Biology ENZYMES Flashcards
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Describe the structure of DNA: Double helix
DNA is structured as a double helix, two intertwined strands twisted into a spiral shape.
Describe the structure of DNA including: Nucleotide
A nucleotide is the building block of DNA, made up of a phosphate group, a deoxyribose sugar, and a nitrogenous base.
Describe the structure of DNA including: Bases (A,T,G,C)
The nitrogenous bases in DNA are adenine (A), thymine (T), guanine (G), and cytosine (C). Adenine pairs with thymine, and guanine pairs with cytosine.
Determine complementary base pairing
Adenine (A) pairs with Thymine (T).
Guanine (G) pairs with Cytosine (C).
This means:
If one strand has an A, the opposite strand will have a T.
If one strand has a G, the opposite strand will have a C.
Define and compare DNA, genes, chromosomes and use models and diagrams to represent the relationship between them
Definitions and Comparison of DNA, Genes, and Chromosomes
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DNA (Deoxyribonucleic Acid)
- Definition: DNA is a long molecule that carries the genetic blueprint of an organism. It is made up of two strands of nucleotides that form a double helix structure. DNA contains all the instructions needed for the growth, development, and functioning of living organisms.
- Key Feature: DNA is the molecule that stores genetic information in the form of sequences of nucleotides.
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Gene
- Definition: A gene is a specific segment of DNA that contains instructions for making a particular protein or RNA molecule. Genes are the functional units of heredity and determine traits and characteristics in an organism.
- Key Feature: A gene is a functional unit of DNA that codes for a trait.
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Chromosome
- Definition: A chromosome is a structure made up of tightly coiled DNA wrapped around proteins (histones). Chromosomes are found in the nucleus of cells and carry many genes. Humans typically have 46 chromosomes (23 pairs) in each cell.
- Key Feature: Chromosomes are large structures that contain many genes organized along their length.
Comparison
Models and Diagrams
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DNA: Represented as a double helix (like a twisted ladder), with two strands of nucleotides held together by complementary base pairs (A-T, G-C).Diagram of DNA:
A - T | | G - C
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Gene: A gene is a specific sequence of bases (A, T, G, C) within the DNA. It can be shown as a small part of the long DNA molecule. In a diagram, it’s often marked as a region within the DNA sequence.Diagram of Gene in DNA:
... ATGCGTACGGTAGC ... <-- Gene portion of DNA sequence
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Chromosome: Chromosomes are made of tightly coiled DNA, containing multiple genes. A chromosome can be depicted as a large “X” shape (during cell division) or as a condensed structure.Diagram of Chromosome:
|--- Gene 1 ---|--- Gene 2 ---|--- Gene 3 ---| |---- DNA ---| |---- DNA ---| |---- DNA ---| Chromosome with multiple genes
Relationship Between DNA, Genes, and Chromosomes
- DNA is the entire molecule that contains all genetic information.
- Genes are specific segments of DNA that encode for traits or proteins.
- Chromosomes are large, organized structures that contain long strands of DNA, and within those strands, multiple genes are arranged.
Thus, DNA is the basic substance, genes are functional units within it, and chromosomes are the structures that house multiple genes within cells.
Feature | DNA | Gene | Chromosome |
|—————-|—————————————-|——————————————|—————————————–|
| Definition | A long molecule containing genetic instructions. | A segment of DNA that codes for a specific protein or function. | A structure made of coiled DNA that contains many genes. |
| Size | Very long molecule (millions of base pairs). | Small segment of DNA (hundreds to thousands of base pairs). | Large structure made up of DNA, can contain thousands of genes. |
| Function | Stores genetic information. | Codes for specific traits or functions (e.g., proteins). | Packages and organizes DNA; carries genetic information during cell division. |
| Location | Found in the nucleus (in eukaryotes) or cytoplasm (in prokaryotes). | Found within DNA, located on chromosomes. | Located in the nucleus of eukaryotic cells. |
Determine mutations in complementary base pairing
Mutations in complementary base pairing are changes in the DNA sequence that can alter the normal pairing of bases (A-T, G-C). Types of mutations include:
- Substitution: One base is replaced by another (e.g., A-T → G-C), which can cause silent, missense, or nonsense mutations.
