Genetics Flashcards
Gene
a. Segments of DNA on a chromosome
ii. Chromatid
a. One of two identical copies of a chromosome
iii. Sister Chromatids
a. Two identical chromosomes
iv. Homologous chromosomes
a. Similar in length, gene position, and centromere location
b. Contain different alleles
iii. Lyonization
a. X-inactivation
b. One of females X chromosomes are inactivated
iv. Mosaicism
a. Two or more populations of cells with different genotypes in an individual who has developed from a single fertilized egg
b. Results from errors in cell division
c. Down Syndrome, Klinefelter syndrome, Turner syndrome
a. Thalassemia
a. Underproduction of hemoglobin
b. Methemoglobinemia
a. Cannot bind heme
c. Sickle cell disease
a. Mutated hemoglobin creates sickle shaped RBCs
mtDNA
a. Several copies of 16,569 bp, double-stranded, circular mtDNA molecule per mitochondria
b. Transcription takes place in mitochondrion, independent of nucleus
c. No introns
d. Inherited through maternal line
e. Mutation rate is 10x higher than nDNA
a. Lack of DNA reoair mechanisms
b. Damage from free radials
nDNA
a. 3.3x10^9 base pairs
b. Many introns
c. Autosomal inheritance
d. Cell cycle regulated
a. Resting mammalian cells in the G1 phase have a DNA content of?
2N
b. During S phase, the content of DNA varies between
2N and 4N
Permanent Cells
i. Remain in G0 and cannot be regenerated
ii. Cardiac muscle cells, neurons, RBCs
Stable Cells
i. Retain ability to exit the G0 phase to enter G1 when stimulated by growth factors
ii. Hepatocytes and epithelial cells of the kidney tubles
Labile cells
i. Never enter G0 and are constantly dividing
ii. Gut epithelium, skin, hair follicles, bone marrow
Mitochondrial Inheritance
- Encodes rRNA, tRNA, and 13 polypeptides involved in oxidative phosphorylation
- Contain no introns
- Inherited through maternal line
- Mutation is about 10x higher than nDNA
- Damage from free oxygen radicals from OxPhos
a. Leber’s Hereditary optic neuropathy
degeneration of retinal ganglion cells, acute or subacute loss of central vision, early teens
b. Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
affects many body systems, particularly brain and nervous system, and muscles, stroke and dementia, lactic acidosis
i. Prader-Willi syndrome
- Deletion of a region of chromosome 15
- Paternal= Prader-Willi Syndrome, short stature, hypotonia, small hand/feet, obesity, uncontrolled eating
- Maternal= Angelman syndrome, intellectual disability, seizures, ataxic gait
- 18- Edwards syndrome,
often IUGR, 95% die in utero, microencephaly, prominent occiput, malformed and low-set ears, small mouth and jaw, cleft lip, rocker bottom feet
- 13-Patau syndrome,
severe developmental abnormalities, most die before birth, heart abnormalities, kidney malformations, microcephaly, malformed ears, closely spaced/absent eyes
ii. Locus heterogeneity
- Disorder caused by mutations in genes at different chromosomal loci
- Only one mutant locus is needed for the phenotype to manifest
- Ex: osteogenesis imperfecta
i. Heteroplasmy
- Presence of more than one type of mitochondrial DNA within a cell
- Symptoms usually do not develop until adulthood because these mutant mitochondrial alleles must undergo many cell division before a sufficient amount are present to cause symptoms (visual problems)
Stem cells
i. Primitive cell
ii. Not terminally differentiated
iii. Can divide without limit
iv. Undergo slow division
v. When divide gives rise to 1 cell with stem cell characteristics and the other with the ability to be differentiated
ii. Founder stem cells
- Proportions of body parts are determined early
- Each tissue has fixed number of founder cell populations
- Controlled by short range signals that operate for a few hundred cell diameters
multipotent
- Ability to give rise to different cell types of a given lineage
- Adult stem cells
- Maintain tissue homeostasis
- Replace damaged cells
Pluripotent
- Ability to give rise to all cells of the embryo and subsequently adult tissues
- Embryonic stem cells
- Transcription factors: Nanog, Oct4, Sox2, and FoxD3
a. Essential for maintaining and establishment - Cripto and GDF-3 are growth factors found in pluripotent cells
- May be possible to induce adult stem cells with transcription factors
Totipotent
- Ability to give rise to all cells of an organism, including embryonic and extraembryonic tissues
- A zygote is totipotent
i. Somatic Cell Nuclear Transfer
- Combines cloning methods with embryonic stem cell technology
- Produces cells which are custom made for patient
- Solves tissue rejection problem as cells express the patient’s genes
- Research has enabled reprogramming of adult cells while omitting embryo step
- HUGE therapeutic potential
- Challenges include: inefficiency and technically demanding
