Inheritance

Question 1

Define inheritance

Answer 1

The transmission of genetic information from generation to generation.

Question 2

Define chromosomes

Answer 2

Thread of DNA, made up of string of genes

Question 3

Define genes

Answer 3

Length of DNA that is the unit of heredity and codes for a specific protein; a gene may be copied and passed on to the next generation

Question 4

Define allele

Answer 4

Any of two or more alternative forms of a gene.

Question 5

Define haploid nucleus

Answer 5

a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg)

Question 6

Define diploid nucleus

Answer 6

a nucleus containing two sets of chromosomes (e.g. in body cells).

Question 7

What is different form of a particular gene is called?

Answer 7

Allele

Question 8

Define mitosis

Answer 8

Nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes

Question 9

Define meiosis

Answer 9

Giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes

Question 10

Gametes are the result of what?

Answer 10

Meiosis,which on fertilization helps to retain the chromosome number specific for a species.

Question 11

Define genotype

Answer 11

The genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG)

Question 12

Define phenotype

Answer 12

The physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed)

Question 13

Define homozygous

Answer 13

Having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding

Question 14

Define heterozygous

Answer 14

Having two different alleles of a particular gene (e.g. Tt or Gg), not pure-breeding

Question 15

Define dominant

Answer 15

An allele that is expressed if it is present (e.g. T or G)

Question 16

Define recessive

Answer 16

An allele that is only expressed when there is no dominant allele of the gene present (e.g. t or g).

Question 17

Define natural selection

Answer 17

The greater chance of passing on of genes by the best-adapted organisms.

Question 18

Define mutation

Answer 18

A change in a gene or chromosome.

Question 19

Define discontinuous variation

Answer 19

Caused by genes alone and results in a limited number of distinct phenotypes with no intermediates, e.g. A, B, AB and O blood groups in humans.

Question 20

Define continuous variation

Answer 20

Influenced by genes and environment, resulting in a range of phenotypes between two extremes, e.g. height in humans.

Question 21

State the role of mitosis

Answer 21

• Helps in growth;
• Repairs damaged tissues;
• Replaces worn out cells;
• Asexual reproduction.

Question 22

Outline the effects of ionizing radiation on the rate of mutation

Answer 22

• Exposure to radiation and some chemicals, such as tar in tobacco smoke, increases the rate of mutation;
• Exposure can cause uncontrolled cell division, leading to the formation of tumours (cancer);
• Exposure of gonads (testes and ovaries) to radiation can lead to sterility or damage to genes in sex cells that can be passed on to children.

Question 23

Explain the importance of natural selection as a possible mechanism for evolution.

Answer 23

Best-adapted organisms are selected to pass on their characteristics to the next generation; the population will lose all the poorly adapted individuals

Question 24

Describe the development of strains of antibiotic resistant bacteria as an example of natural selection.

Answer 24

• Antibiotics(is a chemical that kills bacteria by preventing bacterial cell wall formation) are used to treat bacterial infections)
• A mutation may occur that enables a bacterium to resist being killed by antibiotic treatment, while the rest of the population is killed when treated;
• This bacterium would survive the treatment and breed, passing on the antibiotic-resistant gene to its offspring;