Genetics

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genotype and phenotype! - Genotype: Phenotype= Blue Eyes Genetic makeup of the organism determined by the alleles received Internal information Ex: BB, Bb, or bb - Phenotype vs. Genotype Phenotype: - The physical appearance of a trait determined by the genotype Ex: Brown Eyes, Blue Eyes Genotype=bb Recessive b wwwwwwww Phenotype=Brown Eyes Genotype = Bb or BB Dominant =B I I I Homozygous vs. Heterozygous Homozygous: - Inherit two of the SAME alleles BB= Homozygous Dominant - bb= Homozygous Recessive Heterozygous Inherit two DIFFERENT alleles Bb= Heterozygous B Bb X.X B b B BB bb Simple Dominance Simple Dominance: Dominant allele completely hides the recessive allele Only need ONE dominant allele present i to express the dominant trait Ex: BB or Bb Need TWO recessive alleles to express recessive trait Ex:bb Cleft Chin Widow's Peak Dimples Brown/Black Hair Freckles Dominant Gene Brown Eyes Free Earlobe No Cleft No Widow's Peak No Dimples Blonde Hair Recessive Gene No Freckles Gray/Blue Eyes Attached Earlobe -3)) Different Types of Twins O Splits Splits $ $ Fraternal twins Two sperm fertilise two separate eggs, which develop in womb at same time DNA: 50% maternal, 50% paternal Identical twins Single sperm fertilises single egg, which divides and makes two babies DNA: 100% maternal, 100% paternal Semi-identical twins Two sperm fertilise one egg, which divides and makes two babies DNA: 100% maternal, 78% paternal* *The semi-identical twins in the first known case had 50% paternal DNA Recall..... Alleles are variations of genes carried on homologous chromosomes received from mom and dad Combinations of alleles determine genotype (BB, Bb, bb) which determines the phenotype (brown hair, blue eyes, etc) But how can we predict what the offspring will inherit from its parents??? Allele Brown Locus for eye color gene Allele Blue pair of chromosomes Punnett Square A diagram that predicts the possible genotypes and phenotypes of offspring from a genetic cross Crossing of 1 trait is called a monohybrid cross Outcomes of the cross can be represented as ratios or percentages B B bOb Bb Bb Bb Bb - Genotypic Ratio: - Ratios and Percentages - How often a genotype appears in the diagram Ex: Genotypic Ratio = 1:2:1 Phenotypic Ratio: What physical traits you would expect Ex: Phenotypic Ratio = 3:1 I I I THE PUNNETT SQUARE 1♂ I Bob BBB Bb b Bb bb Genotypic Ratio 1:2:1 BB Bb bb ■ Dihybrid Cross Dihybrid Cross: Predicts the probability of receiving offspring with TWO traits simultaneously. Ex: Hair color and Eye color H=Brown Hair E=Brown Eyes - - - - h= blonde hair e= blue eyes What could be the probability of offspring from two parents that are heterozygous for BOTH traits? Incomplete Dominance • Heterozygous genotype displays a blended phenotype of the two alleles Neither allele is dominant over the other, so we use two different letters to represent the two alleles. Ex: Four O'Clock Flowers Phenotype Red White Pink CRCR CRCW Genotype CRCR CWCW CRCW CWCW Codominance BOTH traits are dominant,so BOTH traits are expressed at the same time!! (No Blending!) Because BOTH traits are dominant, we still use two different letters to represent them. Ex: Roan Cows (Red and White Cows) Phenotype Red White Red AND White Genotype HRHR HWHW HRHW Blood Types Blood types are an example of codominance and multiple alleles Multiple alleles= When 3 or more alleles control a trait Human blood type is controlled by 3 alleles (IA, IB, and i) Alleles IA and IB are codominant Phenotype (blood type) A B AB O Genotypes IAIA or Ai |Bi |B|B or |A|B ii Recall..... Blood type is example of codominance and multiple alleles. • There are 3 alleles involved (Iª, I³, and i ) - A and B are codominance, O is recessive Phenotype (blood type) A B AB O Genotypes IAIA or Ai |Bi |B|B or |A|B ii - Blood Typing Vocab Antigen: Proteins on surface of cell that help identify the- cell (Like ID tags) Determines the blood type of the individual! Ex: A blood type has A antigens, B blood type has B antigens, etc. - Antigen A Antibody Proteins that surround the blood cells to protect them against the opposite antigen. Ex: A blood type will have Anti-B antibodies, B blood type will have Anti-A antibodies, etc. Antigen B I Anti-B antibodies Anti-A antibodies ۷۷ ۲۲ Antigen A Anti-B antibodies vy Blood Typing Antigen B Anti-A antibodies ۲۶۰ Antigens A and B Neither anti-A nor anti-B antibodies Neither antigen A nor B Both anti-A and anti-B antibodies wy How to Identify a Blood