- Insertion: An extra base is added, shifting the reading frame (frameshift mutation).
- Deletion: A base is removed, also causing a frameshift mutation.
- Duplication: A segment of DNA is copied and inserted again.
- Inversion: A DNA segment is reversed.
These mutations can affect gene function, potentially leading to diseases or altered traits.
Explore environmental and other factors that cause mutations and identifying changes in DNA or chromosomes
Mutations can arise from a variety of environmental and biological factors that damage or alter DNA or chromosomes. These factors can cause changes in the DNA sequence or chromosome structure, potentially leading to genetic disorders, cancer, or other health issues. Below are some key factors that cause mutations and the mechanisms by which they occur:
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Environmental Factors
These are external influences that can cause DNA damage or mutations:
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Radiation
- Ionizing Radiation (X-rays, gamma rays): Can break DNA strands or cause base alterations, leading to mutations. It can also cause chromosomal breaks, leading to rearrangements or loss of genetic material.
- Ultraviolet (UV) Radiation: UV light from the sun can cause thymine bases to form dimers (thymine-thymine dimers), distorting the DNA structure and leading to mutations if not repaired.
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Chemical Mutagens
- Cigarette Smoke: Contains carcinogens like benzopyrene, which can bind to DNA and cause mutations.
- Pesticides and Industrial Chemicals: Many chemicals, such as those found in certain pesticides or industrial solvents, can cause mutations by directly altering the DNA structure.
- Aflatoxins: Produced by mold on improperly stored food (like peanuts), these can cause mutations in the p53 tumor suppressor gene, potentially leading to cancer.
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Pollution
- Air, water, and soil pollution can contain carcinogenic chemicals that interact with DNA, leading to mutations. For example, benzene, a known pollutant, can cause mutations by forming adducts with DNA.
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Biological Factors
Certain biological processes can also lead to mutations in DNA or chromosomes:
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Errors in DNA Replication
- During cell division, the DNA replication process can sometimes go wrong, leading to base substitutions, insertions, or deletions. Though cells have proofreading mechanisms, errors can still occur.
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DNA Repair Deficiencies
- Cells have mechanisms to repair damaged DNA, such as mismatch repair and nucleotide excision repair. When these systems are faulty (due to mutations in repair genes like BRCA1 or p53), DNA damage accumulates, increasing the risk of mutations.
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Transposons (Jumping Genes)
- Transposons are sequences of DNA that can move around within the genome. When they “jump” into or near a gene, they can disrupt the normal function of that gene, causing mutations.
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Viral Infections
- Some viruses, such as Human Papillomavirus (HPV) and HIV, can integrate their DNA into the host genome. This integration can disrupt normal gene function and lead to mutations, especially in tumor suppressor genes or oncogenes.
- Retroviruses, like HIV, can insert their RNA into the host genome, potentially causing gene rearrangements or mutations.
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Chromosomal Changes
Chromosomal mutations refer to larger-scale alterations in the chromosome structure or number:
- Deletions: A portion of a chromosome is lost, which can remove important genes.
- Duplications: A portion of the chromosome is duplicated, leading to an increase in gene copies.
- Inversions: A segment of a chromosome is reversed, which can disrupt gene function.
- Translocations: A segment of one chromosome breaks off and attaches to a different chromosome, potentially causing gene fusion or loss of function.
- Aneuploidy: The gain or loss of entire chromosomes (e.g., Down syndrome is caused by an extra copy of chromosome 21).
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Spontaneous Mutations
Some mutations occur without any external influence, due to the natural chemical instability of DNA:
- Tautomeric Shifts: Bases can undergo slight structural changes (tautomerism), which can cause incorrect base pairing during DNA replication.
- Replicative Slippage: Repeated sequences of DNA (such as trinucleotide repeats) can cause the DNA polymerase to slip, leading to insertions or deletions in the repeating sequence. -
Age
As organisms age, the efficiency of DNA repair mechanisms declines, and the accumulation of DNA damage increases. This can increase the likelihood of mutations over time, particularly in cells that divide frequently, such as stem cells. -
Inherited Mutations
- Mutations can be inherited if they occur in the germline (egg or sperm cells). These inherited mutations can predispose individuals to genetic disorders or increase the risk of certain diseases, such as cystic fibrosis, sickle cell anemia, or cancer predisposition syndromes.
