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Genetics – the study of heredity. Based on the study of probability (likelihood). 1. Why should we study genetics?. Disease causes/treatments Biotechnology – agriculture, animal husbandry Breeding Pedigrees- family lineages Evolutionary trends. 1.How are genes passed on to our offspring?.
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Genetics – the study of heredity Based on the study of probability (likelihood)
1. Why should we study genetics? • Disease causes/treatments • Biotechnology – agriculture, animal husbandry • Breeding • Pedigrees- family lineages • Evolutionary trends
1.How are genes passed on to our offspring? 2. Sperm carry ½ and eggs ½ of genetic code.
1. How are sperm & eggs produced? 2. Meiosis – germ cells divide to produce haploid cells (1 set of chromosomes) 3. Haploid =1N
2. Meiosis has 2 divisions to reduce chromosome number
2. What are the phases of meiosis? • Meiosis I • Prophase I- Crossing over of alleles occurs! • Metaphase I- homologous chromosomes side by side • Anaphase I- ho. chrom. separate (not chromatids) • Telophase I- 2 cells with 2 chromatids of every chromos.
Meiosis II • Prophase II- nothing happens • Metaphase II- chromo align single file • Anaphase II- chromatids pull apart • Telophase II- 4 total cells w/ 1 copy of each chromo.
1N + 1N = 2N (a diploid cell) 46 XX= female 46 XY = male 23 pr homologous chromosomes
What are the results of meiosis? • 4 cells • Genetically different • Haploid (1N) • In females, only one egg is used
Dragon genetics activity to learn basic vocabulary Check for understanding following activity: BB Bb Bb Allele/gene Genotype/phenotype
Punnett squares • Designed to PREDICT outcomes (expected ratios)
Single gene crosses • monohybrid: Aa x Aa • Or : AA x Aa • Or Testcross: aa x A_____
Cystic fibrosis • Due to a recessive allele (ff) • Faulty membrane protein does not regulate NaCl • Cells create mucous around them/breeding ground for bacteria • Chromo #7
Huntington disease • Due to a dominant allele • Late onset (35 years+) • Protein (huntingtin) destroys nerve cells • Due to a repeat of more than 21 CAG in a gene • Chromosome 4 (discovered in 1983) • Maracaibo, Venezuela- Huntington research
Di- crosses probability problems • Rh factors- effect on fetus- protein on RBC- rh from RHESUS monkey- Rh neg makes antibodies against Rh protein- • Rh is important during fetal development • Albinism- due to recessive alleles
Review terms • Alleles/gene • Genotype/phenotype • Homozygous/heterozygous • Probability • Offspring/ F1/F2 generations • Dominant/recessive
Quiz • 1. Explain how an allele is related to a gene. • 2. What is the relationship between a genotype and a phenotype? • 3. Which of the following combinations are homozygous? BB Bb bb
4. T-tall t – short Y –yellow y- green • Cross a plant that is heterozygous tall and homozygous for green seeds with a plant that is short and is also homozygous for green seeds. • List the genotypes and ratios for the above cross. • List the phenotypes and ratios for the above cross.
Codominance • Both alleles of a gene express themselves= both proteins are produced • Examples: • AB blood type (protein “A” and protein “B”) • Sickle cell trait ( point mutation in hemoglobin)- produces 3 phenotypes- normal, trait, anemia
Blood type importance Your immune system makes antibodies against foreign proteins. Antibody A attacks blood type A Antibody B attacks blood type B Antibodies A & B attack blood type AB Antibodies A & B DO NOT attack blood type O
blood types- multiple alleles Phenotype (protein) Genotype (alleles) AA or AO BB or BO AB OO • Blood type A • Blood type B • Blood type AB • Blood type O
Blood type lab • Antibodies can cause blood to clump (agglutinate) • This is how blood is “typed” for accuracy for transfusions.
What is the importance of sickle cell trait? • Evolutionary advantage to survive Malaria • “heterozygote” advantage- NS (trait) • “S” cells sickle and the protozoan is killed
Video clip on sickle cell evolution http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html
Normal RBCs vs. Sickle RBCs phenotype genotype NN NS SS • Normal blood cells • ½ normal & ½ can sickle • all can sickle
Incomplete dominance • 2 alleles “blend” their traits and produce a 3rd phenotype • Examples: • Palamino horses (ncomplete & polygenic) • Tay-Sachs enzyme levels (enzymes, some enzymes, no enzyme)
X linked genes • Genes that are located on the X chromosome only • Examples • Hemophilia • Red-green color blindness • Duschene muscular dystrophy • Calico cats • ALD (Lorenzo’s oil disease)
hemophilia • Hemophiliacs lack protein factors for clotting.
Epistatic genes • Genes that “cancel” out other genes
Pedigrees • Family trees that show inheritance
Polygenic inheritance • More than one gene codes for a trait Examples” skin color, eye color, height, hair color Genes are “additive”
Turner’s Syndrome Occurs in females. Missing an entire X chromosome. Non-working ovaries (no menstrual cycle) Short stature and webbed neck Increased risk of heart and cardiovascular problems
Triple X Syndrome • Three X chromosomes • Only one X chromosome is active at a time (little adverse effects) • Tall stature, small head, fold in skin • Learning disabilities. Low self esteem • Fertile
Poly X Syndrome • XXXX and XXXXX • Similar symptoms to XXX • Small head and jaw • Very tall stature • Irregular shaped heart and lungs • Very low IQ 10-15