Basic Units of Heredity DNA (deoxyribose nucleic acid) – Material of the chromosomes that contains all the hereditary information encoded in the sequences of nucleotides Responsible for passing genetic information from generation to generation Located in nucleus of a cell Double helix shape (twisted ladder) Nitrogen bases are attached by weak hydrogen bonds Composed of a long chain of nucleotides

Major Components of DNA The 3 major components of DNA are: - Phosphate Group - 5 Carbon Sugar - 1 of 4 Nitrogen Bases (Nucleotide)

Nucleotides Adenine (A) - Thymine (T) Guanine (G) - Cytosine (C) Each nucleotide is composed of three parts – phosphate group, 5-carbon sugar and 1 of 4 nitrogen bases Four nitrogen base options are adenine (A), guanine (G), cytosine (C), and thymine (T) DNA Base Pairing Rule: Adenine (A) - Thymine (T) Guanine (G) - Cytosine (C)

Packaging of DNA To allow the DNA to be tightly packed, it will coil around proteins called histones. A segment of the DNA wrapped around a histone forms a nucleosome. A chromosome is made up of many nucleosomes in a row Some sort of DNA assessment at end or some activity related to chromosomes. +

Genetic Code Genetic Code – Hereditary information depends upon the order of the different nucleotides in DNA molecule Message to the cell to make certain proteins Triplet codes – arrangement of groups of three nucleotide bases Production of one type of protein is controlled by a sequence (order) of nucleotide triplets Sequence of nucleotides = a gene Alphabet DNA Code Letters Nucleotides Words Three nucleotides Sentences Genes Chapters Chromosomes Book Nucleus

DNA & RNA Contains the sugar deoxyribose Contains the nitrogen bases adenine (A), thymine (T), cytosine (C) and guanine (G) Pairing: A – T & G – C Double-stranded Only one kind Contains the sugar ribose Contains the nitrogen bases adenine (A), cytosine (C), guanine (G) and uracil (U) instead of thymine Pairing: A – U & G - C Single stranded Three kinds: messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA)

Replication Replication – DNA makes exact copies of itself; Exact copies are passed from parent to daughter cells Occurs in Mitosis and Meiosis Two strands that make up DNA double helix will ‘unzip’ by using the helicase enzyme Bonds holding nitrogenous bases break, leaving the molecule in the form of two strands of nucleotides Each strand is a pattern (template) for the new nucleotide strand

Protein Synthesis Protein Synthesis – formation of protein molecules (chain of amino acids) that occurs at cell’s ribosome Proteins – long folded chains of amino acids in a specific sequence. Sequence = Shape = Function

Protein Synthesis Transcription : Translation : Protein Synthesis : DNA acts as a template and messenger RNA (mRNA) copies the specific sequence so that the sequence can be brought out of the nucleus mRNA travels out of nucleus and attaches to a ribosome. DNA is two large to travel freely outside the nucleus Translation : Based upon the mRNA codon, the corresponding transfer RNA (tRNA) anti-codon will be brought over to the ribosome The codon & anti-codon relationship correlates to a specific amino acid Protein Synthesis : Amino acids are connected into by peptide bonds to form a protein The specific sequence of amino acids = shape of protein = function of protein

Codon (mRNA) Amino Acid Chart

Heredity & Genes

Hereditary & Genes In order for genetic information to be passed from generation to generation, it must be accurately replicated before being passed from parent to offspring Heredity – passage of genetic information from parent to offspring Hereditary information is contained in genes, located in the chromosomes Genes – a sequence of nucleotides in DNA that carries coded hereditary information that codes for a protein and therefore determines a inherited trait (characteristics) An inherited trait can be determined by one or by many genes, and a single gene can influence more than one trait

Chromosomes Homologous chromosomes – pairs of chromosomes that carry the same characteristics (but not necessarily the same allele) One homologous chromosome is received from each parent Alleles – pairs of genes that carry the same characteristic and are found at the same location (loci) on pairs of homologous chromosomes Sister chromatid – two identical copies of a strand of DNA connected together by a centromere

Karyotypes Karyotypes – photo displaying the number and appearance of the homologues chromosomes in a cell Karyotypes can be used to determine if any chromosomal abnormalities are present Humans have 46 chromosomes in body cells (diploid = 2n) and 23 chromosomes in sex cells (haploid = n). Having the incorrect amount of chromosomes can result in genetic abnormalities

