Chromosome- a single piece of coiled DNA containing many genes

How do Chromosomes Form- a single length of DNA is wrapped many times around histones, and forms nucleosomes. Nucleosomes then coil up tightly to create chromatin loops. Chromatin loops are then wrapped around each other to form a chromosome

Diploid- Having a pair of each type of chromosome. This means that one pair is derived from the ovum and the other from the sperm

Haploid- Having only one copy of every chromosome. This is where n= 23

Genes- Basic unit of heredity in a living organism. _____ hold information to build and maintain an organism’s cells and pass traits to offspring

What is A Gene- A segment of a chromosome that contains the code for a single protein (enzyme). The enzyme then causes a chemical reaction to allow a trait to be shown/expressed

Allele- Variation of a gene located at a specific location on a chromosome. Each individual organism has two alleles for each trait, which may be homozygous or heterozygous. Alleles are alternate forms of a gene.

Homologous Chromosomes- It is chromosomes that are paired. They are alike with regard to size and also position of the centromere. They also have the same genes, but not necessarily the same alleles, at the same locus or location

Tetrad- Pair of homologous chromosomes. Chromatids of homologous chromosomes are aligned length wise, so that genes of one are adjacent to corresponding genes on the other (total of 4 chromatids)

Synapsis- The forming of a tetrad

Gamete- Specialized sex cells such as an egg or a sperm, which is haploid (n). It only has half the number of chromosomes (23 in humans). A male and female gamete fuse and produce a diploid zygote which develops into a new individual

Inheritance- Passing on genetic information from parent to offspring

Sex Chromosomes- It is 1 pair out of 23, where it is called X and Y, determining individual’s sex (Female= XX, Male= XY)

Autosomes/Somatic Chromosomes- It is 22 pairs out of 23, where it is all chromosomes but sex cells, and it is paired based on similar characteristics

Karyotype- A photograph of a particular set of chromosomes for an individual. In order to prepare a __________, you sample a cell in metaphase, have the chromosomes stained, revealing banding patterns, and then sort and pair afterwards

DNA- contains instructions for making proteins within the cell

Double Helix- basic shape of DNA a double-stranded molecule made of two very long polymers bonded together

Polymer- long molecule made of repeating subunits of monomers (one DNA stand is made of millions of monomers of nucleotides)

Monomer- atoms bonded together to create a larger molecule, many _________ bond together to create various polymers (nucleotides are _________ of DNA)

Nucleotides- basic building blocks of DNA & RNA

Parts of Nucleotides- Deoxyribose pentose sugar, phosphate group & nitrogenous base

Deoxyribose- sugar in DNA

Ribose- sugar in RNA that has an additional oxygen as a hydroxyl group in #2 carbon

Phosphate group- link two sugars together build polymers

Phosphodister Bond- joins two sugars via phosphate vertically (joins two nucleotides)

Condensation Reaction- produces H20 when phosphodiester bonds form

Nitrogenous Bases- 4 different nucleotides that make up a DNA polymer

Purine Deoxyribonucleotides- Guanine & Adenine (have 2 rings)

Pyrimidine Deoxyribonucleotides- Thymine & Cytosine (have 1 ring)

Uracil- takes the place of thymine in RNA

The Backbone- one strand of DNA made of repeating monomers covalently bonded together

Triplet Code- used to send instructions in the cell: to switch genes on and off to make proteins and enzymes

Hydrogen Bond- holds DNA strands together and is weaker than molecular bonds. Millions in a single molecule cause bases to attract each other

Complementary Base Pairs: only bond with each other (A&T or U) (C&G)

Antiparallel- one side up and the other down (in DNA the direction of phosphate (5’end) on one stand and the hydroxyl (OH 3’end) on the other)

Genetic Mutation- a change in the nucleotide sequence of DNA (T pairs with G instead of A)

DNA Replication- process where an original copy of DNA is unzipped and replicated producing two new idenitical molecules of DNA. 

Why DNA Replicates-  as a cell’s chromosomes are copied for cell division, DNA must be copied too, since DNA makes up chromosome. Instructions for making cell parts are encoded in the DNA so each new cell must get a complete set of the DNA molecules.  

