pack 10- skin, hair, fur and cancer

Question 1

what happens to skin in UV light

Answer 1

HIgh UV causes more MSH and MSH receptors to form on melanocytes
more MSH binds to receptors causing gene activation, tyrosinase synthesis and more melanin
melanocytes make more melanosomes which transfer to skin cells and gather around the nucleus
screen it from uv light and causing skin to darken

Question 2

human hair- UV light

Answer 2

chemical and physical changes to melanin and proteins in hair cells cause hair to lighten

Question 3

fur changes- arctic foxes

Answer 3

white winter coat grows under brown summer coat
summer coat moult in autumn
foxes produce fewer MSH receptors in summer- MSH has no effect, no melanin made.

Question 3

siamese cat and himalayan rabbit fur

Answer 3

mutation in tyrosinase gene- enzyme made but inactive at normal body temp
cold extremities- gene active pigment melanin made, extremities black colour
main body- white, warmer, gene inactive

Question 4

multifactoral disease

Answer 4

many factors contribute to risk of developing a disease

Question 5

cancer

Answer 5

disease resulting from uncontrolled cell division which forms a malignant tumour

Question 6

ways cancer can arise

Answer 6

environemental mutagens increase risk
mutations occur in in DNA of tumor supressor genes or protooncogens
cell cycle is disrupted- no stops or breaks in cell cycle
lack apoptosis
abnormal mass (tumour) forms and may invade surrounding tissue
cells dont specialise- growth cant be controlled

Question 7

uncontrolled cell division

Answer 7

shorter interphase
faster cell cycle
no hayflick limit

Question 8

protooncogens

Answer 8

code for proteins which regulate cell cycle
mutations cause oncogenes
oncogenes cause continually active cell cycle

Question 9

tumour supressor genes

Answer 9

code for porteins which halt cell cyle
mutations in genes may inactivate them
genes not expressed
no stop/break in cell cycle

Question 10

spread of cancer cells

Answer 10

cancer cells break off
travel to other parts of body in lymph or blood
casue secondary tumours

Question 11

carcinogens in cigarette smoke

Answer 11

tar- mutations in DNA in lung cells

Question 12

UV radiation

Answer 12

mutations in DNA skin cells- develop from a mole

Question 13

diet low in antioxidants and free radicals

Answer 13

free radicals cause DN mutations. lack antioxidants = free radicals not neutralised

Question 14

viral infections

Answer 14

virus RNA may contain oncogene
can transfer to cell it infects.
affect cell cycle
eg- liver cancer frmo hepatitis