Cell Division real

What does DNA stand for?

Deoxyribonucleic acid. DNA is a polynucleotide (a molecule composed of a chain of nucleotides).

What does each nucleotide consist of?

A nitrogen base, sugar (deoxyribose), and a phosphate group.

What are the nitrogen bases, and who do they pair with?

Adenine bonds to thymine (2H bonds), guanine bonds to cytosine (3H bonds).

What is a molecule of DNA composed of?

Two polynucleotide chains held together by hydrogen bonds between the bases. Phosphodiester bonds hold each sugar to the phosphate group.

Who discovered the structure of DNA, and when?

Watson and Crick discovered the structure of DNA in 1953. They won the Nobel Prize with Maurice Wilkins in 1962.

How did Rosalind Franklin contribute to DNA research?

Her work in X-ray crystallography helped reveal DNA’s structure. The cross-shaped pattern in her images indicated a helical structure.

What are DNA’s regions known as?

Genes, which determine the phenotypical characteristics (traits) of an organism.

What is an alteration in the DNA sequence called?

A mutation.

What can cause mutations?

Chemical agents, UV radiation, natural causes (e.g., viruses), or errors during replication.

How does DNA replication occur?

DNA unzips, and each strand serves as a template for a new complementary strand. The two new DNA molecules are identical.

Why must DNA replicate?

So that during cell division, each new cell receives a complete set of genetic information.

Why do cells divide?

For reproduction (unicellular organisms), growth (from a fertilized egg to ~100 trillion cells), healing, and tissue repair.

What happens during mitosis?

A parent cell divides to produce two identical daughter cells.

What does mitosis refer to?

The division of the nuclear membrane.

What does cytokinesis refer to?

The separation of the cytoplasm and its contents into two equal parts.

What are the stages of the cell cycle?

Mitosis, cytokinesis, and interphase.

What happens during interphase?

G1: Cell growth; S: DNA is replicated; G2: Cell prepares for mitosis; DNA is visible in the nucleus as chromatin (uncoiled).

What happens during prophase?

Centrioles move to opposite poles, chromatin condenses into chromosomes, spindle fibers form, nuclear membrane dissolves.

What happens during metaphase?

Chromosomes align at the equator, spindle fibers attach to centromeres.

What happens during anaphase?

Sister chromatids separate and are pulled to opposite poles by spindle fibers.

What happens during telophase?

Two nuclear envelopes form, chromosomes uncoil into chromatin. In plants, a cell wall forms; in animals, cytokinesis follows.

What is the purpose of mitosis vs. meiosis?

Mitosis maintains genetic continuity, while meiosis produces gametes with half the parent’s chromosomes for sexual reproduction.

What is the difference between asexual and sexual reproduction?

Asexual reproduction does not involve meiosis; sexual reproduction does.

What is asexual reproduction?

A single parent produces genetically identical offspring (clones). E.g., binary fission (amoeba), budding (yeast), fragmentation (sea stars).

What is sexual reproduction?

Two parents combine genetic material to produce genetically unique offspring.

What happens in meiosis?

Two stages of division occur: Meiosis I: Homologous pairs separate (2 haploid cells form); Meiosis II: Sister chromatids separate (4 haploid cells form).

What happens in meiosis interphase?

Chromatin is uncondensed, nuclear membrane is intact.

What happens in early prophase I?

Chromatin condenses, nuclear membrane disappears.

What happens in mid-prophase I?

Chromosomes form tetrads (homologous pairs), centrioles duplicate.

What happens in late prophase I?

Crossing over occurs, exchanging genetic material.

What happens in metaphase I?

Homologous pairs line up at the equator, spindle fibers attach.

What happens in anaphase I?

Homologous pairs separate and move to opposite poles.

What happens in telophase I?

Homologous pairs are fully separated, nuclear membrane reforms.

What happens in meiosis II?

Similar to mitosis but with half as many chromosomes, resulting in four unique haploid cells.

