Topic 8 Flashcards
(29 cards)
What are the two main sources of genetic variation?
Mutation and sexual reproduction.
What is a mutation?
A permanent change in the DNA sequence.
Name three types of gene mutation.
Substitution, insertion, deletion.
What can cause a frameshift mutation?
Insertion or deletion of a base.
What are mutagens?
Agents that increase mutation rate (e.g., UV light, radiation, carcinogens).
What is meiosis?
Cell division producing four genetically different haploid gametes.
How does crossing over during meiosis increase variation?
Exchanges DNA between non-sister chromatids, creating new allele combinations.
What is independent assortment?
Random distribution of maternal and paternal chromosomes during meiosis.
What is random fertilisation?
Any sperm can fertilise any egg, increasing genetic variation.
Describe the genetic code.
Triplet code, universal, degenerate, non-overlapping.
What is transcription?
The process of copying DNA into pre-mRNA.
What happens during RNA splicing?
Introns are removed and exons are joined.
What is translation?
The process of converting mRNA into a polypeptide.
What is a codon?
A sequence of three bases on mRNA.
What is an anticodon?
A complementary three-base sequence on tRNA.
Why do cells with the same DNA look different?
Because of differential gene expression.
What are transcription factors?
Proteins that regulate gene expression by binding to DNA.
What is DNA methylation?
Addition of a methyl group that silences genes.
What does histone acetylation do?
Activates gene expression by loosening chromatin.
What are stem cells?
Undifferentiated cells that can specialise.
What are totipotent cells?
Cells that can form all cell types including placental tissue.
What are pluripotent cells?
Cells that can form all body cell types.
What are multipotent cells?
Cells that can form a limited range of cells.
Give an example of a multipotent stem cell.
Adult stem cells in bone marrow.
