cells and chromosomes Flashcards
Define a chromosome
Made up of DNA and a proteins known as histone. DNA comprises of a double helix running the length of the chromosome with sections along the length called genes.
Define a chromatid
one of two identical copies of a chromosome joined at the centromere prior to cell division
what is the difference between a chromosome and a chromatid
a chromatid is one half of a duplicated chromosome, a chromosome is what replicates to form a set of chromatids
what is a centromere
a specialised region of a chromosome where two chromatids join and to which spindle fibres attach at cell division
when can chromosomes become visible
when the chromatin condenses and coils prior to cell division
what is a sister chromatid and how is it formed
Occurs after the DNA has replicated and made an exact copy of itself. The two copies of the chromosome are sister chromatids and lie parallel along the length joined by a centromere
what is meant by the term haploid cell
A cell which contains one complete set of chromosomes, in humans a haploid cell would contain 23 chromosomes
where would a haploid cell be found in humans
male and female gametes
what is meant by the term homologous pair
chromosomes in a homologous pair are identical in size and shape, carrying the same genetic loci, with genes for the same characteristics. One chromosome of each pair comes from each of the parents.
what is meant by the term diploid cell
A cell that has two complete sets of chromosomes, in humans there is a total of 46 chromosomes in 23 homologous pairs- one set of chromosomes is from the female and the other is from the male
what is the ploidy level
the number of complete sets of chromosomes in a cell
