,; - GENETIC PROBLEMS

XI1. which parental pair could produce a colorblind female?

l. Ho{nozygous normal-vision mother and colorblind father.2. Colorblind mother and normal-vision father'3. Heterozygous normal-vision mother and normal-vision father'

(+.; Heterorygot t norrnal-vision mother and colorblind father-

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Z. A man heterorygous with blood type A marries a woman with blood type AB. Theblood type of their offspring could not be:

'3. O(,, 4. AB

3.

2.8

Onty red tulips result from a cross between homozygous red and homozygous white tulips.

This illustrates the PrinciPle of:

[. independent assortrnent,t2) do*io*""

l. 25'/o 2. 50%

1. multiPle alleles2. incomPlete dominance

f . pink and white2. pink and red

3. segregation4. incomplete dominance

4. 100%

3. pink and pink4. red and white

3. sex linkage,:4. ; independent assorfinent

i3.: homozygous for the trait4 incompletely dominant for the trait

4. ln pea plants, the trait for all tail stems is dominant over the trait for short stems. If nvoheterozygous tall plants are crossed, what percentage of the offspring would be expected to

have the same phenotype as the tr arents? -f ' t'

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A boy has brown hair and blue eyes, and his brother has brown hair and brown eyes. The

fact that they have different combinations of traits is best explained by the concept known as:5.

6. An organism possessing two identical genes for a trait is said to be:

l. heterozYgous for the trait2. hybrid for the trait

7. When two four-o'clock plants are crossed a8 pink four-o'clocks and 52 white four-o'clocks are produced. The phenotypes of the parents are:

GENETIC PROBLEMS 2

g. polydactyly is a human characteristic in which a person has six fingers per hand. The traitfor polydactyly is dominant over the trait for five fingers. If a man who is hetero4rgousfor this trait manies a woman with the normal number of fingers, what are the chances thattheir child would be PolYdactYl?

I.0Y" '2.'soyo 3. 75Yo 4. t000A\.,

g. Which statement describes how two organisms may show the same traig yet have differentgenotyPes for that PhenotYPe?

O Oo, is homozygous dominant and the other heterorygous.Z goth are hetero4/gous for the dominant trait.3. One is homozygous dominant and the other homozygous recessive4. Both are homozygous for the dominant tait.

A child with blood tlrye O has a mother with blood type A and a father with blood brye BThe parental genotypes for blood types must be:

l. IAIA and IBIB2. fi and IBIB

Two pea plants, hybrid for a single trait, produce 60 pea plants.of the pea plants are expected to exhibit the recessive tait?

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10.

11.

12.

13.

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3. IAIB and IAIB agt#^'?-)loi and IBi 'i?'-;,

lY 2. 4s 4.Approximately how many

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ll-','--:60 7,-i:a( +:._:: _l -_:_

Three brothers have blood types A" B, and O. What are the chances that the parents ofthese three will produce a fourth child whose blood type is AB? _r-{l_

T" in,: i- 'l. 0% (2,.-'zs"l" 3.50oA 4. to}% : --**,

, 1 'v- vv li:.,.11*.-.' .,' X vA colorb-lind woman marries a man who has hormal color vision. What are their chancesof having a colorblind daughter

l. independent assortrnent2. segregation

3. 30

3.'dominance-4. incomplete dominance

floz 2. 250h 3.750A 4. 1000AA student crossed wrinkled-seeded (rr) pea plants with round-seeded (RR) pea plants.Only round seeds were produced in the resulting plants. This is caused by:

GENETIC PROBLEMS 3

15. ln peas, flowers located along the stem,(*ig) are dominant to flowers located at the end ofth; stem (terminal.) Let A represent the allele for axial flowers and a represent the allelefor terminal flowers. When plants with axial flowers are crossed with plants having

terminal flowers, all of the offspring have axial flowers. In the cross the genotypes of the

parent Plants are most likelY:

t. aa x aa 2- Aa x Aa i'i.-)'a * * 4' AA x AA

16. ln cabbage butterflies, white color flMJ is dominant and yellow color (w) is recessive. If apure white cabbage butterlly mates with a yellow cabbage butterfly, all the resulting (F1)

tutterllies are heterozygous white. Which cross represents the genotype of the parentgeneration?

