Meiosis

Question 1

What are homologous chromosomes

Answer 1

• homologous chromosomes are two full sets of genes one maternal and one paternal
• they have the same genes in the same loci

Question 2

What is an allele

Answer 2

• these are different versions of the same gene (gene variants)
• the different alleles of a gene will have the same locus

Question 3

Describe prophase 1

Answer 3

• chromosomes condense, the nuclear envelope disintegrates, the nucleolus disappears and the spindle formation occurs
• the difference to mitosis is that, instead of lining up each separate chromosomes the homologous chromosomes pair up forming bivalents
• crossing over occurs and the homologous chromosomes entangle about each other

Question 4

Metaphase 1

Answer 4

• homologous pairs line up along the metaphase plate
• the orientation of the homologous pairs is random and independent
• this is independent assortment and results in different combinations of alleles facing the poles
• this results in genetic variation

Question 5

Anaphase 1

Answer 5

• the homologous chromosomes are pulled to the opposite poles of the cell
• chromatids stay joined and there is no splitting of the centromere
• points of crossing over break off and rejoin which exchanges DNA, these points are called chiasmata
• the exchange in DNA forms recombinant chromatids, this changes the combination of alleles from the original chromatids
• this causes genetic variation

Question 6

Telophase 1

Answer 6

• The chromosomes assemble at the poles of the cell
• the nuclear envelope reforms
• chromosomes uncoil
• the cell undergoes cytokinesis and the cell splits into 2

Question 7

Prophase 2

Answer 7

• the chromosomes still consisting of 2 chromatids condense and become visible again
• the nuclear envelope breaks down and the spindle formation begins

Question 8

Metaphase 2

Answer 8

• the individual chromosomes assemble along the metaphase plate
• independent assortment of Recombinant chromatids
• more genetic variation in metaphase 2

Question 9

Anaphase 2

Answer 9

• the chromatids of the individual chromosomes are pulled apart
• splitting of the centromere

Question 10

Telophase 2

Answer 10

• the chromatids assemble at the poles of the cell
• chromosomes uncoil to form chromatin, the nuclear envelope reforms and the nucleolus becomes visible
• cytokinesis occurs forming 4 haploid cells , all of which are genetically different due to crossing over and independent assortment