Test 3 Biol 117

Cell division

The process by which a parent cell divides into two or more daughter cells.

DNA

The molecule that carries genetic information in all living organisms.

Histones

Proteins that DNA wraps around to form nucleosomes, aiding in chromatin structure.

Nucleosomes

DNA wrapped around histone proteins; basic unit of chromatin.

Genome

The complete set of genetic material in an organism.

Chromosomes

Structures made of DNA and proteins that contain genes.

Diploid

A cell with two sets of chromosomes (2n), one from each parent.

Haploid

A cell with one set of chromosomes (n).

Sex chromosomes

Chromosomes that determine the sex of an organism (X and Y in humans).

Cell cycle

Series of events that a cell goes through as it grows and divides.

G1

Cell growth phase before DNA replication.

S

DNA synthesis phase where the genome is replicated.

Sister chromatids

Identical copies of a chromosome connected by a centromere.

Centrioles

Organelles involved in organizing spindle fibers during cell division.

G2

Final phase before mitosis; cell prepares for division.

M

Mitosis; division of the nucleus.

Karyokinesis

Division of a cell's nucleus during mitosis or meiosis.

Cytokinesis

Division of the cytoplasm to form two daughter cells.

Prophase

Chromatin condenses into visible chromosomes; spindle forms.

Prometaphase

Nuclear envelope breaks down; spindle fibers attach to kinetochores.

Metaphase

Chromosomes align at the metaphase plate.

Anaphase

Sister chromatids are pulled apart to opposite poles.

Telophase

Nuclear envelopes reform; chromosomes decondense.

Phragmoplast

Plant cell structure that guides formation of the cell plate during cytokinesis.

Cyclins

Proteins that regulate progression through the cell cycle by activating CDKs.

Cyclin dependent kinases

Enzymes that, when activated by cyclins, regulate the cell cycle.

Negative regulator molecules

Proteins that stop or slow cell cycle progression when needed.

Chromosomal inversion

A chromosome segment breaks off, flips, and reattaches in reverse order.

Chromosomal translocation

A segment of one chromosome attaches to another nonhomologous chromosome.

Chromosomal non-disjunction

Failure of chromosomes to separate properly during meiosis or mitosis.

Karyotype

A visual profile of all chromosomes in a cell.

P0 (P generation)

Parental generation in a genetic cross.

F1

First filial generation; offspring of the P generation.

F2

Second filial generation; offspring of F1 individuals.

3:1 ratio

Typical phenotypic ratio of dominant to recessive traits in monohybrid crosses.

1:2:1 ratio

Typical genotypic ratio in a monohybrid cross (AA:Aa:aa).

Dominant trait

Trait expressed when at least one dominant allele is present.

Recessive trait

Trait expressed only when two recessive alleles are present.

Homozygous

Having two identical alleles for a trait.

Heterozygous

Having two different alleles for a trait.

Phenotype

Observable physical traits or characteristics.

Genotype

Genetic makeup of an organism.

Incomplete dominance

Heterozygote shows an intermediate phenotype (e.g., red + white = pink).

Codominance

Both alleles are expressed equally in the phenotype (e.g., AB blood type).

Sex-linked traits

Traits controlled by genes on sex chromosomes.

Genes with multiple alleles

More than two allele forms exist in a population for a gene.

Epistasis

One gene affects the expression of another gene.

Template strand

Original DNA strand used to synthesize a complementary strand.

Complementary or Daughter strand

Newly synthesized DNA strand that matches the template by base pairing.

Semiconservative replication

Each new DNA molecule has one old strand and one new strand.

Origin of replication

Specific DNA sequence where replication begins.

Leading strand

DNA strand synthesized continuously toward the replication fork.

Lagging strand

DNA strand synthesized discontinuously away from the replication fork.

Okazaki fragments

Short DNA fragments made on the lagging strand.

DNA polymerase

Enzyme that adds nucleotides to form new DNA strands.

Helicase

Enzyme that unwinds and separates DNA strands.

Topoisomerase

Enzyme that prevents DNA overwinding during replication.

Primer

Short RNA sequence that provides a starting point for DNA synthesis.

RNA primase

Enzyme that synthesizes RNA primers for DNA replication.

How many autosomes, sex chromosomes, and total chromosomes are in the human body at diploid and haploid?

Humans have 22 pairs of autosomes and 1 pair of sex chromosomes (XX or XY). Diploid cells have 46 total chromosomes (2n), while haploid gametes have 23 (n).

How is DNA organized and condensed?

DNA wraps around histone proteins to form nucleosomes, which coil to form chromatin, and further condense into chromosomes during division.

What happens in each stage of the cell cycle?

G1: growth, S: DNA replication, G2: preparation for mitosis, M: mitosis and cytokinesis.

What are the stages of interphase vs mitosis?

Interphase includes G1, S, and G2. Mitosis includes prophase, prometaphase, metaphase, anaphase, and telophase.

What occurs during each stage of mitosis?

Prophase: chromosomes condense; Prometaphase: nuclear envelope breaks; Metaphase: chromosomes align; Anaphase: chromatids separate; Telophase: nuclei reform.

What are the differences in cell division between plant and animal cells?

Animal cells form a cleavage furrow; plant cells form a cell plate guided by the phragmoplast.

What environmental and internal factors regulate the cell cycle?

Signals like growth factors, DNA damage, nutrient availability, and contact inhibition regulate progression.

What stages of the cell cycle are regulated?

Checkpoints exist in G1, G2, and M phases to ensure DNA integrity and proper division.

What is the function of cyclin dependent kinases (CDKs)?

CDKs, activated by cyclins, phosphorylate target proteins to drive the cell through different phases.

How does cancer occur in relation to the cell cycle?

Cancer arises when regulatory mechanisms fail, causing uncontrolled cell division and mutations.

What is the role of the p53 protein?

p53 detects DNA damage, halts the cycle for repair, or triggers apoptosis; mutations in p53 disable this control, promoting cancer.

What happens in each step of meiosis I and II?

Meiosis I separates homologous chromosomes (reduction division), and meiosis II separates sister chromatids.

When do random assortment, recombination, and diploid-to-haploid transition occur in meiosis?

Recombination: Prophase I; Random assortment: Metaphase I; Diploid to haploid switch: after Anaphase I.

What is the difference between pericentric and paracentric chromosomal inversions?

Pericentric includes the centromere; paracentric does not.

How can duplication or deletion of chromosomes affect an organism?

Caused by nondisjunctions, these lead to genetic imbalances like trisomy or monosomy (e.g., Down syndrome).

What did Mendel's experiments show?

Crossing true-breeding purple and white flowers produced all purple F1 and a 3:1 purple:white ratio in F2, demonstrating dominance.

How do you predict phenotypic and genotypic ratios for monohybrid crosses?

Use Punnett squares to show possible allele combinations and determine ratios (phenotypic 3:1, genotypic 1:2:1).

How do you interpret a Punnett square?

Each box represents a possible offspring genotype; compare combinations to find ratios of traits.

What enzymes are required for DNA replication and what do they do?

Helicase unwinds DNA; Primase adds RNA primers; DNA polymerase adds nucleotides; Topoisomerase prevents overwinding; Ligase joins fragments.

What is the directionality and anti-parallel nature of DNA strands?

DNA strands run in opposite directions: one 5'→3' and the other 3'→5'; replication occurs 5'→3'.

Which DNA nucleotides base pair together?

A pairs with T (two hydrogen bonds), and G pairs with C (three hydrogen bonds).