11. CVD - Anomalous Trichromacy Flashcards
Anomalous trichromacy
They are ... by definition as they can colour match with ... primaries. They just don’t make the ... matches as ... and often ... these matches.
Anomalous trichromacy
They are trichromats by definition as they can colour match with 3 primaries. They just don’t make the same matches as normals and often reject these matches.
What type of inheritance pattern does anomalous trichromacy follow?
Sex-linked recessive, as with RG dichromacies.
Characteristics of deuteranomals
Luminous efficiency is not different to ....
Deuteranomals have ... in their wavelength discrimination with one minimum matching normals at ... nm and the other at ... nm; some deuteranomals have better ... discrimination than normals.
Similar saturation discrimination ability to ...; somewhere in between ... and ..., with no .... Suggests that spectral colours look more ....
They make colour matches by adding more ..., measured by a ....
Characteristics of deuteranomals
Luminous efficiency is not different to normals.
Deuteranomals have considerable variation in their wavelength discrimination with one minimum matching normals at 490 nm and the other at 620 nm; some deuteranomals have better red discrimination than normals.
Similar saturation discrimination ability to protanomals; somewhere in between normals and protanopes, with no null point. Suggests that spectral colours look more desaturated.
They make colour matches by adding more green, measured by a Nagel Anomaloscope.
Characteristics of protanomals
Reduced ... to red light, similar to ... but .... Max luminous efficiency (Vλ max) at ... nm and is ... from that of ....
Protanomals have ... in their wavelength discrimination with the same minimum as normals at ... nm and ... nm, but some ... (only one minimum).
Similar saturation discrimination ability to ...; somewhere in between ... and ..., with no .... Suggests that spectral colours look more ....
They make colour matches by adding more ..., measured by a ....
Characteristics of protanomals
Reduced luminosity to red light, similar to protonopes but less so. Max luminous efficiency (Vλ max) at 545 nm and is indistinguishable from that of protonopes.
Protanomals have considerable variation in their wavelength discrimination with the same minimum as normals at 490 nm and 590 nm, but some approach dichromacy (only one minimum).
Similar saturation discrimination ability to deuteranomals; somewhere in between normals and deutanopes, with no null point. Suggests that spectral colours look more desaturated.
They make colour matches by adding more red, measured by a Nagel Anomaloscope.
Colour perceptions of anomalous trichromats
Can only make inferences, but evidence suggests that anomalous trichromats see ... differently from normals, ..., ... colours as ..., and protanomals have ....
Colour perceptions of anomalous trichromats
Can only make inferences, but evidence suggests that anomalous trichromats see metamers differently from normals, fewer colours, saturated colours as desaturated, and protanomals have reduced luminosity to red.
Genetics of congenital Red-Green CVDs
... inheritance pattern means that ... is carried on the ... chromosome and it is ... to the normal gene. ... genes can be ... and are therefore ... or ... due to:
1. Being ...
2. ...
3. Major ...
4. KEY POINT - .... ... determines ... of photopigment.
Genetics of congenital Red-Green CVDs
Sex-linked recessive inheritance pattern means that abnormal gene is carried on the X-sex chromosome and it is recessive to the normal gene. Opsin genes can be abnormal and are therefore non-functional or compromised due to:
1. Being completely missing from gene array
2. Point mutations
3. Major sequence deletions
4. KEY POINT - unequal crossing over. Opsins determines spectral sensitivity of photopigment.
Complications of cone photopigment molecules
... pigment is ...% homologous with ... or ... pigment, whereas ... and ... pigments are ...% identical for ... exons. There are ... codon differences which are enough to account for slightly different ...; ... with a ...nm peak, ... with a ...nm peak, and ... with a ...nm peak. This means there are two types of ... pigment and therefore 2 types of ....
Complications of cone photopigment molecules
S pigment is 43% homologous with L or M pigment, whereas L and M pigments are 96% identical for 6 exons. There are 15 codon differences which are enough to account for slightly different absorption spectra; M with a 530nm peak, L (ala@180) with a 553nm peak, and L (ser@180) with a 557nm peak. This means there are two types of L pigment and therefore 2 types of deuteranope.
Why is the protanopia slope more angled downwards on a yellow vs red-green match graph compared to deuteranopes or normals?
Protanopes have much more dependency of yellow on the red-green mixture; more red means a dimmer yellow intensity match.
Complications of L and M during meiosis
On X chromosome (...), ... of M genes can be transcribed. Not sure which ... is transcribed first, depends on which ... bind to the upstream ....
During ... of meiosis, the maternal and paternal X chromosomes line up and some ... cross over (might be ... or ... of the gene). Having ... of the M genes can lead to ... more commonly. May result in ... which are functional but might ....
Complications of L and M during meiosis
On X chromosome (Xq28), multiple copies of M genes can be transcribed. Not sure which copy is transcribed first, depends on which promoter bind to the upstream Locus Control Region.
During Prophase I of meiosis, the maternal and paternal X chromosomes line up and some genes cross over (might be part or all of the gene). Having multiple copies of the M genes can lead to misalignment mistakes more commonly. May result in hybrid genes which are functional but might have different spectral sensitivities.
Spectral sensitivities of hybrid genes
Ranges from ... to ... nm, depending on the ..., which is enough to cause ... in ....
Spectral sensitivities of hybrid genes
Ranges from 530 to 556 nm, depending on the genotype, which is enough to cause significant differences in spectral sensitivities.
What is the prevalence of the following conditions in men?
Protanopia - ...%
Deuteranopia - ...%
Protanomaly - ...%
Deuteranomoly - ...%
Tritanopia - 1:... (equal in males and females)
What is the prevalence of the following conditions in men?
Protanopia - 1%
Deuteranopia - 1%
Protanomaly - 1%
Deuteranomoly - 5%
Tritanopia - 1:13,000 (equal in males and females)
What are the shifts in spectral sensitivities for protanomals and deuteranomals?
Protanomals -> shift towards green
Deuteranomals -> shift towards red
