Unit 4 Genetic Diversity and Adaptation Flashcards
What is the definition of a mutation?
A change to the quantity or the base sequence of the DNA of an organism
What is a gene mutation?
A change to a sequence of nucleotides or bases within DNA
Two methods of a gene mutation?
Substitution or deletion
What is the general effects of substitution gene mutation? General Effects
A replacement of a nucleotide in the base / nucleotide sequence - change the whole sequence - the triplets are affected - the polypeptide the codes - Different amino acid - function of the protein is not met.
Give an example of how a substitution gene mutation could really affect a protein in the human body?
A replacemet of a nucleotide in the nucleotide sequence - whole sequence is changed - the polypeptide is changed - the protein forms an enzyme- the tertiary structure of this enzyme changed- the active site of the enzyme - can’t fit the substrate.
No ES Complexes can be formed
Explain gene mutation deletion in general terms?
The loss of a nucleotide - hcanges the whole nucleotide sequence - polypeptide is different - cannot function correctly
What are chromosome mutations?
Changes in the structure or the number of whole chromosomes.
What is polyploidy and where does it usually occur?
(Changes in the whole sets of chromosomes)
When organisms have 3 or more sets of chromosomes than the usual 2 chromosomes
Usually occurs in plants
What can changes in the individual chromosomes lead to?
Thus individual pairs of chromsomes fail to separate during meiosis - leads to non-disjunction
Non-disjunction means?
Non-disjunction means that an organism has a gamete containing one fewer or more of a chromosome.
This means during fertilisation the fusion of a normal gamete and that gamete - resultant offspring have more of fewer number of chromosomes in their body cells
What is an example of non-disjunction in the human body?
Down’s Syndrome which means that the human body has an additional chromsome
What is mitosis?
Production fo 2 identical daughter cells which contain the sam enumber of chromosmes as the parent cell
What is meiosis?
Cell Division that leads to the production of 4 non-identical haploid cells which have different number of chromosmes than the parent cell.
Why is meiosis important?
Meiosis means that there is production of gametes which then fuse together during fertilisation.
What is different about the mitosis and meiosis cycles within a fern plant?
Mitosis produces the gametes and meiosis produces the spores
Describe the properties of the diploid cell of an organism?
Diploid cell contains the 2 complete sets of chromosomes - 2 individual sets are provided by the parents
Describe what happens to the diploid cell during the meiosis cycle?
The homologous pairs start to separate so that only one chromosome from each pair enters the daughter cell.
What restores the haploid number back to the diploid number
When the process of fertilization occurs the haploid cells from either gametes of the parents fuse so that it forms the diplolid cells.
What is the human body number for the haploid number?
23
What are the 2 general steps within the process of meiosis?
1) The first divison in which the homologous chromosomes pair up and then are separated astheir chromatids cross over which leads to a process called crossing over.
2) The second division in which the chromatids are separated which produces 4 non-identical daughter cells
What is the importance of crossing over in any organism?
Crossing over allows th random genetic variation within an organism to be established.
What are the 2 ways in which genetic variation within an organism can be achieved?
1) Independent segregation of homologous chromosomes
2) New combinations of maternal and paternal alleles via crossing over
What is a gene?
A length of DNA that carries the code to make a polypeptide and therefore a protein
What is a locus?
The position of a gene on a chromosome or strand of DNA
What is an allele ?
One or more different variations of a gene
What is a homologous chromosome?
A pair of chromosomes that comes from the maternal and paternal parents which have the same gene loci point
Describe in greater detail the gentic recombination of the genes crossing over?
1) The chromatids of each pair become twisted around each other
2) Whilst twisting - tensions are created and portions of the chromatids break off
3) these broken pieces of the chromatids rejoin with the homologous chromosome pairs
4) Usually there are equivalent portions of the chromosomes that are exchanged between the homologous chromosome
5) So there are new genetic combinations are formed from the maternal and paternal parents which leads to an increase in the number of alleles
What does an increase in the numbe rof alleles within a population lead to?
An increase number of alleles increases the genetic variation within the gene pool - more easuily able to adapt to the change in environment so survival and reproductive adavantage
