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1 How did the study of Genetics begin? Clip Gregor Mendel Genetics is the branch 2 of biology that deals with heredity. A great deal of what we know about genetics began with the work of a monk named Gregor Mendel, who experimented with sweet pea plants in the 1800s. 3 Mendel’s Work • Mendel studied the patterns of inheritance in pea plants. • He chose seven traits to follow. 4 • Mendel needed to make sure he had plants that always gave the same offspring-called true breeding. • He “self-pollinated” plants until he got seeds that always gave the same offspring. 5 Some plants can self-pollinate or cross-pollinate with another plant. 6 He took a purple flower plant and crossed it with a white flower plant? He called these the parent generation (P generation) What do you think the offspring looked like? 7 Pollen X F1 8 POLLEN F2 9 Mendel concluded: 2. Something is being passed from parent to offspring. He called these “Factors” 3. Sometimes you can see “it” and sometimes you can’t see “it”. 4. If you can see it- it is dominant. 1. If it’s there and you can’t see itit’s recessive. 5. There are two versions of these “FACTORS”. 6. To show the two version we use a capital letter for the dominant (S) version of the trait and a lower case for the recessive version (s) of the trait. ADD TO NOTES: Each Version is called an Allele. 10 Each chromosome has many genes, but the alleles may be different 11 Alleles are different versions of the same gene. 12 Common Physical Human TraitsDifferent Alleles Trait Dominant Recessive Chin cleft Absent (C) Present (c) Dimples Present (D) Absent (d) Free (F) Attached (f) Almond (A) Round (a) Straight (S) Upward slant (s) Eyebrow position Connected (Y) Not connected (y) Eyebrow shape Bushy (B) Fine (b) Long (L) Short (l) Round (R) Square (r) Present (P) Absent (p) Curly (H) Straight (h) Tongue rolling Can roll (T) Can't roll (t) Widow's peak Present (W) Absent (w) Earlobe shape Eye shape Eye position Eyelash length Face shape Freckles Hair 13 Activity 14 15 We have two copies of all of our chromosomes Why? These are called Homologous Chromosomes 16 BOY OR GIRL? 17 Karyotype 18 DNA codes for Proteins What is a gene? 19 • A segment on the chromosome that codes for a protein. • People have two copies of each gene, one copy inherited from the mother and the other copy inherited from the father. • There are many versions of each genealleles Remember: Genes come in pairs. **One from your mother **One from your father. If the two alleles in the pair are identical, then the condition called homozygous. The term “purebred” is sometimes used. 20.1 • 20 If the 2 alleles are different, the condition is called heterozygous. The term “hybrid” is sometimes used to refer to heterozygous. What the genes/alleles are …RR.…Rr What the organism looks like…… Red…..White 21 Genotype Phenotype 22 How did you end up with the traits and genes that you got? During meiosis, each egg or sperm only gets one copy of each chromosome. 23 Meiosis Review Animation 24 Law of Dominance Mendel’s Laws • States that the dominant allele will prevent the recessive allele from being expressed. •The recessive allele will appear when it is paired with another recessive allele in the offspring. •Remember: Genes Come in Pairs! Law of Segregation (separation) states that gene pairs separate when gametes (sex cells) are formed •Each gamete has only one allele of each gene pair. (haploid) 25 gene pairs separate Goes through Meiosis Mendel’s Laws A a b B S Phase AA aa bb BB Makes a copy A A a a b b B B 26 Law of Independent Assortment states that different pairs of genes separate independently of each other when gametes are formed. Mendel’s Laws Example: Just because you get the gene for brown hair does not mean you will get the gene for blue eyes. Animation 27 REVIEW 1. A trait is a characteristic an individual receives from its parents. 2. Genes carry the instructions responsible for the expression of traits. 3. A pair of inherited genes controls a trait. 4. One member of the pair comes from each parent. 5. Alternative versions of genes are known as alleles. REVIEW Mendel’s Principles of Inheritance • Inherited traits are transmitted by genes which occur in alternate forms called alleles 1. Principle of Dominance - when 2 forms of the same gene are present the dominant allele is expressed 2. Principle of Segregation - in meiosis two alleles separate so that each gamete receives only one form of the gene 3. Principle of Independent Assortment - each trait is inherited independent of other traits (chance) 28 Peas in a pod- Genetics Clip Example EOCT Question: Earlobe shape is a human trait. Some people have free earlobes while others have attached earlobes. Two parents with free earlobes have four children. Three children have free earlobes and one child has attached earlobes. If these parents have another child, what is the probability that the child will have attached earlobes? A 25% B 50% C 75% D 100% 32 Predicting possible outcomes of a genetic cross. 30 Punnett Squares • Geneticist use punnett squares to determine the probability of a combination of alleles. • For example: If a heterozygous black rabbit is crossed with a heterozygous black rabbit, what are the chances the offspring will be black? 31 B=Black b= Brown Genotypes? Phenotypes? 30 31 Claymation Clip Example EOCT question: In humans, a widow’s peak is dominant over a continuous hairline. Mary’s father has a widow’s peak, but Mary and her mother have a continuous hairline. What is the genotype of Mary’s father? A HH B Hh C hh D cannot be determined 33 34 35 Incomplete Dominance 36 37 38 Codominance With codominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together. DO NOT blend together. 