Introduction to Medical Genetics Flashcards
What are some common problems with genetic components?
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?
about 45% consist of LINEs, SINEs, and Alu repeats
Approximately how much of the genome is satellite DNA?
About 10 % consist of alpha satellites, minisatellites, and microsatellites.
Define LINEs.
Long INterspersed Elements
Many copies of almost identical sequences that are typically several THOUSAND bases long
Define SINEs.
Short INterspersed Elements.
Many copies of almost identical sequences usually a few HUNDRED bases long
What is the most common form of SINEs? How long is it? What percentage of DNA does it account for?
Alu sequences is the most common form. This is about 300 bases long and makes up about 10% of human DNA
Describe alpha satellites.
Alpha satellites are a type of satellite DNA.
They are 171 basepairs long with many tandem copies near each chromosome.
They consist of very condensed heterochromatin
Describe minisatellites.
They are a type of satellite DNA. They are tandem repeats that are 60-200 basepairs long.
Originally these were used for restriction fragment lengtch polymorphism (RFLP) analysis to distinguish individuals by DNA
Describe microsatelites.
A type of satellite DNA.
Consists of tandem repeats of 1-14 bases, few to many repeats
Now used for DNA fingerprinting
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 exhange 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
