Ch. 5 Concept Check & Comprehension Questions Flashcards
A female that coils to the left has offspring that coil to the right. What are the genotypes of the mother of these offspring and the maternal grandmother, respectively?
Dd, dd
What is the molecular explanation for maternal effect?
- during oogeneis, nurse cells transfer gene products to the oocyte
- the gene products from nurse cells are needed during the very early stages of development
In fruit flies, dosage compensation is achieved by..
Turning up the expression of genes on the single X chromosome twofold in the male
According to the Lyon hypothesis,
One of the X chromosomes is converted to a Barr body in somatic cells of female mammals
Which of the following is not a phase of XCl? A. Initiation B. Spreading C. Maintenance D. Erasure
D. Erasure
In mice, the copy of the Igf2 gene that is inherited from the mother is never expressed in her offspring. That happens because the Igf2 gene from the mother..
Is not transcribed in the somatic cells of the offspring
A female mouse, Igf2 lgf2-, is crossed to a male that is also lgf2 lgf2-. The expected outcome of the offspring for this cross is..
1 normal - 1 dwarf
The marking process for genomic imprinting initially occurs during..
Gametogenesis
A female born with Angelman syndrome carries a deletion in the AS gene. Which parent transmitted the deletion to her?
Her mother
Extranuclear inheritance occurs due to..
Genetic material that is found in chloroplasts and mitochondria
A cross is made between a green four-o’clock and a variegated four-o’clock. If the variegated plant provides the pollen, the expected outcome of the offspring would be..
All plants with green leaves
Some human diseases are caused by mutations in mitochondrial genes. Which of the following statements is false?
A. Human mitochondrial diseases follow a maternal inheritance pattern
B. Mutations associated with mitochondrial diseases often affect cells with a high demand for ATP.
C. The symptoms associated with mitochondrial diseases tend to improve with age.
D. Heteroplasmy plays a key role in the severity of disease symptoms.
C.
Chloroplasts and mitochondria evolved from an endosymbiotic relationship involving..
Cyanobacteria and purple bacteria, respectively
Experiment showing the inheritance pattern of snail cooking
Explain why all of the offspring in the F2 generation are dextral even though some of them are dd.
Because all of the F1 mothers are Dd, and the genotype of the mother determines the phenotype of the offspring
If a mother is heterozygous, Dd, which gene products will the oocyte receive?
The egg cell will receive both D and d gene products.
Why is the Barr body more brightly staining in a cell nucleus than the other chromosomes?
Because it is very compact
The mechanism of X-chromosome inactivation
At which stage of development does XCl initially occur?
During embryonic development
Why do these two forms of G-6-PD migrate differently?
Because their amino acid sequences are slightly different
What is the function of the Tsix gene?
It is involved in choosing the X chromosome that is not inactivated
Which of these phases occurs in an adult female?
A. Initiation
B. Spreading
C. Maintenance
Only the maintenance phase occurs in an adult female
An example of genomic imprinting in the mouse
What would be the outcome of a cross between a heterozygous female and a male that carries two normal copies of the lgf2 gene?
All of the offspring would be normal because they would inherit an active copy from their father.
Explain why the erasure phase of imprinting is necessary in eggs.
Erasure allows eggs to transmit unmethylated copies of the gene to the offspring.
What is the difference between maintenance methylation and de novo methylation? In what cell types do they occur?
Maintenance methylation is automatic methylation that occurs when a methylated gene replicates and is transferred to daughter cells. It occurs in somatic cells.
De novo methylation is the methylation of a gene that is not already methylated. It occurs in germ-line cells.
On the left side of this figure, explain why the offspring does not have Prader-Willi syndrome but does have Angelman syndrome.
The offspring on the left did not receive a copy of either gene from their mother. Their father silences the AS gene, so they have AS because they do not have an active copy of the AS gene. By comparison, they receive an active PWS gene from their father, which prevents them from having PWS.
How is a nucleoid different from a cell nucleus?
A nucleoid is not surrounded by a membrane as is the cell nucleus.
Why do mitochondria need rRNA and tRNA genes?
To translate proteins within the mitochondrial matrix
What is a reciprocal cross?
A cross in which the sexes and phenotypes of the parents are reversed compared to a first cross
During growth, can a patch of tissue with a white phenotype give rise to a patch with a green phenotype? Explain.
No. Once a patch of tissue is white, it has lost all of the normal chloroplasts, so it could not produce a patch of green tissue.
How have chloroplasts and mitochondria changed since the initial endosymbiosis events, which occurred hundreds of millions of years ago?
Chloroplast and mitochondrial genomes have lost most of their genes during evolution. Many of these have been transferred to the cell nucleus.
