Ch 16 Flashcards
What are the three general rules for genes that follow a Mendelian pattern of inheritance?
- For crosses involving two or more genes, the genes obey Mendel’s law of independent assortment
- Genes are generally passed unaltered from cell to cell, and from generation to generation
- The genes obey Mendel’s law of segregation
True or false: An epigenetic effect causes a change in gene expression without altering the sequence of DNA.
true
Epigenetic inheritance refers to epigenetic changes that occur
during gamete formation.
Genomic imprinting refers to the
marking of DNA so that the phenotype of offspring depends on the parental origin of the gene.
The inheritance pattern of the Igf2 gene in mice, in which only the paternal gene is expressed, is known as:
genomic imprinting
Mendelian inheritance is characterized by three general rules: 1. Except in the case of rare ____enes 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
True or false: As a result of genomic imprinting, individuals with the same genotype may have different phenotypes.
true
Which of the following characterize an epigenetic effect?
- Causes a change in gene expression
* The change must be passed from cell to cell
In what type of inheritance pattern are phenotypes dependent on the parental origin of the alleles?
Genomic imprinting
Modification of a gene or chromosome during gamete formation that alters a gene’s expression but does not change the DNA sequence is known as ______ ______
epigenetic
In genomic imprinting, the transcription of the imprinted gene is inhibited because
imprinting, the transcription of the imprinted gene is inhibited because.
The phenomenon where offspring express a paternal or maternal allele depending on how a particular gene is marked is known a ___
genomic / gentic imprinting
Which of the following is an example of an imprinted gene?
the gene Igf2 in mammals
Methylation patterns are established during the formation of ______
gametes
Individuals may have the same genotype but very different phenotypes as a result of
genomic imprinting
True or false: Only genes inherited from the mother are imprinted.
False
In the phenomenon of genomic _____ , the gene from only one parent is expressed.
imprinting
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
The marking process that occurs during genomic imprinting is the addition of _____ groups to DNA.
methyl
A highly condensed X chromosome is known as a(n) ___
barr body
The calico pattern in cats is due to random X-chromosome inactivation in a
female that is heterozygous for an X-linked gene with black (XB) and orange (XO) alleles.
When are methylation patterns established?
During formation of gametes
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
In genomic imprinting, which genes are silenced?
Genes inherited from either the mother or the father depending on the gene.
In triple X syndrome, how many X chromosomes are converted into Barr bodies and why?
two, because one active X chromosome is needed
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 region on the X chromosome that is known to play a role in Barr body formation is known as the
X inactivation center
A Barr body is a(n)
highly condensed X chromosome.
The Xist gene, which is involved in X inactivation, encodes a(n) ___ molecule.
RNA
In cats, the calico pattern is caused by the random X-chromosome ______ in females that are heterozygous for an X-linked gene with black and _______ alleles.
Inactivation, Orange
How is the Xist gene involved in X inactivation?
It synthesizes RNA, which coats one of the X chromosomes. Proteins then associate with the RNA, promoting compaction into a Barr body.
In humans and other mammals, X chromosomes are counted. This process ensures that any normal somatic cell contains ____
one
In mice, the Agouti gene regulates
the deposition of yellow pigment in hair.
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.
If the Agouti gene in mice undergoes a gain-of-function mutation, the gene will be
over-expressed, resulting in yellow fur.
Which of these sequences plays a critical role in Barr body formation?
The X inactivation center (Xic)
Female mice carrying the Avy allele were divided into a control group (fed a standard diet) and an experimental group (fed a diet supplemented with folic acid and vitamin B12). Both groups were fed their respective diets before and during pregnancy and up to the stage of weaning. Offspring that inherited the Avy allele were then analyzed with regard to their coat color. What do these results show?
Offspring of females fed a supplemental diet had darker coats
What is encoded by the Xist gene of the X chromosome?
An RNA molecule
True or false: Smoking of cigarettes induces the formation of lung cancer only by causing genetic mutations in tumor-suppressor genes.
False
The process of X-chromosome inactivation involves the gene ______, which encodes a very long ______ molecule. This molecule coats one of two X chromosomes, thus starting a process that ultimately leads to compaction of the chromosome into a Barr body.
Xist ; RNA
Extranuclear inheritance patterns involve genes located in the
chloroplasts and mitochondria
Adult, wild-type mice with genotype AA for the Agouti gene will have what color coat hairs?
Brown with black tips
What is the structure of the mitochondria and chloroplasts genomes?
Single, circular DNA molecule
Mice with a gain-of-function mutation in the Agouti gene will have fur that has a(n) ____ color.
yellow
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
The graph shown here represents the effect of diet supplementation on coat color in mice. More than 25% of the offspring with ______ coats had mothers that were fed a supplemental diet, while less than 10% had mothers that were given a standard diet.
heavily mottled
This figure shows a cross in four-o’clock plants. What would be the expected phenotype(s) of the offspring?
All will have white leaves
The role of epigenetics and disease has been most extensively studied with regard to
cancer
In plants, which gamete typically provides most of the cytoplasm to the zygote?
The egg cell
Which organelles demonstrate extranuclear inheritance?
Chloroplasts
Mitochondria
This digram shows an egg cell from a maternal four-o’clock plant with white leaves. The egg cell contains mutant that will produce chloroplasts with very little _________ pigment.
proplastids
Mitochondrial and chloroplast genomes are composed of a single, molecule.
circular DNA
Mitochondrial transmission in eukaryotes typically occurs by what type of inheritance?
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
Which of the following organs are most likely to be affected by a mitochondrial disease?
Heart, eyes, and kidney
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.
When two genes are located close to one another on a chromosome, they tend to be transmitted together. This phenomenon is known as
linkage
In most plant species, chloroplasts are inherited via the ____ cell, because it contributes most of the cytoplasm to the zygote.
egg
In a two-factor cross, genes that are close together on a chromosome do not follow Mendel’s law of
independent assortment
- All normal prolastids
- All mutant proplastids
- A combinations of normal and mutant proplastids
- green leaves
- white leaves
- green, white, or variegated leaves
Bateson and Punnett, and later Morgan, did experiments on the transmission of genes in various organisms. Their results did not conform to Mendel’s law of independent assortment because they observed
many more F2 offspring with the parental combination of traits than predicted
While some eukaryotic species exhibit ___ or ______ inheritance, the most common pattern of mitochondrial transmission in eukaryotes is via maternal inheritance.
biparental & paternal
On this pair of chromosomes, what alleles are linked?
b and c
b+ and c+
What organs are often affected by mutation in human mitochondrial genes?
Kidney Heart Muscle Brain Eyes
When genes are linked, recombinant offspring can be produced by _____ between two chromosomes
crossover
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?
linakge
