3.4.3 Genetic diversity, mutation, meiosis Flashcards
Definition of chromosome mutation (e.g. to each type)
Changes in the structure / number of whole chromosome
Type of chromosome mutation and example
Non disjunction
Chromatids do not separated ,Chromosome separate unevenly by meiosis), result in an extra chromosome
Definition of gene mutation
Change in quantity of bases or bases sequence in the DNA
Result in a change in the amino acid sequence of the polypeptide (primary structure)
Type of gene mutation (substitution)
Substitution (point mutation)
1. New triplet code for different amino acid - polypeptide differ by 1 AA - different primary sequence - different place bonding - different protein = different tertiary shape and function (property of R group)
[in term of enzyme : no enzyme substrate conplex form = no fuction] *
- New triplet code for same amino acid (degenerate code) - same specific protein, no change in primary and tertiary structure and active site shape
- Stop codon - stop translation ,detachment of polypeptide chain from ribosome, stop the production of the polypeptide chain - chain shorten - function protein
Gene mutation (Frame shift + other)
Frameshift (base deletion)
Shift to left - all triplet after read differently - all following AA change - different primary sequence - different bonding - different protein (shape + function)
Insertion
Duplication
Inversion
Translocation of bases
Definition of Alleles
chromatid that produce different form/ type/ version of same genes
so homologous = same gene = not genetically identical
Definition of homologous chromosome
The pair of chromosome , maternal + paternal , same gene loci
Meiosis process
DNA replication - each chromosome duplicated + nuclear membrane break down
Homologous pair on chromosome pair up at the equator of the cell (independent segregation of homologous chromosome)
crossing over + pull to the opposite end of the cell by spindle fibre attach to centromere and separation of centromere
division 1
same process as mitosis (pmat)
division 2
4 haploid daughter cell produce
Mitosis vs meiosis
@1 division vs 2 division
X No need find each other vs need in equator
Genetically identical vs genetically different
X Gametes vs body cell
@2 cell (diploid) vs 4 cell (haploid)
No cross over vs Cross over -chiasmata formation
homologous independent vs Homologous chromosome associate in pairs
How meiosis brings out genetic variation
Crossing over (late prophase) - recombination
Chromatids of homologous exchange equivalent section of DNA
exam : exchange alleles between chromatids
Find other = synapsis
Bivalent = cross-over combined homologous chromosome , go round as 2
Chiasma = par of chromosome where cross over happen
Independent segregation of homologous chromosome (metaphase 1)
Different orientation of homologous pairs on equator
exam : different combinations of maternal and paternal chromosomes / alleles
Mating is random (which male and female pair)
Potential mutation
Random fertilisation (which games of female and male )
Combination calculation of chromosome
N = pairs
No of possible combination = 2^(n)
Combination of random fertilisation = 2^(n)x 2
The biological importance of meiosis
reducing the chromosome number when the cell divides by meiosis
Halve chromosome number to Be haploid
So the chromosome number will not be doubled in further fertilization (diploid as normal if double once)
What can increase the rate of gene mutation
mutagenic agents
appearance of chromosome before and during division 1
Before
chromosome is form of 2 sister chromatid
after DNA replication
sister chromatid is held by centromere
During
Chromosome are arrange in homologous pair
1 of each (pair) is put into daughter cell
to give haploid number (havled)
difference between division 1 and division 2
in 2
separation of sister chromatid by division of centromere
