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Concept explainers
In human gestational development, abnormalities of the closure of the lower part of the midface can result in cleft lip, if the lip alone is affected by the closure defect, or in cleft lip and palate (the roof of the mouth), if the closure defect is more extensive. Cleft lip and cleft lip with cleft palate are multifactorial disorders that are threshold traits. A family with a history of either condition has a significantly increased chance of a recurrence of midface cleft disorder in comparison with families without such a history. However, the recurrence risk of a midface cleft disorder is higher in families with a history of cleft lip with cleft palate than in families with a history of cleft lip alone.
a. Suppose a friend of yours who has not taken genetics asks you to explain these observations. Construct a genetic explanation for the increased recurrence risk of midface clefting in families that have a history of cleft disorders versus families without a history of such disorders.
b. Construct a similar explanation of why the recurrence risk of a cleft disorder is higher in families with a history of cleft lip with cleft palate than in families with a history of cleft lip alone.
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Chapter 21 Solutions
GENETIC ANALYSIS: AN INTEG. APP. W/MAS
- Auricular hypertrichosis is a dominant Y-linked condition. Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. b C STRONGLY AGREE! STRONGLY DISAGREE! There is no such thing as a dominant or recessive Y-linked trait since only one allele is involved making this the most appropriate choice. Not enough information is provided to interpret the statement. Operarrow_forwardIn humans, normal skin color (A) is dominant over albino (a). An albino man marries a normal woman whose mother was an albino and whose father has normal skin color. What is the genotype of the man and the woman? What proportion of their children would be expected to be both normal skin pigmentation and have the trait for albino?arrow_forwardIf diseases such as cardiovascular disease (hypertension and atherosclerosis) are familial, is this an indication that there is a genetic contribution to these traits? What would you do to confirm that genetics is involved in this condition?arrow_forward
- A pedigree analysis was performed on the family of a man with schizophrenia. Based on the known concordance statistics, would his MZ twin be at high risk for the disease? Would the twins risk decrease if he were raised in an environment different from that of his schizophrenic brother?arrow_forwardLike brown eyes, presence of dimples and cleft chin are dominant traits. Sarah has brown eyes and dimples, but no cleft chin. Her father has blue eyes but no dimples. She just married James who has blue eyes, dimples, and cleft chin. His mother has no cleft chin and his father has no dimples. What is the genotype of Sarah? What is the genotype of James?arrow_forwardHuntington disease (HD) is a genetic disorder that usually first appears in middle age and, over time, leads to involuntary movements, impaired speech, difficulty swallowing and speaking, and cognitive decline. There is no cure for HD, and affected individuals eventually die, usually after 10 to 15 years of progressively worsening symptoms. Huntington disease is inherited as an autosomal dominant disorder. Presymptomatic genetic testing for HD is available for people with a family history of the disease. Individuals who have a parent with HD have a 50% chance of inheriting the HD gene and eventually having HD. Some of these individuals want to know if they will eventually get the disease, and they undergo presymptomatic genetic testing. Others do not want to know, given that there is no cure or effective treatment for the disease. If you were at risk for HD, would you want to undergo genetic testing? What are some reasons for and against having a genetic test for HD?arrow_forward
- the possible alleles for bald spot, no bald spot are QQ, Qq. what type of inheritance pattern is being displayed by each gene? complete dominace or codominace?arrow_forwardA man, whose mother has normal fingers, is brachydactylous (very short fingers, rare dominant trait), and his wife is not. Both can taste the chemical phenylthiocarbamide (dominant trait), but both their mothers could not. If they have SEVEN children, what is the probability of: All being brachydactylous? None being brachydactylous? The first child being a brachydactylous non-taster? The first two children being brachydactylous? The first two children being a brachydactylous taster and a non-brachydactylous non-taster in any order?arrow_forwardThick mucous gland secretions, elevated sweat electrolytes, meconium ileus, and difficulty maintaining and gaining weight are associated with which autosomal recessive disorder? Cerebral palsy. Cystic fibrosis Muscular dystrophy. Multiple sclerosisarrow_forward
- Define complex traitarrow_forwardName: Human Phenotypes Simple dominance inheritance pattern: Q: How many phenotypes are evident in patterns of simple dominance? What are they? If a phenotype results from simple dominance, which two genotypes cannot be distinguished? Which phenotype is always representative of the genotype? Now determine your personal inheritance of the following traits. As you read through the following descriptions, you'll identify your trait, and determine your phenotype. Your trait will be one of the two Shape of the face. Most facial characteristics are affected by many different genes acting together (multiple factors or polygenic inheritance). For this trait we have simplified the nature of this trait by assuming it is the result of a single gene. Oval shape is dominant (needs only homozygous (both alleles are the same, either dominant or recessive) or heterozygous (one dominant allele and one recessive allele). Square shape is recessive (requires that both alleles are the recessive allele in…arrow_forwardIn humans, a widow’s peak hairline (H) has complete dominance over the straight hairline (h).What is the genotype for an individual that homozygous dominant for this traitarrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning
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