BIOLOGY - UNIT 5: GENETICS: GOD'S PLAN OF INHERITANCE
Turner's syndrome
(XO) An abnormality in females where one of the sex chromosomes is missing leaving a total of 45 chromosomes; produced by nondisjunction.
Klinefelter's Syndrome
(XXY) An abnormality affecting males where there is an extra X chromosome due to nondisjunction.
mutation
A change in the genetic information code.
crossing over
A condition where non-sister chromatid of homologous chromosomes exchange genes.
chromatid
A double-stranded chromosome following replication attached by a centromere.
deoxyribose
A five-carbon sugar.
holandric gene
A gene located on the Y chromosome in XY species.
DNA
A giant molecule consisting of the sugar deoxyribose, phosphates and nitrogen bases; contain the coded genetic information.
hemophilia
A hereditary condition for bleeding due to the inability to clot properly.
guanine
A nitrogen base found in DNA and RNA; normally pairs with cytosine.
cytosine
A nitrogen base found in DNA or RNA; pairs normally with guanine.
thymine
A nitrogen base found in DNA; normally pairs with adenine.
adenine
A nitrogen base occurring in DNA and RNA; pairs normally with thymine.
RNA
A nucleic acid similar to DNA using ribose for the sugar and the nitrogen base uracil in place of thymine.
spindle fibers
A number of threadlike filaments formed between poles of the cell during cell division to which the centromeres of chromosomes attach; used to pull chromosomes apart and segregate them during anaphase.
hypothesis
A proposed explanation for an observation which has not been experimentally tested.
Y chromosome
A sex chromosome found in males; influencing the degree of maleness.
X chromosome
A sex chromosome; in human males only one is present and in females two are present.
centromere
A structure on the chromosome that holds a pair of chromatids together during replication.
gene pool
All of the genes present in a specific population.
law
An explanation for events which is supported by the results on many experiments by a large number of investigations.
sickle-cell anemia
An hereditary form of anemia.
Rh factor
An inherited protein found on the surface of the red blood cell membrane.
autosome
Any pair of chromosomes other than the sex chromosome.
diploid
Both members of a pair of chromosomes are present.
tetrad
During metaphase I the two pairs of chromatids of the homologous pair of chromosomes comes together; crossing-over can occur at this time.
nondisjunction
Failure of chromosomes to segregate during the formation of gametes, resulting in extra or a shortage of chromosomes in the gamete.
cotyledon
First leaf or leaves produced from the seed.
sex-linked
Genes which are carried on the X chromosome.
gene frequency
How common the gene is in the population.
haploid
One member of a pair of homologous chromosomes is present, such as in a gamete.
sex-chromosome
One of the chromosomes which determine the sex of the individual.
nitrogen base
One of the three major types of chemicals making up a nucleotide in DNA; either guanine, cytosine, adenine, or thymine; the sequence of three codes for an amino acid.
polar body
One of three small cells produced during oogenesis, each contain the haploid number of chromosomes.
oogenesis
Process of development of haploid female gametes.
pedigree
The ancestral history of an individual; a chart showing the history of a trait in the family.
chromosome theory
The behavior of chromosomes explains the inheritance of genes.
nucleotide
The combination of phosphate, sugar, and nitrogen bases in DNA or RNA; the combination of three nucleotides codes a specific amino acid.
codominance
The condition in heterozygotes where both members of an allelic pair contribute to phenotype producing a mixture of phenotypic traits.
Down's Syndrome
The condition of mongoloid idiocy caused by the presence of an extra chromosome 21.
theory
The form of the hypothesis after it has been tested and found to be supported by the data collected as the explanation for the observation.
one-gene-one-enzyme concept
The genetic code of the gene is responsible for the production of a specific enzyme, which regulates the metabolic pathways in the cell during meiosis; the combination of chromosomes in a gamete is due to chance.
sickle-cell trait
The heterozygous condition which is generally phenotypically indistinguishable for normal person; in conditions of low oxygen some cells sickle. An example of incomplete dominance and environmental influence on gene expression.
linkage
The presence of different genes on the same chromosome.
spermatogenesis
The production of haploid male gametes by the male parent.
Prophase I
The stage in the first meiotic division where the doubled chromosomes become visible and nuclear membrane disappears.
Metaphase I
The stage in the first meiotic division where the homologous chromosomes line up as a pair, forming a tetrad of chromatids, at the equator of the cell.
Anaphase II
The stage in the second meiotic division where sister chromatids of a chromosome split and migrate to opposite poles.
Metaphase II
The stage in the second meiotic division where the chromatid pair lines up at the equator of the cell.
Telophase I
The stage of the first meiotic division where the cell divides into two cells each containing one member of each pair of homologous chromosomes.
Telophase II
The stage of the second meiotic division when the cell divides into two cells with each being haploid; these cells become the gametes.
Anaphase I
The stage on the first meiotic division when the homologous chromosomes move to opposite poles but the sister chromatids remain together.
population genetics
The study of a hereditary trait in a large population.
