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Chromosomes

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Homework

Cell Cycle Review

• What are the three big parts of the cell cycle, in order?

• What happens in each one?

Interphase• Put this diagram in your notebooks (you

don’t need the cell pictures or texts)



Most of the cell’slife is spent in interphase.

Interphase then has some sub-phases, like how “adulthood” is broken down into “young adult,” “mature adult,” “middle-age,” etc.

Interphase



G1 (Gap 1) - Cell growth

Interphase




S (Synthesis) - Copy DNA to prepare for later reproduction

Interphase





G2 (Gap 2) - Lots of protein synthesis, and ensuring “good health”

Interphase





G2 (Gap 2) - Lots of protein synthesis, and ensuring “good health”

G0 (Gap zero) - Resting

Interphase



How is interphase analogous to a human life cycle?

Cell Cycle

• The cell reproduction that we are talking about at the moment is called:

• Asexual reproduction. Just by looking at the term, what do you think it probably means?

Cell Cycle

• The cell reproduction that we are talking about at the moment is called:

• Asexual reproduction: Reproduction that does not involve two cells fusing together.• Mitosis is asexual reproduction. Why?

Cell Cycle• Asexual reproduction: Reproduction that does not

involve fertilization (two cells combining their DNA). Produces offspring genetically identical to the parent.• Mitosis• Other examples include:

• Binary fission• Budding• Fragmentation• Parthenogenesis• Spore formation

Cell Cycle

• Sexual reproduction: Reproduction in which two cells contribute their chromosomes to create a new cell with a unique genome.• Example: Fertilization of sperm and egg

Chromosomes

• Chromosome: A very long, supercoiled strand of DNA.• Different organisms have

different numbers of chromosomes in every cell.



Chromosomes• Gene = Region of a

chromosome that codes for one protein.

Chromosomes

• Different chromosomes carry different genes.• For instance, in humans,

everyone has a gene called INSR at the same place on chromosome #19. INSR is a gene that codes for a receptor protein that detects insulin.



Chromosomes

• Everyone has two chromosome #19s in each of your cells, so you have two INSR genes.

• And two chromosome #1s, two #2s, etc.• Demo





Chromosomes

• Homologous chromosomes: Two versions of the same chromosome. They code for all the same proteins, but they may each make those proteins with slightly different sequences and shapes.



Chromosomes• Because we have homolgous

chromosomes, meaning two copies of every chromosome, our cells are called diploid.• Latin/Greek Word Roots: Di

• Diploid: A cell with 2 copies of each chromosome.



Chromosomes

• Diploid:

• Haploid: A cell with only 1 copy of each chromosome.• Sperm and eggs only.





Chromosomes

• So, a normal diploid human cell has 46 chromosomes: 23 kinds of chromosome, 2 versions of each.

• After a human cell undergoes mitosis, how many chromosomes do you think each of the two offspring cells will have?



Chromosomes

• Each cell will have 46! They are identical copies of the parent cell, after all.





Chromosomes

• To get from one diploid cell with that many chromosomes to two offspring also with that many chromosomes, DNA replication will happen during interphase.

• Find three people, and explain to them how DNA replication works.

Chromosomes• DNA Replication

• A strand of DNA “unwinds” and “unzips”• Extra DNA nucleotides are attached to their base

pair partners• This creates two DNA molecules that are entirely

identical to each other

• Keep this in mind for the future.

Download - Chromosomes

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