K.C.S.E Biology Q & A - MODEL 2006PP2QN02
Name two disorder in human caused by gene mutation.
answers
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K.C.S.E Biology Q & A - MODEL 2005PP1QN12
In a garden with plants of same species, 705 plants had red flowers while 224 had white flowers.
a) Work out the ratio of red to white flowered plants b) (i) Using letter R to represent the dominant gene, work out a cross between F1 offspring and a white flowered plant. (ii) What is the genotypic ratio from the cross in b(i) above? c) What is meant by the term allele? K.C.S.E Biology Q & A - MODEL 2004PP1QN12
Across between a red flowered plant and white flowered produced plants with pink flowers.
Using letter R to represent the gene for red colour , and W for white colour a) What were the parental genotypes b) Workout a cross between F1 plants c) Give the i) Phenotypic ratio of F2 plants ii) Genotypic ratio of F2 plants d) Name a characteristic in humans, which is controlled through a mammalian heart?
answers
(a) RR WW
(b) Parental genotypes R W Gametes R W X WW R W Fertilization Offsprings RR RW RW WW (c) (i) Phenotypic ration Red Pink White 1 2 1 (ii) 1RR : 2RW; 1WW (d) (ABO) blood grouping; blood groups; K.C.S.E Biology Q & A - MODEL 2003PP1QN12c
In Drosophila Melanogaster, the inheritance of eye colour is sex – linked. The gene of red eye is dominant. A cross was made between a homozygous red – eyed female and a white – eyed male. Work out the phenotypic ration of F1 generation. (Use R to represent the gene for red eyes).
K.C.S.E Biology Q & A - MODEL 2003PP1QN12b
Name two sex – linked traits in humans.
answers
K.C.S.E Biology Q & A - MODEL 2003PP1QN12
What is meant by the term sex – linkage?
answers
K.C.S.E Biology Q & A - MODEL 2002PP1QN11
Give an example of a sex – linked trait in humans on:
Y CHROMOSOME. X CHROMOSOME.
answers
​Y CHROMOSOME
Tuft and hair sprouting from pinna / baldness; hairy pinna; X CHROMOSOME Colour blindness / haemophilia. K.C.S.E Biology Q & A - MODEL 2001PP1QN14
Tallness in pea plants is due to a dominant gene Two tall pea plants were crossed and their F1 generation were in the ratio of 3 tall: 1 short. Using letter T to represents the gene for tallness and t for shortness give the
(a) (i) genotype of the parents (ii) Gamete of the parents (iii) Genotype ratio of the F1 generation (b) What is meant by the term testcross in genetic studies?
answers
​(a) (i) Tt, Tt
(ii) Tt and Tt (iii) 1TT; 2Tt; 1tt/ 1 tall homozygous; 2 tall heterozygous 1 short homozygous 1:2:1 (b) Crossing a homozygous recessive organism with an organism which shows dominant characteristics. K.C.S.E Biology Q & A - MODEL 2000PP1QN12
The chart below represents the result of successive crosses, staring with redflowered plants and white flowed plants and in which both plants are pure breeding.
(a) What were parental genotype? Use letter R to represent the gene for red colour and r for white colour
(b) (i) What was the colour of the flowers in the first filial generation? (ii) Give a reason for your answer in b (i) above (c) If 480 red flowered plants were obtained in the second filial generation, how many F2 plants and white flowers? Show your working.
answers
(a) RR and rr
(b) (i) red (ii) complete dominant; i.e Rd dominant/ white recessive (c) Ratio of filial generation: 3: 1 (I.e. in every 4 flowers 3 are red 1 is white Therefore 480 red flowers means ¾ of the total number Total number of flowers (480 x 4)/3 = 640 So ¼ of 640 flowers are white in F2 plants ¼ x 640 = 160 flowers K.C.S.E Biology Q & A - MODEL 1998PP1QN12
In a family with four children, three were found to have normal skin pigmentation while one was an albino. Using letter A to represent gene for normal skin pigmentation and a to represent the gene for albinism,
(a) What are the genotypes of the parents? (b) Work out the genotype of (i) Normal pigmentation (ii) The albino child Genotype of normal pigmented children (c) What is the probability that the fifth child will be an albino? K.C.S.E Biology Q & A - MODEL 1997PP1QN16
In a breeding experiment, plants with red flowers were crossed. The produced 123 plants with red flowers and 41 with white flowers
(a) Identify the recessive character Give a reason (b) What was the genotype of the parent plants that gave rise to the plants with a red and white flowers?
answers
​(a) White
Give a reason – Fewer numbers/ lower ratio; lower in numbers/ absence of white in parents & absence in offspring. (b) Heterozygous (c) Double recessive / homozygous (recessive) K.C.S.E Biology Q & A - MODEL 1996PP1QN 18
​In an experiment black mice were crossed and the offspring were back and brown. The gene for black colour is dominant over that of brown colour.
Using letter B to represent the gene for black colour and b to represent the gene for brown colour (a) Work out the genotypes of the F1 generation (b) What is the phenotype ration of the spring ​Give a reason why it is only mutation in genes of gametes that can influence evolution.
ANSWERS
Gametes form new offspringWhat are two organisms considered to belong to the same species?ANSWERS
if they are capable of interbreeding; to produce viable offspringState the function of Deoxyribonucleic acid (DNA) molecule.KNEC ANSWER
Controls/regulates/enzymes/ synthesis is the material for inheritance |
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