Human Genetics Midterm 2 & Final
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What is a Karyotype?
A standard chromosome chart, in which the chromosomes are arranged from largest to smallest (usually).
What is a telomere?
The tip of a chromosome. Consists of repetitive sequences of DNA, and helps keep the genes from unraveling when copied.
What is a Centromere?
A large constriction of a chromosome. Also, the point at which the spindle fibers attach when the cell divides.
Describe a Metacentric Chromosome.
The chromosome has the centromere in the middle, creating two arms of about the same length.
If a chromosome has two arms of the same length, what is it called?
If a chromosome has one long arm and one short arm, it is...?
Describe a submetacentric chromosome.
A chromosome with one long arm and one short one.
What is an acrocentric chromosome?
If the centromere is located almost at the very end of a chromosome, with only a bit after it.
What kind of chromosome has only a small amount of material after the centromere?
A Chromosome with a centromere at the very end. These are not found in humans.
What kind of chromosome has genetic material to only one side of the centromere?
A cross used to discern the genotype of a particular individual. The tested indiv. is crossed with a homozygous recessive individual.
What causes Cystic Fibrosis?
Problems of development of chloride ion channels. (Via genetic problems)
What is a polygenic trait?
A trait that is expressed by multiple genes.
Define multifactorial traits.
A trait that is expressed differently based on environmental factors.
Describe an example of a polygenic trait.
A poppy producing morphine is a polygenic trait. It has several precursors, each metabolized by different enzymes. Each enzyme is produced by a different gene.
What is the equation for heritability?
- H = Vg/(Vg+Ve)
- -> Vg is the variance due to genetics
- -> Ve is the variance due to the environment.
- -> Ve+Vg is total variance of a trait.
What is one of the most useful ways of investigating heritability of Traits?
What order of relatedness are:
- Siblings/Parents (1°)
- Uncle/Aunt/Grandparent (2°)
- 1st Cousin (3°)
Comparison between family members for traits is useful for understanding what association?
Environmental vs genetic variation.
What does Behavior encompass?
Activities, emotions, intelligence, and personality.
Behavioral genetics considers what aspects?
Genetic and epigenetic influences on the brain & nervous system's structure, function, & outcome.
What is Narcolepsy? What is it's incidence?
- The tendency to suddenly fall asleep.
- Affects 1 in 5000.
What is Hypocretin?
A neuropeptide found in dogs and rodents which, when missing, causes a similar challenge to narcolepsy.
The heritability of intelligence varies by age.
True. Preschooler's intelligence has about 40% inheritence; Adolescents are at 60%; Adults are at 80%
What are 3 of the 7 major causes of mental retardation?
- Sing gene disorders,
- Chromosomal disorders,
- Challenges during pregnancy or birth
Compare genetic composition for intelligence VS experience based intelligence.
The genetic composition sets the upper limit or capacity for intelligence while experiences and learning leads to actual intelligence.
What is thebaine?
Thebaine is a precursor to morphine and can not be converted directly to heroine. It still provides a precursor to pharmaceuticals, but makes opiate poppy growth in large quantities less of a security issue.
What is the general mechanism causing addiction, dependence, and tolerance to drugs?
Drug -> Changes in expression of genes for signalling (Transmitters, transduction, receiving, etc.) -> Changes in neural connections in the limbic system -> Changes in behavior/drug effect.
What is one gene in particular that is thought to have an effect on addiction?
The alleles for the gene coding for the dopamine receptor.
What is the neurotransmitter most strongly associated with depression and similar disorders?
What is a common effect of antidepressants?
They selectively inhibit serotonin reuptake. (leave serotonin in the synapse longer.)
Diazepines have what function as an antidepressant?
Enhancement of GABA binding.
Name the three alternatives talked about in class for treatment of depression.
- Nicotine patch
- Diet (esp. omega-3 fatty acids)
Heritability for schitzophrenia is mostly based on environmental influences.
False. It has a pretty strong genetic component; ~ 80%.
Define Metastasis with respect to cancer.
Metastasis is the condition wherein cancer cells spread via the blood stream or lymph vessels.
What is a benign tumor?
A tumor that grows, but does not spread or invade other cells.
What is a malignant tumor?
A cancerous tumor which invades adjacent tissues and/or spreads.
What causes cancer (on a cellular level)?
Loss of cell cycle control (due to a variety of factors).
What is a carcinogen?
A substance that causes cancer. Very often they are also mutagens.
What is an oncogene?
A Gene that triggers cancer if inappropriately activated.
Two mutations are required for many cancers.
True. Many cancers need the activation of an oncogene in addition to the change of a tumor suppressor gene, which would prevent tumor growth.
Describe the means of inherited cancer viability.
Usually, when a cancer gene is inherited it is one of the two needed to cause cancer. This makes it much more likely that they will develop a cancer, as a mutation only needs to occur to on gene rather than two.
What is the usual limit of mitotic divisions for a cell?
40 - 60. This varies depending on cell specialization (many neurons divide a maximum of 1 or 2 times).
What is the p53 gene?
The gene which produces a protein which, if DNA damage can not be rapaired, induces apoptosis.
Name two major breast cancer susceptibility genes.
BRCA1 and BRCA2. They encode proteins which form a complex to repair double-stranded DNA breakages. They are considered Tumor Suppressor Genes.
What are some methods of studying cancer-Environment linkages?
- Population studies
- Case-Control studies
- Prospective Studies (2+ groups that follow different conditions.)
Describe Tay-Sachs disease.
- Autosomal recessive, leads to accumulation of membrane gangliosides. Leads to cell death.
Some jewish communities, since they had a high incidence for Tay-Sachs, worked toward reducing the prevalence of the disease. What did they do?
- Prenatal screening,
- Pregnancy termination for TSD Positive
- Preimplantation genetic diagnoses.
Analysis of one of the 8 cells in an embryo. If it is suitable, the embryo is allowed to divide and implant.
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