biology chapter 11

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1

In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations?

P1 ... P2 ... P3

P1 ... P2 ... F

P ... F1 ... F2

F ... P1 ... P2

F1 ... F2 ... F3

P..F1..F2

2

Which of the following is true about a plant with the genotype AABbcc?

It has recessive alleles at three loci.

It is homozygous at two loci.

It is triploid.

It will not express the recessive c allele.

It is heterozygous at two loci.

It is homozygous at two loci

3

What is an allele?

the dominant form of a gene

the recessive form of a gene

a variety of pea plant used by Mendel

an alternative version of a gene

a type of chromosome

an alternative version of a gene

4

What do we mean when we use the terms monohybrid cross and dihybrid cross?

A dihybrid cross involves organisms that are heterozygous for two characters, and a monohybrid cross involves only one.

A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two progeny

. A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio.

A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations.

A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents.

A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid cross involves only one.

5

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Recessive genes occur more frequently in the F1 generation than do dominant ones.

An organism that is homozygous for many recessive traits is at a disadvantage.

Traits are inherited in discrete units, and are not the results of "blending."

Genes are composed of DNA.

There is considerable genetic variation in garden peas.

traits are inherited in discrete units and are not the results of "blending".

6

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?

segregation of maternal and paternal alleles

recurrent mutations forming new alleles

different possible assortment of chromosomes into gametes

crossing over during prophase I

the tendency for dominant alleles to segregate together

different possible assortment of chromosomes into gametes.

7

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?

the parents were both heterozygous for a single trait

8

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

HT

9

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

50%

10

Mendel accounted for the observation that traits that had disappeared in the F1 generation reappeared in the F2 generation by proposing that

traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.

11

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

anaphase 1 of meiosis

12

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?

one allele was dominant

13

Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes?

four...one

14

You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?

Pink is dominant, and red and white are recessive.

Red is completely dominant

. Both red and white are pleiotropic.

Red shows incomplete dominance over white.

red shows incomplete dominance over white

15

Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?

a combination of epistasis and environmental factors

a combination of complete dominance and environmental factors

incomplete dominance a combination of multiple alleles and codominance

a combination of polygenic inheritance and environmental factors

a combination of polygenic inheritance and environmental factors

16

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

red × roan

roan × roan

red × white

white × roan

The answer cannot be determined from the information provided.

roan x roan

17

Which of the following is an example of polygenic inheritance?

skin pigmentation in humans

the ABO blood group in humans

pink flowers in snapdragons

Huntington's disease in humans

white and purple flower color in peas

skin pigmentation in humans

18

Which of the following provides an example of epistasis?

In cacti, there are several genes for the type of spines.

In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.

Recessive genotypes for each of two genes (aabb) result in an albino corn snake.

In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes.

The allele b17 produces a dominant phenotype, although b1 through b16 do not.

In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing

19

Folk singer Woody Guthrie died of Huntington's disease, an autosomal dominant disorder. Which statement below must be true?

It is very likely that at least one of Woody Guthrie's parents also have had the allele for Huntington's disease.

His daughters will die of Huntington's disease but not his sons.

All of his children will develop Huntington's disease

. His sons will develop Huntington's disease but not his daughters.

There is not enough information to answer the question.

it is very likely that at least one of woody's parents also have had the allele for Huntington's disease