Reproduction and cell division Flashcards
What is the locus of a gene?
The specific location of a gene on a chromosome
What is gene linkage?
The phenomenon seen where genes with similar loci are typically inherited together, since they’re unlikely to be separated during meiosis
What are two types of genetic linkage?
Autosomal linkage and sex linkage
What is autosomal linkage?
The inheritance of genes with similar loci on non-sex chromosomes together
What is sex linkage?
The inheritance of nearby genes together on the same sex chromosome. Expression of these genes is sex dependent
What is meiosis?
The process involved in the production of gametes which produces 4 genetically different haploid daughter cells
Name the stages in meiosis
Prohpase, metaphase, anaphase and telophase (there’s 2 of each)
What does the term haploid mean?
A cell which only has one set of unpaired chromosomes. This term is usually used to describe germ cells.
What does the term diploid mean?
A cell which only has a set of paired chromosomes. The term is usually used to describe somatic cells.
Describe prophase 1
The chromosomes condense, the nuclear envelope breaks down, the centrioles move to the poles of the cell and homologous pairs of chromosomes cross over
What are chiasmata?
The points where homologous chromosomes cross over in meiosis
Describe metaphase 1
The crossed over chromosomes align in the centre of the cell (at the metaphase plate)
Describe anaphase 1
The chromosomes are pulled apart by the spindle fibers
Describe telophase 1
The spindle fibers break down and nuclear envelopes begin to form around the separated sets of chromosomes
Describe prophase 2
The nuclear envelope breaks down, the chromosomes condense, the centrosomes move to opposite poles of the cell and the spindle fibers begin to form
Describe metaphase 2
The chromosomes align in the centre of the cell on the metaphase plate
Describe anaphase 2
The two sister chromatids making up each chromosome are pulled apart by the microtubules
Describe telophase 2
The nuclear envelope beings to reform, the chromosomes condense and the spindle fibers break down
How many daughter cells are formed in meiosis?
4
Which type of cell division produces diploid cells?
Mitosis
Which type of cell division produces haploid cells?
Meiosis
Describe 3 points in the process of meiosis where variation is produced
Prophase 1: chromosomes can cross over at different points.
Metaphase 1 and 2: chromosomes can line up either way around
What is the purpose of meiosis?
To produce gametes (sex cells)