Chromosomal Mutations/Abnormalities  Describe processes that can alter composition or number of chromosomes (i.e., crossing-over, nondisjunction, duplication, translocation, deletion, insertion, and inversion).

Chromosomal Mutations/Abnormalities  A chromosomal mutation is a change in the structure of a chromosome.  There are processes that can alter the composition or number of chromosomes in a cell(s). These processes include:  Crossing-over  Nondisjunction  Duplications  Translocations  Deletions  Insertions  Inversions  A karyotype, or picture of all of the chromosomes found in a cell, can identify changes to chromosome structure and number.

Crossing-Over  Crossing-Over: The exchange (swapping) of segments of homologous chromosomes.  Crossing–over causes gene recombination, or a reassembling of the genes, which increases genetic diversity.

Nondisjunction  Nondisjunction – Failure of sister chromatids to separate during mitosis OR failure of homologous chromosomes to separate during meiosis. Nondisjunction results in extra chromosomes in some cells and missing chromosomes in other cells.  Examples of disorders caused by nondisjunction:  Down Syndrome  Triple X Syndrome  Klinefelter’s Syndrome  Turner’s Syndrome Homologous chromosomes do NOT separate Sister chromatids do NOT separate

Duplication  Duplication: A part of a chromosome (genes) or is copied resulting in EXTRA genetic information.  A duplication results in a chromosome with extra genes. Examine the pictures below:

Translocation  Translocation: The exchange of portions of non-homologous chromosomes. (Remember crossing over is the exchange of segments of homologous chromosomes...these processes are their outcomes are very DIFFERENT!)  During a translocation, genes from a pair of autosomes exchanges with a different pair of autosomes. (Genes from one of Pair 13 might swap with genes from one of Pair 2.)

Deletion  Deletion: A segment of a chromosome (gene) is removed.

Insertion  Insertion: A segment of a chromosome (gene) is added. (SEGMENTS ARE NOT SWAPPED BETWEEN CHROMOSOMES LIKE WE SEE IN A TRANSLOCATION.)

Inversion  Inversion: A segment of a chromosome is removed, flipped over, and reinserted back into the chromosome.

Identify the chromosomal abnormalities!

Protein Synthesis: The process in which amino acids are arranged through the process of transcription (DNA  RNA) and translation (RNA  protein).  BIO.B.2.2 Explain the process of protein synthesis (ie., transcription, translation and protein modification)  BIO.B.2.3 Explain how genetic information is expressed.  BIO.B.2.4 Apply scientific thinking, processes, tools and technologies in the study of genetics.

Protein Synthesis & Gene Expression DNA  RNA  Protein  Traits  Genetic information flows in one direction from DNA to RNA to proteins. This flow of genetic information determines what traits you express. Three important processes occur in cells to allow this flow of genetic information to occur:  Step 1 : Replication  Step 2: Transcription  Step 3: Translation replication transcription translation

What is RNA and why is it needed?  RNA stands for RiboNucleic Acid. It is similar in structure to DNA, but has a few differences that make it a necessary component for transcription and translation to occur. DNARNA Number of strandsDouble (2)Single (1) Type of SugarDeoxyriboseRibose LocationNucleusStarts in the nucleus and exits Nitrogen BasesA, T, G, CA, U, G, C U = uracil Enzyme UsedDNA PolymeraseRNA Polymerase TypesOnly 1Multiple types: mRNA = messenger RNA tRNA = transfer RNA rRNA = ribosomal RNA

Types of RNA  Messenger RNA (mRNA) carries the message that will be translated to form a protein. (messenger)  Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome. (taxi)  Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made.

Transcription – The process that copies the genetic code in DNA onto a strand of mRNA.  Steps:  1 st – DNA unwinds and exposes segments of DNA (genes).  2 nd – The enzyme RNA Polymerase reads the DNA code and helps assemble a mRNA molecule.  3 rd – DNA rezips and stays in the nucleus. mRNA leaves the nucleus and travels to the ribosome. Follow the base pair rules, but remember that RNA does NOT have thymine instead it has uracil! DNA sequence = A T G G C T A A T mRNA sequence = U A C C G A U U A

Transcription

Translation  Translation is the process in which the messenger RNA (mRNA) molecule is translated into a strand of amino acids (polypeptide chain = protein).  Translation converts mRNA messages into polypeptides or proteins. Translation occurs in ribosomes!  A codon is a sequence of three nucleotides of mRNA that codes for an amino acid. codon for methionine (Met) codon for leucine (Leu)

Codon Chart The genetic code matches each RNA codon with its amino acid or function.

