Human Genetics Exam #1 (Chapter 2 and 3)

Germ cells

Sperm and egg cells that contain one copy of the genome and are haploid

Stem cells

Diploid cells that divide to give rise to differentiated cells and replicate themselves through self-renewal

Connective tissue

Tissue type containing various cells and surrounding materials that protect support bind and fill spaces throughout the body

Epithelium

Tight cell layers that form linings to protect secrete absorb and excrete

Muscle tissue

Tissue composed of cells that contract to provide movement against rigid bones

Nervous tissue

Tissue consisting of neurons that transmit electrochemical impulses and neuroglia that support and nourish neurons

Prokaryotic cells

Unicellular organisms in domains Archaea and Bacteria that lack a nucleus and membrane-enclosed organelles

Eukaryotic cells

Cells in domain Eukarya containing a nucleus and other membrane-bound organelles

Ribosomes

Globular assemblies of RNA and protein essential for protein synthesis present in all three domains of life

Carbohydrates

Macromolecules composed of monosaccharides that store energy and contribute to cell structure

Lipids

Macromolecules including fatty acids and sterols that form membranes store energy provide insulation and form hormones

Proteins

Polymers of amino acids that serve as enzymes transport molecules contractile fibers and structural components

Nucleic acids

Polymers of nucleotides such as DNA and RNA that store and transmit genetic information

Plasma membrane

Phospholipid bilayer embedded with proteins and surface carbohydrates that encloses the cell

Nucleus

Prominent organelle surrounded by a nuclear envelope containing nuclear pores chromatin and the nucleolus

Nucleolus

Structure within the nucleus where ribosomes are produced

Rough endoplasmic reticulum

Network of membranous tubules studded with ribosomes involved in protein synthesis

Smooth endoplasmic reticulum

Membranous network lacking ribosomes that synthesizes lipids and stores calcium ions

Golgi apparatus

Stack of flat membrane-enclosed sacs that processes proteins and adds sugars to form glycoproteins and glycolipids

Exosomes

Tiny membrane-bound vesicles released by cells to transport proteins RNA lipids and communication signals between cells

Lysosomes

Membrane-bound sacs containing digestive enzymes that dismantle bacterial remnants worn-out organelles and debris through autophagy

Peroxisomes

Enzyme-studded sacs that break down lipids synthesize bile acids and detoxify oxygen free radicals

Mitochondria

Double-membranous organelles containing their own DNA that produce the majority of the cell's ATP

Cristae

Folds of the inner mitochondrial membrane that hold enzymes catalyzing biochemical reactions

Cytoskeleton

Meshwork of protein rods and tubules including microtubules intermediate filaments and microfilaments that maintains cell architecture

Microtubules

Hollow cytoskeletal rods composed of tubulin dimers that form cilia centrioles and spindle fibers

Microfilaments

Solid cytoskeletal rods composed of actin molecules involved in cell movement and cytokinesis

Signal transduction

Process where membrane receptors bind external ligands and transmit molecular signals inward to trigger cellular reactions

Apoptosis

Genetically programmed sequence of events leading to cellular self-destruction

Cell cycle

Sequence of events associated with cell division comprising interphase mitosis and cytokinesis

Interphase

Major phase of the cell cycle consisting of G1 S and G2 phases where the cell grows replicates DNA and synthesizes structures

S phase

Stage of interphase during which the cell's chromosomes are replicated

Centromere

Specific region where two identical sister chromatids of a replicated chromosome are joined

Prophase

First stage of mitosis where DNA condenses into visible chromosomes spindle assembles and nuclear envelope breaks down

Metaphase

Stage of mitosis where chromosomes attach to spindle fibers and align along the cell's equator

Anaphase

Stage of mitosis where centromeres divide and sister chromatids separate to opposite poles

Telophase

Final stage of nuclear division where spindle disassembles and nuclear envelopes reform around separated chromosomes

Cytokinesis

Division of the cytoplasm and organelles between two daughter cells via microfilament ring contraction

Checkpoints

Groups of interacting proteins that monitor the cell cycle to ensure correct DNA replication and chromosome division

Telomeres

Repeated DNA sequences at chromosome ends that shorten with each division and signal cells to stop dividing

Telomerase

Enzyme produced in stem cells germ cells and cancer cells that prevents telomere shortening

Caspases

Killer enzymes activated during apoptosis that destroy cellular components and tear apart the cytoskeleton

Progenitor cell

Partially specialized cell produced by a stem cell that cannot self-renew

Totipotent cell

Stem cell with the developmental potential to give rise to every cell type

Pluripotent cell

Stem cell with restricted developmental potential capable of forming many but not all cell types

