Chapter 2 Variation

Question 1

What is variation

Answer 1

The difference between individuals within a species

Intra species variation

Question 2

What is variation caused by

Answer 2

The environment
- Genes in meiosis in crossing over, random assortment of homologous chromosome during metaphase 1, fertilisation (random) and mutation – a change in order of DNA code or Nitrogen bases or nucleotides.

Question 3

Allelic variation

Crossing over

Answer 3

The swapping over of sections of chromatid during metaphase 1

Question 4

Allelic variations

Random assortment

Answer 4

Random assortment

Random chance of which egg meets which sperm

Question 5

Allelic variations

Non-disjunction

Answer 5

Failure of chromosome to separate properly during division

Question 6

Variations in chromosomes

What is it?

Answer 6

Alteration can occur in large sections of chromosomes. This can be seen in the karyotype

Question 7

Variations in chromosomes

Monoploidy

Answer 7

▪ Monoploidy refers to a species having 1n set of chromosomes instead of 2n chromosomes.
→ This is observed in many ants, wasps and bees.
→ Male have 1n and make sperm through mitosis; females, rather, have 2n.
→ Half of a male’s genetic information lies dormant until fertilisation (female) or pathogenesis (male).
→ Monoploidy is more conservative but diploid organisms are more common because defective alleles can be masked be their second allele.

Question 8

Variations in chromosomes

Polyploidy

Answer 8

▪ Polyploidy refers to double (2n) triploids (3n) and tetraploids (4n), which occurs when cell divisions fail to produce haploid gametes.
→ Caused by the process of non-disjunction where during anaphase the chromosome are not separated correctly.
→ Results in one daughter cell having more or less chromosome.

Question 9

Variations in chromosomes

Aneuploidy

Answer 9

▪ Aneuploidy refers to the loss of one or more chromosomes from the cell and is caused by non-disjunction.

Aneuploidy occurs via non-disjunction
→ It can happen in meiosis 1or 2 during anaphase where identical chromosome come together and then segregate into separate cells, occasionally two identical chromosomes instead of separating go into the same cell.
→ Trisomy (2n+1) refers to an extra chromosome whilst monosomy (2n-1) refers to the loss of a chromosome.
→ Miscarriages are common.