Key Terms
What is genetics the study of?
Heredity and Inheritance
What is the full form of DNA
What is the significance of mitosis in multicellular organisms? Provide examples of tissues or organs where mitosis plays a critical role.
Mitosis is significant in multicellular organisms for the growth, repair, and maintenance of tissues. It ensures that each new cell receives an identical copy of the parent cell's genetic material. Examples of tissues where mitosis plays a critical role include skin, blood, and gastrointestinal epithelium.
Explain the purpose of Punnett squares in genetics and how they are used to predict the outcomes of genetic crosses.
Punnett squares are tools used in genetics to predict the possible outcomes of genetic crosses between individuals with known genotypes. They provide a visual representation of the possible combinations of alleles that offspring may inherit from their parents.
Outline the use of Pedigree charts
To identify any traits or genetic disorders within generation
Define Karyotype
an individual's complete set of chromosomes
Define Codon
A codon is a DNA or RNA sequence of three nucleotides (a trinucleotide) that forms a unit of genomic information encoding a particular amino acid or signaling the termination of protein synthesis (stop signals).
How does cytokinesis differ between plant and animal cells? Explain the mechanisms involved in each type of cytokinesis and their significance in cell division.
Cytokinesis differs between plant and animal cells mainly in the mechanisms involved due to the presence of a cell wall in plant cells. In animal cells, cytokinesis involves the formation of a cleavage furrow, where the cell membrane pinches inward to divide the cell into two daughter cells. In contrast, plant cells form a cell plate between the dividing cells, which develops into a new cell wall, separating the daughter cells.
In pea plants, tall (T) is dominant over short (t). If a heterozygous tall plant (Tt) is crossed with a short plant (tt), what are the genotypic and phenotypic ratios of their offspring?
For the genotypic ratio: 1 TT : 2 Tt : 1 tt For the phenotypic ratio: 3 tall : 1 short
In a pedigree analysis of a family with a genetic disorder, what would the symbols for affected males, unaffected males, affected females, and unaffected females typically look like? Provide an example of a pedigree symbol for each.
Symbols for affected individuals in a pedigree are typically represented by shaded shapes (square for males, circle for females), while unaffected individuals are represented by unshaded shapes.
Compare homozygous vs heterozygous
Individuals carrying two identical alleles (RR or rr) are known as homozygous. While individual organisms bearing different alleles (Rr) are known as heterozygous.
Name all 4 bases and explain what codes with which.
adenine (A), cytosine (C), guanine (G) [GWA-NeeN] or thymine (T).
Describe the main stages of the cell cycle and explain what happens during each phase.
The main stages of the cell cycle are interphase (consisting of G1, S, and G2 phases) and mitotic phase (consisting of mitosis and cytokinesis). During interphase, the cell grows, replicates its DNA, and prepares for cell division. Mitosis is divided into prophase, metaphase, anaphase, and telophase, where the duplicated chromosomes are segregated and distributed into two daughter nuclei. Cytokinesis follows mitosis, completing the cell division process
In rabbits, black fur (B) is dominant over white fur (b). If two heterozygous black rabbits (Bb) are crossed, what are the expected genotypic and phenotypic ratios of their offspring?
For the genotypic ratio: 1 BB : 2 Bb : 1 bb For the phenotypic ratio: 3 black : 1 white
In a pedigree showing autosomal recessive inheritance, if two unaffected parents have an affected child, what are the genotypes of the parents? Provide a possible genotype for each parent.
In a pedigree showing autosomal recessive inheritance, if two unaffected parents have an affected child, both parents must be heterozygous carriers of the recessive allele. Therefore, their genotypes would be represented as carriers (Aa), with the affected child inheriting one recessive allele from each parent.
Define allele and provide an example of how alleles contribute to genetic variation within a population.
An allele is a variant form of a gene that arises by mutation and is found at a specific location on a chromosome. Alleles can exist in different versions, contributing to genetic diversity within a population. For example, the gene for flower color in pea plants has two alleles: one for purple flowers (P) and another for white flowers (p).
