B11. Inheritance

(0654) Coordinated Sciences 2023/2024

 

Subheadings and key concepts

B11.1 Chromosomes and genes

• inheritance
• chromosome, gene, DNA, allele
• haploid, diploid

B11.2. Cell division

• mitosis
• meiosis: reduction division

B11.3. Monohybrid inheritance

• genotype & phenotype
• homozygous & heterozygous
• dominant & recessive
• genetic diagrams, Punnett Squares

B11.4. Variation and Selection

• variation: continuous and discontinuous
• mutation
• natural selection --> evolution
• selective breeding (artificial selection)

13. Inheritance pdf

#137 Summary of inheritance

Chromosomes are long thread of DNA made up of strings of genes. In a diploid cell, each of a pair of homologous chromosomes carries the same genes in the same position. A diploid cell therefore has 2 copies of each gene.

# 136 Genetic engineering, putting human insulin genes into bacteria

Genetic engineering is a process of taking a gene from one species and putting it into another species.

#135 Variation and antibiotic-resistance strains of bacteria

Variation is the slight individual differences within populations. All living things change and evolve from one generation to the next. As they do so, more variation is produced. 

#134 Artificial and natural selection

Artificial selection is a method used by humans to produce varieties of animals and plants which have an increased economic importance. People use selective breeding to produce new varieties of a species, so that certain desirable traits are represented in successive generations. 

#133 Sickle cell anaemia and its incidence to that of malaria

Normal and sickle red blood cells.
Credit: Wellcome Trust, UK

Sickle cell anaemia is caused by a mutation in the blood pigment haemoglobin. When the faulty haemoglobin is present in a red blood cell, it causes the cell to deform and become sickle-shaped, especially when oxygen levels in the blood become low.

# 132 Mutation, Down syndrome, effect of radiation

Mutation is a unpredictable change in the genes or chromosome number, as a result of fault copying when DNA is replicated, faulty separation of chromosomes during cell division, or exposure to radiation or some chemicals.

# 131 Variation continuous and discontinous

Variation is all the differences which exist between members of the same species. It is caused by a combination of genetic and environmental factors. There are two kinds of variation: continuous and discontinuous.

# 130 Codominance and inheritance of blood group

Sometimes, neither of a pair of alleles is completely dominant or completely recessive. Instead of one of them completely hiding the effect of the other in a heterozygote, they both have an effect on the phenotype. This is called codominance.

# 129 Monohybrid cross and the punnett square

A monohybrid cross involves the crossing of individuals and the examination of one (mono) character (flower colour, pod shape...) and different (hybrid) traits (red colour, white colour) in their offspring.

The Punnett square is a useful tool for predicting the genotypes and phenotypes of offspring in a genetic cross involving Mendelian traits. 

# 128 Cell division – Mitosis and Meiosis

Mitosis is a nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosome.

Meiosis is a reduction division in which the chromosome number is halved from diploid to haploid. 

#127 Chromosomes, DNA, genes and alleles

In the nucleus of every cell there are a number of long threads called chromosomes. 

# 126 Inheritance - key definitions

Inheritance is the transmission of genetic information from one generation to the next, leading to continuity of the species and variation within it.