39 Codominance • Both phenotypes are expressed at the same time. • Example: Blood Types Genotype IOIO Phenotype Type O IAIO IAIA I BI O I BI B Type A Type A Type B Type B IAIB Type AB There are 3 alleles for blood typemultiple alleles 40 Codominance R = allele for red flowers W = allele for white flowers red x white ---> red & white spotted 41 42 Polygenic traits Many traits are controlled by more than one gene. Ex: Skin Color 43 Sex Linked Traits Traits associated with particular sexes are called sex-linked or X-linked traits. Examples of Sex-linked Traits: •Red-green colorblindness •Hemophilia 44 45 Linked Genes • Occurs when particular alleles are inherited jointly. • They tend to be inherited together, for example, red hair and freckles. 1st 22 are Autosomes, the last pair (XY) are sex chromosomes) 46 Charts that show relationships within a family Pedigree 47 47 • • • • • 13 How many boys? __________________ 12 How many Girls? __________________ 3 How many generations? _______________ 4 How many with the disorder? ____________ 6 How many marriages are shown? ____________ 1. How many generations? 2. How many carriers? 3. How many affected males? 4. How many affected females? 5. Autosomal or sex-linked? 48 Autosomal-Dominant What can you tell by the pedigree? Dominant or recessive? Autosomal or sex-linked? SEX-LINKED What can you tell by the pedigree? Dominant or recessive? Autosomal or sex-linked? SEX-LINKED What can you tell by the pedigree? Dominant or recessive? Autosomal or sex-linked? Autosomal Dominant or recessive? -Dominant Autosomal or sex-linked? NO carriers when Dominant. Autosomal -Recessive Carriers when recessive. • Pedigree Practice-Smart board 49 Huntington’s Disease • Progressive, degenerative disease that causes certain nerve cells in your brain to waste away. • Experience uncontrolled movements, emotional disturbances and mental deterioration. • No cure. Fatal. ages:3060 • Dominant Allele 49 1/2 Colorblindness • Sex-linked trait • Gene for color vision located on the X chromosomes. • Males are more likely to have colorblindness because they have only one X chromosome 50 What do you see? The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots. 51 52 53 Down Syndrome • 3 copies of chromosome #21. • Sister chromatid DO NOT separate during Meiosis. • (or homologues fail to separate ) • Nondisjunction • Also called: Trisomy 21 54 Nondisjunction • Sister chromatid DO NOT separate during Meiosis. • Or homologues fail to separate during Meiosis. Down Syndrome - Trisomy 21 55 56 Nondisjunction 57 58 Cystic Fibrosis • CF is caused by a recessive allele on chromosome #7. • More than 1,000 different mutations in the CFTR gene have been identified • Deletion of 3 bases. • Affects the body's respiratory and digestive systems. 59.1 Cystic Fibrosis • 1 in 29 Caucasian Americans have the allele. – Asian & African-less likely to have. – More than 10 million Americans carry the cystic fibrosis gene • Treatments: – Pancreatic enzyme replacement therapy to allow proper food digestion – Bronchodilators (also used by people with asthma) that help keep the airways open – Inhaled antibiotics to kill the bacteria that cause lung infections – Chest physical therapy, in which the patient is repeatedly clapped on the back to free up mucous in the chest Gene therapy ?????? Currently in clinical trials 59.2 Hemophilia 60 61 Sickle Cell 62 Mis-shaped blood cells. People who carry the tendency to have sickle cell anemia are less likely to die from malaria. Sickle Cell •Most commonly affects AfricanAmericans. •About 1 out of every 500 AfricanAmerican babies born in the United States has sickle cell anemia. Mis-shaped blood cells. Interesting fact: Unlike normal red blood cells, which can live for 120 days, sickleshaped cells live only 10 to 20 days. 63 Tay-Sachs • Progressively destroys nerve cells (neurons) in the brain and spinal cord. • Harmful quantities of a fatty acids accumulate in the nerve cells of the brain. • Caused by insufficient activity of an enzyme called beta-hexosaminidase A that catalyzes the biodegradation of acidic fatty materials • More common in people of Ashkenazi (eastern and central European) Jewish heritage • Fatal 64 Gene Therapy 65 Example EOCT question: What is nondisjunction? A. failure of chromosomes to separate during meiosis B. failure of the cytoplasm to divide properly C. the insertion of a gene into a different chromosome D. the deletion of a gene from a chromosome 66 Which of the following shows how information is transformed to make a protein? A DNA RNA protein B gene chromosome protein C cell respiration ATP protein D ATP amino acid protein 67 Information on mRNA is used to make a sequence of amino acids into a protein by which of the following processes? A replication B translation C transcription D transference 68 Pea plants have seeds that are either round or wrinkled. In this cross, what will be the phenotypic ratio of the offspring? A B C D 69 50% RR and 50% Rr 25% RR, 50% Rr, and 25% rr 50% round seeds and 50% wrinkled seeds 100% round seeds What is a source of genetic variation? A mutation B adaptation C replication D transcription 70 In Mendel’s experiments with a single trait, the trait that disappeared in the first generation and reappeared in the next generation is called the 71 A homozygous trait B dominant trait C recessive trait D heterozygous trait •What pattern of inherita nce is this? 72 Human Genome Project What would one gene say to another? Cloning