NSC Agricultural Sciences Basic Agricultural Genetics: 4.1 Gregor Mendel was the first

Question

4.1 Gregor Mendel was the first person to study how the characteristics of pea plants are transferred from parents to offspring.

4.1.1 Name the term that refers to the study in the statement above.  
4.1.2 State TWO of Mendel’s laws of inheritance.

4.2 Feather colour in chickens is controlled by the following two pairs of genes:

Colour gene – with the alleles B = black and b = white  
Epistatic gene – with the alleles L = no colour and I = with colour

Genotype    Phenotype  
BBLl       4.2.1  
BbLl        4.2.2  
bbLl        4.2.3  
Use the above information to complete the table (4.2.1 – 4.2.3).

4.3 The diagram below shows parents and their offspring. (Bb) represents a form animal with horns (polled) and (bb) a form animal with no horns.

B  
   B  
   b  Bb  
   b  bb

4.3.1 Identify a phenotype visible in the offspring.  
4.3.2 Calculate the percentage of offspring with the homozygous recessive phenotype.

4.4 A dominant homozygous boar was mated with a heterozygous sow. In the F1-generation, all the offspring were red. In the F2-generation, a genetically unknown boar was mated with a heterozygous sow from the F1-generation above resulting in half the offspring being white.

4.4.1 Use the letters (R) for red and (r) for white to draw a Punnet square and determine the ratio of the genotypes in the first crossing.  
4.4.2 Indicate, from the information above, the genotype of the unknown boar used in the F2-generation.

4.5 In a breeding programme two green pepper cultivars were crossed to produce offspring for a specific purpose.

4.5.1 Give the genetic term for each of the following:
(a) A drastic improvement in the yield of the offspring was achieved  
(b) The two individual cultivars were picked based on the records of their respective offspring  
(c) Measuring the biological characteristics of populations using computer technology.

4.5.2 Explain why the two cultivars above were used in the breeding programme.

4.6 The table below indicates the values of different hereditary traits for sheep.

HEREDITARY CHARACTERISTICS  BIRTH WEIGHT  POST-WEANING GAIN  LEAN MEAT  FLEECE WEIGHT  
HERITABILITY (%)   53  60  37  57  
4.6.1 Identify the characteristic with the lowest improvement in the breeding programme.

4.6.2 Refer to the table above and indicate the hereditary characteristic that should be focused on for the most effective improvement in the following situations:
(a) A farmer having a feedlot  
(b) A stud farmer supplying pure-bred animals to other commercial multior farmers to be used for breeding  
(c) A wool farmer.

4.6.3 Name ONE other factor to improve the post-weaning gain (production output) in a flock of sheep.

4.7 CROSSINGS A, B and C below represent different breeding systems applied in cattle production systems.

Holstein stud bull  X Breeding of inferior cows and repeated breeding with their offspring

Hereford bull  X Hereford cow (bull's daughter)

Afrikaner bull  X Shorthorn cow

4.7.1 Identify the breeding systems represented by CROSSINGS A, B and C.

4.7.2 State TWO disadvantages of the breeding system represented by CROSSING B.

4.8 The picture below shows a technique used to insert genetic material into the nucleus of a cell.

4.8.1 Identify, in the picture above, the technique used to genetically modify organisms.

4.8.2 Differentiate between conventional hybrid cultivars and GMOs.

4.8.3 State TWO potential risks associated with genetically modified organisms.

4.1 Gregor Mendel was the first person to study how the characteristics of pea plants are transferred from parents to offspring - NSC Agricultural Sciences - Question 4 - 2021 - Paper 2

Worked Solution & Example Answer:4.1 Gregor Mendel was the first person to study how the characteristics of pea plants are transferred from parents to offspring - NSC Agricultural Sciences - Question 4 - 2021 - Paper 2

Name the term that refers to the study in the statement above.

State TWO of Mendel’s laws of inheritance.

4.2.1

4.2.2

4.2.3

Identify a phenotype visible in the offspring.

Calculate the percentage of offspring with the homozygous recessive phenotype.

4.4.1 Use the letters (R) for red and (r) for white to draw a Punnet square and determine the ratio of the genotypes in the first crossing.

Indicate, from the information above, the genotype of the unknown boar used in the F2-generation.

Give the genetic term for (a) A drastic improvement in the yield of the offspring was achieved.

4.5.1 (b) The two individual cultivars were picked based on the records of their respective offspring.

4.5.1 (c) Measuring the biological characteristics of populations using computer technology.

Explain why the two cultivars above were used in the breeding programme.

Identify the characteristic with the lowest improvement in the breeding programme.

Refer to the table above and indicate the hereditary characteristic that should be focused on for the most effective improvement in the following situations: (a) A farmer having a feedlot.

4.6.2 (b) A stud farmer supplying pure-bred animals to other commercial multior farmers to be used for breeding.

4.6.2 (c) A wool farmer.

Name ONE other factor to improve the post-weaning gain (production output) in a flock of sheep.

Identify the breeding systems represented by CROSSINGS A, B and C.

State TWO disadvantages of the breeding system represented by CROSSING B.

Identify, in the picture above, the technique used to genetically modify organisms.

Differentiate between conventional hybrid cultivars and GMOs.

State TWO potential risks associated with genetically modified organisms.

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