Ask A Scientist Molecular Biology Archive

name         Korah E.
status       educator
age          40s

Question -   Our family appears to have several members who are
blue-grey color blind.  Another family member claims that there is no
such condition, and that it is genetically impossible (two of the
blue-grey color blind people are female).  Is there such a form of color
blindness, and can it be manifested in females?  How does it work: which
cones are not working/formed properly; how is the gene transmitted?
---------------------------------------
Color vision is determined by the cones in the retina in your eye.  There are
3 types of cones.  They each are responsible for a kind of color vision.
It is kind of like having only 3 colors in a color ink cartridge, but the
combinations and amounts can produce any color.  The cones are coded for by
different genes.  Red Green color blindness is caused by a defect in a gene
found on the X chromosome.  But this is only one kind of color blindness,
there are others involving the other sets of cones in the eye.  I do not know
which chromosomes those genes are found on, but it is possible for them genes
to be found on other chromosomes than the X.  And at any rate, just because a
trait is sex-linked, it is possible for females to be affected if the mother
is at least a carrier and the father is affected.  It is true that if those
women have fathers who are not affected, it is probably not sex-linked.

vanhoeck
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Hi Korah:

  I do not know what "blue-grey" colorblindness is.
Based on the slide below, missing blue cones will cause a person to
confuse blues and yellows. In thinking about what might cause missing
blue cones, I went to OMIM (Online Mendelian Inheritance in Man), and
searched for colorblindness, resulting in a list of 45 conditions (see
below) for which a single gene has been identified. Wow - 45! Some of
these are actual colorblindness and others are conditions in which
colorblindness may sometimes or always be a symptom. The famous X-linked 
colorblindness gene involved in red-green colorblindness is on the X 
chromosome and affects mostly boys, but the other genes are in various 
positions on the chromosomes. Depending on their mode of inheritance, 
either gender may be affected.
Enjoy exploring OMIM. Mendelian inheritance refers to single gene 
conditions, as opposed to multifactorial inheritance involving a 
combination of various genetic and environmental factors.
Height is an example of a multifactorial trait. Nevertheless there are
single genes known to influence height, such as the gene for 
achondroplasia, a form of dwarfism. Vision is just as complicated, or
more so, with layers of causation superimposed. E.g., an albino might
have inherited a colorblindness gene or genes besides the two copies of
the albinism gene.
Remember we have two copies of every gene on chromsomes 1 - 22 (the
autosomes). Females have two copies of every gene on the X chromosome;
males have one copy of every X gene and one copy of every gene on the Y
chromosome. The question of dominant or recessive inheritance relates to 
whether the trait will be present in a person who has only one affected 
gene, along with one normal version or allele of the same gene
(dominant), or whether both genes need to be affected in a person who =
has the condition (recessive).
I hope this is of help and does not make matters worse.

OMIM Home Page -- Online Mendelian Inheritance in Man
NCBI GenBank OMIM=99 Online Mendelian Inheritance in Man, Home Page. =
Welcome
to OMIM(TM), Online Mendelian Inheritance in Man. ... Browsing OMIM. ... =

www.ncbi.nlm.nih.gov/omim/ - 5k - Cached - Similar pages
Select Entries from OMIM --
Online Mendelian Inheritance in Man
45 entries found, searching for "colorblindness"


*303800 COLORBLINDNESS, PARTIAL, DEUTAN SERIES; CBD
*190900 TRITANOPIA
*303900 COLORBLINDNESS, PARTIAL, PROTAN SERIES; CBP
304000 COLORBLINDNESS, PARTIAL TRITANOMALY
*303700 COLORBLINDNESS, BLUE-MONO-CONE-MONOCHROMATIC TYPE; CBBM
#262300 ACHROMATOPSIA 3; ACHM3
#216900 ACHROMATOPSIA 2; ACHM2
*309550 FRAGILE SITE MENTAL RETARDATION 1; FMR1
*309200 MAJOR AFFECTIVE DISORDER 2; MAFD2
#310500 NIGHT BLINDNESS, CONGENITAL STATIONARY, TYPE 1; CSNB1
*300100 ADRENOLEUKODYSTROPHY; ALD
*305660 GAMMA-AMINOBUTYRIC ACID RECEPTOR, ALPHA-3; GABRA3
*309630 METACARPAL 4-5 FUSION; MF4
*305900 GLUCOSE-6-PHOSPHATE DEHYDROGENASE; G6PD
*306700 HEMOPHILIA A
*306900 HEMOPHILIA B; HEMB
*309100 MACULAR DYSTROPHY, X-LINKED
#310300 EMERY-DREIFUSS MUSCULAR DYSTROPHY; EDMD
#310200 MUSCULAR DYSTROPHY, DUCHENNE TYPE; DMD
*300600 ALBINISM, OCULAR, TYPE II; OA2
*300017 FILAMIN A; FLNA
268040 RETINOHEPATOENDOCRINOLOGIC SYNDROME
161700 NECROTIZING ENCEPHALOMYELOPATHY, SUBACUTE, OF LEIGH, ADULT
*605080 CYCLIC NUCLEOTIDE-GATED CHANNEL, BETA-3; CNGB3
*310400 MYOTUBULAR MYOPATHY 1; MTM1
*312420 RENIN-BINDING PROTEIN; RENBP
#313200 SPINAL AND BULBAR MUSCULAR ATROPHY, X-LINKED 1; SMAX1
#313400 SPONDYLOEPIPHYSEAL DYSPLASIA TARDA, X-LINKED
*314900 XM SYSTEM
*309500 RENPENNING SYNDROME 1; RENS1
*600053 CYCLIC NUCLEOTIDE-GATED CHANNEL, ALPHA-3; CNGA3
*110300 ABO BLOOD GROUP; ABO
*308840 L1 CELL ADHESION MOLECULE; L1CAM
*308700 KALLMANN SYNDROME 1; KAL1
*305435 F-CELL PRODUCTION 1; FCP1
#302800 CHARCOT-MARIE-TOOTH PERONEAL MUSCULAR ATROPHY, X-LINKED; CMTX1
#300376 MUSCULAR DYSTROPHY, BECKER TYPE; BMD
*254150 MUSK, INABILITY TO SMELL
#223100 HYPOLACTASIA, ADULT TYPE
*180020 RETINAL CONE DEGENERATION
*164500 SPINOCEREBELLAR ATAXIA 7; SCA7
#163500 NIGHT BLINDNESS, CONGENITAL STATIONARY; CSNB3
*143000 HORNER SYNDROME
*138850 GONADOTROPIN-RELEASING HORMONE RECEPTOR; GNRHR
*305200 EHLERS-DANLOS SYNDROME, TYPE V

Best regards,
Sarina Kopinsky
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