Biology 2nd Quarter Exam Reviewer Part 1

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The term "genotype" refers to the set of alleles an organism inherits for a specific trait. It represents the genetic makeup of an individual and determines the characteristics or traits that will be expressed. The genotype can consist of different combinations of alleles, which may result in different phenotypes or observable traits. The other options, "phenotype" refers to the physical or observable characteristics of an organism, "karyotype" refers to the number and appearance of chromosomes in the nucleus of a cell, and "no type" is not a valid term in this context.

Gregor Mendel is the correct answer because he was a Catholic monk who conducted experiments on pea plants in the mid-19th century. Through his experiments, Mendel formulated the principles of heredity, which laid the foundation for modern genetics. His work demonstrated the existence of dominant and recessive traits, as well as the concept of genetic inheritance. Mendel's discoveries were not widely recognized during his lifetime, but his work was rediscovered and appreciated in the early 20th century, solidifying his place as the father of modern genetics.

The Law of Independent Assortment states that the transmission of a gene is not affected by the transmission of other sets of genes. This means that the inheritance of one gene does not influence the inheritance of another gene. Each gene segregates independently during the formation of gametes, resulting in different combinations of genes in offspring. This principle is a fundamental concept in genetics and helps explain the variation observed in offspring.

Identical twins are formed from the same fertilized egg, also known as a zygote. During early development, the zygote splits into two separate embryos, each with its own set of genetic material. As a result, identical twins share the same DNA and are genetically identical. This is why they often look very similar and may even have the same physical characteristics. Fraternal twins, on the other hand, are formed from two separate eggs fertilized by two different sperm, so they are no more genetically similar than any other siblings.

The correct answer is dominant because dominant alleles are always expressed or observed in a hybrid. This means that even if an individual carries both a dominant and a recessive allele for a particular trait, the dominant allele will be the one that is visible or manifested in the phenotype. In contrast, recessive alleles are only observed when an individual carries two copies of the recessive allele. Semi-dominant alleles exhibit an intermediate phenotype when present in a heterozygous individual, which does not align with the given explanation.

A mutation refers to a permanent change in the genetic material of an organism. This can occur due to various factors such as errors during DNA replication or exposure to mutagens like radiation or chemicals. Mutations can result in changes to the DNA sequence, which can then lead to alterations in the traits or characteristics of the organism. Therefore, the given statement accurately describes a mutation as a permanent change in the genetic material of the organism.

The pair of genes that determine the sex of a human being is the 23rd pair. This pair consists of two sex chromosomes, one from each parent. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The presence of the Y chromosome determines the development of male characteristics. Therefore, the 23rd pair of chromosomes is responsible for determining whether an individual is male or female.

Translation is the process by which the genetic information encoded in the RNA molecule is used to synthesize a specific protein. During translation, ribosomes read the mRNA sequence and assemble amino acids in the correct order to form a protein. This process is a key step in the central dogma of molecular biology, which describes the flow of genetic information from DNA to RNA to protein. Transcription, on the other hand, refers to the synthesis of RNA from a DNA template, while mutation refers to changes in the DNA sequence.

Phenotype refers to the physical appearance of an organism. It includes observable traits such as color, size, shape, and behavior. The phenotype is influenced by both genetic factors (genotype) and environmental factors. It is the result of the interaction between an organism's genes and its environment. The genotype represents the genetic makeup of an organism, while the karyotype refers to the number and appearance of an organism's chromosomes. "No type" is not a valid term in this context.

Transcription is the process in which genetic information is transferred from DNA to RNA. It involves the synthesis of an RNA molecule using a DNA template. During transcription, the DNA sequence is "transcribed" into an RNA sequence, allowing the information to be carried from the nucleus to the cytoplasm where it can be used for protein synthesis. This term accurately describes the transfer of information from DNA to RNA.

Allele is the correct answer because it is a term used in genetics to describe the different forms of a gene. Genes are segments of DNA located on chromosomes, which carry the genetic information. Alleles are alternative versions of a gene that can produce different traits or characteristics. Each individual inherits two alleles for each gene, one from each parent, and these alleles can be the same (homozygous) or different (heterozygous). Therefore, allele is a distinct type of gene that plays a crucial role in determining an organism's traits.

A human baby with an XY chromosome in his cells is considered male. In humans, the presence of a Y chromosome determines male development, while the absence of a Y chromosome results in female development. The XY chromosome combination indicates that the baby has inherited a Y chromosome from the father and an X chromosome from the mother, which is characteristic of males. Therefore, the correct answer is male.