2. WW x Ww tl.)WW x ww 4. Ww x Wwl.Wwxww

17. When a mouse with black fur is crossed with a mouse with white fir, all F1 generationoffspring trave gray fiu. Which phenotype results can be expected in the F2 generation?- /'Jt '.1, ',,t. t00o/o gray -.-t=l _3. s}yoblac( 50% whiteZ. 2so/oUlack Tl%ow\ute '; .'",'-. ,'-4.-125Y"blac( 50%o gray,25%ow\ttte

18. There are multiple alleles for the ABO blood goup. Why are there only trvo of thesealleles normally present in any one individual?

l. There are not enough nucleotides in a red blood cell to produce a third allele.,./f)tEu"h parent contributes only one allele for the ABO blood goup to the offspring.'-3.

Each allele in the ABO goup must be either dominant or recessive.4. Blood goup alleles are not segregated during meiosis.

XY19. Which will most probably be true of the children of a iolorblind man and a woman with

normal color vision?\,

l. Atl males will carry the gene for color blindness-2. Nl males will be colorblind.3. All females will be colorblind.7|'Ntfemales will carry the gene for color blindness.

\-/20. A father has type A blood and his child has rype O blood. Which blood goup genotype

does the child's mother probably have?

2. I"lb a r3'J. I I 4. Iblb

The offspring of a cross between Bb x Bb illustrates the pattern of heredity known as:

l. I"I"

l. dominance2. segregation

3. independent assorftnent4. sex linkage

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4GENETIC PROBLENIS

On your al^wer sheet, write the best atawer to each question. Use the following information

for questions 22 - 28'

22. What is the woman's genotYPe?'t"

23. What is tle,man's genotYPe?;'i.

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24. What is the genot)?e of the man's mother?.a .,.

25. What is the genotype of the woman's parents?l, ',

7,6. If the man and woman have four children, how many would be expected to beheterozYgous for eYe color?

L27. How many of the children would be expected to have blue eyes?

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I' humans, the gene for brown eyes, B, is dominant to the gene for blue eyes, b, , i ,- - i )A bro*o-eyed man, whose mother *ui blu.-eyed and whose father was brown-

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eye{ and a blue-eyed womalL both of whose parents were brown-eye4 marry'

28. How many of the-phildren would be expected to have brown eyes?t-

For questions 29 & 30 refer to the follov'ing tnformation:

ln pigeons, checkered pattern is dependent on a dominant gene C, and plainputt.rn is dependent on recessive allele c. Red color is controlled by a dominantgene B and brown color is controlled by recessive gene b.

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29. What is the result of a cross between a homozygoul checkered, redpigeon and ahomozygous Plain' brown Pigeon?

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30. A male pigeon who's genotype is CcBb is mated with the following female cCbB

How many pigeons will be plain and brown?

31. In rabbits, black frr is dependent on dominant gene B and brown fi.r on the recessiveallele b. Normal length fiu is determined b1' a dominant gene R and short fi,u on recessivegene r'

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Show the results of a cross befween rwo heterozygous black ,,orrnil'l.ngth fur rabbits.How many offspring will probably be homozygous for both traits? What is the ratio ofphenotypes? , \ I :t,i ,Lr-,

rl, !t', 1,., i/'''tit'i' i-.t,- t r..

"fi-.r,ftf--ir

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5GEI{ETIC PROBLEMS

32. Rolling the tongue is dominant over non-rolling and rurattached ears are dominant overattached ears.

'.) '' '' f.-If a tongue rollin! woman with attaihed ears has a child who is a non-ioller with

,"r.. unattached ears, what are the probably genotypes of the woman, her husban4 and

the child? ' i'.. I i ,) ,;f

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33. In sheep, white coud ii dominant to black. Occasionally, a black sheep appears in theflock. The farmer cannot sell black wool. How can the gene for black coat be eliminatedfrom the flock?

34. In guinea pigs with colored hair, the hair may be black (B) or brown (b). Black isdominant to brown hair. Also, the hair may be short (S) or long (s). Short hair is dominantto long hair. ln each cross described so far, we have begun with homozygous individuals.This time we will cross animals of heterozygous genotypes: BbSs x BbSs.What is their phenotype? What will be the genotypes and phenotypes of the F1 offspring?

35. So far, we have spoken of traits as dominant or recessive. But there are other possibilities.In shorthorn cattle, for instance, when a red bull is crossed with a white cow, theheterozygous offspring are neither red nor white. lnstead, they are roan, which means theyhave mixed red and white hairs. In a cross between a roan bull and a roan cow, what atethe chances that the calf will be white? *ul are the chances it will be ioan or red?

ri,:i36. Work out a cross of roan x red.

37 . If a four-o'clock plant with red flowers is crossed with a white-flowered four-o'clocl