Principles of Genetics

BIOL 309

What type of cells undergo Mitosis?

Somatic Cells (body cells like skin, blood, or bone).

What type of cells undergo Meiosis?

Germline cells (to produce gametes like sperm and eggs).

How many daughter cells are produced in Mitosis?

Two genetically identical daughter cells.

How many daughter cells are produced in Meiosis?

Four genetically unique daughter cells.

How many rounds of division occur in Meiosis?

Two rounds of division.

What does “clonal replication” mean in the context of Mitosis?

It means the offspring cells are exact genetic copies of the parent cell.

What is a key event in Meiosis that doesn’t happen in Mitosis?

The pairing of homologous chromosomes (and their subsequent separation).

In which process are the resulting cells not identical?

Meiosis (due to genetic recombination and independent assortment).

Somatic Cell

Any cell of a living organism other than the reproductive cells.

Gamete

A mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction.

Mitosis

Making two

Meiosis

the process that the cells eventually made me

Describe the main bacterial chromosome.

It is one large, circular, double-stranded DNA molecule.

Where is bacterial DNA located?

It is not contained in a nucleus (it floats freely in the cytoplasm).

What are plasmids in bacteria?

Additional small pieces of DNA separate from the main chromosome.

How do bacterial chromosomes replicate?

A process called fission

Does meiosis occur in bacteria?

No, bacteria do not undergo meiosis

What eukaryotic process is bacterial fission most similar to?

It is a mitosis-like process.

What happens to the chromosome before the mother cell divides?

The chromosome is duplicated.

What is the genetic outcome for the two daughter cells after fission?

Each daughter cell receives one copy of the chromosome.

Define a Clone in a bacterial context

A population of genetically identical cells.

What is a Colony?

A visible mass of bacterial cells.

Are the daughter cells produced in fission different or identical?

They are genetically identical (clones)

In bacterial fission, what does the mother cell produce?

Two daughter cells

Where are chromosomes located in Eukaryotes?

They are contained within a nucleus.

How do Eukaryotic cells compare in size to bacteria?

They are usually at least 10X bigger than bacteria.

What is the purpose of Meiosis in eukaryotes?

Sexual reproduction; it reduces the chromosome number before gametes fuse.

What is the purpose of Mitosis in eukaryotes?

replication of cells.

Which two eukaryotic organelles contain their own chromosomes?

Mitochondria and Chloroplasts

T/F: Mitochondria uses mitosis to replicate.

False, they use fission

What are the four main stages of the cell cycle?

G1 (Growth), S (DNA synthesis), G2 (preparation for Mitosis), and M (Mitosis).

During which specific phase of the cell cycle is DNA synthesized?

The S phase.

At what stage of the cell cycle are karyotypes usually prepared?

After chromosomes have condensed during prophase.

Does the length of the cell cycle stay the same for all cells?

No, it depends on the cell type and the organism.

Where is DNA kept in a Eukaryote vs. a Bacterium?

Eukaryotic DNA is in a nucleus; Bacterial DNA is not contained in a nucleus.

What happens to chromosomes during Prophase?

They condense into rod-shaped bodies.

Describe the chromosome position in Metaphase.

Chromosomes migrate to the equatorial plane (the center) of the cell

What is disjunction and when does it occur?

The splitting of the centromere and separation of sister chromatids; occurs during Anaphase.

What two events mark the end of mitosis during Telophase?

• Chromosomes decondense.

• A nuclear membrane reforms around them.

Sister Chromatids

The two identical halves of a duplicated chromosome held together by a centromere.

Cytokinesis

The process following mitosis that physically divides the cytoplasm into two daughter cells.

What is the difference between 2N and 1N

2N is the diploid count, 1N is the haploid count (found in Gametes).

What is crossing over (Recombination)?

Two chromatids are exchanged, sharing genes on the same chromosome. (prophase I)

Independent Assortment

The 50-50 chance a gamete gets a paternal or maternal chromosome, resulting in ~8 million possible combinations.

How many combinations can occur from Random Fertilization?

A zygote represents 1 of 64 trillion possible diploid combinations.

Meiosis I

Maternal and paternal homologous chromosomes separate

Meiosis II

Sister chromatids separate.

What did Mendel prove.

Mendel used his experiments with sweet peas to prove how traits are inherited through generations.

What is a True Breeding variety?

A strain that, through self-pollination over many generations, has become homozygous at all genes.

In a Monohybrid Cross, what is the phenotypic ratio of the F2 generation?

3:1 (75% dominant, 25% recessive)

Genotype

Genetic makeup (e.g., DD, Dd, dd).

Phenotype

Observable physical appearance

What are the three ways Meiosis "shuffles the deck" for genetic variation?

• Independent Assortment

• Crossing Over

• Random Fertilization

How many rounds of division occur in Meiosis?

Two rounds of division.

What unique process happens to chromosomes in Meiosis?

Replication and pairing of homologous chromosomes.

In which cell types do Mitosis and Meiosis occur, respectively?

Somatic cells (Mitosis) and germline cells (Meiosis).