The number of PAIRS of chromosomes in a somatic cell is 23 because somatic cells are diploid, meaning they have two sets of chromosomes. Each set consists of 23 individual chromosomes, for a total of 46 chromosomes in a somatic cell.

An organism that has a set of two different types of alleles for a trait is called a hybrid. In genetics, alleles are alternative forms of a gene that determine specific traits. When an organism inherits two different alleles for a trait from its parents, it is considered a hybrid. This is because the organism exhibits a combination of traits from both parents, resulting in a unique genetic makeup.

The number of chromosomes in a sperm cell is 23. This is because sperm cells are haploid, meaning they contain half the number of chromosomes compared to other cells in the body. In humans, the normal diploid number of chromosomes is 46, with 23 chromosomes coming from the mother's egg cell and 23 chromosomes coming from the father's sperm cell during fertilization. Therefore, a sperm cell only carries one set of chromosomes, which is 23 in total.

The correct answer is central dogma. The central dogma is a principle in molecular biology that describes the flow of genetic information. It states that DNA contains the instructions for creating proteins, and these instructions are transferred to RNA through a process called transcription. The RNA then serves as a template for protein synthesis through a process called translation. This principle explains how genetic information is transferred and expressed in living organisms.

Co-dominance occurs when both alleles in a gene pair are fully expressed in the phenotype of an individual. In the case of blood type AB, both the A and B alleles are present and functional, resulting in the production of both protein A and protein B. This is different from incomplete dominance, where the phenotype is a blend of the two alleles, and overdominance, where the heterozygote has a phenotype that is superior to both homozygotes.

A pure-breed myopic person would have the genotype NN, which means they are homozygous dominant for myopia. This means that they have two copies of the dominant allele (N) for myopia and do not have any copies of the recessive allele (n) for normal eyesight. Therefore, their genotype is homozygous dominant.

Cytosine and thymine are both pyrimidine bases found in DNA. Pyrimidine bases are one of the two types of nitrogenous bases, the other being purine bases. Cytosine and thymine are important components of DNA as they form base pairs with guanine and adenine, respectively, during DNA replication and transcription. These base pairs contribute to the stability and structure of the DNA molecule.

The base of a DNA nucleotide forms a hydrogen bond with the base of another nucleotide. This hydrogen bonding between the bases, adenine (A) with thymine (T) and guanine (G) with cytosine (C), allows for the complementary pairing of the DNA strands. The base pairing is crucial for DNA replication and the transmission of genetic information.

The complementary DNA sequence of a given DNA sequence is formed by replacing each nucleotide with its complementary base pair. In DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). Therefore, the complementary sequence of C - A - T - G - C - T would be G - T - A - C - G - A.

The principle described in the answer is known as the Law of Segregation. This law states that during the formation of gametes, the two alleles for a gene segregate from each other so that each gamete carries only one allele for each gene. This ensures that each offspring receives one allele from each parent. This principle was proposed by Gregor Mendel and is one of the fundamental principles of genetics.

A codon is a sequence of three nucleotides in DNA or RNA that specifies the incorporation of a specific amino acid during protein synthesis. It is not considered a part of the DNA nucleotide itself, but rather a unit that helps in the translation of genetic information into proteins. The DNA nucleotide consists of a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine).

Transfer RNA (tRNA) is the correct answer because it pairs up with the mRNA during protein synthesis. tRNA carries specific amino acids to the ribosomes, where they are assembled into a protein chain according to the instructions encoded in the mRNA. This process ensures that the correct amino acids are added in the correct order, allowing for the production of a functional protein. mRNA is responsible for carrying the genetic information from the DNA to the ribosomes, while rRNA is a component of the ribosomes themselves. Therefore, neither mRNA nor rRNA are directly involved in carrying amino acids for protein production.

When a heterozygous man with myopia (Nn) marries a homozygous woman with normal eyesight (nn), the possible genotypes of their children are NN, Nn, Nn, and nn. Therefore, the genotypic ratio of the children will be 2:2, with two children having myopia (Nn) and two children having normal eyesight (nn).

Messenger RNA (mRNA) is the correct answer because it is responsible for carrying the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm. mRNA pairs up with the separated DNA strands and acts as a template for protein synthesis. Ribosomal RNA (rRNA) and transfer RNA (tRNA) are involved in protein synthesis as well, but they do not directly pair up with the separated DNA strands. Therefore, they are not the correct answers. "None of the above" is not the correct answer because mRNA is the specific type of RNA that pairs up with the separated DNA strands.

