Lesson 3 - Meiosis
Lesson Objectives
Content Objective: Describe how the processes in meiosis contribute to genetic variation in cells.
Language Objective: Draw diagrams showing chiasmata in crossing over and the and describe how variation occurs in Meiosis.
Book Reference: 415-422
Syllabus Details:
Meiosis
Homologous chromosomes separate in meiosis I
Sister chromatids separate in meiosis II
Chromosomes replicate in interphase before meiosis
Diploid nuclei have pairs of homologous chromosomes
Haploid nuclei have one chromosomes of each pair
One of diploid nucleus divides by meiosis to produce four haploid nuclei
The halving of the chromosomes number allows a sexual life cycle with fusion of gametes
DNA is replicated before meiosis so that all chromosomes consist of two sister chromatids
The early stages of meiosis involved pairing of homologous chromosomes and crossing over followed condensation
Gametes are haploid so contain only one allele of each gene
The alleles of each gene separates into different haploid daughter nuclei during meiosis
Separation of pairs of homologous chromosomes in the first division of meiosis halves the chromosome number
Crossing Over and Independent Assortment
Crossing over and random orientation promotes genetic variation
Crossing over is the exchange of DNA material between non-sister homologous chromatids
Crossing over produces new combinations of alleles on the chromosomes of the haploid cells
The number of chromosomes is a characteristic features of member of a species
Independent assortment of genes in due to random orientation of homologous chromosomes pairs in meiosis I
Drawing diagrams to show chiasmata formed by crossing over
Orientation of pairs of homologous chromosomes prior to separation is random
Activites
Activity 1
For next class: You need to use the following resources to prepare a set of notes that address the syllabus statements under meiosis in the box above..
Your goal is not full understanding of everything, but a set of notes that we will build on as a class.
The WORST thing you can do for this, is not to create a set of notes and not read anything. You will be hopelessly lost.
Video Menu
Meiosis - Part 1 - Alex Lee (10:23)
Phases of Meiosis - Bozeman Science (10:46)
Reading Menu
Pearson book Pg. 415-422
Bioninja - Meiosis SL and HL (Interphase and stages of meiosis only)
Activity 2
Mitosis and Meiosis Comparison - Amoeba Sisters
-Create a comparison of mitosis and meiosis in your notes.
-Highlight where events (random assortment and crossing over) are occurring that increase genetic variation
Activity 3
Home Learning
A. Strengthen Your Skills
Chromatid Numbers/Chromosome Numbers - Amoeba Sisters - Good if you are confused about chromosome numbers
B. Expand Your Knowledge