Genetics, Human Reproduction, and Cell Cycle: Key Concepts for Biology

What is genetics?

The study of how traits are inherited from parents to offspring.

What is DNA?

A molecule made of nucleotides that stores genetic information.

What is a gene?

A segment of DNA that codes for a protein and determines traits.

What is a chromosome?

A tightly coiled structure of DNA containing many genes.

How many chromosomes do humans have?

46 total (23 pairs).

What are alleles?

Different versions of the same gene.

What is the difference between homozygous and heterozygous?

Homozygous = same alleles; heterozygous = different alleles.

What is the difference between genotype and phenotype?

Genotype = genetic makeup; phenotype = observable traits.

What is the law of segregation?

Each parent gives one allele for each gene.

What is the law of independent assortment?

Genes for different traits are inherited independently.

What is polygenic inheritance?

One trait controlled by many genes.

Why are most sex-linked traits X-linked?

The X chromosome carries more genes than the Y.

What is a pedigree?

A family tree used to track inheritance of traits.

What is an example of a genetic disorder?

Down syndrome (Trisomy 21), Turner syndrome (XO), Klinefelter (XXY).

What is the main function of the endocrine system?

Maintains homeostasis using hormones.

What is homeostasis in the endocrine system?

Regulation of body systems like mood, glucose, sleep, and energy.

What is a hormone?

Chemical messenger released into blood to target organs.

What is negative feedback?

A system that increases or decreases hormone levels to maintain balance.

What is positive feedback?

A process where the response increases the original signal.

What does the pancreas produce?

Insulin (regulates blood glucose).

What is ACTH?

Hormone that stimulates adrenal glands to release cortisol.

What is TSH?

Stimulates thyroid gland to release thyroid hormones.

What is FSH?

Stimulates egg and sperm development.

What is the difference between steroid and nonsteroid hormones?

Steroid = lipid-soluble; nonsteroid = protein-based.

What are the primary sex organs?

Testes (male) and ovaries (female) that produce gametes.

What are secondary sex organs?

Structures that support reproduction (uterus, ducts, glands).

What is the male reproductive function?

Produce, store, and deliver sperm.

What is the female reproductive function?

Produce eggs and support fertilization and pregnancy.

What is the sperm pathway?

Testes → epididymis → vas deferens → urethra → penis.

What is the egg pathway?

Ovary → fallopian tube → uterus → vagina.

Where does fertilization occur?

Fallopian tube.

What is the function of the seminal vesicle?

Produces fructose for sperm energy (60% of semen).

What is the function of the prostate gland?

Produces alkaline fluid to protect sperm in acidic vagina.

What is semen?

Sperm + gland secretions.

What is fertilization?

Sperm and egg unite to form a zygote.

What is a blastocyst?

Early embryo that implants in uterus.

What is the function of the placenta?

Transfers nutrients, oxygen, and waste between mother and fetus.

When does the fetal stage begin?

Week 8.

What are the key developmental stages?

Cleavage, morphogenesis, differentiation, growth.

What is the summary of trimesters?

1st = organs form; 2nd = movement; 3rd = growth and maturation.

What are the phases of the cell cycle?

G1 (growth), S (DNA replication), G2 (prep), M (mitosis), cytokinesis.

What is G0?

Resting phase where cells do not divide.

What is DNA replication?

Copying DNA before cell division.

What is transcription?

DNA → mRNA in nucleus.

What is translation?

mRNA → protein at ribosomes.

What is the difference between mitosis and meiosis?

Mitosis = body cells; Meiosis = gametes.

What is cancer?

Uncontrolled cell division due to mutations.

What causes cancer?

Mutations, radiation, chemicals, viruses, inherited genes.

What are the types of tumors?

Benign (non-spreading) vs malignant (spreads).

What are checkpoints in the cell cycle?

G1, G2, and M checkpoints prevent damaged DNA from dividing.