Molecular Genetics Unit 3 Quiz

Study Notes

UNIT 3: MOLECULAR GENETICS

DNA structure resembles a ladder; sides are made of sugar-phosphate molecules; rungs are made of nitrogenous bases.
Adenine bonds to thymine with 2 hydrogen bonds; cytosine bonds to guanine with 3 hydrogen bonds.
DNA is a double helix, two strands coiled around each other.
DNA strands are antiparallel; one end has a phosphate group (5' end), the other a hydroxyl group (3' end).
Conservative replication produces two original parental strands together and two entirely new strands; semi-conservative replication produces two double helices, each with one original and one new strand. DNA uses semi-conservative replication.

DNA Replication Steps

Enzymes involved in DNA replication include DNA polymerase, helicase, primase, and ligase.
Steps: DNA unwinding, primer synthesis, DNA elongation (leading and lagging strand synthesis), and joining fragments.

DNA Replication Locations

DNA replication occurs in the nucleus of eukaryotic cells.

Leading and Lagging Strands

A leading strand replicates continuously, while a lagging strand replicates discontinuously in fragments (Okazaki fragments). This is because DNA polymerase can only add nucleotides to the 3' end of a growing strand.

DNA Repair Mechanisms

Proofreading repair: DNA polymerase corrects errors during replication.
Mismatch repair: Enzymes remove and replace mismatched bases after replication.
Excision repair: Enzymes remove damaged DNA segments and replace them with correct nucleotides.

UNIT 4: THE EXCRETORY SYSTEM

Homeostasis is the maintenance of a relatively stable internal environment.
Positive feedback amplifies a response (e.g., childbirth); negative feedback reduces a response (e.g., body temperature regulation).
Thermoregulation is maintaining a constant body temperature.
- Cooling mechanisms: sweating, vasodilation, and evaporative heat loss
- Heating mechanisms: shivering, vasoconstriction, and increasing metabolic rate.
Examples of nitrogenous waste: urea, ammonia, uric acid. Mammals generally excrete urea.

Excretory System Structures and Function

Blood enters the kidney via the renal artery, which branches to afferent arterioles, leading to the glomerulus (capillary network).
Filtration occurs in the glomerulus. Small molecules (e.g., water, salts) pass through the glomerulus into the Bowman's capsule; large molecules (e.g., proteins) remain in the blood.
Blood leaves glomerulus via the efferent arterioles and enters the peritubular capillaries in the medulla.

Stages of Urine Formation

Filtration: Water and small solutes are filtered from blood.
Reabsorption: Useful substances (water, nutrients) are reabsorbed into the blood.
Secretion: Certain waste products are actively secreted from the blood to the filtrate.

UNIT 4: THE ENDOCRINE SYSTEM

Hormones are chemical messengers that travel in the blood and affect specific target cells.

Endocrine Glands and Locations

Diagrams showing endocrine glands and their locations in the body would be helpful.

Types of Hormones

Steroid hormones are lipid-based molecules; they enter cells and directly affect gene expression.
Peptide hormones are protein-based molecules; they bind to receptor proteins on the cell surface and trigger a cellular response through a second messenger system.

Master Gland

The pituitary gland is sometimes called the master gland as it controls many other endocrine glands.

Anterior vs. Posterior Pituitary

Anterior pituitary produces and secretes hormones; posterior pituitary stores and releases hormones produced by the hypothalamus.

Brain Homeostasis Center

The hypothalamus maintains homeostasis by regulating various factors, including heart rate, body temperature, and water balance, and works closely with the pituitary gland to regulate hormonal responses.

Description

Test your knowledge on the structure and replication of DNA in this quiz from Unit 3 of Molecular Genetics. Questions cover key concepts like the ladder structure, bonding pairs, and the enzymes involved in DNA replication. Enhance your understanding of this fundamental aspect of genetics!