Skin, hair and fur colour

Question 1

what happens in the skin at higher UV light to protect the DNA in skin cells from mutations

Answer 1

more MSH and MSH receptors are produced (receptors on the melanocyte)
more melanin is produced
more melanosomes collect around the nucleus of the skin cell and give more protection

Question 2

process of the formation of melanin from low exposure to UV light

Answer 2

MSH binds to MSH receptor
melanin is made inside the melanocyte cell
packaged into melanosomes
melanosomes are transferred into skin cell
collect around nucleus which protects it from being damaged by UV light

Question 3

process of the formation of melanin at high exposure to UV light

Answer 3

UV light increases amount of MSH and MSH receptors
melanocytes become more active so more melanin is produced
more melanosomes form around nucleus of the skin to protect it more
more melanin the darker the skin appears

Question 4

what happens if exposure to UV light increases in hair cells

Answer 4

physical and chemical changes occur in the melanin and other proteins in the hair causing it to become lighter since melanin is broken down

Question 5

what enzyme do some animals used to make melanin

Answer 5

tyrosinase

Question 6

what is the reaction for melanin in animals

Answer 6

tyrosinase
tyrosine ————– melanin

Question 7

what is the effect of the mutant allele for tyrosinase in Himalayan rabbits

Answer 7

enzyme is inactive at normal body temperatures so no melanin is made (white bunny)
however the tips of the rabbit (nose, ears, feet) are cooler so enzyme tyrosinase is active so melanin is made at the tips (black)

Question 8

how does an artic fox begin to grow its white coat under its brown fur in the summer ready for winter

Answer 8

in the summer fewer MSH receptors are made
without receptors MSH has no effect so melanin is not produced
white undercoat for winter will begin to form under the summer brown fur it already has