What is incomplete. dominance? blending: combination of genes in which a mixture of both traits shows

Transcription

1 27 incomplete dominance: blending of traits carried by to or more different genes blending: combination of genes in hich a mixture of both traits shos dominance? What is incomplete

2 28 genes for most hair, skin, and eye colors. Four-o clock floers Four-o clock floers are usually red or hite. Many genes in humans also sho incomplete dominance. They include is a blend of black and hite. gene, and a eaker, recessive gene. The dominant gene usually ins. This kind of gene combination is called blending. The offspring of pure black and pure hite Andalusians are gray. Gray Not all genes, hoever, are completely dominant nor completely reces zhun] fol. Others have genes for hite feathers. Neither of these genes is dominant. Andalusian fol Some of these chickens have genes for black feathers. parent is pure hite WW), the offspring ill be pink a blend of red of four-o clock floers, shorthorn cattle, and Andalusian [an-dub-lew sive. The genes of certain traits are equally strong. Neither trait is hidden. offspring have pink floers RW). a pure red RR) crosses ith a pure hite WW), the colors blend. The The dominant trait shos up in the offspring. The recessive trait stays Red and hite are equally strong traits. Neither color is dominant. When Heredity is sometimes like this. Most traits have a stronger, dominant ere equally matched. plete dominance, genes combine and a mixture of both traits shos up. Three good examples of incomplete dominance are found in the colors stronger team ins. Some games end in ties. This shos that the teams dominant. We say there is incomplete dominance. In cases of incom and hite RW). The blended calf is called a mn calf. In most games, there is a stronger team and a eaker team. Usually, the I. S C) IN What Shorthorn cattle In cattle, if one parent is pure red RR) and the other

3 29 c) only pink. c) neither red nor hite is a) only red. a) red is dominant over hite. 3. In four-o clock floers, d) both red and hite. b) only hite. are 2. The offspring of crossed pure red and pure hite four-o clock floers 1. Fill in the Punnett square in Figure A. floer red Figures A, B, and C sho three examples of incomplete dominance. Figure A The crossing of pure red RR) and pure hite WW) four-o clock floers. IL JDNRCiTA?jDf;jC BLUE :1 Ei:IG dominant. incomplete dominance? 5. Blended four-o clock floers have 6. Blended four-o clock floers are 7. Just by looking at the chart in Figure A ho can you tell that there is pure, hybrids c) genes for both red and hite. hite. red. a) only genes for the color 4. Pink is a blend of hich to colors? and d) pink is dominant over red. d) only pink genes. b) hite is dominant over red. b) only genes for the color RW RW RW 13 A R

4 30 pure, hybrids dominant. c) a blend of black and hite. c) neither black nor hite is d) black and hite. 8. Compiete the Punnett square in Figure B. 9. The offspring of crossed pure black and pure hite Andalusian a) only hite a) black is dominant over b) only black. B S chickens are hite. hite. c) genes for both black and black. hite. a) only genes for the color 11. What color are the offspring of black and hite chickens? dominant. black. b) hite is dominant over b) only genes for the color 10. In Andalusian chickens, 12. Gray is a blend of hich to colors? 13. Blended Andalusian fol have 14. Blended Andalusian fol are and d) both black and hite are d) only grey genes. Figure B The crossing of pure black BB) and pure hite WW) Andalusian chickens. SW SW W BW chicken chicken gray parent parent black chicken chicken gray hite

5 pure, hybrids a) only red. a) red is dominant over hite. 20. Roans are red. c) genes for both hite and a) only genes for the color h4te. b) only genes for the color red. d) only pink genes. colors. nance of red and hite c) there is incomplete domi c) a blend of red and hite. d) red and hite. d) pink is dominant over hite. b) only hite. b) hite is dominant over red. 15. Complete the Punnett square in Figure C. 16. The offspring of crossed pure red and pure hite shorthorn tattle are 17. In shorthorn cattle, 18. What are red and hite blended cattle called? 19. Roans have Figure C The crossing Gf pure red RR) and pure hite WW) shorthorn cattle. B RW RW RW.1 pink pink 1 1 RB red parent hite parent R B calf 31

6 32 and recessive eye pure given trait. color. 10. Examples of incomplete dominance in humans are found in are equally the color is dominant. the 2. Not all genes are completely recessive nor completely. Some 3. An individual that has only dominant or recessive genes for a trait is 5. A condition here the genes for a given trait are equally strong is called 6. A combination of genes in hich a mixture of both traits shos up is called 7. To examples of offspring of incomplete dominance are and for that trait. for that trait. 4. An individual that has both dominant and recessive genes for a trait is 1. A hidden trait is called a trait. hite pink four-o clock floer hybrid strong roan calf red skin blending dominant incomplete dominance spaces provided. Some ords may be used more than once. Complete each statement using a term or terms from the list belo. Write your ansers in the kill. i I ale btncti 1 I. 8. In four-o clock floers and roan cattle, neither the color nor 9. Incomplete dominance produces offspring ith genes for the

7 33 1. KR a) recessive pure 2. Kr b) control heredity Column A Column B space provided. C Match each term in Column A ith its description in Column B. Write the correct letter in the MATCHING C your ansers in the spaces provided. Belo are several scrambled ords you have used in this Lesson. Unscramble the ords and rite WORD SCRAMBLE 1. Are the parents in this cross pure or hybrids? 5. Why is neither gene in this cross represented by a loer case letter? 2. What color are the parents? 3. Will all of the offspring produced by this cross be hybrids? 4. What colors ill the offspring be? W = hite feathers B B = black feathers W W Complete the Punnet square for feather color in chickens. 8W = gray feathers B 5. DHSYIRB 4. RATTI 3. DLEBN 2. SEERVICES 1. TOMANDIN 4 4. incomplete dominance d) dominant pure 3. rr c) blends traits 5. genes e) hybrid