Chapter 16: Transmission of Genetic Information from Parents to Offspring II Flashcards
The Mendelian inheritance patterns follow three general rules. What are they?
16.1
- except in the case of rare mutations, genes are passed unaltered from cell to cell, and from generation to generation
- the genes obey Mendel’s law of segregation
- for crosses involving two or more genes, the genes obey Mendel’s law of independent assortment
Define epigenetic inheritance.
16.1
modification of a gene or chromosome during gamete formation that alters a gene’s expression but does not change the DNA sequence
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?
16.6
linkage
Epigenetics is the study of?
16.1
mechanisms that lead to changes in gene expression that can be passed from cell to cell, are reversible, but do not involve a change in the sequence of DNA
What are some common types of molecular changes that can have an epigenetic effect that alters gene expression?
16.1
DNA methylation, chromatic remodeling, covalent histone modification, and localization of histone variants
The phenomenon where offspring express a paternal or maternal allele depending on how a particular gene is marked is known as what?
16.2
genomic imprinting
T or F: A gene can be marked by females during egg formation and by males during sperm production.
16.2
false; either or, not both
Do imprinted genes follow a Mendelian pattern of inheritance?
16.2
No
What is the function of the Igf2 imprinted gene?
16.2
it encodes a growth hormone called insulin-like growth factor 2; the mutation (Igf2-) blocks the function of the hormone
Individuals may have the same genotype but very different phenotypes as a result of what?
16.2
genomic imprinting
What serves as the marking process that occcurs during the imprinting of certain genes including Igf2?
16.2
DNA methylation
Genomic imprinting refers to the:
16.2
marking of DNA so that the phenotype of the offspring depends on the parental origin of the gene
What is the function of DNA methylation in genomic imprinting?
16.2
it silences gene expression by inhibiting the initiation of transcription or by causing the chromatin in a region to become more compact
Draw a diagram of genomic imprinting via DNA methylation in both females and males! :)
16.2
A male mouse that is homozygous for the functional allel of the Igf2 gene is mated to a female that is heterozygous, carrying one functional copy and one mutant (nonfunctional) copy of the gene. What would be the expected outcome of this cross?
all normal size offspring (paternal allele is expressed)
In the somatic cells of female mammals, the genes on one fo the two copies of the X-chromosome are not expressed. This phenomenon is known as?
16.3
X-chromosome inactivation
T or F: During embyonic development in female mammals, one of the X chromosomes undergoes an epigenetic change called X-chromosome inactivation.
16.3
true
In triple X syndrome, how many X chromosomes are converted into Barr bodies and why?
16.3
two, because one active X chromosome is needed
The short region on the X-chromosome where X-chromosome inactivation begins is called:
16.3
X-inactivation center (XiC)
The Xist gene, which is involved in X inactivation, encodes what type of molecule?
16.3
RNA molecule
The expression of a specific gene is required for the compaction of the X chromosome into a Barr body. Which gene is this?
16.3
Xist gene (X inactive specific transcript)
Which statement regarding X-chromosome inactivation is false?
a. Xic is the site where X-chromosome inactivation begins
b. Xic is where the Xist gene is located
c. The Xist gene on the inactivated X chromosome (the Barr body) is not expressed
d. The product of the Xist gene coats the inactivated X chromosome
16.3
c. The Xist gene on the inactivated x chromosome (the Barr body) is not expressed
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?
16.3
all of the X chromosomes are inactivated except for one
The Xist gene product is a long ____ molecule that ________ for a protein.
16.3
RNA; does not code
How is the Xist gene involved in X inactivation?
16.3
It synthesizes RNA, which coats one of the X chromosomes. Proteins then associate with the RNA, promoting compaction into a Barr body.
T or F: Cells of humans and other mammals have the ability to cunt X chromosomes and allow only one X chromosome to be active.
16.3
true
When mice carrying the Avy allele exhibit a darker coat color, this phenotype is thought to be caused by dietary factors that result in…
16.4
a greater level of DNA mehtylation and a decrease in the expression of the Agouti gene
When an association occurs between an environmental agent that causes an epigenetic change and a particular disease, this association can be due to what factors?
16.4
- the epigenetic change directly contributes to the disease symptoms
- the disease symptoms arise first, and they cause subsequent epigenetic changes to happen
- the association is indirect because a third factor is involved
Which organelles demonstrate extranuclear inheritance?
16.5
chloroplast and mitochondria
What is encoded by the Xist gene of the X chromosome?
16.3
an RNA molecule
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 orgnanelles in the egg cell?
16.5
maternal inheritance
What accounts for the wide array of coat color seen in mice carrying the A vy allele of the Agouti gene?
16.5
epigenetic modification of the new promoter of the Agouti gene
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?
16.5
Some offspring will have green leaves, some will have white leaves, and some will have variegated leaves.
In most plant species, chloroplasts are inherited via which cell? Why?
16.5
they are inherited via the egg cell, because it contributes most of the cytoplasm to the zygote
Chloroplats are inherited only from the pollen in ____ inheritance.
16.5
paternal
In plants, which gamete typically provides most of the cytoplasm to the zygote?
16.5
the egg cell
What is extranuclear inheritance?
16.5
the transmission of genes located outside the nucleus
What types of organs are most liley to be affected by mitochondrial disease?
16.5
organs that require high ATP levels
Who performed a two-factor cross in sweet peas that involved flower color and pollen shape?
16.6
Bateson and Punnett
Bateson and Punnet, 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…
16.6
many more F2 offspring with the parental combination of traits than predicted
If two genes are linked, is it possible for recombinant offspring to occur?
16.6
yes, if crossing over occurs