Incomplete dominance occurs when neither allele in a gene pair is dominant over the other, resulting in a blending or intermediate phenotype. In this case, the traits governed by the alleles are not completely expressed, but rather a combination of both alleles is observed. This is different from co-dominance, where both alleles are fully expressed without blending, and overdominance, where the heterozygous genotype has a phenotype that is more advantageous than either homozygous genotype. Therefore, the given answer of "incomplete dominance" is the correct explanation for the given statement.

A codon is a group of three nucleotide bases that correspond to a specific amino acid. In the process of protein synthesis, codons in mRNA molecules are recognized by complementary anticodons in tRNA molecules, allowing the correct amino acids to be added to the growing polypeptide chain. Codons act as the genetic code, providing the instructions for the sequence of amino acids in a protein.

The complementary mRNA sequence of a DNA sequence is formed by replacing each DNA base with its complementary RNA base. In DNA, Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C). However, in RNA, Thymine (T) is replaced with Uracil (U). Therefore, the complementary mRNA sequence of the given DNA sequence C – A – T – G – C – T is G – U – A – C – G – A.

The correct answer is phosphate because the phosphate group in a DNA nucleotide is the point of attachment for another nucleotide's sugar part called deoxyribose. The phosphate group forms a bond with the sugar molecule, creating the backbone of the DNA strand. This backbone structure is essential for the stability and integrity of the DNA molecule.

The two purine bases are guanine and adenine. Purine bases are one of the two types of nitrogenous bases found in DNA and RNA. They are characterized by a double-ring structure. Cytosine and thymine are pyrimidine bases, which have a single-ring structure. Therefore, the correct answer is guanine and adenine.

DNA is composed of nucleotides, each of which consists of a sugar-phosphate backbone and a nitrogenous base. The statement "part of the structure is a base" is correct because DNA contains four different nitrogenous bases (adenine, guanine, cytosine, and thymine) that make up its genetic code. DNA is directly involved in the process of transcription, where the genetic information is transcribed into RNA. Additionally, DNA has a phosphate part where other nucleotides attach to form the sugar-phosphate backbone. However, DNA is not directly involved in the process of translation, which is the synthesis of proteins from RNA. Finally, DNA does not have uracil (U) as a base; instead, it has thymine (T).

The Law of Independent Assortment states that during the formation of gametes, the alleles for different traits segregate independently of each other. A dihybrid cross involves studying the inheritance of two different traits simultaneously. By crossing individuals that are heterozygous for both traits, the offspring will show all possible combinations of the alleles for each trait. This allows for the observation of independent assortment, as the alleles for one trait are not influenced by the alleles for the other trait. Therefore, a dihybrid cross is the best way to illustrate the Law of Independent Assortment.

When a heterozygous man (Nn) with myopia marries a homozygous woman (NN) with myopia, the possible genotypes of their children will be NN (myopia) and Nn (myopia). Since myopia is completely dominant over normal eyesight, all the children will have myopia. Therefore, the phenotypic ratio of the children will be 4:0, meaning all the children will have myopia and none will have normal eyesight.

Since John has a homozygous genotype for dimples (DD), all of his offspring will inherit at least one dominant allele for dimples (D). Martha, on the other hand, is heterozygous for dimples (Dd), so there is a 50% chance that each of her offspring will inherit the recessive allele for dimples (d). Since the question asks for the probability of the offspring having no dimples (dd), and there is a 50% chance of inheriting the recessive allele from Martha, the probability is 50% multiplied by 0%, which equals 0%.

The correct answer is: Permanent changes in genetic material happen in this kind of mutation, Result of incorrect pairing of nucleotide bases, Source of new traits and new forms of traits.

DNA mutations can result in permanent changes in the genetic material of an organism. These changes can occur due to incorrect pairing of nucleotide bases during DNA replication, which can lead to alterations in the genetic code. Down's syndrome, a genetic disorder caused by an extra copy of chromosome 21, is an example of a mutation that results from the breaking of chromosomes. Mutations can also serve as a source of new traits and new forms of traits, contributing to genetic diversity in populations.

RNA is a nucleic acid that contains bases, which are part of its structure. It is directly involved in the process of translation, where it carries the genetic information from DNA to synthesize proteins. RNA also has Uracil (U) as a base instead of Thymine (T), which is found in DNA. Additionally, RNA has a phosphate part where other nucleotides can attach to form the RNA molecule.

Chromosome mutation refers to permanent changes in genetic material, which aligns with the first statement. The incorrect pairing of nucleotide bases can lead to mutations, but this statement does not specifically refer to chromosome mutations. Down's syndrome is an example of a chromosome mutation, as it is caused by an extra copy of chromosome 21. Breaking of chromosomes can also result in chromosome mutations. Lastly, chromosome mutations can be a source of new traits and new forms of traits through changes in the genetic material.