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Magazine Chapter 28: Problem 10
True/False: Mark the following statements as true (T) or false (F). If the statement is false, correct it to make it a true statement. ______ a. Sex-linked disorders tend to affect males more than females. ______ b. The X and Y chromosomes are called autosomes. ______ c. A person with two different alleles is homozygous for that trait. ______ d. Blood typing cannot be used to conclusively prove paternity. ______ e. A dominant allele will mask or suppress a recessive allele.
Short Answer
Expert verified
a. T, b. F (sex chromosomes), c. F (heterozygous), d. T, e. T.
Step by step solution
01
Statement Analysis a
Statement a is: 'Sex-linked disorders tend to affect males more than females.' This statement is true. Sex-linked disorders, usually located on the X chromosome, affect males more because they have only one X chromosome compared to females, who have two. Thus, if a disorder is on the X chromosome, males will express the disorder as they lack a second X chromosome to counterbalance it.
02
Statement Analysis b
Statement b is: 'The X and Y chromosomes are called autosomes.' This statement is false. The X and Y chromosomes are not autosomes; they are called sex chromosomes. Autosomes are the 22 paired chromosomes that do not determine sex.
03
Statement Correction b
To correct statement b, it should read: 'The X and Y chromosomes are called sex chromosomes.'
04
Statement Analysis c
Statement c is: 'A person with two different alleles is homozygous for that trait.' This statement is false. A person with two different alleles for a particular gene is heterozygous, not homozygous. Homozygous means having two identical alleles for a trait.
05
Statement Correction c
To correct statement c, it should read: 'A person with two different alleles is heterozygous for that trait.'
06
Statement Analysis d
Statement d is: 'Blood typing cannot be used to conclusively prove paternity.' This statement is true. Blood typing can exclude a potential father but cannot definitively identify a child's father, unlike DNA testing, which provides concrete evidence.
07
Statement Analysis e
Statement e is: 'A dominant allele will mask or suppress a recessive allele.' This statement is true. In genetics, a dominant allele's traits will manifest in the individual's phenotype, while the effects of a recessive allele will be masked unless both alleles are recessive.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sex-Linked Disorders
Sex-linked disorders primarily affect males more than females due to their distinct genetic makeup involving the sex chromosomes. Males possess one X and one Y chromosome. Since most sex-linked disorders are X-linked, a male receiving a single defective X chromosome will express the disorder. This is because he lacks a second X chromosome that might carry a normal gene to compensate for it. Females, on the other hand, have two X chromosomes, providing a chance that one normal X may counteract a faulty one. This pattern explains why conditions like hemophilia and color blindness are more commonly seen in males.
- Males have one X chromosome: higher susceptibility.
- Females have two X chromosomes: potential for balance.
- Common X-linked disorders: hemophilia, color blindness.
Autosomes vs Sex Chromosomes
In human genetics, chromosomes are categorized into two types: autosomes and sex chromosomes. Autosomes consist of 22 pairs and are identical in both males and females. These chromosomes are crucial as they encompass genes that govern most of the body's hereditary traits unrelated to sex. However, the X and Y chromosomes, known as sex chromosomes, determine an individual鈥檚 sex and related traits. While females possess two X chromosomes, males have one X and one Y chromosome, denoting genetic sex differences. Accurate terminology is key in understanding genetic disorders and transmission patterns. Remember, X and Y are sex chromosomes, not autosomes.
- Autosomes: 22 pairs, non-sex-related traits.
- Sex chromosomes: X and Y, determine sex.
- Males: one X, one Y; Females: two X's.
Homozygous vs Heterozygous
The terms homozygous and heterozygous describe two possible genetic scenarios concerning alleles. An individual is homozygous for a trait if they hold two identical alleles, meaning their genetic code for that trait is the same on both chromosomes. If an individual has two different alleles for a gene, they are termed heterozygous. This distinction is crucial when predicting the inheritance patterns of certain traits. In cases where one allele is dominant, a heterozygous pairing will express the dominant trait. It's essential for students to grasp these definitions to understand topics like Punnett squares and genetic probabilities.
- Homozygous: identical alleles, example: AA or aa.
- Heterozygous: different alleles, example: Aa.
- Dominance affects expression in heterozygotes.
Blood Typing in Paternity
Blood typing serves as a useful tool in determining paternity, but it is not definitive. It works on the principles of inheritance patterns, where an individual's blood type is a combination of alleles inherited from their parents. Certain combinations of parental blood types can exclude paternity (if a child鈥檚 blood type is incompatible with the father鈥檚), but they cannot conclusively determine paternity. For example, if a child has an AB blood type, and one parent is type O, that parent cannot be the child's biological parent. However, DNA testing offers more precise results in confirming biological relationships.
- Blood typing: useful for ruling out, not confirming paternity.
- Works through allele inheritance patterns.
- DNA testing: more reliable for conclusive results.
Dominant and Recessive Alleles
Understanding dominant and recessive alleles is fundamental in genetics. A dominant allele is one that can express its trait even if only one copy is present in the genotype. This means in a pair of alleles, if one is dominant, it will mask the presence of the recessive allele in determining the organism's phenotype. For a recessive trait to manifest in the phenotype, an individual must have two copies of the recessive allele. This concept is pivotal in predicting how traits and genetic conditions are inherited across generations, shedding light on family genetic histories.
- Dominant alleles: express with one copy, mask recessive.
- Recessive alleles: require two copies to manifest.
- Essential for understanding inheritance patterns.