Identifying Mutations in DNA or Chromosomes
Mutations can be detected and analyzed through various techniques:
- Polymerase Chain Reaction (PCR): A method to amplify specific segments of DNA, allowing researchers to detect mutations in specific genes.
- Gel Electrophoresis: Used to compare the sizes of DNA fragments to identify insertions, deletions, or duplications.
- DNA Sequencing: Determines the exact sequence of nucleotides in a DNA segment, allowing for precise identification of base substitutions, insertions, or deletions.
- Fluorescence in situ Hybridization (FISH): A technique used to identify chromosomal abnormalities, such as translocations or aneuploidy, by using fluorescent probes that bind to specific chromosome regions.
- Karyotyping: A method of visualizing chromosomes under a microscope, used to detect large chromosomal mutations like deletions, duplications, or changes in chromosome number.
Conclusion
Mutations can be caused by a variety of factors, including environmental exposure (radiation, chemicals, pollution), biological processes (errors in DNA replication, transposons), and chromosomal changes. Identifying mutations through DNA sequencing, PCR, and other techniques is crucial for understanding genetic disorders, cancer, and the genetic basis of diseases.
Determine the haploid and diploid number of chromosomes of an organism
The haploid and diploid numbers of chromosomes refer to the number of chromosomes found in different types of cells in an organism. Here’s the distinction:
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Diploid Number (2n)
- The diploid number refers to the total number of chromosomes in a somatic cell (any cell other than sperm or egg cells).
- A diploid cell contains two sets of chromosomes, one from each parent. In humans, for example, the diploid number is 46 chromosomes (23 pairs of chromosomes). -
Haploid Number (n)
- The haploid number refers to the number of chromosomes in a gamete (sperm or egg cell).
- A haploid cell contains only one set of chromosomes. In humans, the haploid number is 23 chromosomes, which is half of the diploid number.
How to Determine the Haploid and Diploid Numbers:
- The diploid number is typically the total chromosome count found in the body cells (somatic cells) of the organism.
- The haploid number is half the diploid number and is found in the gametes (egg and sperm cells).
Example: Humans
- Diploid Number (2n): 46 chromosomes (23 pairs).
- Haploid Number (n): 23 chromosomes.
Example: Fruit Fly (Drosophila melanogaster)
- Diploid Number (2n): 8 chromosomes (4 pairs).
- Haploid Number (n): 4 chromosomes.
Example: Pea Plant (Pisum sativum)
- Diploid Number (2n): 14 chromosomes (7 pairs).
- Haploid Number (n): 7 chromosomes.
In summary:
- Diploid number: Total chromosomes in somatic cells (2n).
- Haploid number: Chromosomes in gametes (n), half the diploid number.
Explain mitosis and meiosis (overview and stages)
Overview of Mitosis and Meiosis
Mitosis and meiosis are both processes of cell division, but they serve different purposes and result in different outcomes.
- Mitosis is responsible for producing two genetically identical daughter cells, which is used for growth, repair, and asexual reproduction.
- Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four genetically unique gametes (sperm or egg cells) used in sexual reproduction.
Mitosis – Cell Division for Growth and Repair
Mitosis produces two genetically identical diploid cells from a single diploid cell. It occurs in somatic cells (non-reproductive cells). The stages of mitosis are:
1. Interphase (Preparation Phase)
- G1 (Gap 1): The cell grows, synthesizes proteins, and prepares for DNA replication.
- S (Synthesis): The cell’s DNA is replicated, so there are two copies of each chromosome.
- G2 (Gap 2): The cell continues to grow and prepares for division by synthesizing proteins and organelles.
Note: Interphase is technically not part of mitosis but is essential for the preparation of the division process.
2. Prophase
- Chromosomes condense and become visible.
- The nuclear envelope begins to break down.
- The mitotic spindle (composed of microtubules) starts to form from the centrosomes.
- The centrioles (in animal cells) move toward opposite poles of the cell.
