The cell cycle. Mitosis and meiosis. Laboratory work
Answers are for parents and teachers.
1
Draw a diagram of the phases of mitosis and give the numbers of chromosomes and chromatids in each phase (for a human cell).
G1: 46 chromosomes, 46 chromatids; after S, prophase and metaphase: 46 chromosomes, 92 chromatids; anaphase: 92 chromosomes; end of telophase: 46 chromosomes per cell.
2
Write three sentences on the biological importance of mitosis and of meiosis.
Mitosis – growth, regeneration, asexual reproduction and exact transfer of hereditary information. Meiosis – producing haploid gametes, keeping the chromosome number at fertilisation, and combinative variation.
3
A double-stranded DNA has 3600 nucleotides in total. What is its length in nm? (0.34 nm between neighbouring pairs; number only.)
612
4
The mRNA sequence is AUG GAA UUU GGU UAA. Write the DNA template strand and say how many amino acids are coded before the stop codon.
DNA: TAC CTT AAA CCA ATT; 4 amino acids.
5
Why does a bacterial cell reproduce by binary fission and not by mitosis?
It has no nucleus, spindle or several linear chromosomes: the circular DNA is copied and the cell splits in two between the attached copies.