Lecture 4 (pres 3 starting slide 66 to end) Flashcards
how many opsin genes do OLD world monkeys have?
- how about NEW world monkeys?
- ->what’s special about them?
OLD: TWO opsin genes
NEW: ONE opsin gene, but THREE variants
Which color system is considered to be “primordial” (origin)?
-which developed as a result of evolutionary pressure?
primordial: Blue/Yellow
evolutionary: Red/Green
sunsets show the effect of ____ scatter (which wavelength reflected?), while blue skies demonstrate ____ scatter
sunset: MIE scatter: LONGER wavelengths reflected - red
blue sky: RAYLEIGH scatter: SHORTER wavelengths reflected - blue
Early morning/day particles are (larger/smaller) thus exhibiting what type of scatter? Atmospheric particles become (larger/smaller) toward end of day, scattering what color, i.e. what type of scatter?)
early: small scatter BLUE (short wavelength) i.e. RAYLEIGH scatter
later: large scatter RED (longer wavelengths) i.e. MIE scatter
Daylight locus extends from blue-orange, paralleling WHICH color system?
blue-yellow
L and M cone opsins are located on which chromosome (generally)?
Where is the S cone opsin located?
L/M: X-chromosome - thus R/G is LINKED) - (Xq28)
S: chromosome 7 (7q32)
The sequence of ___ ___ determines the spectral characteristics of the cones
amino acids (composing the opsins cyano/chloro/erythrolabe)
T/F: Crossover is common between L and M opsin genes.
-what’s the result of this consequence?
True
-shifts in absorbtion spectra of L and M opsins, depending on which exons (6 total) were swapped
Recall: L absorption ~560, M absorption ~530. Swapping L cones shifts opsin spectral sensitivity toward (shorter/longer) wavelengths?
shift L opsin–> shift toward SHORTER absorbtion wavelength (i..e 560–> 540 or 550)
shift M opsin–> shift toward HIGHER absorption (i.e. 530–> 540-550)
Among the 6 exons comparable in L and M cone genes, which two CAN’T be swapped?
- Which two are most COMMONLY swapped?
- Swapping of which two causes the LARGEST spectral shift?
CAN’T swap 1, 6
Common: exon 3 (serine for alanine)
Largest SHIFT: exon 5 (shift 21nm) b/c that swaps THREE amino acids instead of just 1 or 2 - greatest shift in absorption)
T/F: Heterozygous (two DIFFERENT X chromosomes) females can still only be trichromats
FALSE - they CAN be tetrachromats, but they likely don’t have superior vision to trichromats (retinal wiring missing) - UNLESS they’re new world monkeys, which DO have the wiring in place!
ProtanOPES - no ___ cones
ProtanOMALY - ____ in spectral sensitivity (toward shorter or longer wavelength)?
L - absorption sensitivity same as M gene
-SHIFT toward shorter wavelength (toward 540-550ish)
DeuteranOPES - no __ cones
DeuteranOMALY - ____ in spectral sensitivity (toward shorter or longer wavelength)?
M –>absorbtion sensitivity same as L gene
-SHIFT toward LONG wavelengths (540-550ish)
OPIA implies (mono/di/trichromatism), while ANOMALY i.e. anomalous trichomat implies what/
opia: at least DIchromat
- anomalous TRI chromat - three cones, ONE is abnml
define: protanopia
missing L cone: single M gene (or multiple genes with the first two encoding M genes) that have IDENTICAL spectral sensitivity
define: protanomaly
first two genes encoding M genes differ in spectra
does a deuteranomalous or protanomalous observer have BETTER wavelength discrimination? Why?
Deuteranomalous - b/c shifting toward Longer wavelength causes larger SEPARATION (when M cones are shifted) than if you were to shift toward Shorter wavelengths
define: deuteranopia
missing M cone: single L gene (or multiple genes with the first two encoding L genes) are IDENTICAL in their absorption/spectral sensitivity
define: deuteranomaly - recall, is their CV severely impaired or nearly normal?
first two genes encoding L genes differ in absorbtion spectra (shifts toward Longer wavelength causing larger separation)
-nearly NORMAL CV
inherited TRITAN CVD are usually autosomal ___, and are 50% likely to be passed down because they’re NOT ___-linked
-what’s the underlying cause of a tritan CVD? Substitution of ___ ___
DOMINANT, sex
-amino acids
complete achromatopsia - mutation in all three opsins
-most common cause is d/t a mutation in what gene?
CNGB3 - encodes a protein for ion channels
difference b/w a complete monochromat and an incomplete monochromat?
complete - NO cones - NO color discrimination
incomplete - ONE cone - color discrimation only @ mesopic levels
T/F: you can determine if two parents will have a CVD child by asking them whether they are color deficient
FALSE - must ask about GRANDPARENTS, esp on mother’s side. Mother could be a CARRIER - even though she’s normal and expresses one X, she may pass down a color-deficient X (since she has two) and if they have a boy, he’d be CVD.
most COMMON type of red-green CVD?
deuteraNOMALY (nearly-nml CVD)
