Chromosomes and Mitosis

This set of flashcards covers essential concepts related to chromosomes, mitosis, and cell cycle regulation, aiding in reviewing and reinforcing key ideas from the lecture.

What is a chromosome composed of?

DNA-binding proteins and DNA

How many different types of chromosomes do humans have?

23

What does haploid number (n) represent?

the number of different types of chromosomes

What is ploidy?

the number of each type of chromosome

What is a haploid cell?

A cell that has one of each type of chromosome

What is a diploid cell?

A cell that has two of each type of chromosome

Define homologous chromosomes.

different versions of the same chromosome type

What are sister chromatids?

The identical copies formed by the replication of a chromosome

What phase of the cell cycle does mitosis occur?

M phase

Why must chromosome replication occur before mitosis?

to ensure each daughter cell receives a complete set of chromosomes

What are transcription factors (TF)?

proteins that regulate the expression of genes

What can TFs recruit?

RNA polymerase and proteins that modify histones

What is feedback inhibition?

a regulatory mechanism where the end product of a biosynthetic pathway inhibits an earlier step in the pathway

What is the role of kinetochores in cell division?

protein structures on chromatids that attach to microtubules to help pull chromosomes apart during mitosis

What happens during prophase of mitosis?

chromosomes condense and become visible

What is the metaphase of mitosis characterized by?

chromosomes line up in the middle of the cell

What happens during anaphase?

sister chromatids are pulled apart to opposite sides of the cell

Describe telophase.

nuclei reform around each set of separated chromosomes, and the chromosomes decondense.

What is cytokinesis?

the process of dividing the cytoplasm and cell membrane to form two separate daughter cells.

What are the two major phases of the cell cycle?

interphase and mitotic phase

What occurs during DNA replication (S phase)?

each chromosome is replicated to produce sister chromatids.

What are microtubules' role during mitosis?

help move chromosomes by forming the mitotic spindle and pulling chromatids apart.

What is a negative feedback loop in biology?

a process where the output of a system reduces its activity

Explain the significance of 'G1' and 'G2' phases.

G1 and G2 are growth phases that occur before and after the S phase of DNA synthesis.

What is the function of cyclins in the cell cycle?

proteins that regulate the progression of the cell cycle by activating cyclin-dependent kinases (CDKs).

Why is the cell cycle considered 'deeply conserved' in eukaryotes?

The mechanisms controlling the cell cycle are largely similar across different eukaryotic organisms.

What is the structure of Eukaryotic genomes?

Long, linear chromosomes

What is phosphorylation?

Changes physical structure —> alters protein function

What are kinases?

Proteins that phosphorylate other proteins

What does alternative splicing do?

Generates diverse proteins

Does tryptophan binding to the repressor change its shape?

Yes, its a conformational change

What does transcription of the Trp operon followed by translation of the mRNA produce?

Enzymes that synthesize tryptophan

What can repress transcription?

Trp repressor

What is tryptophan essential for?

Cell growth

Is there any transcription of the Trp operon when tryptophan is present?

No because it regulates its own feedback inhibition

What kind of feedback is tryptophan on a example of?

Negative

What happens if you repress one gene in an operon?

You inhibit the entire genome

What genetic information is present in two homologous chromosomes?

Same genes but different alleles

What genetic information is present in two non homologous chromosomes?

Different genes

What genetic information is present in two sister chromatids?

Identical copies of single chromosome

What genetic information is present in two non-sister chromatids?

Chromatids from homologous chromosomes - similar genes but different alleles

Why must chromosome replication occur before mitosis?

To ensure each daughter cells has only half of necessary DNA

What macromolecules are present in eukaryotic cells?

Histones, DNA, TFs and nucleic acids

What does the term 'tetraploid' mean?

a cell that has four sets of chromosomes.

What is a replicated chromosome?

A chromosome with two identical DNA molecules

What is a gene?

Segment of DNA that codes for a protein or RNA product

What is a chromosme?

Complex of DNA-binding proteins and DNA

How many chromosomes do humans have?

23

How many telomeres does each chromatid and chromosome have?

Chromatid —> 2

Chromosome —> 4

How do you discover amount of chromatids of sperm cells from an image of karyotypes?

Divide by 2 because each sperm cell inherits half of homologous chromosome at each chromosome type

How do you find max allele number?

It is equal to amount of diff versions of each chromosome

What must cells do in order to make a copy of themselves?

1. Duplicate their DNA

2. Split evenly (every cell must get a copy of every piece of DNA)

3. Physically spilt the cell

What is the M phase?

Mitosis: physical splitting of DNA and cells

What is interphase?

Between M phases

What is the name for DNA replication in Interphase?

S phase

Why are the stages of replication of DNA separated from the division of DNA into different cells?

To check for errors

What are G1 and G2 phases?

Growth phases before and after S phase

What is the G0 phase?

When cells are not actively dividing (outside of cell)

What is the order of the cell cycle?

G1 —> S phase —> G2 —> M phase

Problem: chromosomes will get tangled in cell division

Wrap all DNA up to make them compact

Problem: how will we move chromosomes?

Use motor proteins to move chromosomes along microtubules

Problem: how will we attach microtubules?

Kinetochores (one per sister chromatid)

Problem: microtubules outside the nucleus, DNA inside

Dissolve the nucleus

What is an allele?

Type of gene that has portions of its sequence that are different from other alleles

Why does DNA wrap around histones?

Electrical interaction: histone + and DNA -

What is mitosis?

Distribution of each chromosome of parent cells to daughter cells

Why do many anti-cancer drugs target mitosis?

Because without mitosis cells can’t divide

When replicated and condensed chromosomes move to the center of the cell, how are sister chromatids pulled apart?

Microtubules attach to sister chromatids then kinesins pull microtubules and chromosomes into position to pull sister chromatids apart

What are somatic cells?

Rest of cells in body: mitosis and cell division

What are germ cells?

Reproductive cells: meiosis

What stage of mitosis?

G2: gap to make sure DNA synthesis is complete

What stage of mitosis?

Prophase

What stage of mitosis?

Prometaphase

What stage of mitosis?

Metaphase

What stage of mitosis?

Anaphase

What stage of mitosis?

Telophase