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Lesson chromsomes and the cell cycle
1. Title: Cell cycle (again)
Objectives: Today we are learning to answer the
following questions:
• What are the various stages of the cell cycle
• Explain the meaning of the term homologous pair of
chromosomes
• What is meant by sister chromatids
• Describe with the aid of diagrams the main stages
of mitosis.
2. What is DNA ?
What is the point of genetic material?
What is a gene?
DNA (Deoxyribonucleic acid)
Provides a code that codes for
proteins, controls activity of the cell
A sequence of DNA that codes
for one protein
3. • DNA is held on chromosomes
• Made of DNA & histone proteins = Chromatin
•Humans have 46 chromosomes arranged in 23
homologous pairs
•Homologous pair – 2 chromosomes that contain the
same genes; humans = 1 maternal, 1 paternal
• The number of chromosomes varies between
species
4.
5. Sister Chromatids = 2 identical
chromatids connected by a
centromere.
Original and replicated
strand joined at the
centromere
The
Chromosomes
replicate during
interphase
Homologous
chromosomes
6.
7. Put the stages of mitosis in order
Then answer the questions:
1.When a cell divides by mitosis how many cells are
made?
2.Comment on the similarities and differences of
daughter cells to each other and the parent cell.
3.Species such as yeast reproduce by cell division,
Describe the genetic make up of yeast colonies.
8. The process of creating 2 genetically
identical daughter cells from 1 parent
cell = MITOSIS
Division of somatic (body) cells is by mitosis –
remember
• Mitosis make two cells
• Mitosis makes toes
9. What is happening at each stage of the cell
cycle?
How many chromosomes are in the nucleus
during each stage?
12. Why do cells need to divide?
What are the processes by which cells divide?
1. Growth (mitosis)
2. Repair damage (mitosis)
3. Replace worn out cells (mitosis)
4. Gamete creation (meiosis)
13. Chromosomes visible
with light microscope
Chromosomes visible
with light microscope
Chromosomes visible
with light microscope
Chromosomes visible
with light microscope
Chromosomes are not
visible with light microscope
Prophase
Metaphase
Anaphase
Telophase
Editor's Notes
9-905
The humangenome is the genome of Homo sapiens, which is stored on 23 chromosome pairs. Twenty-two of these are autosomal chromosome pairs, while the remaining pair is sex-determining. The haploid human genome occupies a total of just over 3 billion DNAbase pairs. The Human Genome Project (HGP) produced a reference sequence of the euchromatic human genome, which is used worldwide in biomedical sciences.The haploid human genome contains ca. 23,000 protein-coding genes, far fewer than had been expected before its sequencing.[1][2] In fact, only about 1.5% of the genome codes for proteins, while the rest consists of non-coding RNA genes, regulatory sequences, introns, and (controversially named) "junk" DNA.[3