Describe the structure of a DNA molecule, including the components it is composed of and how they are arranged.
DNA is a double-helix molecule composed of nucleotides. Each nucleotide consists of a phosphate group, a sugar molecule (deoxyribose), and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). The structure is arranged as a double helix, with the sugar-phosphate backbones forming the outer edges and the nitrogenous bases paired in the interior via hydrogen bonds (A with T, and C with G).
Describe the process of crossing over during meiosis and its significance in genetic recombination. How does crossing over contribute to the diversity of offspring?
Crossing over during meiosis is the exchange of genetic material between homologous chromosomes, occurring during prophase I. It results in the recombination of alleles, creating new combinations of genes on chromatids. This process generates genetic diversity among offspring by shuffling genetic material, increasing variability within a population and providing the basis for evolution.
In fruit flies, red eyes (R) are dominant over white eyes (r). If two flies heterozygous for eye color (Rr) are crossed, what is the probability of their offspring having white eyes?
The probability of offspring having white eyes is 25% or 1/4.
Explain how consanguinity can affect the inheritance pattern of genetic disorders within a family. Provide an example of a disorder that may be more prevalent in families with consanguineous marriages.
Consanguineous marriages increase the likelihood of offspring inheriting two copies of a rare, harmful allele carried by both parents. This can lead to an increased prevalence of autosomal recessive disorders within the family. For example, cystic fibrosis is more prevalent in families with consanguineous marriages because the chance of both parents being carriers of the CFTR gene mutation is higher, increasing the likelihood of affected offspring.
What is meant by the term "codominance" in genetics? Provide an example of a trait that exhibits codominance and describe how it manifests in the phenotype.
Codominance is a genetic phenomenon in which both alleles of a gene are fully expressed in the phenotype of a heterozygous individual. This results in the simultaneous expression of both traits without blending. An example of codominance is the ABO blood group system in humans, where the IA and IB alleles are codominant. Individuals with the IAIB genotype express both the A and B antigens on their red blood cells.
What role does DNA play in inheritance, and how does it determine the traits and characteristics of an organism?
This information is encoded in the sequence of nucleotides along the DNA molecule. During reproduction, DNA is passed from parents to offspring, ensuring the transmission of genetic traits from one generation to the next. The specific sequence of nucleotides within the DNA molecule dictates the sequence of amino acids in proteins, which ultimately governs the structure and function of cells, tissues, and organisms.
What distinguishes mitosis from meiosis in terms of purpose and outcome? Explain how each process contributes to genetic diversity.
Mitosis and meiosis are two types of cell division with distinct purposes and outcomes. Mitosis is involved in growth, repair, and asexual reproduction, producing two daughter cells with the same number of chromosomes as the parent cell (diploid). In contrast, meiosis occurs only in germ cells (cells that give rise to gametes) and is involved in sexual reproduction, producing four daughter cells with half the number of chromosomes as the parent cell (haploid). Meiosis contributes to genetic diversity through independent assortment of chromosomes and crossing over during prophase I.
In chickens, feather color is determined by two alleles: black (B) is dominant over white (b), and the allele for a lack of feathers (F) is dominant over the allele for feathers (f). If a homozygous black, feathered chicken (BBFF) is crossed with a white, feathered chicken (bbff), what are the expected genotypic and phenotypic ratios of their offspring?
For the genotypic ratio: 1 BBFF : 2 BBFf : 1 Bbff : 2 BbFF : 4 BbFf : 2 Bbff : 1 bbFF : 2 bbFf : 1 bbff For the phenotypic ratio: 9 black, feathered : 6 black, no feathers : 3 white, feathered : 4 white, no feathers
Explain the 5 types of inherited traits a pedigree can show
Autosomal dominant traits appear in every generation, while autosomal recessive traits may skip generations and often require both parents to be carriers. X-linked dominant traits can appear in both genders but are passed differently, while X-linked recessive traits are more common in males and usually inherited from carrier mothers. Y-linked traits pass exclusively from father to son. Understanding these inheritance patterns is essential for interpreting pedigrees and identifying genetic conditions within families.