 An anticodon is a set of three nucleotides of tRNA that is complementary to a mRNA codon.  An anticodon is carried by a tRNA.  For translation to begin, tRNA binds to a start codon and signals the ribosome to assemble.  A complementary tRNA molecule binds to the exposed codon, bringing its amino acid close to the first amino acid.  The ribosome helps form a polypeptide bond between the amino acids.

Protein Synthesis

Organelle Roles in Protein Synthesis  What role do the following organelles play in forming a protein?  Ribosomes – site of protein synthesis (assembly)  Endoplasmic reticulum – aids in the production, processing and transportation of certain proteins  Golgi apparatus – final processing and packaging of proteins before they leave a cell  Nucleus – contains the instructions (DNA) for making a protein

How do mutations impact phenotype?  Genetic mutations alter or change the DNA sequence in a chromosome. The following are types of gene mutations that may or MAY NOT affect the phenotype (physical appearance) of an organism:  Point mutation – A single-base is copied wrong and results in a different nucleotide sequence and POSSIBLY a different amino acid sequence and protein.  There are a number of mutations that are considered point mutations. They include:  Silent mutations – there is NO change in amino acid sequence or the type of protein assembled.  Missense mutations – there IS a change in amino acid sequence AND the type of protein assembled.  Nonsense mutations - there IS a change in amino acid sequence and it results in a STOP codon stopping the formation of the protein.  Frame-shift mutation – The addition or removal (insertion or deletion) of one or more nucleotides which results in a different amino acid sequence and therefore makes a different protein.

Point Mutation vs. Frameshift Mutation mutated base

What do we do with this knowledge?…. Biotechnology & Genetic Engineering!  Biotechnology – Any procedure or method that uses living things to develop or modify products or processes for specific use. The term is commonly associated with genetic engineering.  Genetic engineering has impacted the fields of medicine, forensics and agriculture.  The following are examples of biotechnology/genetic engineering:  Selective breeding – The process of breeding organisms that results in offspring with desired genetic traits.  Gene splicing – A type of gene recombination in which the DNA is intentionally broken and recombined using lab techniques.  Cloning – A process in which DNA, a cell or an organism is copied from an original source, therefore resulting in organisms which are There are many types of cloning including DNA cloning, reproductive cloning, therapeutic cloning (stem cell cloning).  Genetically modified organisms – An organism whose genetic material has been altered through some type of genetic engineering technology.  Gene therapy – The intentional insertion, alteration, or deletion of genes within an individual’s cells and tissues for the purpose of treating a disease.

Forensics  Forensics: The science of tests and techniques used during the investigation of crimes.  DNA Fingerprinting  DNA Gel Electrophoresis

Introduction to Genetics BIO.B.1.2 – Explain how genetic information is inherited.

A closer look at chromosomes… Chromosomes are located in the nucleus of all eukaryotic cells. Chromosomes are made up of long strands of DNA. A gene is a piece of DNA that directs a cell to make a certain protein. The proteins made are responsible for specific traits. Traits are distinguishing characteristics that are inherited (such as eye color, hair color, etc...).

How do we know traits are inherited?  Genetics is the study of inheritance. Inheritance is the process in which genetic material is passed from parents to their offspring.  Gregor Mendel, the Father of Genetics, laid the groundwork for genetics in the mid 1800’s by studying pea plants and their traits. His experimentation on pea plants led to the following conclusions: 1. Traits are inherited as discrete units called genes. Each gene has a locus, or a specific position on a pair of homologous chromosomes. 2. Organisms inherit two copies of each gene, one from each parent. 3. The two copies segregate during gamete formation because gametes (eggs and sperm) only receive one copy of each gene.  The last two conclusions led to the “Law of Segregation.” Father of Genetics

Alleles  An allele is any alternative form of a gene (variation in nucleotide sequence) occurring at a specific location on a chromosome. Alleles are often represented by letters.  Each parent donates one allele for every gene.  Homozygous describes two alleles that are the same at a specific locus.  Heterozygous describes two alleles that are different at a specific locus. RR Rr

Dominant vs. Recessive Alleles  Dominant alleles are represented by uppercase letters; recessive alleles by lowercase letters.  A dominant allele is expressed as a phenotype when at least one allele is dominant. (Rr or RR = dominant; therefore the pea is round). Both heterozygous (Rr) and homozygous (RR) genotypes produce a dominant phenotype.  A recessive allele is expressed as a phenotype only when two copies are present. (rr = recessive; therefore the pea is wrinkled).  Most traits do not follow simple dominant versus recessive patterns of inheritance (ex. Hair color, skin color, eye color, height, etc…).

