homologous
chromosomes. Homozygous also refers to a genotype consisting of two identical alleles of a
gene for a particular trait. An individual may be homozygous dominant (AA) or homozygous
recessive (aa). Individuals who are homozygous for a trait are referred to as homozygotes.
Hybrids
Offspring that are the result of mating between two genetically different kinds of parents--the
opposite of purebred.
Meiosis
Cell division in specialized tissues of ovaries and testes which results in the production of sperm
or ova. Meiosis involves two divisions and results in four daughter cells, each containing only
half the original number of chromosomes--23 in the case of humans.
Mendelian genetics
Inheritance patterns which can be explained by simple rules of dominance and recessiveness of
genes.
Modifying gene
Agene that can alter the expression of another gene in the phenotype of an individual.
Mutation
An alteration of genetic material such that a new variation is produced. For instance, a trait
that has only one allele (A) can mutate to a new form (a). This is the only mechanism of
evolution that can produce new alleles of a gene.
Principle of independent assortment
Gregor Mendel's second principle of genetic inheritance. It states that different pairs of genes
are passed to offspring independently so that new combinations of genes, present in neither
parent, are possible. In other words, the distribution of one pair of alleles does not influence
