Lecture 4 (pres 3 starting slide 66 to end)

Question 1

how many opsin genes do OLD world monkeys have?

• how about NEW world monkeys?
• ->what’s special about them?

Answer 1

OLD: TWO opsin genes

NEW: ONE opsin gene, but THREE variants

Question 2

Which color system is considered to be “primordial” (origin)?

-which developed as a result of evolutionary pressure?

Answer 2

primordial: Blue/Yellow
evolutionary: Red/Green

Question 3

sunsets show the effect of ____ scatter (which wavelength reflected?), while blue skies demonstrate ____ scatter

Answer 3

sunset: MIE scatter: LONGER wavelengths reflected - red

blue sky: RAYLEIGH scatter: SHORTER wavelengths reflected - blue

Question 4

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?)

Answer 4

early: small scatter BLUE (short wavelength) i.e. RAYLEIGH scatter
later: large scatter RED (longer wavelengths) i.e. MIE scatter

Question 5

Daylight locus extends from blue-orange, paralleling WHICH color system?

Answer 5

blue-yellow

Question 6

L and M cone opsins are located on which chromosome (generally)?

Where is the S cone opsin located?

Answer 6

L/M: X-chromosome - thus R/G is LINKED) - (Xq28)

S: chromosome 7 (7q32)

Question 7

The sequence of ___ ___ determines the spectral characteristics of the cones

Answer 7

amino acids (composing the opsins cyano/chloro/erythrolabe)

Question 8

T/F: Crossover is common between L and M opsin genes.

-what’s the result of this consequence?

Answer 8

True

-shifts in absorbtion spectra of L and M opsins, depending on which exons (6 total) were swapped

Question 9

Recall: L absorption ~560, M absorption ~530. Swapping L cones shifts opsin spectral sensitivity toward (shorter/longer) wavelengths?

Answer 9

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)

Question 10

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?

Answer 10

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)

Question 11

T/F: Heterozygous (two DIFFERENT X chromosomes) females can still only be trichromats

Answer 11

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!

Question 12

ProtanOPES - no ___ cones

ProtanOMALY - ____ in spectral sensitivity (toward shorter or longer wavelength)?

Answer 12

L - absorption sensitivity same as M gene

-SHIFT toward shorter wavelength (toward 540-550ish)

Question 13

DeuteranOPES - no __ cones

DeuteranOMALY - ____ in spectral sensitivity (toward shorter or longer wavelength)?

Answer 13

M –>absorbtion sensitivity same as L gene

-SHIFT toward LONG wavelengths (540-550ish)

Question 14

OPIA implies (mono/di/trichromatism), while ANOMALY i.e. anomalous trichomat implies what/

Answer 14

opia: at least DIchromat

- anomalous TRI chromat - three cones, ONE is abnml

Question 15

define: protanopia

Answer 15

missing L cone: single M gene (or multiple genes with the first two encoding M genes) that have IDENTICAL spectral sensitivity

Question 16

define: protanomaly

Answer 16

first two genes encoding M genes differ in spectra

Question 17

does a deuteranomalous or protanomalous observer have BETTER wavelength discrimination? Why?

Answer 17

Deuteranomalous - b/c shifting toward Longer wavelength causes larger SEPARATION (when M cones are shifted) than if you were to shift toward Shorter wavelengths

Question 18

define: deuteranopia

Answer 18

missing M cone: single L gene (or multiple genes with the first two encoding L genes) are IDENTICAL in their absorption/spectral sensitivity

Question 19

define: deuteranomaly - recall, is their CV severely impaired or nearly normal?

Answer 19

first two genes encoding L genes differ in absorbtion spectra (shifts toward Longer wavelength causing larger separation)

-nearly NORMAL CV

Question 20

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 ___ ___

Answer 20

DOMINANT, sex

-amino acids

Question 21

complete achromatopsia - mutation in all three opsins

-most common cause is d/t a mutation in what gene?

Answer 21

CNGB3 - encodes a protein for ion channels

Question 22

difference b/w a complete monochromat and an incomplete monochromat?

Answer 22

complete - NO cones - NO color discrimination

incomplete - ONE cone - color discrimation only @ mesopic levels

Question 23

T/F: you can determine if two parents will have a CVD child by asking them whether they are color deficient

Answer 23

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.

Question 24

most COMMON type of red-green CVD?

Answer 24

deuteraNOMALY (nearly-nml CVD)