Introduction to Medical Genetics Flashcards
What are some common problems with genetic components that may not be obvious?
Cancer, diabetes, and disease susceptibility
Name 4 types of genetic disorders with examples.
- Chromosomal disorders (Down syndrome, Turner syndrome)
- Single-gene disorders (hemophilia, cystic fibrosis)
- Multifactorial disorders (diabetes, heart disease)
- Mitochondrial disorders (LHON, MERRF)
Why have the percent of deaths associated with genetics disorders increased so drastically over the last 100 years?
- Public health measures (clean water, etc.) has decreased the likelihood of other preventable deaths
- Medical advances, including antibiotics, have decreased other deaths
- Better diagnosis of genetic disorders
While genetics plays an obvious role in genetic diseases, do they play a role in environmental diseases or infectious diseases? Why?
Genetics also plays a role in diseases such as diabetes and heart disease, and can even play a role in infectious diseases in regards to an individuals susceptibility and immunity.
Define genotype and phenotype? Compare and contrast the two. Can you have a genetic mutation that doesn’t present in symptoms? Which other factors could affect phenotype?
Genotype is genetic make up. Phenotype is the observable results. Sometimes an individual may have a mutation, but the effect is not observable. This can be do to compensation by other parts of the body, or environmental factors.
How is the human genome organized?
Organized into chromosomes. Specifically 23 pairs, with 1 pair being sex chromosomes, and 22 pairs being autosomes.
Describe the morphology of a chromosome. What is the difference between chromosomes labeled metacentric, submetacentric, and acrocentric?
Chromosomes consist of the short arm (p) on top and the long arm (q) on bottom. These are formed as an x-shape that are connected in the middle by a centromere.
How much of the genome is classified as dispersed repetitive segments?
What are these repetitive segments? Define them.
about 45% consist of LINEs, SINEs, and Alu repeats
LINEs (Long INterspersed Elements) - many copies of almost identical sequences, usually several thousand bases
SINEs (Short INterspersed Elements) - many copies of almost identical sequences, usually a few hundred bases long
Alu repeats - the most common form of SINE, ~300 bases, makes up almost 10% of human DNA
Approximately how much of the genome is satellite DNA?
What are the classifications of satellite DNA? Define them.
About 10 % Of the genome consists of alpha satellites, minisatellites, and microsatellites.
Alpha satellite - 171 base pairs long, many tandem copies near each centromere, constitutive heterochromatin
Minisatellite - a few copies of 60-200 bases, tandem repeats, used to be used for DNA profiling
Microsatellites - tandem repeats of 1-14 baes, single copies scattered in genome, used for DNA fingerprinting now
Describe how genetic variation occurs.
Each parent goes through meiosis to produce haploid gametes which then mix.
While maternal and paternal haploids mix recombination occurs, resulting in crossing over which increases variation through the generations
Describe how recombination occurs.
How many strands are involved? Where do they cross over?
Two strands from homologous chromosomes are involved.
Crossing over occurs between two strands, and at the point of crossing this is called the “chiasma”.
As the centromeres separate the chiasma resolved by moving to the ends of the arms, resulting in genetic material exchange between homologous chromosomes.
How many times can recombination occur? What can this result in?
Crossovers can occur multiple times in one pair of chromosomes.
This can result in “hiddin” recombonation, if you are only checking for specific genes as it may have occured in different areas
How does distance between genes affect their rate of recombination? What is the specific distance that represents a 1% chance of recombination?
The closer the genes are, the less likely they are to be separated.
1 centimorgan of distance is equal to a 1% chance of recombination.
How does gametogenesis differ between sexes?
- Size and number of products.
Males produce 4 small sperm
Females produce _1 large ovum and 3 small polar bodie_s
- Timing
Males begin gametogenesis as puberty.
Females begin as a fetus, suspend at Prophase I until ovulation to Metaphase II, and complete only if fertilized.
