IB myp 4-5 Biology – Practice Questions- All Topics
Topic :Evolution-Meiosis
Topic :Evolution– Weightage : 21 %
All Questions for Topic : Life Cycles,Natural Selection,Cell division,Mitosis,Meiosis,Reproduction,Biodiversity,Inheritance and variation,DNA and genetics
Question
c .The total available genes in a population is called the gene pool. Describe two sources of genetic variation in a gene pool.Meiosis allows for the crossing over of genes and can cause genetic variation. This usually takes place in prophase of the mitotic phase.
▶️Answer/Explanation
Ans:
Statement of two sources (2 max):
- sexual reproduction / two parents
- mutation
- crossing over
- random assortment
- arrival of new individuals
Correctly linked statement of how the variation occurs in that source, for example:
- new combination of genes from two individuals
- change in DNA sequence resulting from external event
- exchange of small segments DNA within a chromosome
- new combination of chromosomes
- new traits brought from a different gene poo
Question:
Every chromosome has a linear sequence of genes on it, usually with sections of non-coding DNA between one gene and the next. Chromosomes that have the same sequence of genes (and therefore the same structure) can pair up during meiosis. Special stains can be used to show differences in structure between chromosomes. These reveal that body cells normally have two of each type of chromosome, with the same sequence of genes.
● Do all humans have the same sequence of genes on their chromosomes?
▶️Answer/Explanation
Ans: Yes – humans generally have the same sequence of genes on their chromosomes; this is a fundamental characteristic of a species; allowing chromosomes to pair up in meiosis; in rare cases
part of the sequence of genes on a chromosome is reversed; or a series of genes are moved to a new position; although generally humans have genes in the same sequence there can be differences in the alleles of these genes that are present.