meiosis: reduction division

Question 1

meiosis and sexual reproduction

Answer 1

meiosis is important in sexual reproduction because it involves combining the genetic information of one parent with that of the other parent to produce a genetically unique individual

Question 2

diploid vs haploid

Answer 2

a diploid cell (2n) has two complete sets of paired chromosomes (one from each parent). a haploid cell (n) has a single set of unpaired chromosomes. during meiosis, a single diploid cell divides and produces four haploid reproductive cells

Question 3

stages of meiosis (5)

Answer 3

meiosis consists of two successive nuclear divisions: meiosis I and meiosis II. each division consists of the stages prophase, metaphase, anaphase and telophase. cytokinesis then splits the cytoplasm of the cell.
before meiosis, the cell grows and the dna replicates. the phases in meiosis II are the same as in mitosis.

Question 4

homologous chromosomes (5)

Answer 4

• every cell has two of each chromosome - we say it is a homologous pair
• they are similar in shape, position and information but not identical
• one chromosoms from each pair is from the mother, the other from the father
• paternal and maternal chromosomes may carry different versions of the same gene
• sister chromatids are from the same chromosome, with replicated dna connected at the centromere

Question 5

production of gametes (sex cells) (6)

Answer 5

• gametes are produced from germ cells in the ovary and testes.
• in higher organisms gametes are produced in the germ cells of the reproductive organs.
• in animals these are testes and ovaries; in flowering plants, anthers and ovules.
• the production of gametes is known as gametogenesis
• male sex cells (spermatozoa) are produced by spermatogenesis.
• female sex cells (ova) are produced by oogenesis

Question 6

consequences of abnormal meiosis: aneuploidy (3)

Answer 6

• aneuploidy is the term used to describe a problem caused in an organism by an extra or missing chromosome.
• these meiotic disorders can cause male infertility, spontaneous abortions and can affect offspring.
• aneuploidy occurs in humans when more than a diploid set of chromosomes is found making up the genome.

Question 7

consequences of abnormal meiosis: polyploidy

Answer 7

polyploidy is when cells have more than two complete sets of chromosomes