bio 112 cell cycle + mitosis

What is chromatin?

Loose, uncondensed DNA wrapped around proteins.

What is a chromosome?

A condensed structure of DNA and proteins.

What are histones?

Proteins that DNA wraps around.

What are sister chromatids?

Two identical copies of a replicated chromosome.

What is a centromere?

The region holding sister chromatids together.

What are homologous chromosomes?

A matching pair of chromosomes, one from each parent.

What are alleles?

Different versions of the same gene.

What are autosomes?

Chromosomes that are not sex chromosomes.

How many chromosomes do humans have?

46 chromosomes (23 pairs).

What is a karyotype?

A summary of an organism's chromosome number and types.

What is the cell cycle?

The series of events in which a cell grows and divides.

What are the two main parts of the cell cycle?

Interphase and M phase.

What happens during G1 phase?

The cell grows and performs normal functions.

What happens during S phase?

DNA is replicated.

What happens during G2 phase?

The cell grows and prepares for division.

What happens during M phase?

Mitosis and cytokinesis occur.

What is mitosis?

Division of the nucleus into two daughter nuclei.

What is the function of mitosis?

Growth, tissue repair, and cell replacement.

What is the mitotic spindle?

Microtubules that help separate chromosomes.

What is a kinetochore?

A protein structure where spindle fibres attach.

What happens during prophase?

Chromosomes condense and the spindle begins forming.

What happens during prometaphase?

The nuclear envelope breaks down and spindle fibres attach.

What happens during metaphase?

Chromosomes line up in the middle of the cell.

What happens during anaphase?

Sister chromatids separate and move to opposite poles.

What happens during telophase?

Nuclear envelopes reform around chromosomes.

What is cytokinesis?

Division of the cytoplasm into two cells.

How does cytokinesis occur in animal cells?

An actin ring forms a cleavage furrow.

How does cytokinesis occur in plant cells?

A cell plate forms a new dividing wall.

What are the results of mitosis?

Two genetically identical daughter cells.

What is meiosis?

Cell division that reduces chromosome number by half.

What is the function of meiosis?

Produces haploid reproductive cells.

How many divisions occur during meiosis?

Two: meiosis I and meiosis II.

What is diploid (2n)?

A cell containing two sets of chromosomes.

What is haploid (n)?

A cell containing one set of chromosomes.

What happens during prophase I?

Homologous chromosomes pair and crossing over occurs.

What is synapsis?

Pairing of homologous chromosomes.

What are chiasmata?

Visible crossover points between non-sister chromatids.

What happens during metaphase I?

Homologous chromosome pairs line up randomly.

What happens during anaphase I?

Homologous chromosomes separate.

What happens during telophase I?

Two haploid cells form.

What happens during prophase II?

Spindle apparatus forms again.

What happens during metaphase II?

Chromosomes line up individually in the middle.

What happens during anaphase II?

Sister chromatids separate.

What happens during telophase II?

Four haploid cells are produced.

What separates during meiosis I?

Homologous chromosomes.

What separates during meiosis II?

Sister chromatids.

What are the results of meiosis?

Four genetically different haploid cells.

What are gametes?

Haploid reproductive cells, such as eggs and sperm.

What is fertilization?

Fusion of two haploid gametes.

What is a zygote?

The diploid cell formed after fertilization.

What is crossing over?

Exchange of DNA between non-sister chromatids.

When does crossing over occur?

Prophase I of meiosis.

What is independent assortment?

Random distribution of maternal and paternal chromosomes.

When does independent assortment occur?

Metaphase I of meiosis.

What are two major sources of genetic variation in meiosis?

Crossing over and independent assortment.

What is asexual reproduction?

Reproduction involving one parent without gamete fusion.

What are advantages of asexual reproduction?

Fast reproduction, one parent needed, and many offspring.

What are disadvantages of asexual reproduction?

Little genetic variation and greater vulnerability to changes.

Give an example of asexual reproduction.

Hydra reproduces through budding.

What is sexual reproduction?

Reproduction involving fusion of haploid gametes.

What are advantages of sexual reproduction?

Produces genetic diversity among offspring.

What are disadvantages of sexual reproduction?

Requires more time, energy, and usually finding a mate.

What is nondisjunction?

Failure of chromosomes to separate properly.

What is aneuploidy?

An abnormal number of particular chromosomes.

What is monosomy?

One chromosome is missing (2n − 1).

What is trisomy?

One extra chromosome is present (2n + 1).

What causes Down syndrome?

An extra copy of chromosome 21 (Trisomy 21).

What is a mutation?

A permanent change in DNA.

What is a point mutation?

A change affecting one or a few adjacent base pairs.

What is a silent mutation?

A DNA change that does not change the amino acid.

What is a missense mutation?

A mutation that changes an amino acid.

What is a nonsense mutation?

A mutation that creates an early stop codon.

What is a frameshift mutation?

An insertion or deletion that shifts the reading frame.

What causes sickle-cell anemia?

A missense mutation in the hemoglobin gene.

What is a deletion mutation?

Removal of a chromosome segment.

What is an inversion mutation?

A chromosome segment flips and reattaches.

What is a duplication mutation?

An extra copy of a chromosome segment.

What is a translocation mutation?

A chromosome segment attaches to a different chromosome.