study guide bio 4

chromosome

a thread-like structure in a cell that carries genetic information (DNA).

gene

a small section of DNA that contains instructions for a specific trait (like eye color or blood type).

alleles

are different versions of the same gene.

homozygous

means having two identical alleles for a gene.
Example: AA or aa.

heterozygous

means having two different alleles for the same gene.
Example: Aa (one dominant allele and one recessive allele).

genotype

the genetic makeup of an organism, specifically the alleles it has for a trait.
Example: AA, Aa, or aa.

phenotype

physical appearance or observable trait of an organism.
Example: brown eyes, tall height, curly hair.

Compare & Contrast

1. Eye color gene is located on a chromosome.

2. This gene has two alleles: B (brown) and b (blue).

3. A person’s genotype might be Bb.

4. Because B is dominant, the phenotype is brown eyes.

5. Bb is heterozygous, while BB or bb would be homozygous.Eye color gene is located on a chromosome.

Mendel’s laws of segregation and independent assortment

• What it says:
  Genes for different traits are inherited independently of each other, as long as they are on different chromosomes.

• Key idea: The inheritance of one trait does not affect the inheritance of another trait.

• What it says:
  Each organism has two alleles for a trait, but these alleles separate (segregate) during the formation of gametes, so each gamete gets only one allele.

• Key idea: Alleles are separated randomly.

Incomplete Dominance

Neither allele is completely dominant over the other. The heterozygous phenotype is a blend of the two alleles.

Codominance

Both alleles are fully expressed in the heterozygous condition. Neither is dominant or recessive.

polygenic inheritance

• A trait that is controlled by more than one gene. Each gene may have two or more alleles, and their effects add up to produce the trait.

• Key feature:
  Traits show a range of variation, not just a few distinct forms.
  

Examples:

1. Human height – controlled by many genes, so people can be very short, tall, or anywhere in between.

why most sex-linked traits are actually X-linked rather than Y-linked?

Because the X chromosome is bigger and has more genes, while the Y chromosome is small and has few genes.

how to read a pedigree

Symbol	Meaning
⬜ Square	Male
⬛ Filled square	Affected male
⬜○ Circle	Female
● Filled circle	Affected female
◯ Half-filled	Carrier female (for X-linked recessive)
— Horizontal line connecting male & female	Mating / marriage
	Vertical line

why genes may influence general patterns of behavior, but do not cause specific, individual behaviors? 

• Genes → tendencies or traits

• Environment + experience → specific behaviors

• Result: Genes influence general patterns, but not exact actions.

different types of chromosomal disorders

Disorder	Cause	Example / Features
Down syndrome (Trisomy 21)	Extra copy of chromosome 21	Intellectual disability, distinct facial features
Turner syndrome (Monosomy X)	Missing one X chromosome in females	Short stature, infertile, webbed neck
Klinefelter syndrome (XXY)	Extra X chromosome in males	Tall, infertile, some female characteristics
Trisomy 18 (Edwards syndrome)	Extra chromosome 18	Severe intellectual disability, heart defects
Trisomy 13 (Patau syndrome)	Extra chromosome 13	Severe physical abnormalities, often fatal

functions of the endocrine system

• Regulates growth and development

  • Hormones like growth hormone (GH) control how the body grows and develops.

• Controls metabolism

  • Hormones like thyroxine regulate how the body uses energy.

• Maintains homeostasis

  • Keeps internal conditions stable (like blood sugar, water balance, and blood pressure).

  • Example: Insulin lowers blood sugar; glucagon raises it.

• Controls reproduction

  • Hormones like estrogen, progesterone, and testosterone regulate sexual development, menstrual cycles, and sperm production.

• Responds to stress

  • Hormones like adrenaline and cortisol prepare the body for “fight or flight.”

• Regulates mood and behavior

  • Hormones can affect emotions and mental states.

  • Example: Serotonin and melatonin influence sleep and mood.

Endocrine Glands

Glands that release hormones directly into the blood.

Hormones

Chemical messengers produced by glands that regulate body functions.

Feedback Mechanism

A system where hormone levels control their own production.

