Inheritance Flashcards
Define inheritance
The transmission of genetic information from generation to generation.
Define chromosomes
Thread of DNA, made up of string of genes
Define genes
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
Define allele
Any of two or more alternative forms of a gene.
Define haploid nucleus
a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg)
Define diploid nucleus
a nucleus containing two sets of chromosomes (e.g. in body cells).
What is different form of a particular gene is called?
Allele
Define mitosis
Nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes
Define meiosis
Giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes
Gametes are the result of what?
Meiosis,which on fertilization helps to retain the chromosome number specific for a species.
Define genotype
The genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG)
Define phenotype
The physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed)
Define homozygous
Having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding
Define heterozygous
Having two different alleles of a particular gene (e.g. Tt or Gg), not pure-breeding
Define dominant
An allele that is expressed if it is present (e.g. T or G)
Define recessive
An allele that is only expressed when there is no dominant allele of the gene present (e.g. t or g).
Define natural selection
The greater chance of passing on of genes by the best-adapted organisms.
Define mutation
A change in a gene or chromosome.
Define discontinuous variation
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.
Define continuous variation
Influenced by genes and environment, resulting in a range of phenotypes between two extremes, e.g. height in humans.
State the role of mitosis
- Helps in growth;
- Repairs damaged tissues;
- Replaces worn out cells;
- Asexual reproduction.
Outline the effects of ionizing radiation on the rate of mutation
- 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.
Explain the importance of natural selection as a possible mechanism for evolution.
Best-adapted organisms are selected to pass on their characteristics to the next generation; the population will lose all the poorly adapted individuals
Describe the development of strains of antibiotic resistant bacteria as an example of natural selection.
- 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;
