Genetics - Chapter 5 quiz

When a genotype is ___ some individuals with the genotype do not have the associated phenotype.
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Terms in this set (19)
When a genotype is ___ some individuals with the genotype do not have the associated phenotype.
incompletely dominant
The severity or extent to which a phenotype is expressed is its ____.
Expressivity
The same phenotype may result from different genotypes due to _____.
Genetic heterogeneity
An environmentally caused condition whose symptoms are similar to those of a known inherited disorder is called a ____.
phenocopy.
A _____ allele may result in a phenotypic class that does not survive long enough to reproduce.
lethal.
Which of the following statements describe mitochondrial DNA?

Carries 37 genes

Fewer types of DNA repair than nuclear DNA

Inherited from the mother only

One copy per cell

No crossing over

Complex packaging with histones

High exposure to oxygen free radicals
Carries 37 genes

Fewer types of DNA repair than nuclear DNA

Inherited from the mother only

One copy per cell

No crossing over

Complex packaging with histones

High exposure to oxygen free radicals
A pair of college sweethearts do a DNA test to find out their respective ancestries. They are shocked to find that they share nearly 1% of their genome. What is their likely relationship?

First cousins

Second cousins

Third Cousins

They are not related
First cousins

Second cousins

Third Cousins

They are not related

Mitochondrial DNA is inherited only from the mother, not from the father. It is present as multiple copies per mitochondrion and many copies per cell. Mitochondrial DNA is exposed to oxygen free radicals. It is not packaged with histones, as the nuclear DNA is. Crossing over does not occur in mitochondrial DNA. It carries out fewer types of DNA repair than nuclear DNA and carries 37 genes.

Third cousins share approximately 0.781% of their genomes. These two people are likely third cousins.
Classify each genotype into its corresponding blood type.

Blood Type A
Blood Type B
Blood Type AB
Blood Type O
Blood Type A -IAIA, IAi
Blood Type B - IBIB, IBi
Blood Type AB -IAIB
Blood Type O - ii
Imagine that the genes for long nose hair and buck teeth are on the same chromosome. A man with long nose hair and buck teeth has one chromosome with genes N and b and one chromosome with genes n and B. For each of the four possible combinations below, indicate if the gametes contain a parental or recombinant meiotic product.
1. NB Recombinant product
2. nb Recombinant product
3. nB Parental product
4. Nb Parental product

Because the man's original chromosomes contain one chromosome with N and b, and the other with n and B, Nb and nB are the parental products. NB and nb would only result from crossing over, and are therefore the recombinant products.
Imagine that the genes for eyelash length and hair texture are on the same chromosome. A man with long eyelashes and straight hair has one chromosome with the E gene and the S gene, and a second chromosome with the recessive genes, e and s. Assuming crossing over does not occur in meiosis, what combinations of genes should you see in his gametes? Check all that apply.

ES
es
Es
eS
ES
es
Es
eS

Because the two genes are found on the same chromosome, we do not expect them to assort independently. Instead, the E allele will stay with the S allele, and the e allele will stay with the s allele. The gametes from this man should contain ES and es.
Determine whether the following statements about the factors that alter Mendelian ratios are true or false. In epistasis, the blocked gene is expressed normally, but the product of the modifier gene inactivates it. An allele combination that produces a phenotype in everyone who inherits it is not penetrant. A phenotype is variably expressive if symptoms vary in intensity among different people. On a molecular level, genetic heterogeneity occurs when a single protein affects different body parts, participates in more than one biochemical reaction. Phenocopies are genetically caused traits that appear to be inherited.In epistasis, the blocked gene is expressed normally, but the product of the modifier gene inactivates it. True An allele combination that produces a phenotype in everyone who inherits it is not penetrant. False A phenotype is variably expressive if symptoms vary in intensity among different people. True On a molecular level, genetic heterogeneity occurs when a single protein affects different body parts, participates in more than one biochemical reaction....False Phenocopies are genetically caused traits that appear to be inherited. False Explanation: 1. In epistasis, the blocked gene is expressed normally, but the product of the modifier gene inactivates it. 2. An allele combination that produces a phenotype in everyone who inherits it is completely penetrant. 3. A phenotype is variably expressive if symptoms vary in intensity among different people. 4. On a molecular level, pleiotropy occurs when a single protein affects different body parts, participates in more than one biochemical reaction. 5. An environmentally caused trait that appears to be inherited is a phenocopy.You are working in the lab, studying what you suspect to be a mitochondrial disease. You isolate mitochondria from a child with this disease, and sequence the mitochondrial genome. You also sequence the mitochondrial genomes of the parents. You are surprised to find that the child has a mutation in a very important mitochondrial gene, but that neither of her parents have this mutation. Further, both parents are healthy. What most likely explains this finding? (multi-choice) The child most likely has a different mutation in a nuclear gene that is causing her symptoms. Because mitochondrial DNA mutates much more quickly than nuclear DNA, the girl likely incurred a new mutation in her mitochondrial DNA. You probably missed isolating the relevant mitochondria from her mother. You probably missed isolating the relevant mitochondria from her father.The child most likely has a different mutation in a nuclear gene that is causing her symptoms. Because mitochondrial DNA mutates much more quickly than nuclear DNA, the girl likely incurred a new mutation in her mitochondrial DNA. You probably missed isolating the relevant mitochondria from her mother. You probably missed isolating the relevant mitochondria from her father. Explanation You suspect that the girl has a mitochondrial disease, and you find a mutation in a mitochondrial gene. This suggests that this mutation is causing her disease, and there is no reason to suspect that she may have an additional nuclear mutation. Although it's possible that you missed isolating the relevant mitochondria from her mother, her mother is healthy, so she is also fairly unlikely to have the same mutation. Also, mitochondria are inherited from one's mother, so she probably did not inherit this mutation from her father. Instead, the most likely explanation is that she incurred a new mutation in her mitochondrial DNA, due to the high mutation rate in the mitochondrial genome.When a single gene locus affects more than one trait, this is called ____.pleiotropyWhen a single gene locus has more than two possible alleles, this is called ____.multiple allelesWhen the phenotype of heterozygotes is intermediate between the homozygotes, this is called ____.incomplete dominanceWhen the phenotype of heterozygotes shows some aspects of both homozygotes, this is called ____.codominanceWhen alleles at one gene locus can mask the expression of alleles at another gene locus, this is called ____.epistasisWhen different genes produce the same phenotype, this is called ____.genetic heterogeneityIn humans, the melanocortin 1 receptor (MC1R) is a key protein involved in human skin and hair color. Several versions of the MC1R gene with changes in single nucleotides have been reported. One of these has the amino acid histidine where the amino acid aspartate normally is found at a certain location in the MC1R protein. Another version has a tryptophan where an arginine should be. Both of these versions of the gene are associated with red hair, whereas the wild type version of this gene is associated with dark hair. What phenomenon is occurring with these genes? (multi-choice) multiple alleles incomplete dominance codominance epistasismultiple alleles Explanation Because there are multiple different versions of the same gene described here, this is an example of multiple alleles. There is nothing in the question that suggests codominance, epistasis, or incomplete dominance is occurring.