Chapters 11 and 16 Flashcards
Chromosome
Structure found inside the nucleus of a cell. A chromosome is made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes.
Diploid
A cell that contains two copies of each chromosomes.
Haploid
Presence of a single set of chromosomes in organisms cells. Sexually reproducing organisms are diploid. In humans, only the egg and sperm cells are haploid.
Homologous chromosomes
Two chromosomes in a pair, normally one inherited from mother and one from the father.
Heredity
The sun of all biological processes by which particular characteristics are transmitted from parents to their offspring.
Genetics
The scientific study of jeans and heredity- of how certain qualities or traits are passed from parents to offspring as a result of changes in DNA sequence.
Gregor Mendel
Worked in 1860’s. Was the first person to analyze patterns of inheritance. Deduced the fundamental principles of genetics.
Traits
Specific characteristics of an individual.
Hybrid
Offspring of parents are different and genetically determined treats. The parents may be of different species, genera, or (rarely) families.
Phenotype
The physical appearance of an organism.
Genotype
The genetic makeup of DNA.
True-breeding
Produces only offspring that express the same phenotype generation after generation.
Crossing
To deliberate breeding of two individuals that results in offspring that carry part of the genetic material of each parent.
P generation
The parental generation are genetically pure individuals.
F1 generation
First filial generation. The initial cross between two genetically distinct plants.
F2 generation
Second filial generation of individuals which arises as a result of inbreeding amongst individuals of F1 generation.
Allele
Alternate versions of the same gene.
Dominant allele
Exert its affect whenever it is present.
Recessive allele
One who’s effects are masked
Homozygous
An organism is homozygous for that allele if both alleles are identical.
Heterozygous
An organism is heterozygous for that gene if the alleles are different.
Homozygous dominant
An organism carries two copies of the same dominant allele.
Homozygous recessive
An organism carries two copies of the same recessive allele.
Locus
The site a gene occupies in the chromosome.
Principle of segregation
Describes how how pairs of gene variants are separated into reproductive cells.
Monohybrid cross
The hybrid of two individuals with homozygous genotypes which result in the opposite phenotype for a certain genetic trait.
Punnet square
Used to track the possible genotypic (genes) and phenotypic (appearance) outcomes of mating.
Phenotypic ratio
The relative number of offspring manifesting in a particular trait or combination of traits.
Genotypic ratio
The ratio of different genotypes in the offspring from a genetic cross.
Test cross
A cross between a homozygous genetic individual and a corresponding suspected heterozygote to determine the genotype of the latter.
Dihybrid cross
Breeding experiment between two organisms which are identical hybrids for two traits.
Law of Independent Assortment
Describes how different genes independently separate from one another when reproductive cells develop.
Linked genes
Genes that do not independently assort, because they are going on the same chromosome (can’t do a dihybrid cross!)
Autosome
One of the numbered chromosomes, as opposed to the sex chromosomes. (22 pairs)
Sex chromosome
A type of chromosome involved in sex determination.
1pair
Sex
Sex of humans and other mammals is determined by the sex chromosomes - X, Y chromosomes
Barr body
A densely staining inactivated condensed X chromosome that is present in each somatic cell of most female mammals and is used in test of genetic femaleness (as in a fetus). Also called sex chromatin.
X-linked gene
Any gene located on a sex chromosome. Most are found on the X chromosome
Red-green colorblindness
A common human sex-linked disorder. A form of colorblindness in which red and green are perceived as identical.
Hemizygous
The presence of two identical alleles at a particular gene locus.
Incomplete dominance
Both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype. Partial dominance.
Codominance
The heterozygote simultaneously expresses phenotypes of both homozygotes.
ABO blood groups
A system used to group human blood into different types, based on the presence r absence of certain marker on the surface of red blood cells.
Pleiotropy
Multiple effects of a single human gene
Polygenic inheritance
The additive effects of two or more genes on a single phenotype.
Karyotype
Visualizes an individual’s chromosome composition
Pedigree
A “family tree” that shows inheritance patterns within a family over generations.
Autosomal dominant
A single copy of a mutation on an autosomal chromosome is sufficient to cause disease.
Autosomal recessive
Two copies of an abnormal gene must be present in order for the disease or trait to develop.
X-linked recessive
Genetic conditions associated with mutations in genes on the X chromosome.
Human genome project
International, collaborative research program who’s goal was the complete mapping and understanding of all the genes of human beings. All genes together are known as “genome”
Single nucleotide polymorphism (SNP)
A variation at a single position in a DNA sequence among individuals.
Polyploidy
Presence of multiple sets of chromosomes
Aneuploidy
Abnormalities caused by the presence of a single extra chromosome (trisomy, 2n+1) or the absence of a single chromosome (monopsony, 2n-1)
Nondisjunction
The failure of chromosomes to separate, which produces daughter cells with abnormal numbers of chromosomes.
Down syndrome
A condition in which an individual has an extra chromosome 21, and affects about one out of every 700 children.
Recombination
Pieces of DNA are broken and recombined to produce new combinations of alleles.
Duplication
Type of mutation in which one or more copies of DNA segment.
Inversion
Chromosomal defect in which a segment of the chromosome breaks off and reattaches in the reverse direction.
Deletion
A type of genetic change that involves the absence of a segment of DNA
Reciprocal translocation
Occurs when part of one chromosome is exchanged with another.
Fragile X Syndrome
A genetic conditions that causes a range of developmental problems including learning disabilities and cognitive impairment.
Sickle Cell Disease
An inherited disease in which the red blood cells have an abnormal crescent shape, block small blood vessels, and do not last as long as normal red blood cells
Substitution
A type of mutation in which one nucleotide is replaced by a different nucleotide.
Gene therapy
A technique that modifies a persons genes to treat or cure disease.