Target Cells / Organs

Cells or organs that respond to a specific hormone.

steroidal and nonsteroidal hormones based upon their method of action on their target cells

• Steroidal: pass through the membrane, change gene expression → slow & lasting

• Nonsteroidal: bind to membrane receptors, use second messengers → fast & temporary

Define negative feedback and positive feedback of hormones to maintain homeostasis.

Negative Feedback

• Definition: A process where hormone secretion is reduced or stopped once the desired effect is achieved, to maintain balance.

Positive Feedback

• Definition: A process where hormone secretion is increased to amplify a response until a specific event occurs.

• Negative feedback: “Stop when done” → keeps balance

• Positive feedback: “Keep going” → drives a process to completion

Hypothalamus

• Releasing/inhibiting hormones → Anterior pituitary → Control pituitary hormone release

• ADH → Kidneys → Water reabsorption, maintain blood pressure

• Oxytocin → Uterus, mammary glands → Uterine contractions, milk ejection

Anterior Pituitary

• GH → Bones, muscles → Stimulates growth

• TSH → Thyroid → Stimulates thyroid hormone release

• ACTH → Adrenal cortex → Cortisol release

• FSH → Ovaries/Testes → Egg/sperm production

• LH → Ovaries/Testes → Ovulation, testosterone production

• Prolactin → Mammary glands → Milk production

Posterior Pituitary

• ADH → Kidneys → Water reabsorption

• Oxytocin → Uterus, mammary glands → Contractions, milk ejection

Thyroid Gland

• T3/T4 → Most cells → Regulate metabolism, growth, development

• Calcitonin → Bones → Lowers blood calcium

Parathyroid Glands

PTH → Bones, kidneys, intestines → Raises blood calcium

Adrenal Cortex

• Cortisol → Most tissues → Metabolism, stress response, anti-inflammatory

• Aldosterone → Kidneys → Sodium/water retention, potassium excretion

Adrenal Medulla

Epinephrine/Norepinephrine → Heart, blood vessels, muscles → “Fight or flight”: ↑heart rate, ↑blood pressure, ↑glucose

Pancreas

• Insulin → Liver, muscle, fat → Lowers blood glucose

• Glucagon → Liver → Raises blood glucose

Ovaries

• Estrogen → Reproductive organs, bones → Female sexual characteristics, menstrual cycle

• Progesterone → Uterus → Prepares for pregnancy

Testes

Testosterone → Reproductive organs, muscles, bones → Male sexual characteristics, sperm production

Pineal Gland

Melatonin → Brain/body → Regulates sleep-wake cycle

hormones necessary for male growth and development

Testosterone, Growth Hormone (GH), Insulin-like Growth Factor 1 (IGF-1), Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH)

female growth and
development

Estrogen, Progesterone, Growth Hormone (GH), Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH)

difference between primary and secondary endocrine organs

1. Primary Endocrine Organs

• Definition: Organs whose main function is hormone production.

• Examples:

  • Pituitary gland – controls other glands, produces multiple hormones

  • Thyroid gland – produces T3, T4, calcitonin

  • Parathyroid glands – produce parathyroid hormone

  • Adrenal glands – produce cortisol, aldosterone, adrenaline

  • Pineal gland – produces melatonin

2. Secondary Endocrine Organs

• Definition: Organs that have other primary functions, but also produce hormones.

• Examples:

  • Heart – produces atrial natriuretic peptide (ANP)

  • Kidneys – produce erythropoietin (EPO)

  • Pancreas – endocrine (insulin, glucagon) + exocrine (digestive enzymes)

  • Ovaries/Testes – reproductive organs + sex hormones

  • Liver – produces IGF-1 in response to GH

environmental chemical messengers that function in similar ways to hormones

Chemicals from the environment that mimic or block natural hormones and affect the body’s growth, development, or reproduction.

