K.C.S.E Biology Q & A - MODEL 2013PP2QN04
In an investigation, a variety of pea plants grown from seeds with smooth coats were crossed with plants grown from seeds with wrinkled coats. All the seeds obtained in the first filial (F1) generation had smooth seed coats.
​(a) Using the letter R to represent the gene for smooth seed coat, work out the genotype of the F1 generation. Show your working.
(b) If the F1 generation was sel fed, determine the phenotypic ratio of the second filial (F,) generation. Show your working. (c) If the total number of seeds in the F, generation was 14 640, calculate the number of seeds with wrinkled coats. Show your working.
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K.C.S.E Biology Q & A - MODEL 2013PP1QN26
Name two sex linked traits in human beings.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN26
What is meant by the term sex linked genes?
answers
K.C.S.E Biology Q & A - MODEL 2012PP2QN01
In a certain plant species which is normally green, a recessive gene for colour (n) causes the plants to be white in colour. Such plants die at an early age. In the heterozygous state, the plants are pale green in colour but grow to maturity.
(a) Give a reason for the early death of the plants with the homozygous recessive gene. (b) If a normal green plant was crossed with the pale green plant, what would be the genotype of the first filial generation (F1 generation)? Show your working. (c) If heterozygous plants were self-pollinated and the resulting seeds planted, work out the proportion of their offspring that would grow to maturity. What is the probability of a couple with blood group AB getting a child with blood group AB?26/6/2020
K.C.S.E Biology Q & A - MODEL 2012PP1QN08
What is the probability of a couple with blood group AB getting a child with blood group AB?
K.C.S.E Biology Q & A - MODEL 2011PP2QN02
Name two disorders in humans that are determined by sex-linked genes.
answers
K.C.S.E Biology Q & A - MODEL 2011PP2QN02
In humans, hairy ears is controlled by a gene on the Y Chromosome.
(a) Using letter Y^H to represent the chromosome carrying the gene for hairy ears, work out a cross between a hairy eared man and his wife. (b) (i) What is the probability of the girls having hairy ears? (ii) Give a reason for your answer in (b(i) above.
K.C.S.E Biology Q & A - MODEL 2011PP1QN24
What would be the expected results from a test cross?
ANSWERS
K.C.S.E Biology Q & A - MODEL 2011PP1QN24
Differentiate between the following terms:
(i)dominant gene and recessive gene: (ii) continuous variation and discontinuous variation.
ANSWERS
​(i) Dominant gene expresses itself phenotypically in both its homozygous and heterozygous states while recessive gene can only express itself phenotypically in the homozygous state;
(ii) Continuous variation is a characteristic for which there is a continuum or range while discontinuous variation is a characteristic for which there are discrete categories or units; K.C.S.E Biology Q & A - MODEL 2010PP2QN05
When pure breeding black guinea pigs were crossed with pure breeding white guinea pigs, the offspring had a coat with black and white patches.
(a) Using letter G to represent the gene for black coat colour and letter H for white coat colour, work out the genotypic ratio of F2. (b) State the phenotypic ratio of F2. (c) (i) Name the term used when two alleles in heterozygous state are fully expressed phenotypically in an organism. (ii) Give an example of a trait in human beings where the condition whose term is named in (c) (i) above expresses itself. K.C.S.E Biology Q & A - MODEL 2010PP1QN27
Give an example of a genetic disorder caused by:
(i) non-disjunction; (ii) gene mutation.
answers
(i) Down’s syndrome/Turner’s syndrome/Klinefelter’s syndrome;
(ii) Albinism/single cell anaemia/haemophilia/colour blindness;
K.C.S.E Biology Q & A - MODEL 2010PP1QN27
What is meant by the term non-disjunction?
answer
K.C.S.E Biology Q & A - MODEL 2009PP2QN03
Give an example of biological control
answers
K.C.S.E Biology Q & A - MODEL 2009PP2QN01
When the offspring of purple and white flowered pea plants were crossed, they produced purple and white flowered plants in the ratio of 3: 1 Using letter H to represent the gene for purple colour
(a) State the genotype of: (i) Parents (ii) F1 Generation (b) Work out the cross between plants in the F1 generation (c) Account for the colour the flowers in plants of the F1 generation
K.C.S.E Biology Q & A - MODEL 2008PP2QN02
What is a test – cross?
answers
K.C.S.E Biology Q & A - MODEL 2008PP2QN02
A pea plant with round seeds was crossed with a pea plant that had Wrinkled seeds the gene for round seeds is dominant over that for wrinkled seeds
Using letter R to represent the dominant gene state: (a) The genotype of parents if plant with round seed was heterozygous (b) The gametes produced by the round and wrinkled seed parents
K.C.S.E Biology Q & A - MODEL 2007PP2QN05
What is meant by hybrid vigour?
answer
K.C.S.E Biology Q & A - MODEL 2007PP2QN05
What is genetic engineering?
answer
K.C.S.E Biology Q & A - MODEL 2007PP2QN05
In maize the gene for purple colour is dominant to the gene for white colour. A pure breeding maize plant with purple grains was crossed with a heterozygous plant.
(a) (i) Using letter G to represent the gene for purple colour, work out the genotype ratio of the offspring (ii) State the phenotype of the offspring
K.C.S.E Biology Q & A - MODEL 2007PP1QN20
What is a test- cross?
ANSWER
K.C.S.E Biology Q & A - MODEL 2007PP1QN20
Explain how the following occur during gene mutation:
(i) Deletion (ii) Inversion
ANSWERS
(i) Occurs when some nucleotides of a part of a gene break off and disappear
(ii) Occurs when the nucleotides of a part of gene become inverted by taking a 1800 turn.
K.C.S.E Biology Q & A - MODEL 2007PP1QN20
What is meant by the term allele?
ANSWER
K.C.S.E Biology Q & A - MODEL 2006PP2QN02
In mice the allele for black fur is dominant to the allele for brown fur. What percentage offspring would have brown fur form across between heterozygous black mice? Show your working. Use letter B to represent the allele for black colour.
K.C.S.E Biology Q & A - MODEL 2006PP2QN02
Describe the following chromosomal mutations.
a. Inversion b. Translocation.
answers
(i) Occurs when chromatids/ chromosomes break at 2 places and when rejoining the Middle piece rotates and joins in an inverted position.
(ii) Occurs when a section of chromatid break off and becomes attached to another chromatid of another chromosome. |
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