K.C.S.E Biology Q & A - MODEL 2019PP2QN04
In cats, the gene for fur colour is sex-linked. Letter G represents the gene for ginger fur colour while letter B represents the gene for black fur colour in a given cat species. These genes are co-dominant. Heterozygous females have ginger and black patches of fur and their phenotype is described as tortoise-shell.
​(a) With reference to the information given above, what is meant by the term co-dominance?
(b) Explain why male cats with a tortoise-shell phenotype do not usually occur. (c) A tortoise-shell female was crossed with a black male. Determine the genotypes and phenotypes of the offspring.
answers
K.C.S.E Biology Q & A - MODEL 2018PP1QN18
​A tall, light skinned lady with pimples on her face has long hair and limps.
(a) List two features which the lady has that are due to inheritance.
(b) Explain why most recessive genes are expressed phenotypically in male offspring of humans.
answers
​(a) Height (tallness);
Long hair; Skin colour (light); (b) Most of the genes are sex-linked and are carried on the X - chromosomes; boys receive X chromosomes from the mother (and Y chromosomes from the father); if the X carries a recessive gene, it is more likely to be phenotypically expressed in boys;
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
State how in-breeding leads to reduced hybrid vigour
answer
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
State two advantages of using genetically modified varieties in bean farming.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
In beans, the gene for purple colour is dominant over the gene for white colour. A pure breeding bean plant with purple colour was crossed with a heterozygous bean plant.
Using the letter P to represent the gene for purple colour, work out the genotypic ratio of the offspring.
answer
K.C.S.E Biology Q & A - MODEL 2017PP1QN16
The following are text messages on a celiphone that represent gene mutation.
​(a) Identify the type of gene mutation represented in each case
I II (b) State Mendel’s First Law. (c) State two disadvantages of genetically modified plant products.
answers
​a. I — Deletion;
II- Inversion; b. The characteristics /traits of an organism are determined by internal factors/ genes (which occur in pairs). Only one of the genes can be carried in a gamete/ passed onto the next generation; c. Most have lost most of the original (desirable) qualities e.g taste; Poor/undesirable qualities are perpetuated through subsequent generations; Products’ qualities are irreversible- can’t get original species/qualities;
K.C.S.E Biology Q & A - MODEL 2016PP2QN02
Explain why people with sickle cell trait have an adaption survival advantage over normal individuals in malaria endemic regions.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2016PP2QN02
Differentiate between sickle cell anaemia and sickle cell trait.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2016PP2QN02
How is sex determined in man?
ANSWERS
K.C.S.E Biology Q & A - MODEL 2015PP2QN03
A female with sickle cell trait marries a normal man. The allele for sickle cell is HbS and the normal allele is HbA. Determine the probability that their first born will have the sickle cell trait. Show your working..
ANSWERS
K.C.S.E Biology Q & A - MODEL 2015PP2QN03
State two examples of discontinuous variation.
ANSWERS
​ (i) Sex;
(ii) ABO blood group system/Rhesus factor; (iii) Ability to roll tongue; (iv) Free or attached earlobe; (v) Presence/ absence of hair in the nose! on the ear pinna; (vi) Finger prints; ability to taste PTC (phenythiocarbamide) PTV (phenylthio urea) (vii) Winglength in prosophila; (viii) Size of abdomen in drosophila; (ix) Eye colour in prosophila; (x) Smooth/wrinkled seed coats in pea plants; (xi) Green/yellow seed coats/seed coat colour in pea plants; (xii) Polymorphism/melanic and non melanic forms in moths.
K.C.S.E Biology Q & A - MODEL 2015PP2QN03
What is meant by the term genetics?
ANSWER
K.C.S.E Biology Q & A - MODEL 2015PP1QN04
Colour blindness is a sex linked trait controlled by a recessive gene b. If a mother is a carrier and the father is normal, what is the chance that their son will be colour blind? Show your working.
answers
K.C.S.E Biology Q & A - MODEL 2014PP2QN04
Explain why people with sickle cell trait have an adaptive survival advantage over normal individuals in malaria endemic regions.
answers
K.C.S.E Biology Q & A - MODEL 2014PP2QN04
Differentiate between sickle cell anaemia and sickle cell trait.
answers
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