Chromosomes & Sex Linkage

Mind Map by clairegillian95, updated more than 1 year ago
Created by clairegillian95 almost 6 years ago


First year Genetics & Society (Sex Linkage) Mind Map on Chromosomes & Sex Linkage, created by clairegillian95 on 04/03/2014.

Resource summary

Chromosomes & Sex Linkage
1 Y chromosome has SRY (sex-determining region Y) gene which encodes TDF (testis determining factor)
2 Haemophilia
2.1 Some blood clotting disorders are controlled by X-linked genes
2.2 Clot formation requires platelets and the protein fibrin
2.2.1 Fibrin is produced in a series of steps mediated by many protein factors
2.3 Individuals with severe haemophilia have factor VIII levels that are less than 1% of normal
2.4 Moderate haemophiliacs (1-5% of normal factor VIII) have bleeding episodes after traumatic events
2.5 Factor VIII
2.5.1 Can be purified from donor human plasma
2.5.2 Can be produced by genetically modified hamster cells
2.6 Queen Victoria was a carrier of haemophilia
2.6.1 Had an affected son & 2-3 carrier daughters
2.6.2 Granddaughter was a carrier of haemophilia Only son (& heir to throne) had haemophilia Rasputin controlled bleeding episodes by hypnosis and herbs
3 Red-green Colourblindness
3.1 X-linked recessive trait
3.2 Red & green colourblindness are controlled by 2 genes on the X chromosome
3.3 Anomalously trichromatic people have all three photopigments, but one or more may be abnormal
4 Duchenne Muscular Dystrophy (DMD)
4.1 X-linked trait
4.2 Dystrophin links the cytoskeleton to proteins in the membrane
4.3 Rapid progression of muscle degeneration
4.3.1 Leads to motor impairment and death
5 Inheritance
5.1 Carrier females can produce affected sons and normal sons
5.2 Affected females always have affected fathers
5.3 Affected males...
5.3.1 ...give their X chromosomes to their daughters who will be affected
5.3.2 ...give their Y chromosomes to their sons who will be normal
6 Barr Bodies
6.1 X0 females have no Barr Bodies
6.2 XXY males have 1 Barr Body
6.3 XXX females have 2 Barr Bodies
6.4 Inactivated X chromosomes
6.4.1 Genes of this X chromosome are not transcribed
6.4.2 Consist of highly compacted chromatin (heterochromatin)
7 Dosage Compensation
7.1 Inactivation of one of the X chromosomes in XX females equalizes X-linked gene expression between males and females
7.1.1 X inactivation occurs in early embryonic development
8 Two cell possibilities in female mammals:
8.1 Maternal X is active. Paternal X is Barr Body
8.1.1 All the descendants of this cell will inactivate the paternal X chromosome.
8.2 Paternal X is active. Maternal X is Barr Body
8.2.1 All the descendants of this cell will inactivate the maternal X chromosome
9 Mammal females are mosaics
9.1 A mixture of two cell types:
9.1.1 The proportions of these two cell types varies from female to female
10 Anhidrotic Ectodermal Dysplasia (AED)
10.1 X-linked disease
10.2 Teeth and nail abnormalities
10.3 Absence of sweat glands
10.4 XXe- females are heterozygous for the AED allele
10.4.1 Mixture of 2 cell types
10.5 Mosaic phenotypes can be seen in 3 generations of females, all heterozygous for the X-linked AED gene
11 Genes, Proteins, and DNA
11.1 Genes are made of DNA
11.2 Our genome has ~20,000 protein-encoding genes
11.3 Our genes are packaged in chromosomes
11.4 Central Dogma of Molecular Biology and Genetics
11.4.1 Genes packaged in chromosomes are located in the nucleus. The cellular machinery (ribosomes) to make proteins is located in the cytoplasm.
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