Question

Which processes contribute directly to genetic variaion?

? What is meant by ploidy? Diploid? Haploid?

? Know the phases of meiosis?

? Know the differences between meiosis and mitosis.

? What is the major difference between metaphase of mitosis and metaphase I of meiosis?

? What is the major difference between meiosis II & mitosis?

? What is crossing over? ? What is synapsis?

? What are chiasmata?

? What are autosomes?

? What are sex chromosomes? What are the sex chromosomes in human male? Human female?

? What are homologous chromosomes?

? What is genetic recombination?

? What is fertilization? What are gametes?

? What are histones? What is chromatin?

? How many autosomes do humans have? Have many pairs of autosomes? How many pairs of sex chromosomes? What is the total number of chromosomes that human have? ? What are the sites of crossing over called?

? What is a karyotype?

? What is Down syndrome?

? What is polyploidy?

? What is nondisjunction?

? What is trisomy and monosomy

Answer 1

1) Meiosis contributes directly to genetic variation. During fertilisation, one gamete from each parent combines to form a zygote. Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote.

2) Ploidy refers to the number of sets of homologous chromosomes in the genome of a cell. It is generally used to indicate the number of chromosome sets in a cell.

Haploid cells have only half the number of total chromosomes.

Diploid cells contain two complete sets (2n) of chromosomes.

3) Meiosis is a cell division process in which the chromosome number is reduced by half and produce four haploid cells. Each haploid cell is genetically distinct from the parent cells. Meiosis has four phases: prophase, metaphase, anaphase, and telophase.

4) Mitosis and meiosis are the processes of dividing a diploid cell.

          Mitosis results in two genetically identical, diploid, daughter cells. It generally takes place during growth, repair, cloning and asexual reproduction. Diploid cell has two same copies of each chromosome. All cells in the body are formed by the process of mitosis except for the sex cells.

           Meiosis results in four haploid cells that are not genetically identical. In order to obtain haploid sex cells, meiosis requires two cell divisions. Chromosomes are divided randomly, hence the daughter cells are not genetically identical in meosis.