Know the disorders of the Endocrine system

1. Pituitary Disorders (growth) 2. Thyroid Disorders 3. Parathyroid Disorders 4. Adrenal Disorders (cortisol) 5. Pancreatic Disorders 6. Reproductive Gland Disorders

1. Pancreas (Insulin)

Secretion	Effect
Hypersecretion	Hypoglycemia → low blood sugar, shakiness, sweating, confusion
Hyposecretion	Diabetes mellitus → high blood sugar, frequent urination, thirst, weight loss

Thyroid (T3 & T4)

Secretion	Effect
Hypersecretion	Hyperthyroidism / Graves’ disease → weight loss, rapid heartbeat, nervousness, heat intolerance
Hyposecretion	Hypothyroidism / Cretinism in children → fatigue, weight gain, slow metabolism, slowed growth, mental retardation (if untreated in children)

Adrenal Cortex

Secretion	Effect
Hypersecretion	Cushing’s syndrome → weight gain, rounded face, high blood sugar, high blood pressure
Hyposecretion	Addison’s disease → fatigue, low blood pressure, muscle weakness, darkening of skin

Adrenal Medulla

Secretion	Effect
Hypersecretion	Pheochromocytoma (rare) → high blood pressure, rapid heartbeat, sweating
Hyposecretion	Rarely a problem, but can contribute to low stress response

broad functions of both the male and female reproductive systems.

Male Reproductive System –

• Produce sperm (male gametes)

• Produce male sex hormones

• Deliver sperm to the female reproductive tract

• Support fertilization

Female Reproductive System — 

• Produce eggs (female gametes)

• Produce female sex hormones (Estrogen and progesterone) 

• Provide environment for fertilization and development (Fallopian tubes: site of fertilization Uterus: supports implantation and fetal development)

• Support childbirth

• Nourish offspring after birth (Mammary glands) 

Male Reproductive System

Primary Organs

• Testes – produce sperm and testosterone

Accessory Organs / Ducts

• Epididymis – stores and matures sperm

• Vas deferens (ductus deferens) – transports sperm from testes to urethra

• Urethra – carries sperm (and urine) out of the body

Accessory Glands

• Seminal vesicles – produce seminal fluid

• Prostate gland – adds fluids to semen

• Bulbourethral (Cowper’s) glands – secrete lubricating fluid

External Genitalia

• Penis – delivers sperm

• Scrotum – houses and protects testes, regulates temperature

Female Reproductive System

Primary Organs

• Ovaries – produce eggs (ova) and female sex hormones (estrogen and progesterone)

Accessory Organs / Ducts

• Fallopian tubes (oviducts) – transport eggs from ovaries to uterus; site of fertilization

• Uterus – houses and nourishes developing fetus

• Cervix – lower part of uterus, opens to vagina

External Genitalia (Vulva)

• Vagina – receives sperm, serves as birth canal

• Labia majora and minora, clitoris – protective and sensory structures

Accessory Structures

• Mammary glands (breasts) – produce milk to nourish offspring

pathway sperm travels through the male reproductive system AND the pathway eggs travel through

Pathway of Sperm — Testes → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Penis

Pathway of Egg — Ovary → Fimbriae → Fallopian tube (fertilization) → Uterus → Cervix → Vagina

Distinguish between and summarize the two specific, linked cycles that compose the monthly
menstrual cycle.

• Ovarian hormones (estrogen & progesterone) control the uterine cycle.

• Ovulation (ovarian cycle) marks the transition from the proliferative to secretory phase in the uterus.

2. Uterine (Menstrual) Cycle

1. Follicle-Stimulating Hormone (FSH)

Female

Ovaries

Stimulates growth and maturation of ovarian follicles; promotes estrogen production

Male

Testes (Sertoli cells)

Stimulates sperm production (spermatogenesis)

Luteinizing Hormone (LH)

Female

Ovaries

Triggers ovulation; stimulates progesterone production by corpus luteum

Male

Testes (Leydig cells)

Stimulates testosterone production

Human Chorionic Gonadotropin (hCG)

Female

Ovaries (corpus luteum)

Maintains corpus luteum, which secretes progesterone to support early pregnancy

Male

Testes

Stimulates testosterone production in fetus during development (not significant in adult males)

