Class 4: Genetics Flashcards
Chromosomes
organization of DNA, each chromosome is a single piece of DNA
Chromatids
the two exact copies of DNA that make up each chromosome. (23 sets of chromatids with 23 from mom and 23 from dad)
Ploidy, euploidy, aneuploidy
Ploidy - the number of sets of copies (chromatids) of each chromosome. Euploidy - normal number of chromosomes (46 for humans) Aneuploidy - abnormal number of chromosomes.
Human genome and chromosome complement:
the organism’s complete set of DNA (including all of the chromosomes, the genes on the chromosomes and the DNA in between the genes.)
Autosomes
(pairs of 1-22, 44 total- all but sex chromosomes)
sex chromosomes
(X and Y)
46, XY:
Normal male
45, XO
Turner Syndrome: The only viable monosomy. Most spontaneously abort. Female with ovarian dysfunction requiring estrogen therapy, 99% infertile
48, XXYY:
Considered variation of Klinefelter syndrome (47, XXY) which presents as hydogonadism, low testosterone, inability to make sperm, gynecomastia, sparse facial hair & small testes.
Diploid and haploid, N and C
Diploid - having two sets of copies of chromatids for each chromosome (2N, 2C). Nearly all cells in the human body are diploid. Haploid - having one set of chromatids for each chromosome (1N, 1C.) How much a gamete (sperm or egg cell) has.
Nondisjunction, meiotic errors (esp. during oogenesis, as relevant to maternal age):
Decrease in egg quality ~35yoa and more prevalent ~40yoa. Nondisjunction refers to errors in chromosome separation during mitosis or meiosis. Most embryonic aneuploidy (in particular trisomic embryos) result from maternal meiotic errors (errors in meiosis).
What are the ways that genetic diversity is generated in sexual reproduction?
1) Genetic material from two parents 2) Tetrad Line Up 3) Recombination or crossing over.
What does it mean if a drug is a SARM?
If a drug is a SARM then it is a Selective Androgen Receptor Modulator. It is a pharmacological intervention that can bind to androgen receptors and have agonistic or antagonistic effects. SARMs are tissue specific, being able to have selective agonistic activity in one tissue while antagonistic activity in another.
How might a SARM be used for contraception?
A SARM could be thought of as a designer Testosterone. It can still be introduced into the system as an endogenous androgen and induce negative feedback but the design of the SARM is to eliminate many of the bad side effects of introducing testosterone into the system. Because a SARM is tissue specific it allows the drug to have specific effect on the target tissue alone without producing adverse side effects. For instance, oral testosterone is toxic to the liver. But a SARM could go directly to muscle tissue (only one example) & promote anabolic effects without affecting the liver.
Male germ cells go through mitosis and meiosis (at different stages
of their development) - make sure you understand these processes and contrast with female
Mitosis in male germ cells begins in utero. Meiosis does not begin until onset of puberty and continues throughout the lifetime.
This can be contrasted with the female development where mitosis and meiosis begin in utero but freeze at prophase I while the germ cells are 2N 4C. They restart oogenesis at ovulation progressing to Metaphase or Meiosis II or Metaphase II (finish meiosis I and enter halfway into meiosis II) Eggs will only exit from metaphase II arrest and complete meiosis if fertilized.
