Chapter 9 - Genetic Diversity, Mutation And Meiosis Flashcards
What are gametes
Haploid sex cells (sperm and eggs)
What is meant by haploid
A cell with a single set of unpaired chromosomes (one of each homologous pair)
What is meant by a diploid
A cell with 2 complete sets of chromosomes (homologous pairs, one from each parent)
What is meant by fertilisation
Fusion of 2 haploid gametes to form a zygote
What is the definition of meiosis
Cell division to form gametes
What is the definition of mitosis
Cell division for growth and repair
How many divisions are there for meiosis
2 divisions
Meiosis I and II
How many daughter cells are produced in Mitosis
2
How can daughter cells in mitosis be described
Genetically identical to each other and their parent cell
Why are daughter cells in meiosis genetically different from each other and their parent cell
- Crossing over
- Independent segregation
What is meant by gene mutation
Change to base sequence of DNA during DNA replication
What is meant by crossing over
The exchange of alleles between homologous chromosomes, resulting in a different combination of alleles
When does crossing over occur
In metaphase I
Draw a representation of crossing over
In folder
What is meant by independent segregation
Formation of random combinations of chromosomes in metaphase I, instead of homologous pairs
What is a substitution mutation
Swapping one base for another
What is meant by a nonsense substitution mutation
When swapping one base for another codes for a stop codon instead of an amino acids
What is meant by a silent substitution mutation
Mutation that has no effect on amino acids and therefore phenotype
What is meant by a deletion mutation
One base is removed causing a frameshift
What is meant by a frameshift
When all following triplets/codons change due to deletion of one base
How can gene mutations cause a non-functional protein
- Change in DNA triplet during replication
- Change in mRNA codon
- Change in anticodon
- Different amino acid
- Change in primary structure
- Different bonding (hydrogen and ionic)
- Change in tertiary structure of protein
- Change shape of active site/variable region
- Unable to form enzyme-substrate or antigen-antibody complex
Why may a gene mutation cause no change to primary structure
- DNA is degenerate
- Each amino acid is coded for by more than one codon
- Change to DNA base but not change amino acid coded for
- So no Change in primary structure
- No change to bonding
- No change to tertiary structure
- Can still form complex
What is an example of a chromosome mutation
Chromosome non-disjunction
What is meant by chromosomes non-disjunction
When chromosomes don’t separate properly in Meiosis I or II
What is the result of chromosomes non-disjunction
An uneven number of chromosomes in the gametes
What is an example of a disease caused by chromosome non-disjunction
Down’s syndrome
