Bio 30 - Unit 3

Genetics: the study of patterns of inheritance, genes and genetic variation

Genes: units of instruction, located on chromosomes, which produce or influence a specific trait

Alleles: two or more alternate forms of a gene

Mitosis: nuclear division; maintains the number of chromosomes

Meiosis: cell division; reduces the number of chromosomes

Meiosis 1: separates the matching pairs of chromosomes

Meiosis 2: separates the sister chromatids into individual chromosomes

Chromosomes: DNA tightly packed into a thick, condensed strand

Chromatin: a mixture of DNA and proteins that form that chromosomes found in eukaryotic cells

Chromatid: one of the two identical halves of a chromosome that has been replicated in preparation for cell division

Centromere: a constricted region of a chromosome, holds the sister chromatids together; plays a key role in helping the cell divide up DNA during division

Somatic cells: body cells that perform the function it is specialized to do

Homologous chromosomes: chromosomes of similar length and banding patterns

Autosomes: Chromosome pairs 1 through 22

Sex chromosome: chromosome #23

Ploidy: a term used to describe the number of chromosomes sets in a nucleus

Haploid: One set of chromosomes - found in gametes and spores

Diploid: Two sets of chromosomes

Growth 1: growth of organelles

Synthesis: replication of DNA

Growth 2: Another growth phase where all of the organelles double

Interphase: time between the divisions where the cell performs the majority of its purposes including preparing for cell division

Cytokinesis: cytoplasmic division

Prophase: nuclear membrane disappears, centromeres migrate, chromosomes condense, spindle fibres appear

Metaphase: chromosomes line-up on the equator (poles), spindle fibres are attached to the centromeres

Anaphase: centromeres divide, sister chromatids migrate to opposite poles

Telophase: nuclear membrane forms, spindle fibres disappear

Cytokinesis: division of the cytoplasm

Aging: a symptom of changes that are deleterious, progressive, universal and irreversible

Cancer: a group of disease involving abnormal cell growth with the potential to invade or spread to other parts of the body; mitosis out of control

Telomere: structures made from DNA sequences and proteins found at the end of chromosomes

Telomerase: an enzyme that lengthens telomeres on chromosomes

Synapsis: a process where homologous chromosomes pair together

Tetrads: chromosomal pairs created through synapsis

Crossing over: the breaking and exchanging of segments of non-sister chromatids

Prophase 1: cross-over/synapsis occurs, nuclear membrane disappears

Metaphase 1: tetrads line up on the equator, spindle fibres attach to the centromeres

Independent assortment: how the tetrads can line up two different ways before they separate in metaphase 1

Anaphase 1: tetrads separate and homologous chromosomes are moved by being pulled to opposite poles of the cell

Segregation: when tetrads separate and homologous chromosomes move to opposite poles of the cell in anaphase 1

Telophase 1: reforming of the nucleus,cytoplasm splits, preparation for meiosis 2

Spermatogenesis: a form of gametogenesis that makes sperm cells; creates 4 functional cells

Oogenesis: a form of gametogenesis that makes egg cells; creates 1 functional cell

Polar bodies: potential egg cells that do not have sufficient nutrients to become a functional egg cell; they die from unequal cytokinesis

Nondisjunction: failure of one of more chromosomes to separate correctly during anaphase or meiosis or mitosis

Trisomy: one extra chromosome (2n + 1)

Monosomy: one missing chromosome (2n - 1)

Karyotype: complex set of chromosomes of an individual

Binary fission: splitting of one cell into two cells

Budding: a new individual develops form some generative anatomical point of parent organism

Parthenogenesis: growth and development of an embryo without fertilization

Gregor Mendel: father of genetics; tracked and recorded the transmission of seven visible traits through several generations of pea plants

Law of dominance: with complete dominance, the dominant allele (R) prevents or masks the expression of the recessive form

Law of segregation: Mendel’s 1st law - the homologous pairs separate and the gametes receive one of each homologous during meiosis (anaphase 1)

Law of independent assortment: Mendel’s 2nd law - genes for different traits will sort into gametes independently from each other during meiosis (anaphase 1) unless that are linked genes (on the same chromosome)

Phenotype: observable traits determined by the genes of an organism

Genotype: the heritable info or genes (DNA) that determine the phenotype/trait

Test cross: the genotype of an organism displaying the dominant genotype is unknown, cross what is known with a homozygous recessive

Incomplete dominance: a third phenotype that is a blend of the others (when an individual receives the heterozygous genotype)

Codominance: both alleles are expressed equally

Polygenetic inheritance: traits that are controlled by many genes

Order of dominance: order of which phenotype is dominant over the other

Sex-linked inheritance (x-linked): gene located on the “x” chromosome

Thomas Morgan: Used fruit flies to discover sex-linked inheritance

Pedigree charts: a diagram that shows how a particular trait is passed on through the generations

Recombinants: any offspring that do not resemble the parents, occurs from crossing-over

DNA: a polymer composed of four different types of nucleotides (monomers) that can be arranged in endless combinations

Nucleotides: composed of a deoxyribose sugar, a phosphate group and one of 4 possible nitrogen bases

Purines: Double ring nitrogen bases; adenine and guanine

Pyrimidines: single ring nitrogen bases; thymine and cytosine

Complimentary base pairs: Erwin Chargaff discovered that within a segment of DNA, the number purines equals the number of pyrimidines

Rosalind Franklin: discovered the double helix shape of DNA using an x-ray diffraction image

Jason Watson and Francis Crick: made a 3-D model of DNA that resembles a twisted ladder

Helicase: breaks the hydrogen bonds between nitrogen bases

DNA polymerase: makes more DNA; adds free floating nucleotide to the exposed nitrogen bases according to the complementary base rule

Ligase: enzyme that attaches the sugar and phosphate back to the nitrogen bases

Transcription: makes mRNA from DNA

Translation: makes proteins from mRNA

RNA: a single stranded genes that exist throughout the cell