3. Metaphase
- The chromosomes line up along the metaphase plate (the cell’s equator).
- Spindle fibers attach to the centromere of each chromosome, securing them in place.
4. Anaphase
- The centromeres split, and the sister chromatids (identical copies of each chromosome) are pulled apart toward opposite poles of the cell by the spindle fibers.
5. Telophase
- Chromatids reach the poles and begin to uncoil, returning to their chromatin form.
- The nuclear envelope re-forms around each set of chromosomes.
- The spindle fibers dissolve.
6. Cytokinesis
- This is the final step where the cytoplasm divides, resulting in two distinct daughter cells. In animal cells, a cleavage furrow forms and pinches the cell into two. In plant cells, a cell plate forms, eventually leading to the creation of a new cell wall.
Result of Mitosis: Two genetically identical diploid daughter cells.
Meiosis – Cell Division for Sexual Reproduction
Meiosis reduces the chromosome number by half, producing four genetically unique haploid gametes (sperm or egg cells) from one diploid cell. This process involves two rounds of division: Meiosis I and Meiosis II.
Meiosis I – Reduction Division (Chromosome Number Halved)
Meiosis I reduces the chromosome number from diploid (2n) to haploid (n).
1. Prophase I
- Chromosomes condense and become visible.
- Homologous chromosomes (chromosomes of the same type, one from each parent) pair up in a process called synapsis to form tetrads (pairs of homologous chromosomes).
- Crossing over occurs: sections of chromatids may exchange between homologous chromosomes, increasing genetic variation.
- The nuclear envelope breaks down, and the spindle fibers form.
2. Metaphase I
- The tetrads (paired homologous chromosomes) align along the metaphase plate.
- Spindle fibers attach to the centromeres of each homologous chromosome.
3. Anaphase I
- Homologous chromosomes are separated and pulled toward opposite poles of the cell (each chromosome still consists of two sister chromatids).
- Independent assortment occurs, where the way chromosomes align and separate is random, contributing to genetic diversity.
4. Telophase I
- Chromosomes reach the poles and the nuclear envelope reforms.
- The cell divides through cytokinesis, resulting in two haploid daughter cells (each containing half the original chromosome number).
Meiosis II – Division Similar to Mitosis (Chromosome Number Remains Haploid)
Meiosis II separates the sister chromatids of each chromosome and results in four haploid cells.
1. Prophase II
- Chromosomes condense again.
- A new spindle forms in each of the two haploid cells.
- The nuclear envelope breaks down.
2. Metaphase II
- Chromosomes line up along the metaphase plate in each haploid cell.
3. Anaphase II
- The sister chromatids of each chromosome are pulled apart toward opposite poles of the cell.
4. Telophase II
- Chromatids reach the poles and the nuclear envelope reforms.
- Cytokinesis divides the two haploid cells, resulting in a total of four genetically unique haploid gametes.
Result of Meiosis: Four genetically diverse haploid gametes, each with half the chromosome number of the original cell.
Key Differences Between Mitosis and Meiosis
Conclusion
- Mitosis produces two identical diploid cells for growth and repair.
- Meiosis reduces the chromosome number by half, producing four genetically diverse haploid gametes for sexual reproduction.
Both processes are essential for life: mitosis enables organisms to grow and repair, while meiosis contributes to genetic diversity in offspring.
Feature | Mitosis | Meiosis |
|—————————–|————————————————|———————————————|
| Purpose | Growth, repair, asexual reproduction | Sexual reproduction, forming gametes |
| Number of Divisions | One division (Prophase, Metaphase, Anaphase, Telophase) | Two divisions (Meiosis I and Meiosis II) |
| Chromosome Number | Daughter cells are diploid (2n) | Daughter cells are haploid (n) |
| Genetic Variation | Identical daughter cells (no variation) | Genetic variation through crossing over and independent assortment |
| Number of Daughter Cells| Two daughter cells | Four daughter cells |
Define:
* Sex chromosomes, autosomes, homologous chromosomes
Definitions:
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Sex Chromosomes
- Definition: Sex chromosomes are chromosomes that determine the sex (gender) of an organism. In humans and many other species, there are two types of sex chromosomes: X and Y.