Genes influence the development of traits!  All of an organism’s genetic material is called the genome.  A genotype refers to the makeup of a specific set of genes. Examples: Tt, RR, bb  A phenotype is the physical expression or appearance of a trait. Examples: tall, round, blue View this video entitled “What are phenotypes?”

Punnett Squares  The Punnett square is a grid system for predicting all possible genotypes and phenotypes resulting from a cross.  The axes represent the possible gametes of each parent.  The boxes show the possible genotypes of the offspring.  Punnett squares display the probability that an event will occur.

Punnet Squares & Probability  Probability is the likelihood that something will occur.  Probability predicts an average number of occurrences, not an exact number of occurrences.  Probability =number of ways a specific event can occur number of total possible outcomes  Probability applies to random events such as meiosis and fertilization.

Monohybrid Crosses  Monohybrid crosses examine the inheritance of only one specific trait. Mendel’s “Law of Segregation” is evident in monohybrid crosses, and states that during gamete formation the two copies of a gene will segregate or separate. In other words a sperm or egg cell does NOT inherit both copies of mom’s genes AND both copies of dad’s genes.  Example: Trait = Fur ColorB = brown OR b = white Bb x Bb BbBb

Dihybrid Cross  Dihybrid crosses examine the inheritance of two traits. Mendel’s “Law of Independent Assortment” is evident in dihybrid crosses, and states that allele pairs separate independently of each other during meiosis. In other words the inheritance of one trait has no influence over the inheritance of a different trait.  Example:Trait = Fur color & Fur length

Sex-Linked Inheritance  The chromosomes (autosomes vs. sex chromosomes) on which genes are located can affect the expression of traits.  Two copies of each autosomal gene affect phenotype (because autosomes are made of homologous chromosomes); however this is not the case for sex-linked genes because they aren’t always homologous.(genes on sex chromosomes).  Mendel’s rules of inheritance apply to autosomal genetic disorders. – A heterozygote for a recessive disorder is a carrier. A carrier is an individual that carries one gene for a disorder and can pass it on to his or her offspring, A carrier does NOT show signs or symptoms of the disorder. – Disorders caused by dominant alleles are uncommon. (dominant)

Sex-Linked Inheritance  Males and females can differ in sex-linked traits.  Genes on sex chromosomes are called sex-linked genes.  Y chromosome genes in mammals are responsible for male characteristics.  X chromosome genes in mammals affect many traits since both males AND females have at least one X chromosome.  All of a male’s sex-linked genes are expressed because male’s do NOT have a second copy of sex-linked genes (only one X and one Y).  The gene for color-blindness is sex-linked and located on the X chromosome.  B = Normal Vision  b = Colorblind

Non-Mendelian Genetics  Many factors can influence the expression of traits. Non- Mendelian Genetics accounts for these factors by studying the following:  Incomplete Dominance  Co-dominance  Multiple Alleles  Polygenic Traits  Epistatic Genes

Incomplete Dominance  In incomplete dominance, neither allele is completely dominant nor completely recessive.  Heterozygous phenotype is intermediate between the two homozygous phenotypes.  For example if a red rose is crossed with a white rose the F1 generation would all be pink roses.

Co-Dominance  Co-dominant alleles will both be completely expressed.  Co-dominant alleles are neither dominant nor recessive.  Example: ABO blood types  “A” blood type is co- dominant to “B” blood type; therefore a third blood type “AB” is formed.  Many genes have more than two alleles and this concept is referred to as multiple alleles.

Polygenic Traits  Many genes may interact to produce one trait.  Polygenic traits are produced by two or more genes. Order of dominance: brown > green > blue.

Epistatic Genes  An epistatic gene can interfere with other genes. The gene for albinism is an example of an epistatic gene.

Pedigrees  A pedigree is a chart for tracing genes within a family. Pedigrees allow you to track genotypes and/or phenotypes over multiple generations.