Estrogen

Female

Ovaries, uterus, breasts, bones

Development of female reproductive organs, secondary sexual characteristics, thickens uterine lining

Male

Testes, brain, bones

Supports sperm maturation, bone health, and brain function (minor compared to females)

Progesterone

Female

Uterus, breasts

Maintains uterine lining for pregnancy, prepares mammary glands for milk production

Male

Minimal effect

Precursor for testosterone and other steroid hormones; role less significant

birth control types

1. Surgical Sterilization - Male: Vasectomy & Female: Tubal ligation (“tubes tied”)

2. Hormonal Control - pills, patch, ring, IUD, injectable hormones

3. Physical Barriers - condoms

4. Abortion - medical (induce miscarriage) and surgical

Discuss the ways fertility may be enhanced artificially

hormones, Assisted Reproductive Technologies (ART) - IVF, Surgical Treatments and lifestyle measures 

STDS

Bacterial STDs -

• Chlamydia, Gonorrhea, Syphilis

Viral STDs -

• HIV/AIDS

• Genital Herpes

• Human papillomavirus (HPV)

Parasitic / Other STDs -

• Pubic lice “crabs”

• Trichomoniasis

Assess the methods that you can use to protect yourself against STDs

Abstinence & Use of Barrier Methods

Summarize the process of fertilization in humans

Ovulation → Sperm transport → Sperm binds egg → Gamete fusion → Zygote formation → Implantation

Discuss the four processes that occur during development from a zygote to a full-term fetus.

Cell division → Layer formation → Organ formation → Growth & maturation

Describe the function of the placenta.

To support the fetus by transferring nutrients, removing wastes, producing hormones, providing immune protection, and serving as a selective barrier.

Discuss embryonic development from each trimester (specifically know week 6).

• Weeks 1–2: Fertilization, cleavage, blastocyst formation, implantation in the uterus.

• Weeks 3–5:

  • Gastrulation (formation of three germ layers: ectoderm, mesoderm, endoderm)

  • Neural tube begins to form

  • Early heart formation and primitive circulation

• Week 6 (Key Week):

  • Heart is beating

  • Limb buds appear (arms and legs start forming)

  • Facial features start forming (eyes and ears begin development)

  • Brain and spinal cord develop rapidly

• Weeks 7–12:

  • Major organs continue to form (organogenesis)

  • External genitalia begin to differentiate

  • Fingers and toes start to form

  • Embryo is about 5–6 cm long by week 12

  • Second Trimester (Weeks 13–26)

    • Rapid growth of fetus

    • Development of fine hair (lanugo) and vernix caseosa on skin

    • Movements can be felt by mother (“quickening”)

    • Eyes can open, ears function

    • Skeletal system continues ossification (bone formation)

    • By end of second trimester, fetus is about 30 cm long and weighs ~1 kg

    ---

    Third Trimester (Weeks 27–40)

    • Rapid weight gain and growth

    • Lungs mature and begin producing surfactant for breathing

    • Fat deposits increase, skin smooths

    • Brain develops rapidly

    • Fetus positions head-down in preparation for birth

    • By week 40, full-term fetus: ~50 cm long, ~3–4 kg

Compare and contrast sex development in a male versus a female embryo

• Male: XY chromosomes → SRY gene on Y chromosome triggers testes development

• Female: XX chromosomes → no SRY gene → ovaries develop by default

Relate the changes that occur in the fetus during the stage known as fetal development (2 & 3
trimesters).

• 2nd trimester = growth & organ maturation

• 3rd trimester = weight gain & final organ readiness for birth

three phases of labor and delivery

1. First Stage – Dilation Phase

• Definition: The period from the onset of true labor contractions until the cervix is fully dilated (10 cm).

2. Second Stage – Expulsion Phase

• Definition: The period from full cervical dilation to delivery of the baby.

3. Third Stage – Placental Phase

• Definition: The period from delivery of the baby until the placenta is expelled.

Summarize the activities of each of the phases of the cell cycle

G₁ = grow, S = copy DNA, G₂ = prepare, M = divide

• Mitosis: Prophase → Metaphase → Anaphase → Telophase → Cytokinesis

Describe the process of DNA replication.

the process where a cell copies its DNA before it divides. It happens during the S phase of the cell cycle.

how DNA can be altered and subsequently repaired during and after DNA replication.