- Humans: Females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The presence of two X chromosomes typically results in female development, while the presence of an X and a Y chromosome typically results in male development.
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Autosomes
- Definition: Autosomes are all the chromosomes in an organism that are not sex chromosomes. They carry the majority of an organism’s genetic information, determining traits unrelated to gender.
- Humans: Humans have 22 pairs of autosomes (for a total of 44 autosomes), which are numbered 1 to 22, based on size and structure.
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Homologous Chromosomes
- Definition: Homologous chromosomes are pairs of chromosomes that have the same structure and carry the same types of genes, but may have different versions (alleles) of those genes. One chromosome in each pair comes from the mother, and the other comes from the father.
- Example: In humans, chromosome 1 from the mother and chromosome 1 from the father are homologous chromosomes. Although they carry the same types of genes (such as eye color or blood type), they may carry different versions (alleles) of those genes.
Summary:
- Sex chromosomes determine gender (X and Y chromosomes).
- Autosomes are non-sex chromosomes that carry most of an organism’s genetic information.
- Homologous chromosomes are pairs of chromosomes, one from each parent, that have the same genes but may carry different alleles.
Define: Alleles
Alleles
- Definition: Alleles are different versions or variants of a gene that can exist at a specific locus (position) on a chromosome. They arise due to mutations or genetic variation and can lead to different traits or characteristics in an organism. Each individual typically has two alleles for each gene—one inherited from the mother and one from the father.
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Example: For the gene that determines eye color, there might be different alleles for brown, blue, or green eyes. In this case:
- Brown (B) and blue (b) could be two different alleles for the eye color gene.
- An individual might inherit one allele for brown eyes (B) from one parent and one allele for blue eyes (b) from the other parent.
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Types of Alleles:
- Dominant allele: An allele that expresses its trait even if only one copy is present. (e.g., B for brown eyes is dominant over b for blue eyes).
- Recessive allele: An allele that expresses its trait only if two copies are present (one from each parent). (e.g., b for blue eyes will only show if both alleles are b).
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Genotype vs. Phenotype:
- Genotype refers to the genetic makeup of an individual, the combination of alleles they possess for a particular gene.
- Phenotype is the observable trait or characteristic, such as eye color, that results from the interaction of alleles.
Example of Alleles in a Punnett Square:
For a gene with two alleles (B and b):
- BB: Homozygous dominant (brown eyes)
- Bb: Heterozygous (brown eyes, since B is dominant)
- bb: Homozygous recessive (blue eyes)
Define: Dominant/recessive
Dominant and Recessive Alleles
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Dominant Allele
- Definition: A dominant allele is an allele that expresses its trait in the phenotype even when only one copy of the allele is present in the genotype. In other words, if an individual has at least one dominant allele for a given gene, the trait associated with that allele will be visible in the organism.
- Notation: Dominant alleles are typically represented by uppercase letters (e.g., A, B).
- Example: For the gene determining pea plant flower color, the allele for purple flowers (P) is dominant. A pea plant with the genotype Pp (heterozygous) will have purple flowers, as the dominant P allele “masks” the effect of the recessive p allele.
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Recessive Allele
- Definition: A recessive allele is an allele whose trait is only expressed in the phenotype if two copies of the allele (homozygous recessive) are present in the genotype. If only one recessive allele is present (in a heterozygous individual), the trait is not expressed because it is masked by the dominant allele.
- Notation: Recessive alleles are typically represented by lowercase letters (e.g., a, b).
- Example: For the same pea plant flower color gene, the allele for white flowers (p) is recessive. A pea plant must have the genotype pp (homozygous recessive) for the flower color to be white. If it is Pp (heterozygous), the plant will have purple flowers due to the dominance of the P allele.
Summary:
- Dominant allele: Expresses its trait even with only one copy (e.g., P for purple flowers).
- Recessive allele: Only expresses its trait when two copies are present (e.g., p for white flowers).
Genotype Examples:
- Dominant homozygous (two dominant alleles): AA or PP
- Heterozygous (one dominant, one recessive allele): Aa or Pp
- Recessive homozygous (two recessive alleles): aa or pp
In a heterozygous individual, the dominant allele masks the effect of the recessive allele.