What does diploid (2n) mean?

A cell has two sets of chromosomes.

What does haploid (n) mean?

A cell has one set of chromosomes.

What is spermatogenesis?

Sperm formation; four sperm are produced in the testes.

What is oogenesis?

Egg formation; one viable egg and three polar bodies are produced in the ovaries.

What are homologous chromosomes?

Chromosomes inherited from each parent.

What is a cleavage furrow?

The indentation in the cell membrane during cytokinesis.

What is independent assortment?

Chromosomes align randomly during metaphase, contributing to genetic variation.

What is crossing over?

The exchange of genetic material between homologous chromosomes.

What are gametes?

Sperm or egg cells formed at the end of meiosis.

What is nondisjunction?

Failure of chromosomes to separate properly during meiosis.

What is monosomy?

A missing chromosome.

What is trisomy?

An extra chromosome.

What is a genetic disorder?

A condition caused by abnormalities in DNA.

What is epigenetics?

The study of how behaviors and environment affect gene expression without changing DNA sequences.

What are GMOs?

Genetically modified organisms with inserted genes for desirable traits.

What is IVF?

In vitro fertilization, where an egg is fertilized outside the body.

How is prenatal genetic testing/screening conducted, how is the sample obtained?

A thin needle is inserted through the woman's abdomen into the amniotic sac to withdraw a sample of fluid from around the developing baby.

What can be tested for with PGT?

Down syndrome, chromosome changes, anemia, cystic fibrosis.

Can all the fetus's genetic traits be tested for with PGT?

No.

What is the basis of the CRISPR-Cas9 system? What in nature is it based on?

Based on the bacterial immune system, which remembers and destroys viruses that infected them before.

What can be done using CRISPR-Cas9?

Target and modify typos in human genomes to treat genetic diseases.

Can CRISPR be used in living animals?

Yes.

How is a DNA fingerprint created?

DNA is collected from cells/samples, then mixed with an enzyme to produce DNA fragments. The banding patterns are visible and can be compared.

What is a DNA fingerprint used for?

Identifying crime suspects, determining biological relationships, identifying missing persons, identifying genetic disorders, tracking endangered species.

Can you learn your specific genetic traits from a DNA fingerprint?

No.

What is cloning? From a scientific standpoint, what procedures would be used to clone a human?

Cloning is the process of creating an identical copy of an organism, including its DNA. In the context of cloning a human, it typically involves somatic cell nuclear transfer (SCNT). This procedure involves taking a somatic cell from the individual to be cloned and transferring its nucleus into an egg cell from which the nucleus has been removed.

Is cloning humans different procedurally from cloning animals? Are there any physiological risks to cloning humans? Are these risks different for animals? Why or why not?

The procedures for cloning animals and humans are largely the same, primarily relying on somatic cell nuclear transfer (SCNT). However, human cloning raises more ethical concerns. Physiological risks for humans are believed to be greater due to the complexity of human development and the potential for health issues.

What is imprinting? What role does imprinting play in cloning humans? Animals?

Imprinting refers to a genetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner. In cloning, imprinting is a major issue as clones may inherit the wrong pattern of gene expression.

How does cloning differ from sexual reproduction?

Cloning produces an organism that is genetically identical to the donor organism, whereas sexual reproduction combines genetic material from two different parents, creating genetically unique offspring.

What role do meiosis and mitosis play in maintaining the integrity of the genetic code during cloning? Sexual reproduction?

Meiosis ensures genetic diversity through the reduction of chromosome number, while mitosis is used during cloning to create an exact copy of the original genetic material.

Will Jason II be “identical” to Jason I? Why or why not?

Jason II, as a clone, would be genetically identical to Jason I in terms of DNA, but environmental factors and experiences can cause differences.

What is the difference between a somatic cell and a sex cell?

A somatic cell is any cell in the body that is not a reproductive cell, containing a full set of chromosomes, while a sex cell is a reproductive cell containing half the number of chromosomes.