Biology 101 Chapters 15 Thru 19

Gametes are reproductive cells that have half the number of chromosomes as compared to other cells in the body. Since humans are diploid and have 46 chromosomes in total, each human gamete will have 23 chromosomes. This is because during the process of meiosis, the chromosomes are divided equally between the two resulting gametes, ensuring the correct number of chromosomes in the offspring.

Monosomy refers to a condition where an individual has only one copy of a particular chromosome instead of the usual two. In the case of XO Turner Syndrome, affected individuals have only one X chromosome instead of the usual two. This condition occurs in females and can lead to various physical and developmental abnormalities, such as short stature, infertility, and heart defects.

Polyploid is the correct answer because it refers to an organism with extra sets of chromosomes. Polyploidy occurs when an organism has more than two sets of chromosomes, which can result in increased genetic diversity and potential advantages in adaptation and evolution. Polyploidy is commonly found in plants and some animal species, and it can lead to changes in physical characteristics and reproductive capabilities.

In an X-linked trait, it is the contribution of the mother that determines whether a son will display the trait. This is because the mother is the one who passes down the X chromosome to her son. If the mother carries the gene for the trait on one of her X chromosomes, there is a 50% chance that she will pass it on to her son, resulting in the son displaying the trait. The father, grandmother, grandfather, and siblings do not directly determine whether a son will display the trait in an X-linked inheritance pattern.

Polyploid cells are cells that have more than two complete sets of chromosomes. This can occur naturally or as a result of errors during cell division. Polyploidy is common in plants and some animals, but it is rare in humans. In polyploid cells, the number of chromosomes is usually a multiple of the normal number. This can lead to changes in the organism's characteristics and can have both positive and negative effects on its survival and reproduction.

The correct answer is XCXc. This is because color blindness is an X-linked recessive trait, meaning it is carried on the X chromosome. The father, who is color blind, has one X chromosome with the color blindness allele (Xc) and one normal X chromosome (XC). The daughter inherits one X chromosome from the father, which could be either Xc or XC, and one X chromosome from the mother (XC). Therefore, the daughter's genotype is XCXc, meaning she is a carrier of the color blindness trait but does not express it herself.

The chromosome theory of inheritance states that genes occupy specific positions on chromosomes, homologous chromosomes segregate from each other during meiosis, and chromosomes assort independently during meiosis. This means that genes are located on chromosomes, and during the process of meiosis, homologous chromosomes separate and chromosomes can randomly assort to create different combinations of traits. Therefore, all of the given statements are true according to the chromosome theory of inheritance.

Fertilization is the process by which haploid gametes, such as sperm and egg, combine to form a diploid zygote. During fertilization, the sperm penetrates the egg and their genetic material combines, resulting in the formation of a new individual with a complete set of chromosomes. This process is essential for sexual reproduction in organisms and is the first step in the development of a new organism. Embryogenesis, mitosis, and gastrulation are all subsequent processes that occur after fertilization. Meiosis, on the other hand, is the process by which haploid gametes are formed in the first place.

If two genes are linked, it means that they are located on the same chromosome. This is because genes that are close together on a chromosome have a higher chance of being inherited together as a unit, rather than undergoing independent assortment.

XO is the only known viable human monosomy. This refers to Turner syndrome, where an individual is born with only one X chromosome instead of the usual two. This condition typically affects females and can result in various physical and developmental abnormalities, such as short stature, infertility, and heart problems. The absence of a second sex chromosome is the defining characteristic of XO monosomy.

Human gametes, such as sperm and eggs, are haploid, meaning they contain only one set of chromosomes. This is because during the process of meiosis, the number of chromosomes is halved to ensure that when fertilization occurs, the resulting zygote will have the correct number of chromosomes. Therefore, each human gamete contains only one set of chromosomes, making the correct answer 1.

If all of the sons, and none of the daughters, are color-blind, it indicates that color blindness is caused by an X-linked recessive allele. This is because males have one X chromosome and one Y chromosome, while females have two X chromosomes. If the trait is X-linked recessive, it means that the gene for color blindness is located on the X chromosome. Since males only have one X chromosome, if they inherit the recessive allele for color blindness, they will be affected. On the other hand, females need to inherit the recessive allele on both X chromosomes to be affected, which is why none of the daughters are color-blind in this scenario.

If the mother is heterozygous for a recessive sex-linked trait, it means she carries one dominant allele and one recessive allele. The husband, on the other hand, has the dominant allele. Since the recessive trait is sex-linked, it is carried on the X chromosome. The mother can pass either the dominant or the recessive allele to her sons, while the father will always pass the dominant allele. Therefore, half of their sons will receive the recessive allele from the mother and will have the recessive trait, while the other half will receive the dominant allele from the father and will not have the recessive trait.

Color blindness is an X-linked recessive trait, which means it is carried on the X chromosome. Males have one X chromosome and one Y chromosome, while females have two X chromosomes. In order for a male to be color-blind, he only needs to inherit one copy of the color-blindness gene from his mother. However, for a female to be color-blind, she needs to inherit two copies of the gene, one from each parent. Since the unaffected male in this scenario does not have the color-blindness gene, he cannot pass it on to his daughter, making it impossible for him to have a color-blind daughter.

The woman is a carrier for red-green color blindness, which means she has one normal gene and one gene for color blindness. Since color blindness is a sex-linked trait, it is passed down from the mother to her children. However, the husband is normal for this trait, meaning he does not have the gene for color blindness. In order for their daughter to be red-green color-blind, she would need to inherit the gene for color blindness from both her mother and her father. Since the husband does not have the gene, there is no chance for their daughter to be red-green color-blind. Therefore, the chances are 0%.

Since the father passes the Y chromosome to his son, the son cannot inherit an X-linked recessive allele from his father. Therefore, the probability is 0%.

This observation would be the most decisive evidence against the idea that the disorder is caused by mitochondrial DNA. Mitochondrial DNA is passed down exclusively from the mother, so if fathers with the disorder are able to pass it on to all their children, it suggests that the disorder is not solely caused by mitochondrial DNA.

Down's Syndrome is an example of trisomy, specifically trisomy 21. Trisomy occurs when there is an extra copy of a chromosome in the cells. In the case of Down's Syndrome, there is an extra copy of chromosome 21. This additional genetic material leads to various physical and cognitive characteristics associated with the syndrome.