Upgrade to remove ads
Only $2.99/month

Cellular Regulation Genetics

Terms in this set (58)

Mitosis
duplication process - two genetically identical "daughter" cells are produced from a single "parent" cell
Meiosis
generation of "daughter" cells that are distinct from one another and from the original parent cell
Genetics
study of biologic inheritance
Chromatin
substance that gives the nucleus a granular appearance and is observable in non-dividing cells
Chromosomes
discrete, dark-staining organelles that are formed with the chromatin condenses
Genes
-basic units of inheritance (contained inside chromosomes)
-Approximately 20,000 - 25,000 genes
-An error to one of these genes often leads to a recognizable genetic disease
Deoxyribonucleic acid (DNA)
-primary constituent of chromatin
-Genes are composed of sequences of DNA
DNA - three basic components
-5-carbon monosaccharide deoxyribose
-1 phosphate molecule
-4 types of nitrogen bases
-Cytosine
-Thymine
-Adenine
-Guanine
Mutagens
-increase the frequency of mutations
-ex, radiation and chemical such as nitrogen mustard
-Mutations are rare events
-Somatic mutations are passed on to successive generations of that cell
RNA
-DNA is formed and replicated in the cell nucleus but protein synthesis takes place in the cytoplasm
-DNA code is transported from nucleus to cytoplasm and subsequent protein is formed through two processes: transcription; translation
-mediates this process
-Uracil is a base rather than thymine
Homologous
22 of the 23 chromosome pairs, the 2 members of each pair are virtually identical
Autosomes
-the 22 homologous pairs in males and females
Karyotype
-ordered display of chromosomes
-Some natural display can be expected from person to person
Euploid cells
-cells with a multiple of the normal number
-cells with a multiple of the normal number
-Both haploid and diploid are euploid
Polyploid
-when a euploid cell has more than the diploid number of chromosomes
Triploidy
zygote that has three copies of each chromosome
Tetraploidy
condition in which euploid cells have 92 chromosomes
Aneuploidy (autosomal)
-cell containing three copies of one chromosomes
-Partial trisomy - extra portion of a chromosome is present in each cell
-Trisomy X (sex chromosome aneuploidy)- instead of two X chromosomes females have three or more
-Turner - single X and not X or Y (45 chromosomes)
-Klinefelter - at least 2 X and 1 Y in each cell
Disjunction
Normal separation of chromosomes during cell division
Nondisjunction
-Usually the cause of aneuploidy
-Failure of homologous chromosomes or sister chromatids to separate normally during meiosis or mitosis
Down Syndrome (Trisomy 21)
-Most well-known example of aneuploidy
-1:800 births
-Mental retardation; low nasal bridge; epicanthal folds; protruding tongue; poor muscle tone
-Risk increases with maternal age >35
Translocation
-the interchanging of material between nonhomologous chromosomes
-Reciprocal translocation occurs when two chromosomes break and the segments are rejoined in an abnormal arrangement
-May be involved in more than one gene
Mendelian traits
traits caused by single genes
Locus
Position along a chromosome a gene occupies
Allele
Different forms of a gene at a particular locus
Polymorphic
locus that has two or more alleles that each occur with an appreciable frequency
Homozygous
when two alleles are identical
Heterozygous
when two alleles are not identical
Genotype
composition of genes at a given locus
Phenotype
outward appearance of an individual - results from both genotype and environment
Dominant
allele whose effects are observable
Recessive
allele whose effects are hidden
Carrier
individual who has a disease gene but it phenotypically normal
X-linked Recessive
-Effects more males than female (females require two copies for disease expression)
-X inactivation: one X chromosome in the somatic cells of females is permanently inactivated
-Barr bodies: inactivated X chromosomes are observable in many interphase cells as highly condensed intranuclear chromatin bodies
-Normal females have one Barr body in each somatic cell
- normal males have none
Sex-limited
can occur in only one sex
Inherited uterine and testicular defects
Sex-influenced
occurs more often in one sex compared to the other
Sickle Cell Disease
-Group of disorders characterized by the production of abnormal hemoglobin S within the erythrocytes
-Autosomal recessive
