Biology Test

What are the 3 components of the cell theory?

all living things are composed of cells, cells are the basic units of life, all cells come from pre-existing cells

What are organelles?

A specialized part of a cell that carries out specific functions necessary for its survival

Prokaryotic Cells

Prokaryotic cells: pro = before; karyon = nucleus, lacks a nucleus and membrane-bound organelles, all prokaryotic cells are unicellular

Eukaryotic Cells

Eukaryotic cells: eu = true; karyon = nucleus, contains a nucleus and membrane-bound organelles, plant and animal cells have the same basic structure and function in similar ways

The nucleus (structure & function)

Structure: Nuclear membrane, nuclear pores, nucleolus.

Function: Stores genetic information (DNA), controls cell activities.

Nucleolus: a membrane-free organelle that floats in the nucleus and makes ribosomes (make protein)

What is DNA?

located in the nucleus and contains the instructions for the cell

What is the structure of DNA?

double helix (twisted ladder)

Sugar-phosphate backbone: (sides of ladder)

Paired nitrogenous bases (steps of ladder)

Base pair rule

Adenine(A) pairs with Thymine (T)

Guanine(G) pairs with Cytosine (C)

What is a nucleotide?

Building block of DNA (sugar + phosphate + nitrogenous base)

What are the different forms of DNA?

Uncoiled double helix: loose form

Chromatin: DNA wrapped around proteins

Chromosomes: Tightly packed DNA for cell division

What is a karyotype?

A picture of an organism's chromosomes arranged in pairs

How many chromosomes are in human cells?

46 chromosomes (23 pairs of homologous chromosomes)

Somatic Cells

Body cells (46 chromosomes, diploid)

Sex Cells (Gametes)

Sperm & egg (23 chromosomes, haploid)

Autosomes

22 pairs (non-sex chromosomes)

Sex Chromosomes

1 pair (XX for female, XY for male)

Genes

Segments of DNA that code for proteins

Proteins

molecules that perform functions in the body (enzymes, hormones, transport proteins)

Cell division purpose

grow, repair, and reproduce

3 steps of DNA replication

Unwinding: strands are separated, each strand acts as a template for a new strand

Complementary Base Pairing: Bases along each template are matched with free nucleotides

Stitch Together: Nucleotides are stitched together to form the sugar-phosphate backbone, completes the new strand of DNA

Interphase

cell grows and duplicates DNA before division

Mitosis (PMAT)

Prophase: spindle fibers extend, X-shaped chromosomes, nucleus disappears

Metaphase: chromosomes line up at the equator

Anaphase: sister chromatids separate

Telophase: two nuclei in one cell

Cytokinesis

Cell membrane splits, forming two identical daughter cells.

Animal: Cleavage furrow pinches cell

Plant: Cell plate forms

Cancer

A disease that results from uncontrolled cell division, cancer cells don't respond to instructions and continue to grow → forms tumours

Chromatin

Unwound DNA

Chromatid

One-half of a duplicated chromosome

Chromosome

Condensed DNA

Centromere

Region where sister chromatids are joined

Centrioles

Help organize spindle fibers

Spindle Fibers

Move chromosomes during mitosis

Binary fission

Prokaryotes/bacteria

Budding

Yeast

Fragmentation

Starfish

Vegetative reproduction

Potatoes and strawberries

Somatic cell nuclear transfer

Dolly the sheep

Diploid (2n)

Cells with both sets of homologous chromosomes (somatic cells)

Haploid (n)

Cells that contain only one set of chromosomes, no homologous pairs (human sex cells/gametes)

Fertilization counterbalance

Diploid (2n) → Meiosis → Haploid (n) → Fertilization → Diploid (2n)

Meiosis 1

Homologous Chromosomes Separate

Prophase I: chromosomes condense and attach to spindle fibres, Tetrads (4 chromatids) cross over and exchange genetic information

Metaphase I: Tetrads (homologous chromosomes) line up and go through independent assortment (random)

Anaphase I: Homologous chromosomes separate and move to opposite poles of the cell

Telophase I & Cytokinesis: chromosomes decondense, cleavage furrow forms and cytoplasm divides

Meiosis II

Sister Chromatids Separate

Interphase II: does not occur to ensure DNA doesn't replicate

Prophase Il: Chromosomes condense and attach to spindle fibres

Metaphase II: Chromosomes line up at the equatorial plate in a single row

Anaphase Il: Sister chromatids separate

Telophase Il & Cytokinesis: Four unique gametes form

Gamete Formation in Humans

Spermatogenesis (males): Produces 4 sperm cells

Oogenesis (females): Produces 1 egg cell and 3 polar bodies

Genetic Variation in Meiosis

Crossing Over (Prophase I): Exchange of DNA between homologous chromosomes, Independent Assortment (Metaphase I): Random alignment of chromosome pairs, Random Fertilization: Any sperm can fertilize any egg.

First trimester

Zygote → Embryo → Fetus, Major organs and systems begin forming

Second trimester

Time of growth, bone formation occurs

Third trimester

Weight of fetus more than doubles, most major nerve tracks are formed in brain