3.4.3 Genetic diversity can arise as a result of a mutaiton or during meiosis Flashcards
(23 cards)
What is a gene mutation?
A gene mutation is the change to one or more nucleotide bases or its sequence which arise spontaneously during DNA replication
What are the two types of mutation?
Substitution and Deletion
What is substitution?
A base in the genetic code is swapped for another base.
What is the positive effect of substitution?
Due to DNA being degenerate, the substituted base may not have a change on the amino acid it codes for.
What is the negative effect of substitution?
The substituted base can lead to a change in the amino acid that it codes for
What is deletion?
The complete removal of one nucleotide from the normal DNA sequence
What happens to the genetic code after a deletion?
The position of the base triplets shift to the left leading to different aminno acids being coded for
What are mutagenic agents?
Mutagenic agents increase the chance of a mutation to occur
What are example of mutagenic agents?
Ultraviolet light
Chemical
Bacteria
What are chromosome mutations?
Changes in the structure or number of chromosomes spontaneously
What is polyploidy?
It is when an organism has an extra set of chromosomes and mainly occurs in plants
What is non-disjunction?
It is when a gamete has 1 more or less chromosome and it is what causes downsyndrome (21st chromosome)
What is polyploidy and non-disjuction?
They are types of chromosome mutations
What is a diploid cell?
A diploid cell contains two of each chromosome (one maternal and the other paternal)
What is a haploid cell?
A haploid cell contains one of each chromosome (gametes)
What happens during fertilization?
Two haploid cells fuse together to form a diploid zygote
What is meiosis?
Meiosis is a type of cell division and occurs in the reproduuctive organs of eukaryotic organisms
What is the process of meiosis?
- The DNA unravels and replicates so there are two copies of each chromatid
- The DNA then condenses to dorm sister chromatids (joined together by a centromere)
- Meiosis I - the chromosomes arrange themselves into homolgous pair
- These homologous pairs seperate
- Meiosis II - the pairs of sister chromatids are then seperated
- Four haploid cells that are genetically different from each other are produced
What are the 3 key ideas of meiosis?
2 division occur
1 cell become 4 cells
Each cell is genetically difgferent from each other
How are variation maintained in gametes?
Crossing over (Recombination) and Independent segregation
What is the process of crossing over?
- Chromatids of each pair become twisted around each other
- During the twisting, tensions are created and portions of the chromatids break off
- The broken portions might rejoin (RECOMBINATION) with the chromatids of its homologous partner
- New genetic combination of maternal and paternal alleles are produced
What is Independent segregation?
The random separation of homologous chromosomes during meiosis, resulting in different combinations of maternal and paternal genes in the resulting gametes
How to calculate all the possible chromosome combination?
2^n =
where n is the number of homologous pairs