-Homozygous form: most severe
-African American
-
Sickle-cell thalassemia
-Heterozygous
-Child simultaneously inherits another type of abnormal hemoglobin from one parent
Klinefelter Syndrome
-47, XXY
-Have a male appearance but usually sterile
-50% develop female-like breasts (gynecomastia)
-Occurs 1:1000 male births
-Voice is high-pitched
-Sparse body hair, small testicles
Turner's Syndrome
-Not considered to be intellectually disabled
-There may be impairment of spatial and mathematical reasoning
-Found only in females
-Short stature; webbing of neck; widely spread nipples
-Coarctation of the aorta
-75% inherit X chromosome from mother
-Due to only having one X and no Barr bodies
-1:5000 newborn females
Fragile X Syndrome
-Associated with intellectual disability
-Affects 1 in 4000 males and 1 in 8000 females
-Females who inherit the mutation do not necessarily express the disease condition but they can pass it on
-Males who inherit the disease on the x chromosome expresses the condition because he only has one X chromosome
Autosomal Dominant
-Very rare - fewer than 1 in 500
-One allele required for observable effect
-50% chance of recurrence
-Males and females affected equally
-Vertical transmission in pedigree
-No generations are skipped
Huntington's Disease
-Also known as chorea
-Rare, hereditary, degenerative hyperkinetic movement disorder diffusely involving the basal ganglia and cerebral cortex
-Onset between 25 and 45
-Inherited from both mothers and/or fathers
-Involuntary fragmentary movements
-Cognitive deficits include loss of working memory and reduced capacity to plan, organize and sequence
Penetrance
percentage of individuals with a specific genotype who exhibit the expected phenotype
Incomplete penetrance
means that individuals who have the disease-causing genotype may not exhibit the disease phenotype at all
Autosomal Recessive
-Rare, occurs in about 1 in 2500 births
-Males and females are affected in equal proportions
-Marriage between related individuals is sometimes present
-May be seen in siblings of affected individuals but usually not in their parents
-On average, one fourth of the offspring of carrier parents will be affected
Tay Sachs
-Autosomal Recessive
-80% of individuals diagnosed are of Jewish ancestry
-Onset of disease is 4-6 months
-Symptoms: exaggerated startle; seizures; developmental repression; dementia and blindness
-jewish
X-linked
-X-linked dominant or Y chromosome traits are few
-Hemizygous
Hemizygous
-males only having one X chromosome
-If a male inherits a recessive disease gene on the X chromosome he will be affected by the disease because the Y chromosome does not carry a normal allele to counteract the effects of the diseased gene
Duchenne Muscular Dystrophy
-Commonly in boys (1 in 3500)
-Caused by mutation in the dystrophin gene - poorly anchored fibers tear themselves apart under repeated stress of contraction - free calcium enters the muscle cells, causing cell death and necrosis
-Muscle weakness, difficulty walking and large calves
-Weakness worsens over years with a loss of ability to ambulate by 8-13 years old
Polygenic traits
some traits results that are produced from several genes acting together
Multifactorial inheritance
-when environmental factors influence the expression of the trait
-Height; IQ
Many of the patterns of disease are polygenic or multifactorial
-the threshold of liability must be crossed before the disease is expressed
-ex,Pyloric stenosis
Genomics
The study of all of the genes in the human genome including their interactions with each other and the environment
Pharmacogenomics
-Study of how an individual's genetic makeup affects the body's response to drugs
-Drugs and/or dosing are starting to be adapted to differing genetic make=ups, thus increasing efficacy and improving safety
Gene Therapy
-The treatment or alleviation of human disease by adding exogenous wild-type genes to correct the defective function of mutations
-Human Genome Project
-Viral Vectors for gene insertion
Human Genome Project
- provides basis for "correcting" heritable disorders
Limitations
-Logistics: when, how, how completely
-Somatic gene therapy
-Germ line gene therapy
-Viral vectors for gene insertion
-Not replacing defective gene, MASKING it
-Can segregate from the defective gene
-Not possible for genetic defects that express in all somatic cells
YOU MIGHT ALSO LIKE...