Genetics Review Chapter 12

1. The passing on of characteristics from parents to offspring is known as ____________. Heredity The study of patterns of inheritance and variations in organisms is called ______________. Genetics 2. Gregor Mendel studied ________ plants. pea 3. What is the difference between pollination and fertilization? Pollination is the transfer of the male pollen grain to the pistil. Fertilization is when the male and female gametes actually fuse together. 4. What are the three generations of a cross called? Describe what each includes. P1 – The first generation in the cross F1 – The second generation (the offspring of the P1 generation) F2 – The third generation (the offspring of the F1 generation)

5. If a homozygous tall plant is crossed with a homozygous short plant, what percentage of the F2 generation will be short if the F1 generation is self-fertilized? (Tall is dominant over short) P1: TT x tt F1: All Tt F2: 75% Tall, 25%short 6. Why did Mendel call his cross a hybrid? The plants were a cross between two parents that show different forms of a trait 7. Mendel concluded _______ factors controlled each trait. The difference forms of the genes are called _____________. Two, alleles 8. When Mendel crossed a tall pea plant with a short pea plant, why were all of the offspring tall? The allele for tall was dominant over the allele for short TT tTt t

9. Describe the Law of Segregation During meiosis, the factors that control each trait separate, and only one factor from each pair is passed to the offspring 10. What is the difference between an organism’s genotype and its phenotype? Genotype – the genetic combination of the organism Phenotype – the physical traits of the organism 11. If an organism has the same two alleles for a trait, the organism is ____________. Homozygous If an organism has two different alleles for a trait, the organism is ____________. heterozygous 12. What is the only way an organism can show a recessive trait? If it is homozygous for the recessive trait

13. Define incomplete dominance. Give an example. –when one allele is not completely dominant over another. The phenotype expressed is somewhere between the two possible parent phenotypes. –An example is the flower color of snapdragons (RR – red, rr – white, Rr – pink) 14. What possible gametes could an organism give an offspring if they had the following genotypes: –TT – T or T –Bb – B or b –AaBb – AB, Ab, aB, ab –PPGg – PG, Pg, PG, Pg 15. Describe the Law of Independent Assortment. The inheritance of alleles for one trait is not affected by the inheritance of alleles for a different trait if the genes are on different chromosomes.

16. The sex chromosomes for a female are ________. XX The sex chromosomes for a male are ________. XY A mother can pass on an _____ or an _______. X or X A father can pass on an ______ or a ________. X or Y 17. What are the chances of a couple having a boy if they already have two daughters? 50% 18. Sex-linked traits are carried on the _____ or ______ chromosomes. Most sex-linked traits are carried on the ________ chromosome. X or Y; X 19. Can a male be heterozygous for a sex-linked trait? Why or why not? No; a male has only one of each sex chromosome so it can only carry one allele for any sex-linked trait.

20. Human blood types demonstrate _______ alleles that demonstrate ___________ where heterozygous alleles are expressed equally. Multiple; codominance 21. What are the possible genotypes for each blood type (A, B, AB, and O)? –A – I A I A, I A i –B – I B I B, I B i –AB – I A I B –O – ii 22. If a man has type A blood and a woman has type B blood, could they be the parents of a baby with type O blood? Yes if they are I A i and I B i 23. If a man has type AB blood and a woman has type B blood, could they be the parents of a baby with type O blood? No, an I A I B parent would have no i to give an ii offspring

Blood Type Frequencies WhiteAfrican American HispanicAsian O +37%47%53%39% O -8%4% 1% A +33%24%29%27% A -7%2% 0.5% B +9%18%9%25% B -2%1% 0.4% AB +3%4%2%7% AB -1%0.3%0.2%0.1%

24. To make a Punnett square, the possible _______ from each parent are put on the top and sides of the square. gametes 25. What are polygenic traits? Give an example. Polygenic traits are controlled by two or more genes. These traits often show a great variety of phenotypes, e.g. skin color. 26. What is a pedigree? A chart to show an inheritance pattern (trait, disease, disorder) within a family through multiple generations. It can be used to track the genotype and phenotype of the family members and the genetic characteristics (dominant/recessive, sex-linked) of the trait.

27. If a pedigree showed that more offspring had a trait than those who did not, what could that tell you about that trait? The trait is probably dominant 28. If a pedigree showed that more male offspring had a trait than female offspring, what could that tell you about the trait? The trait is probably sex- linked

29. Black fur (B) is dominant to white fur (b) in rabbits. For the following crosses, show a Punnett square and the possible genotypes and phenotypes for their offspring. a. A homozygous black rabbit with a white rabbit –Parents: BB x bb –Genotype: 100% Bb –Phenotype: All Black b. A heterozygous black rabbit with a white rabbit –Parents: Bb x bb –Genotype: 50%Bb 50% bb 2Bb: 2bb –Phenotype: 50% Black 50% white BB bBb b Bb b bb bBbbb

30. Black fur (B) is dominant to white fur (b) in rabbits. Long ears (L) are dominant over short ears (l). For the following crosses, show a Punnett square and the possible genotypes and phenotypes for their offspring. a.Two rabbits heterozygous for both fur color and ear length Parents: BbLl x BbLl Genotype: 1BBLL: 2BBLl; 1BBll: 2BbLL: 4BbLl; 2Bbll; 1bbLL; 2bbLl: 1bbll Phenotype: 9 Black fur Long ears: 3 Black fur Short ears 3 White fur Long ears 1 White fur Short ears BLBlbLbl BLBBLLBBLlBbLLBbLl BlBBLlBBllBbLlBbll bLBbLLBbLlbbLLbbLl blBbLlBbllbbLlbbll

30. Black fur (B) is dominant to white fur (b) in rabbits. Long ears (L) are dominant over short ears (l). For the following crosses, show a Punnett square and the possible genotypes and phenotypes for their offspring. b. A homozygous black fur, long eared rabbit with a white, short eared rabbit Parents: BBLL x bbll Genotype: All BbLl Phenotype: All Black fur long ears BL blBbLl blBbLl blBbLl blBbLl

31. Hemophilia is a sex-linked trait. The trait for hemophilia is reccesive (h) to the normal allele (H). For the following crosses, show a Punnett square and the possible genotypes and phenotypes for their offspring. a. A father with hemophilia crossed with a normal mother who is a carrier for the disease –Parents: X H X h and X h Y –Females: 50% Normal, 50% hemophilia –Males: 50% Normal, 50% hemophilia b. A hemophiliac mother and a normal father –Parents: X h X h and X H Y –Females: 100% Normal –Males: 100% hemophilia XhXh Y XHXH XHXhXHXh XHYXHY XhXh XhXhXhXh XhYXhY XHXH Y XhXh XHXhXHXh XhYXhY XhXh XHXhXHXh XhYXhY

32. For the following crosses, show a Punnett square and the possible genotypes and phenotypes for their offspring. a. A man with type O blood and a female with type AB –Parents: ii and I A I B –Genotype: 2 I A i : 2 I B i –Phenotype: 50% Type A, 50% Type B b. A man with type B blood (whose mother is type O) and a woman with type AB –Parents: I B i and I A I B –Genotype: 1 I A I B : 1 I B I B : 1 I A i : 1 I B i –Phenotype: 25% Type A 50% Type B 25% Type AB ii IAIA IAiIAiIAiIAi IBIB IBiIBiIBiIBi IBIB i IAIA IAIBIAIB IAiIAi IBIB IBIBIBIB IBiIBi