Sample. Identifying blood type is extremely important especially for blood transfusions! Giving someone the wrong blood can be fatal! To test a blood sample, a scientist will use: Antiserum- An Antibody that is capable of causing agglutination (clumping of cells) If the antibody matches with the surface antigen, it will cause agglutination The clumping identifies the surface antigen, therefore, identifying the blood type! - - ■ Blood Test Example In the diagram, the blood sample was placed in wells and tested with specific antiserum - Well A uses antiserum A that has Anti-A antibodies! Well B uses Antiserum B that has Anti-B antibodies! What blood type do you think this is based on the test results?! A B What Makes Blood Positive or Negative?? Rh Factor Another protein antigen that can found on the surface of the red blood cells If the Rh protein is present= POSITIVE - If the Rh protein is absent = NEGATIVE Ex: Someone that is AB+ has A and B antigens as well as the Rh antigen! Someone that is A-, only has A antigens (no Rh antigen) TYPE 0+ B+ AB+ A- 0- B- AB- YOU CAN GIVE BLOOD TO A+, AB+ 0+, A+, B+, AB+ B+, AB+ AB+ A+, A-, AB+, AB- EVERYONE B+, B-, AB+, AB- AB+, AB- YOU CAN RECEIVE BLOOD FROM A+, A-, 0+, 0- 0+, 0- B+, B-, 0+,0- EVERYONE A-, O- 0- B-, 0- AB-, A-, B-, O- AB+= Universal Receiver due to the presence of ALL antigens on the red blood cells (A, B, and Rh), so no antibodies in plasma O- = Universal Donor Due to not having ANY antigens, the red blood cells won't react with any antibodies! TYPE A+ 0+ B+ AB+ A- 0 B- AB- YOU CAN GIVE BLOOD TO A+, AB+ 0+, A+, B+, AB+ B+, AB+ AB+ A+, A-, AB+, AB- EVERYONE B+, B-, AB+, AB- AB+, AB- YOU CAN RECEIVE BLOOD FROM A+, A-, 0+, 0- 0+, 0- B+, B-, 0+,0- EVERYONE A-, O- 0- B-, 0- AB-, A-, B-, O- || Interaction of multiple pairs of Ex: Skin color Frequency Polygenic Traits Determined by at least 100 different genes. More dominant alleles present, the more melanin produced = the darker the skin tone! aabbcc 0 genes 1 Skin Color AaBbCc AaBbcc aaBbCC aaBBCC AabbCc AAbbCc AAbbCC aaBbCc AabbCC AABBcc Aabbcc AAbbcc AABbcc AaBbCC AaBBCC aaBbcc aaBBcc aaBBCc AaBBCc AABbCC aabbCc aabbCC AaBBcc AABbCc AABBCC AABBCC 2 3 4 Number of dominant alleles 6 ■ Polygenic Traits Cont. Ex: Hair Color There are roughly 124 genes involved in hair color The color actually expressed depends on the cells called melanocytes that create melanin (the pigment). M TM EUMELANIN PHEOMELANIN MAN MAT == ■ Ex: Eye Color Polygenic Traits Cont. About 150 different genes involved in eye color Mostly determined by 2 genes on chromosome 15 OCA2= Determines how much P protein is produced in melanocytes HERC2= Controls OCA2 Ex: Mutation in this gene can cause a reduction in OCA2 expression lighter color eyes. I HERC2 I I I HERC2 HERC2 No pigment Some pigment OCA2 Lots of pigment OCA2 OCA2 pigment granule melanocytes Pigment No Pigment ZWAN No Pigment nucleus - Trâits Can Be Influenced By The Environment The environment has the potential to change how a particular phenotype will be expressed. Ex: - Hydrangea Flowers: When in acidic soil, flowers bloom blue When in basic soil, flowers bloom pink Arctic Fox: Enzymes will make pigments during certain time of the year for better camouflage digrao - -• 1 pair is known as the sex chromosomes that determine the sex of the offspring! - Recall... We have 23 chromosomes located in gamete cells ■ Males = XY Females = XX I I Sex Determination In Humans I I I Dad XY ♂¹ Mom XX X X XX X XX Y XY XY Ơ Ơ Offspring Sex-Linked Traits! Traits that are located on the X or Y chromosome. Most are recessive If the trait is recessive, need TWO of the same alleles to show it! Ex: Color Blindness Carried on X chromosome - Females have two X's, therefore, need BOTH X chromosomes to carry the allele Ex: X³Xb = Not Colorblind, XbXb-Colorblind Males only have one X and one Y, so they only need the one to have the trait (This is why it occurs most often in males!) Ex: XBY = Not Colorblind, XbY= Colorblind Inheritance of Traits - Pedigree-A diagram to display a family's history of how a specific trait is inherited over several generations TOTO 11st generation (grandparents) I 2nd generation Kparents, aunts, and uncles) 3rd generation (two sisters) | Ww Ww ww WW ww Ww Widow's peak WW or Ww WW Ww Ww WW WW 1 No widow's peak - In A Pedigree... You can see how a genetic disorder runs in a family Carriers are individuals who are heterozygous for an inherited disorder, but DO NOT show symptoms. Carriers can pass the allele for the disorder to their offspring