Genetics and Cell Division

This set of flashcards covers essential vocabulary and key concepts in genetics and cell division, useful for exam preparation.

Hydrogen bonds

Weak bonds that hold two strands of DNA together between complementary bases.

Cytosine and Guanine

Complementary bases that pair together in DNA.

5′ and 3′ designations

Refers to the numbering of carbon atoms in deoxyribose in DNA.

DNA replication direction

Proceeds in the 5′ → 3′ direction.

Helicase

The enzyme that unwinds the DNA double helix during replication.

Okazaki fragments

Short DNA segments formed on the lagging strand during DNA replication.

DNA ligase

Enzyme that joins DNA fragments together during replication.

Eukaryotic DNA replication

Occurs in the nucleus.

PCR (Polymerase Chain Reaction)

Technique used to amplify specific DNA sequences.

Gel electrophoresis

Method to separate DNA fragments by size.

Anaphase

Stage of mitosis where sister chromatids separate.

S phase

Part of the cell cycle where DNA is replicated.

Somatic cells

Body cells that undergo mitosis.

46 chromosomes

Number of chromosomes in each daughter cell after mitosis.

M (spindle) checkpoint

Checkpoint ensuring proper attachment to spindle fibers.

Proto-oncogenes

Genes that stimulate normal cell division but may cause cancer when mutated.

Meiosis I

Stage of meiosis that separates homologous chromosomes.

Crossing over

Exchange of genetic material between homologous chromosomes during prophase I.

Meiosis

Process that produces four genetically unique haploid cells.

Aneuploid

Gamete with an extra or missing chromosome.

Turner syndrome

Condition resulting from monosomy X (XO).

Down syndrome

Condition caused by trisomy 21.

Law of Segregation

Principle stating that alleles for a trait separate during gamete formation.

Heterozygous individual

An individual with two different alleles for a trait.

Genotype ratio (Aa × Aa)

1:2:1.

Independent assortment

Process where homologous pairs align randomly during metaphase I.

True-breeding organisms

Organisms that are homozygous for a trait.

Dihybrid cross (AaBb × AaBb)

Generates a 9:3:3:1 phenotypic ratio.

Asexual reproduction

Reproduction involving one parent with no genetic variation.

Internal fertilization

Fertilization that occurs inside the body.

r-strategists

Organisms that produce many offspring with little parental care.

K-strategists

Organisms that produce few offspring and invest heavily in parental care.

Amniotic egg

Structure that allows development on land by preventing desiccation.

Oviparity

Reproduction method where organisms lay eggs.

Viviparity

Reproduction method involving live birth.

Acrosome

Structure in sperm that helps penetrate the egg covering.

Fertilization site in humans

Usually occurs in the fallopian tubes.

Oogenesis

Process that produces one egg and polar bodies.

Gastrulation

Process that forms the three germ layers.

Leading strand

S synthesized continuously toward the replication fork.

Lagging strand

Synthesized discontinuously away from the replication fork.

Primase

Enzyme that synthesizes RNA primers for DNA replication.

DNA polymerase

Enzyme that adds new nucleotides to the growing DNA strand and proofreads.

Genetic variation sources

1. Crossing over, 2. Independent assortment, 3. Random fertilization.

Mitosis

One division that produces two identical diploid cells for growth/repair.

Meiosis

Two divisions that produce four unique haploid cells for sexual reproduction.

Proto-oncogene

Normal gene that promotes cell division; mutation can lead to uncontrolled division (oncogene).

Tumor suppressor

Gene that slows/stops the cell cycle; mutations can lead to unchecked cell cycle.

Homologous chromosomes

Chromosomes that have the same genes, one from each parent, but are not identical.

Sister chromatids

Identical copies of a chromosome connected at the centromere.

Nondisjunction

Failure of chromosomes to separate during meiosis, leading to abnormal gamete chromosome numbers.

Law of Independent Assortment

Genes for different traits assort independently during metaphase I.

Sexual reproduction

Involves two parents, resulting in genetic variation, typically slower but increases adaptability.

Three germ layers

Ectoderm (skin, nervous system), Mesoderm (muscles, bones, circulatory system), Endoderm (digestive, respiratory linings).