Unwinding of Double Helix- used in DNA replication, where each strand of DNA becomes a new template for a new strand. Each double stranded DNA contains the original copy and one new strand. Parent DNA molecule and two daughter molecules are identical (same nucleotides in same order) 

Helicase- The enzyme (protein) that breaks the hydrogen bonds between nitrogenous bases to “unzip” or “unwind” the DNA helix. This is the first step in DNA replication. 

DNA polymerase-  An enzyme that moves along the single strands of DNA and helps each free nucleotide bind to a new complementary base to form base pairs. This is the second step to DNA replication and happens as the DNA unzips. 

Semi-Conservative Model of Replication- one daughter strand is paired with a parent strand, one old one new is semi-conservative 

New cells are produced for: growth and to replaced damaged or old cells, all cells are derived from pre-exisiting cells

Prokaryotes: organisms whose cells lack a nucleus and other organelles, for ex. bacteria

Eukaryotes: organisms whoses cells contain membrane-bound organelles for ex. Animals 

Eukaryotic Chromosomes: store genetic information, have between 10-50 chromosomes in their body cells, human body cells have 46 chromosomes (23 pairs)

Chromatin: is uncoiled and can’t be seen when cells arn’t dividing 

Histones: a protein which DNA is tightly coiled around 

Chromatid: Duplicated chromosomes which area held together by the centromere 

Centromere: holds the sister chromatids together 

Asexual reproduction: a single cell dividing to make 2, identical daughter cells 

Sexual reproduction: involces two cells (egg & sperm) joining to make a new cell (zygote) that is not identical to the original cells 

5 Phases of the Cell Cycle: Interphase (G1 - primary growth, phase) (S synthesis; DNA replicated) (G2 - secondary growth phase), Mitosis, Cytokinesis 

Interphase (G1 Stage): 1st growth stage after cell division, Cells mature by making more cytoplasm & organelles, so daughter cells have all organelles, Cell carries on its normal metabolic processes

Interphase (S Stage): Synthesis stage (DNA Replication)

Interphase (G2 Stage): 2nd growth stage, occurs after DNA has been copied, all cell structures needed for division are made (ex. Centrioles which move to poles), both organelles & proteins are synthesized

Mitosis (karyokinesis): Division of the nucleus, only occurs in eukaryotes, has 4 stages, doesn’t occur in some specialized cells such as brain cells

Early Prophase: Chromatin in nucleus condenses to form visible chromosomes (creats absence of space in nucleus), Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal)

Late Prophase: Nuclear membrane & nucleolus are broken down, chromosomes continue condensing & are clearly visible, spindle fibers called kinetochores attach to the centromere of each chromosome (Only called kinetochores only if they grab the centromere of the chromosome called the astor if it doesn't) Spindle finished forming between the poles of the cell 

Metaphase: Chromosomes, attached to the kinetochore fibers, move to the center of the cell, chromosomes are now lined up at the equator (or metaphase plate), preparing for the actual division of the chromosomes

Anaphase: Occurs rapidly, high forced, sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers 

Telophase: Sister chromatids at opposite poles, Spindle disassembles (disappears), Nuclear envelope (nuclear membrane) forms around each set of sister chromatids, Nucleolus reappears, Cytokinesis occurs, Chromosomes reappear as chromatin

Cytokinesis: division of the cytoplasm, Division of the cell into half, in plant cells, cell plate forms at equator to divide cell, In animal cells, cleavage furrow forms to split cell 

Daughter Cells of Mitosis: Have the same number of chromosomes as each other and as the parent cell from which they were formed, Identical to each other, but smaller than parent cell, Must grow in size to become mature cells (G1 of Interphase)

Checkpoints in the Cell Cycle: messages sent to the cells nucleus to “divide, or not to divide” at: G1, S Synthesis phase (DNA Replication): cyclins/cyclin dependent kinase signals the division, G2 gap phase 2- cell size/energy reserves are assessed and if all chromosomes have been replicated correcntly, M checkpoint (metaphase): spindle checkpoint, are the sister chromatids attached correctl