(17)Chapter 18: Epigenetics, Linkage, and Extranuclear Inheritance

Which of the following hypotheses did Thomas Hunt Morgan propose for the unexpected results he obtained when studying transmission of genes in Drosophila?

-The likelihood of a crossover between genes is related to how far apart they are on the chromosome. -Genes located on the same chromosome are more likely to be inherited together, violating Mendel's law of independent assortment. -Crossing over occurs during meiosis, allowing chromosomes to create new allele combinations.

What observations did Carl Correns make when studying the four-o'clock plant (Mirabilis jalapa), leading him to discover maternal inheritance?

-When the maternal plant had green leaves, the offspring always had green leaves. -When the maternal plant had variegated leaves, the offspring were green, white, or variegated. -When the maternal plant had white leaves, the offspring always had white leaves.

In humans and other mammals, X chromosomes are counted. This process ensures that any normal somatic cell contains _______ active X chromosome(s).

1

Males with Klinefelter syndrome have an XXY chromosome composition; thus ____ Barr body or bodies would be found in the cells of a male with Klinefelter syndrome.

1

Indicate the number of Barr bodies resulting from each chromosome composition. XX (normal female): _______ ; X0 (Turner syndrome): ______ ; XXX (triple X syndrome): _____ ; XXY (Klinefelter syndrome): ______ .

1 /0 /2 /1

What are the three general rules for genes that follow a Mendelian pattern of inheritance?

1. For crosses involving two or more genes, the genes obey Mendel's law of independent assortment 2. Genes are generally passed unaltered from cell to cell, and from generation to generation 3. The genes obey Mendel's law of segregation

Some people are born with abnormalities in the number of their sex chromosomes. For example, people born with triple X syndrome have three X chromosomes, and those born with Klinefelter syndrome have two X chromosomes and one Y. How does X inactivation proceed in these cases?

All of the X chromosomes are inactivated except for one.

A highly condensed X chromosome is known as a(n) _____ body.

Barr

If two X chromosomes are present in a mammalian cell, one of them is converted to a(n)

Barr body.

Which of the following statements are true regarding epigenetics? Choose all that apply.

Epigenetic changes are transmissible from cell to cell. Epigenetic changes may be transmitted to offspring. Variations of gene expression that are unrelated to DNA sequence variants. Variations are reversible from one generation to the next.

Which of the following statements about eukaryotic genes is TRUE?

Most, but not all genes, are found in the nucleus

Leaf pigmentation in four-o'clock plants is inherited via the chloroplast genome. A female plant with variegated leaves is crossed with a male plant with white leaves. What is the result of this cross?

Some offspring will have green leaves, some will have white leaves, and some will have variegated leaves.

Which of these sequences plays a critical role in Barr body formation?

The X inactivation center (Xic)

The region on the X chromosome that is known to play a role in Barr body formation is known as the ___ ____ ____.

X inactivation center

In statistics, changes in two variables that follow a pattern is termed a(n)

association

In a mammalian cell that contains two X chromosomes, one of the X chromosomes will become a(n) ______ ______ .

barr body

Adult, wild-type mice with genotype AA for the Agouti gene will have what color coat hairs?

brown with black tips

In a eukaryotic cell, where are genes found?

chloroplasts / the nucleus / mitochondria

The cells of humans and other mammals have the ability to ______ their X chromosomes, and are therefore able to inactivate all but one of them.

count

Thomas Hunt Morgan recognized that some genes in Drosophila violated the law of independent assortment. He proposed that such genes were located on the same chromosome and that new combinations of alleles could be created only if _____ ______ occurred during meiosis.

crossing over

Genomic imprinting is an example of a phenomenon called _______ inheritance.

epigenetic

What type of inheritance describes genomic imprinting?

epigenetic

The term ______ describes changes in gene expression that are not related to variations of the DNA sequence, yet are transmissible and are reversible?

epigenitics

When German botanist Carl Correns crossed four-o'clock plants with different leaf pigmentation, he observed that the leaf pigmentation pattern of the offspring depended solely on the pigmentation of the _______ plant.

female

X-chromosome inactivation refers to the process that occurs in

female mammals, when the genes of one of the two X chromosomes are not expressed.

The gene Igf2 encodes a(n)

growth hormone.

A Barr body is a(n)

highly condensed X chromosome

In the somatic cells of female mammals, the genes on one of the two copies of the X chromosome are not expressed. This phenomenon is known as X-chromosome ______.

inactivation

One of the first imprinted genes to be identified was a gene in mice called Igf2. This gene encodes a growth hormone called _______ -like growth ______ 2 (Igf2).

insulin / factor

When two genes are located close to one another on a chromosome, they tend to be transmitted together. This phenomenon is known as ______.

linkage

Which phenomenon describes the presence of two genes very close to each other on the same chromosome, and which are transmitted together as a unit?

linkage

In a particular plant, the pigmentation of the offspring depends exclusively on the pigmentation of the female parent. This phenomenon is known as _____ inheritance.

maternal

In most plant species, chloroplasts are inherited via the ______ cell, because it contributes most of the cytoplasm to the zygote.

maternal

In most plant species, inheritance of the chloroplast genome follows a(n) _____ inheritance pattern.

maternal

When German botanist Carl Correns crossed four-o'clock plants with different leaf pigmentation, he observed that the leaf pigmentation pattern of the offspring depended solely on the pigmentation of the ____ plant

maternal

How are mitochondria inherited in humans?

maternal inheritance

The chloroplast genome, which can encode genes that function in the production of pigment, is transmitted to offspring via protoplastids in the cytoplasm of the egg cell. This is an example of what type of inheritance pattern?

maternal inheritance

What is the phenomenon called in which a trait of the offspring is solely determined by the value of the trait in the female parent because it is passed on via the organelles in the egg cell?

maternal inheritance

The marking process that occurs during genomic imprinting is the addition of _______ groups to DNA.

methyl

Mendelian inheritance is characterized by three general rules: 1._______ Except in the case of rare , genes are passed unaltered from generation to generation; 2. ____ Each gene obeys Mendel's law of ; and 3. ______ During crosses, two or more genes obey Mendel's law of independent .

mutations segregation assortment

In a testcross, offspring that have the same combination of traits as the parental generation are called

nonrecombinants

Offspring that do not differ from the parental generation in their combination of traits are known as parentals or _____.

nonrecombinants

In genomic imprinting, the transcription of the imprinted gene is inhibited because

the DNA is methylated.

In mice, the Agouti gene regulates

the deposition of yellow pigment in hair.

In most plant species, which gamete provides most of the cytoplasm to the zygote?

the egg cell

A true association occurs when

two variables follow a pattern.

In triple X syndrome, how many X chromosomes are converted into Barr bodies and why?

two, because one active X chromosome is needed