Inherited Traits Gregor Mendel, “father of genetics” developed the Genes Chromosome Theory In sexual reproduction, during fertilization, the male and female parents contribute genetic information to zygote. Therefore, one-half of genetic information is received from each parent Determined some traits are always expressed when the allele is present in the cell (Dominant Trait) and some traits are hidden by the dominant trait (Recessive Trait) Dominant trait is written as an uppercase letter Recessive trait is written as a lowercase letter Species Chromosome Number – each body cell of an organism normally contains the same number of chromosomes as each body cell in the parent organism (unique to a species) Homo sapiens (Humans) have 46 chromosomes

Punnett Squares Punnett Square – diagram that is used to predict an outcome of a particular cross or breeding experiment Each box corresponds to 25% of the offspring population Types of Pairs – Homogenous (homozygous) Dominant (BB) – both dominant alleles are present and the dominant trait is expressed Homogenous (homozygous) Recessive (bb) – both recessive alleles are present and the recessive trait is expressed Heterogeneous (heterozygous) (Bb) – one dominant and one recessive allele is present and the dominant trait is expressed (the recessive trait is overshadowed by the dominant trait)

Hereditary and Environment Genes determine an organism’s heredity, the expression of genes can be modified by interactions between genes and their environment Himalayan rabbit fur color can be affected by temperature. The gene for black fur is active at low temperatures.

Variation Reproduction results in new organisms that closely resemble their parents. However, within each species there will be some variation (differences) in traits Types of Reproduction: Asexual reproduction – Involves only one parent so genetic material is copied directly from single parent (little to no variation; variation possible from mutations) Sexual reproduction – Involves two parents so it brings together genetic traits from two parents to produce an organism with a new combination of traits Offspring resembles its parents but is also genetically different Genetic variations are responsible for better species survival and play an important role in evolution

Mutations Mutation – any change or mistake in the genes or chromosomes of an organisms that can be inherited Sorting and recombination of genes during meiosis and fertilization produce a greater variety of gene combinations Results in more variation (diversity) among organisms (ie: biodiversity) Random chance events that occur naturally or be caused mutagenic agents Mutagenic agents – cause cellular mutations. Examples – x-rays, ultraviolet light, radioactive substances, chemicals, asbestos fibers, drugs, alcohol Changes produce new characteristics (increased variation)

Mutations To be inherited, the mutation must occur in the reproductive cells. If they only occur in body cells, the mutation will only be passed on to other body cells (not any future offspring). Most mutations are harmful because mutations upset normal cell function A beneficial mutation is one that results in traits that make an organism better adapted to its environment The World’s Strongest Toddler – (0 – 2.0 min, 12:40 – 17:00, 24:30 – 27:00, 29:00-30:00) https://www.youtube.com/watch?v=HEhzoCOqZJ8

Gene and Chromosome Mutations Gene Mutation - A change in the genetic code of DNA Chromosome Mutations – occur when there is a change in the number or structure of chromosomes Mutation Cause Crossing Over Chromatids break, exchange segments, and rejoin during meiosis. Linked genes are separated resulting in variations among offspring Nondisjunction Pairs of homologous chromosomes fail to separate during meiosis resulting in gametes containing 1 chromosome more or less Down syndrome Nondisjunction of human chromosomes #21. Offspring has an extra chromosome

Mutations Mutation Cause Polyploidy An entire set of chromosomes fails to separate during meiosis. The resulting gamete contains twice the normal chromosome number. Fatal in animal offspring. In plants, offspring often larger or more vigorous than normal plants. Deletions A chromosome segment is lost Translocation A chromosome breaks off and becomes reattached to nonhomologous chromosomes Inversion A chromosome segment breaks off and becomes reattached at a new point on the original chromosomes

Linkage & Crossing Over Linkage – traits located on the same chromosome that tend to be inherited together Crossing-over – chromatids break, exchange segments and rejoin during meiosis. Linked genes are separated resulting in variation among offspring Mitosis – type of cell division that results in two daughter cells identical to the parent cell and to each other (Video - https://www.youtube.com/watch?v=VlN7K1-9QB0 ) Meiosis – type of cell division in which the daughter cells contain half the number of chromosomes found in the parent cell; occurs only in gamete formation (Video - https://www.youtube.com/watch?v=D1_-mQS_FZ0 ) Meiosis & Crossing over Video - https://www.youtube.com/watch?v=pdJUvagZjYA