Module 4 - Genetic diversity can arise as a result of mutation or during meiosis Flashcards
Simply explain how DNA is passed from one generation to another.
A haploid sperm and a haploid come together during fertilisation making a diploid cell (zygote). Fertilisation is random meaning different zygotes are produced which have different combinations of chromosomes
What is a homologous pair?
This is a pair of chromosomes - one maternal and one paternal - that are genetically identical but they can have different alleles
What happens before meiosis takes place?
DNA unravels and replicates so there are two copies of each chromosome called chromatids. DNA condenses to form double-armed chromosomes. Chromatids joined by the centromere
Briefly explain each part of meiosis?
In meiosis 1, chromosomes arrange themselves in homologous pairs. These pairs separate and half the chromosomes number. 2 diploid cells are produced. In meiosis 2, pairs of sister chromatids split producing 4 haploid cells
What are 2 ways in which meiosis increases genetic diversity?
Crossing over and independent segregation
What happens in crossing over?
This is when homologous pairs come together and a section of one chromatid per chromosome swap sections of DNA. They have the same genes but different combinations of alleles.
What is meant by the independent segregation of chromosomes
When a chromosome from each homologous pair moves into each daughter cell, the process is completely random so the 4 haploid cells produced have completely different combinations of alleles which then leads to complete genetic variation
3 differences between mitosis and meiosi
- Mitosis produces 2 daughter cells whereas meiosis produces 4
- mitosis produces diploid cells whereas meiosis produces haploid cells
- mitosis produces genetically identical cells whereas meiosis produces genetically different cells.
Haploid and diploid difference
Haploid 2n
Diploid n
What is a chromosome mutation? What can it lead to?
An error created during meiosis. Leads to inherited conditions because errors are present in gametes.
What is meant by non-disjunction?
This is the failure of chromosomes to separate properly
What are 2 types of mutations?
Deletion and Substitution
What is meant by deletion?
This is when one base is remove from a sequence which causes a frameshift of base triplets therefore the DNA sequence after the deletion will create a change in the polypeptide
What is meant by substitiution?
This is when one base is substituted for another base
Why might substitution mutations not impact the protein being made?
Some base triplets are degenerate which means that multiple DNA triplets code for the same amino acid therefore the mutation may code for the same amino acid.
