Personal tools
You are here: Home → College of Science & Math → (COS) Biology → BIO120 Meiosis and Mitosis-OPEN University

BIO120 Meiosis and Mitosis-OPEN University

Document Actions
  • RSS Feed
  • Send this
  • Print this
  • Content View
  • Bookmarks
   

Open University

S103_5
8 Hours 

Level
Introductory

Course Home (Click Here)

Course Description

This Unit looks at how units if inheritance are transmitted from one generation to the next. First you will look at what happens to the chromosomes of animals and plants during the process of sexual reproduction. Then you will examine how genes are transmitted in particular patterns from generation to generation. These two approaches combine to illustrate how the patterns of inheritance can be explained by the behaviour of chromosomes during sexual reproduction.

Learning Outcomes

After studying this Unit you should know:

  • the number of chromosomes is characteristic of each species and can vary enormously between species
  • genetics is based on the concept of the gene as the unit of inheritance
  • that sexual reproduction always includes two distinctive processes: the production of gametes, which involves meiosis, and fertilisation. The two processes are accompanied by changes in the chromosome number, from diploid to haploid and from haploid to diploid, respectively
  • a particular phenotypic character is determined by the two copies of a gene that an organism possesses and these two copies are identical in a pure-breeding variety
  • when organisms with contrasting characters for which they are pure-breeding are crossed, the dominant character appears in the first offspring or first filial generation and the recessive character is masked
  • the genotypic ratios of a cross result from the separation of the two copies of a gene to different gametes in equal numbers, and because gametes combine at random at fertilisation. The expected ratios in genetics do not tell us the actual ratios observed, but rather the most probable ratios
  • the behaviour of chromosomes at meiosis explains the segregation of the two copies of a gene and the independent assortment of genes. The linkage of genes on a chromosome can be broken by means of crossing over
  • recombination – the production of new combinations of alleles – arises during meiosis from independent assortment of chromosomes and crossing over between homologous chromosomes
  • the amount of crossing over between linked genes differs according to their distance apart.

 

Introduction

  • Introduction Resource
  • This Unit looks at how units if inheritance are transmitted from one generation to the next. First you will look at what happens to the chromosomes of animals and plants during the process of sexual reproduction....

 

Unit introduction

  • Unit introduction Resource
  • Living organisms use the components of the world around themselves and convert these into their own living material. An acorn grows into an oak tree using only water, oxygen, carbon dioxide, some inorganic...

 

1: Meiosis and the life cycle

 

2: Like begets like

  • 2: Like begets like Resource
  • It is possible to follow a character, such as eye colour or hair colour in humans, that is handed down from generation to generation. Such characters are said to be inherited characters (or heritable characters)...

 

3: Patterns of inheritance

  • 3.1: Inheritance of colour in maize Resource
  • We can trace the inheritance of characters in animals and plants by following the phenotype from generation to generation, in breeding experiments. We will describe work with maize (Zea mays), alternatively...
  • 3.2: A breeding experiment: stage one Resource
  • In the first stage of the breeding experiment, shown in Figure 5, plants from the pure-breeding purple-grained variety are crossed with (fertilised by) plants from the pure-breeding white-grained variety....
  • 3.3: A breeding experiment: stage two Resource
  • We now turn to the second stage of the breeding experiment, but this time we will follow the phenotypes and genotypes simultaneously. The purple (Gg) grains of the F1 generation are planted and when these...
  • 3.4: Predicting the outcome of crosses Resource
  • By knowing the pattern of inheritance of genes as described above, it is possible to make some predictions about the phenotypes and genotypes of each generation in breeding experiments. This section considers...

 

4: Why not an exact 3:1 ratio?

  • 4: Why not an exact 3:1 ratio? Resource
  • Before we leave the maize breeding experiments we will look more closely at some actual values obtained for the F2 generation and how closely they fit the expected phenotypic ratio of 3:1. Table 2 gives...

 

5: Inheritance of more than one pair of contrasting characters

 

6: Summary

  • 6: Summary Resource
  • The number of chromosomes is characteristic of each species and can vary enormously between species.

 

References and Acknowledgements

There are currently no items in this folder.

Copyright 2007, by the Contributing Authors. Cite/attribute Resource. administrator. (2010, January 29). BIO120 Meiosis and Mitosis-OPEN University. Retrieved March 13, 2010, from Free University Courses OCW Courses OpenCourseWare Freeversity Foundation Web site: http://freeversity.org/science-and-mathematics/biology/bio120-meiosis-and-mitosis-open-university. All Rights Reserved