Multipotent cell

Stem cell that has only a few developmental choices available

Induced pluripotent stem (iPS) cells

Somatic cells reprogrammed in the lab to differentiate into various cell types without using embryos

Human microbiome

Ecosystem of trillions of bacteria fungi and viruses living on and inside the human body

Gametes

Sex cells such as sperm and oocytes that carry one set of chromosomes

Gonads

Paired reproductive organs consisting of testes in males and ovaries in females

Seminiferous tubules

Network of tubes in the testes where sperm cells are manufactured

Epididymis

Tubular structure in the male reproductive system where sperm mature and are stored

Oocytes

Female sex cells that mature within the ovaries

Cervix

Tubular lower part of the uterus that extends downward into the upper vagina

Homologous chromosomes

Chromosome pairs that contain the same genes in the same order but may carry different alleles

Meiosis

Specialized cell division that halves the chromosome number from diploid to haploid to produce gametes

Meiosis I

First meiotic division known as the reduction division that reduces chromosome number from 46 to 23

Meiosis II

Second meiotic division known as the equational division that separates sister chromatids into four haploid cells

Synapsis

Pairing of homologous chromosomes during prophase I of meiosis

Crossing over

Process in prophase I where homologous chromosomes exchange genetic material to create new allele combinations

Independent assortment

Random alignment and distribution of maternal and paternal homologous chromosome pairs during metaphase I

Spermatogenesis

Formation and maturation of sperm cells beginning at puberty and continuing throughout life

Spermatogonium

Diploid stem cell in the seminiferous tubules that divides by mitosis to yield a stem cell and a primary spermatocyte

Primary spermatocyte

Diploid cell that undergoes meiosis I to produce two haploid secondary spermatocytes

Secondary spermatocytes

Haploid cells produced during meiosis I that undergo meiosis II to form equal-sized spermatids

Acrosome

Special vesicle on the head of a sperm cell containing enzymes that penetrate egg membrane layers

Oogenesis

Formation and maturation of egg cells beginning during fetal development and completing only upon fertilization

Primary oocyte

Diploid female germ cell that arrests in prophase I until puberty

Polar body

Small cell produced during unequal meiotic division of oocytes that contains little cytoplasm and eventually degenerates

Secondary oocyte

Large haploid cell produced by meiosis I that arrests in metaphase II until fertilized

Paternal age effect

Single-gene dominant mutations in sperm caused by increased mitotic divisions in older male stem cells

Embryo

Human organism during the first eight weeks of prenatal development

Fetus

Prenatal human organism from the ninth week of development until birth

Zygote

Single diploid cell formed by the fusion of sperm and oocyte nuclei during fertilization

Cleavage

Period of rapid mitotic cell division following fertilization without cell growth

Blastomeres

Individual early cells produced during cleavage divisions

Morula

Solid ball of 16 or more blastomeres formed by the third to fourth day after fertilization

Blastocyst

Hollow fluid-filled ball of cells comprising the inner cell mass and outer trophoblast

Inner cell mass

Clump of cells inside the blastocyst that develops into the embryo proper

Trophoblast

Outer layer of blastocyst cells that secretes hCG to prevent menstruation and forms extraembryonic membranes

Human chorionic gonadotropin (hCG)

Hormone secreted by the trophoblast that prevents menstruation and serves as an indicator of pregnancy

Implantation

Process where the blastocyst nests into the uterine lining around seven days post-fertilization

Gastrula

Three-layered embryonic structure formed at the end of the second week during gastrulation

Ectoderm

Outermost primary germ layer giving rise to skin nervous system sensory organs and lens of the eye

Mesoderm

Middle primary germ layer giving rise to muscle bone blood connective tissue kidneys and reproductive organs

Endoderm

Innermost primary germ layer giving rise to epithelial linings of the digestive tract respiratory tract liver and pancreas

Placenta

Organ formed from chorionic villi by week 10 that provides nutrient exchange waste removal and hormone secretion for the fetus

Dizygotic twins

Fraternal twins resulting from the fertilization of two separate oocytes by two separate sperm cells

Monozygotic twins

Identical twins resulting from a single fertilized egg that splits early in development

Organogenesis

Process during the embryonic period where the three germ layers differentiate into distinct organs

Critical period

Time window during prenatal development when specific physical structures are vulnerable to damage from genetic or environmental disruptions

Teratogens

Chemical or environmental agents such as drugs alcohol or viruses that cause structural birth defects

Progeroid syndromes

Rare single-gene genetic disorders that accelerate changes associated with normal aging

Hutchinson-Gilford progeria syndrome

Severe progeroid condition caused by a mutation in the LMNA gene leading to defective lamin A (progerin) and rapid apoptosis