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Study Guide for Genetics TestWhere do the alleles of the offspring come from?Hint: 1 from Mom and 1 from DadHow would you write a dominant allele? What does dominant mean?With a capital letter, the dominant trait is the one that is shown, stronger.How would you write a recessive allele? What does recessive mean?With a lower case letter, the recessive trait is hidden when a dominant one is present.If a person has 1 allele for dimples and 1 for no dimples, what trait will show up?The dominant trait for dimples will show up.Write the 2 alleles for homozygous dominant. For heterozygous. For homozygous recessive. (Use whatever letter you would like)DD is homozygous dominant, Dd is heterozygous and dd is homozygous recessive. Can a person with no dimples ever be heterozygous? Why or why not? (Remember…dimples is dominant and no dimples is recessive)They cannot be heterozygous because the dominant allele will be shown so they will have dimples.Define: Phenotype – physical appearance like dimples, brown hair, or A bloodGenotype – genes or alleles for a trait, like Dd or AA (we use letters)Homozygous – same form of the trait like DD or ddHeterozygous – different forms of the trait like DdCo-dominance – when two traits are dominant like A and B in blood types are both dominant so a person with genes AB will have AB blood. When you flip a coin, and you got a heads the first time, does that mean that you have less of a chance of getting a heads they second time? Why or why not?Each time you flip a coin you still have a 50 % chance of getting either heads or tails. What happens the first time does not influence what happens during later events.Give an example of a phenotype and a genotype.Phenotype = freckles genotype = Ff14. T = CAN taste PTCt = CAN’T taste PTC Tt x Tt T tTTTtTttt T tWhat is the probability of TT? 25%What is the probability of Tt? 50%What is the probability of tt? 25%What is the probability you can taste PTC? 75%What is the probability you can’t taste PTC? 25%15. Cross an AB blood type mother with a homozygous B blood type father: A BABBBABBBAB x B B B What blood type(s) do the offspring have? AB and B bloodAre the offspring heterozygous or homozygous? 50 % heterozygous and 50% homozygousAre the parents homozygous or heterozygous? AB heterozygous and B homozygousWhat is the co-dominance? When two traits are both dominant they both showWhich blood type shows co-dominance? AB shows co-dominance16. Make a Punnet square for dimples crossing DD x ddD = Dimplesd = no dimples D D DdDd Dd Dd d dWhat is the probability of a person having dimples? 100%What is the probability of a person having no dimples? 0 %What is the probability of a person being DD? 0 %What is the probability of a person being Dd? 100 %What is the probability of a person being dd? 0 %18. How many chromosomes do humans have in each body cell? Humans have 46 chromosomes19. How many pairs of chromosomes do humans have in each body cell? Humans have 23 pairs of chromosomes20. How many chromosomes are in human sex cells? (I.E. Sperm and Egg cells) In human sex cell there are 23 chromosomes for egg and 23 for sperm ( 12 from each parent)21. Write the symbols for the chromosomes that these people have: Men: X Y` Women: X X22. Which chromosome is smaller, X or Y? The Y chromosome is smaller than the X chromosome.23. All eggs carry an X chromosome.24. ? the sperm carry an X chromosome and the other ? carry a Y25. Explain the difference between identical and fraternal twins. Use a diagram if helpful. Identical twins = 1 egg & 1 sperm = splits into 2 babies = same gender Fraternal twins = 2 eggs & 2 sperm = 2 separate babies = can be different genders26. List 3 characteristics that are inherited. 1) natural hair and eye color 2) cleft chin 3) dimples27. List 3 characteristics that are acquired. 1) ear piercing 2) reading and speaking 3) scars or tattoos28. Explain the difference between acquired and inherited traits. Inherited traits are the ones you are born with that come from genes from your parents. Acquired traits are the ones you learn or practice or get after you are born from the environment. ................
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