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Lecture 5

BIOL 1090 Lecture Notes - Lecture 5: Prophase, Autocrine Signalling, Sister Chromatids

Course Code
BIOL 1090
Andrew Bendall

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Biology 1090 Seminar 1
The Myostatin (MSTN) gene
-Mice lacking the MSTN gene had approximately twice as much muscle as normal mice
-MSTN gene encodes for a protein (myostatin) that is produced and released by myocytes
-Myostatin acts on the cell’s autocrine function to inhibit muscle cell growth and differentiation
-mutations to this gene leading to a lack of myostatin OR non-functional myostatin lead to a “double
muscle” phenotype in these organisms
Genetic Disorders involving the Myostatin (MSTN) gene
-double-muscle phenotype is a heritable disorder in many mammals (recessive pattern)
results in an increase of muscle fibres
-Animals have an increased ability to convert food into lean muscle, while having decreased fat
lead to almost a 25% increase in muscle mass
DNA Condensation
-When mitosis begins, each chromosome has been
Haploid (n) vs Diploid (2n) vs DNA content (c)
-Haploid: ‘c’ amount of DNA and ’n’ chromosomes
BECAUSE you have either one
parental cell or one maternal cell
c = weight of DNA
n = number of unique genes
-Diploid: 2c amount of DNA and 2n (2 unique chromosomes)
chromosomes because now you have one of mom’s genes and one of
dads genes
During Meiosis 1………
-Crossing over involves breakage of chromatids and the change of
the broken pieces between homologous chromosomes (non-
sister chromatids)
-Following crossing over, homologous chromosomes start to pull
apart, but remain joined at the cross over junctions (called
-Same number of genes BUT now different combination of
genes on recombinant chromatids
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