Đề thi, bài tập trắc nghiệm online Di truyền học – Đề 2

For a monohybrid cross of two heterozygous individuals (Aa x Aa), the expected phenotypic ratio is 3:1. This ratio arises from the segregation of alleles during gamete formation and the combination of these alleles in the offspring, resulting in three dominant phenotypes for every one recessive phenotype.

A point mutation is a change in a single nucleotide base in DNA. Deletion is the removal of nucleotides, insertion is the addition of nucleotides, and frameshift mutations occur when insertions or deletions alter the reading frame of a gene.

Telomeres are repetitive DNA sequences at the ends of chromosomes that protect them from degradation, end-to-end fusion, and maintain chromosome stability. They do not initiate DNA replication; origins of replication do that. They are involved in chromosome structure but their primary role is protection of chromosome ends.

Gene mapping is the process of determining the location of genes on chromosomes and the relative distances between them. It involves constructing genetic maps or linkage maps. Identifying gene function is gene annotation. Determining gene sequence is DNA sequencing. Manipulating genes is genetic engineering.

DNA ligase is an enzyme that joins DNA fragments together by catalyzing the formation of phosphodiester bonds between the 3'-OH and 5'-phosphate ends of DNA strands. Helicase unwinds DNA, DNA polymerase synthesizes DNA, and DNases degrade DNA.

Conjugation is the process where bacteria directly transfer genetic material (usually plasmids) between cells through direct cell-to-cell contact or a bridge-like connection between two cells. Transformation is the uptake of DNA from the environment. Transduction is DNA transfer mediated by bacteriophages. Mutation is a change in DNA sequence.

Restriction enzymes are used to cut DNA at specific recognition sequences. This is essential for genetic engineering to isolate and manipulate specific DNA fragments. DNA ligase joins DNA fragments, DNA polymerase replicates DNA, and DNA repair enzymes fix damaged DNA.

Pleiotropy occurs when one gene influences multiple phenotypic traits. Polygenic inheritance is when multiple genes affect one trait. Linked genes are on the same chromosome. Tissue-specific genes are expressed only in certain tissues.

The gene pool is the total collection of genes in a population at a given time, consisting of all alleles for all genes in that population. It's not just genes in a single organism, a whole species, or a family lineage, but specifically within a population.

A frameshift mutation is caused by insertions or deletions of nucleotides in a DNA sequence that is not a multiple of three. This shifts the reading frame of the genetic message, leading to a completely different protein sequence downstream of the mutation.

Replication is the process of copying DNA to produce two identical DNA molecules. Transcription is the process of creating RNA from DNA, and translation is the process of creating proteins from RNA. Mutation is a change in the DNA sequence.

In a dihybrid cross with independent assortment, the typical phenotypic ratio in the F2 generation is 9:3:3:1. This ratio arises from the independent segregation of alleles for two different genes and their combinations in the offspring.

Uracil is a nitrogenous base found in RNA, not DNA. DNA uses thymine (T) instead of uracil (U). Adenine (A), guanine (G), and cytosine (C) are common to both DNA and RNA, but in DNA, adenine pairs with thymine, while in RNA, adenine pairs with uracil.

RNA uses uracil (U) instead of thymine (T), which is used in DNA. RNA is typically single-stranded, while DNA is double-stranded. DNA contains deoxyribose sugar, while RNA contains ribose sugar. Both DNA and RNA have a phosphate backbone.

In incomplete dominance, the heterozygous phenotype is a blend of the homozygous phenotypes. In codominance, both alleles are fully and separately expressed in the heterozygous phenotype (e.g., blood type AB). The other options misrepresent these concepts.

The central dogma of molecular biology describes the flow of genetic information as DNA -> RNA -> Protein. DNA is transcribed into RNA, and RNA is translated into protein. While reverse transcription (RNA to DNA) exists, the primary direction is DNA to RNA to protein.

Hemophilia is a classic example of a sex-linked (specifically X-linked recessive) genetic disorder. Cystic fibrosis, sickle cell anemia, and Tay-Sachs disease are autosomal recessive disorders.

Mitochondrial DNA (mtDNA) is maternally inherited because mitochondria are primarily inherited from the egg cell. This maternal inheritance pattern makes mtDNA useful for tracing maternal lineage and studying human migration patterns. mtDNA is not paternally inherited and is found in mitochondria, not the nucleus. While mtDNA mutation rate is higher than nuclear DNA, it is still reliable for lineage studies and has been widely used in genetic research.

Phenotype refers to the observable characteristics of an organism, including physical traits, biochemical properties, and behavior. Genotype is the genetic makeup of an organism. Allele is a variant form of a gene. Locus is the specific position of a gene on a chromosome.

Gel electrophoresis is used to separate DNA fragments based on their size. Smaller fragments migrate faster through the gel. PCR amplifies DNA, DNA sequencing determines the nucleotide sequence, and transformation introduces foreign DNA into cells.

In autosomal dominant inheritance, affected individuals typically have at least one affected parent. Autosomal recessive inheritance can skip generations. Sex-linked disorders often affect males more frequently. In dominant inheritance, even heterozygotes are affected.

The Hardy-Weinberg principle describes the conditions under which allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences. It serves as a null hypothesis to study evolutionary changes.

Transfer RNA (tRNA) molecules bring amino acids to the ribosome during translation. mRNA carries genetic information, rRNA is a component of ribosomes, and the ribosome itself (specifically rRNA) catalyzes peptide bond formation.

Genes are the basic units of heredity, containing instructions for building proteins and determining traits. While chromosomes are structures containing DNA, DNA is the molecule carrying genetic information, and nucleotides are the building blocks of DNA, the gene is the specific unit of heredity.

DNA polymerase is the enzyme responsible for adding nucleotides to the growing DNA strand during replication, using the existing strand as a template. Helicase unwinds DNA, primase synthesizes RNA primers, and ligase joins DNA fragments.

Homozygous refers to having two identical alleles for a specific gene. Heterozygous refers to having two different alleles. Hemizygous refers to having only one allele for a gene (e.g., in males for X-linked genes). Polyploid refers to having more than two sets of chromosomes.

Transcription is the process that synthesizes mRNA using DNA as a template. Replication duplicates DNA, translation synthesizes proteins from mRNA, and transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings.

Ribosomes are the sites of protein synthesis. They translate the mRNA sequence into a chain of amino acids, forming a protein. DNA replication is carried out by DNA polymerase. Transcription is done by RNA polymerase. RNA processing occurs in the nucleus before translation.

Polymerase chain reaction (PCR) is used to amplify (make many copies of) a specific DNA sequence. Restriction enzymes cut DNA, gel electrophoresis separates DNA fragments, and DNA sequencing determines the sequence of DNA.

Epigenetics is the study of heritable changes in gene expression that occur without alterations in the DNA sequence itself. These changes can be mediated by DNA methylation, histone modification, and non-coding RNAs. Gene mutations are changes in DNA sequence. Gene flow is about population genetics. Gene editing is a technique to modify genes.