How DNA Can Be Altered (Mutations)

1. Errors During DNA Replication

2. Environmental Factors (Mutagens)

3. Spontaneous Changes3. Spontaneous Changes

How DNA Is Repaired

1. Proofreading (During DNA replication)

2. Mismatch Repair (After DNA replication)

3. Nucleotide Excision Repair

4. Base Excision Repair

5. Double-Strand Break Repair

Indicate where in the body mitosis occurs; where meiosis occurs

Mitosis: happens in somatic cells (body cells).

Meiosis: In the ovaries and testes to make eggs and sperm.

how cell division is normally regulated

Cells use a combination of signals, checkpoints, and proteins to control when they divide. This prevents uncontrolled growth (cancer) and ensures healthy cells.

which genes/proteins start and stop the cell from undergoing mitosis

START - Cyclins + CDKs → push cell into mitosis

• Ras, Growth Factors → stimulate cell division

• Proto-oncogenes = “go” genes

STOP - p53 → detects damage, stops cycle

• p21 → blocks CDKs

• Rb → prevents cell cycle progression

• Tumor suppressor genes = “stop” genes

why cell differentiation occurs even though all cells have exactly the same genetic
information

Cells become specialized (differentiated) because they express different sets of genes, not because their DNA is different.

why some scientists believe that there is a limit to how many times a cell can divide (telomeres)

Because telomeres get shorter with each division.

Define Cancer

a disease in which cells grow and divide uncontrollably because the normal controls on the cell cycle are lost.

List the types of cancerous states

Hyperplasia → Dysplasia → Carcinoma in situ → Malignant tumor → Metastasis.

Discuss how hyperplasia can lead to tumor formation.

Extra cell division increases mutation risk → abnormal cells form → uncontrolled growth → tumor.

Differentiate between normal and abnormal cells

Normal cells divide only when needed; abnormal cells divide uncontrollably.

name and relate the normal functions of the three specific types of genes that, when mutated,
contribute to cancer formation

1. Proto-oncogenes

• Normal Function:

  • Promote cell growth and division when needed

  • Act like the “gas pedal” of the cell cycle

• Mutation Effect:

  • Becomes an oncogene

  • Gas pedal gets stuck → cells divide uncontrollably

2. Tumor Suppressor Genes

• Normal Function:

  • Stop or slow down cell division

  • Detect DNA damage and trigger apoptosis if needed

  • Act like the “brakes” of the cell cycle

• Mutation Effect:

  • Brakes fail → damaged cells keep dividing

  • Examples: p53, Rb

3. DNA Repair Genes

• Normal Function:

  • Detect and fix errors in DNA during replication

  • Maintain genome stability

• Mutation Effect:

  • Errors accumulate → mutations in other genes increase risk of cancer

  • Examples: BRCA1, BRCA2

Discuss the role of the immune system in cancer prevention

immune system surveys the body for abnormal cells and can recognize and destroy potential cancer cells before they form tumors.

several current diagnostic techniques and discuss why they are important for cancer treatment

1. Imaging Techniques

2. Biopsy

3. Blood Tests

4. Genetic and Molecular Testing

5. Endoscopy

Name the three conventional or classical cancer treatments

surgery, radiation therapy, chemotherapy

Identify several cancer treatments that are recent advances as treatment methods

Immunotherapy, targeted therapy, hormone therapy, gene therapy, cryoablation, nanotechnology.

What is the deadliest type of cancer and state the leading risk factor for causing this type of
cancer.

Lung cancer

Common types of cancer in men and women

Men

1. Prostate cancer – most common

2. Lung cancer – second most common

3. Colorectal (colon and rectum) cancer – third most common

Women

1. Breast cancer – most common

2. Lung cancer – second most common

3. Colorectal (colon and rectum) cancer – third most common

Explain the “ABCDE” rule for skin melanomas

Asymmetry, Border, Color, Diameter, Evolving