(a) Define the following terms: (i)… | Biology

Question 1 Report

(a) Define the following terms:
(i) gene
(ii) gene mutation.

(b) Name two structures each of plants and animals where the following processes take place:
(i) mitosis
(ii) meiosis.

(d) State three applications of the knowledge of genetics in medicine.

Answer

(a) Definitions

(i) Gene: A gene is a unit of hereditary material located at a specific position (locus) on a chromosome. It is a segment of DNA that carries the coded information for the synthesis of a particular protein and thus controls the expression of a particular characteristic (trait) which is transmitted from parents to offspring.
(ii) Gene mutation: A gene mutation is a sudden, permanent and heritable change in the base sequence of the DNA of a single gene. It alters the genetic message (for example by substitution, insertion or deletion of a base) so that a different protein, or no functional protein, is produced.

(b) Structures where the processes take place

Process	Plants	Animals
(i) Mitosis	Apical meristems of root tip; apical meristems of shoot tip (also cambium)	Skin (epidermis); bone marrow (also growing tissues generally)
(ii) Meiosis	Anther (pollen mother cells); ovule (embryo sac / megaspore mother cell)	Testes (seminiferous tubules); ovaries

(c) Four advantages of cross breeding two different breeds of cows

It combines the desirable qualities of both breeds in the offspring (for example high milk yield of one breed with the heat/disease tolerance of the other).
It produces offspring showing hybrid vigour (heterosis), giving faster growth, greater size and higher productivity than either parent.
It can produce animals more resistant to local diseases, ticks and harsh climatic conditions, reducing losses.
It improves the economic value of the stock, giving better beef and/or milk quality, higher fertility and greater profit to the farmer.

(d) Three applications of the knowledge of genetics in medicine

Genetic counselling: Prospective parents (for example carriers of the sickle-cell gene) are advised on the risk of transmitting hereditary diseases to their children.
Diagnosis and screening of hereditary diseases: Conditions such as sickle-cell anaemia, haemophilia, colour blindness and Down syndrome can be detected before or after birth.
Blood group and tissue matching: Knowledge of inheritance of blood groups guides safe blood transfusion and organ transplantation (tissue compatibility).

(Also acceptable: production of medicines such as insulin and vaccines by genetic engineering; and forensic use in determining paternity.)

Answer Details

(a) Definitions

(i) Gene: A gene is a unit of hereditary material located at a specific position (locus) on a chromosome. It is a segment of DNA that carries the coded information for the synthesis of a particular protein and thus controls the expression of a particular characteristic (trait) which is transmitted from parents to offspring.
(ii) Gene mutation: A gene mutation is a sudden, permanent and heritable change in the base sequence of the DNA of a single gene. It alters the genetic message (for example by substitution, insertion or deletion of a base) so that a different protein, or no functional protein, is produced.

(b) Structures where the processes take place

Process	Plants	Animals
(i) Mitosis	Apical meristems of root tip; apical meristems of shoot tip (also cambium)	Skin (epidermis); bone marrow (also growing tissues generally)
(ii) Meiosis	Anther (pollen mother cells); ovule (embryo sac / megaspore mother cell)	Testes (seminiferous tubules); ovaries

(c) Four advantages of cross breeding two different breeds of cows

It combines the desirable qualities of both breeds in the offspring (for example high milk yield of one breed with the heat/disease tolerance of the other).
It produces offspring showing hybrid vigour (heterosis), giving faster growth, greater size and higher productivity than either parent.
It can produce animals more resistant to local diseases, ticks and harsh climatic conditions, reducing losses.
It improves the economic value of the stock, giving better beef and/or milk quality, higher fertility and greater profit to the farmer.

(d) Three applications of the knowledge of genetics in medicine

Genetic counselling: Prospective parents (for example carriers of the sickle-cell gene) are advised on the risk of transmitting hereditary diseases to their children.
Diagnosis and screening of hereditary diseases: Conditions such as sickle-cell anaemia, haemophilia, colour blindness and Down syndrome can be detected before or after birth.
Blood group and tissue matching: Knowledge of inheritance of blood groups guides safe blood transfusion and organ transplantation (tissue compatibility).

(Also acceptable: production of medicines such as insulin and vaccines by genetic engineering; and forensic use in determining paternity.)

(a) Define the following terms: (i) gene (ii) gene mutation. (b) Name two structures each of plants and animals where the following processes take place: (i...