Define: Dominance: Incomplete, co-dominance
Dominance: Incomplete Dominance and Co-dominance
Dominance refers to the relationship between alleles of a gene and how they influence the organism’s phenotype (observable traits). While complete dominance is the most common form (where one allele fully masks the expression of the other), there are two other types of dominance: incomplete dominance and co-dominance.
1. Incomplete Dominance
- Definition: In incomplete dominance, neither allele is completely dominant over the other. Instead, the heterozygous individual exhibits a blend of the two traits. The resulting phenotype is intermediate between the two homozygous phenotypes.
- Key Points:
- The heterozygous phenotype is a mixture or blending of the two alleles.
- This results in an intermediate phenotype that is distinct from both the homozygous dominant and homozygous recessive phenotypes.
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Example: In snapdragon flowers, the allele for red flowers (R) is incompletely dominant over the allele for white flowers (r).
- RR = Red flowers
- rr = White flowers
- Rr = Pink flowers (a blend of red and white)
2. Co-dominance
- Definition: In co-dominance, both alleles are fully expressed in the heterozygous individual. Instead of blending, both traits appear together, with each allele contributing equally to the phenotype.
- Key Points:
- Both alleles are visibly expressed in the organism’s phenotype, with neither allele being dominant or recessive.
- The individual shows both traits simultaneously, not a mix of them.
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Example: In human blood types, the alleles for A and B blood types are co-dominant.
- IA (A allele) and IB (B allele) are both expressed in individuals with genotype IAIB.
- IAIA or IAi results in Type A blood.
- IBIB or IBi results in Type B blood.
- IAIB results in Type AB blood, where both A and B antigens are expressed on the surface of red blood cells.
Summary of Dominance Types
Key Takeaways:
- Incomplete dominance: The heterozygote shows a mix of the two traits (e.g., pink flowers from red and white parents).
- Co-dominance: Both traits are expressed fully and separately in the heterozygote (e.g., both A and B blood types in a person with AB blood).
Type of Dominance | Definition | Example |
|—————————|—————————————————————|——————————|
| Complete Dominance | One allele completely masks the expression of the other. | Purple flowers in pea plants (P = purple, p = white) |
| Incomplete Dominance | Neither allele is fully dominant; the heterozygous phenotype is an intermediate blend of both alleles. | Pink flowers in snapdragons (R = red, r = white) |
| Co-dominance | Both alleles are equally expressed in the heterozygous individual, with no blending. | AB blood type in humans (IA and IB alleles) |
Define: * Homozygous/heterozygous
Homozygous and Heterozygous
These terms describe the genetic makeup (genotype) of an organism with respect to a particular gene or trait. They refer to the alleles present for a specific gene.
1. Homozygous
- Definition: An organism is homozygous for a gene if it has two identical alleles for that gene, one inherited from each parent.
- Key Points:
- Homozygous dominant: Both alleles are the same and dominant (e.g., AA).
- Homozygous recessive: Both alleles are the same and recessive (e.g., aa).
- Example:
- For flower color in peas, if the plant has two dominant alleles (AA) or two recessive alleles (aa), it is considered homozygous for that gene.
2. Heterozygous
- Definition: An organism is heterozygous for a gene if it has two different alleles for that gene, one inherited from each parent.
- Key Points:
- The two alleles are different, one being dominant and the other recessive (e.g., Aa).
- The dominant allele will determine the organism’s phenotype in a heterozygous pair.
- Example:
- If a plant has one dominant allele (A) and one recessive allele (a) for flower color, its genotype is Aa (heterozygous), and the flower will show the dominant trait (e.g., purple flowers in the case of A being dominant over a).
Summary of Homozygous and Heterozygous
Key Points:
- Homozygous: Same alleles for a trait.
- Heterozygous: Different alleles for a trait.
Term | Definition | Example |
|—————-|——————————————————|——————————|
| Homozygous | Two identical alleles for a gene (either both dominant or both recessive) | AA (homozygous dominant) or aa (homozygous recessive) |
| Heterozygous | Two different alleles for a gene (one dominant and one recessive) | Aa (heterozygous) |
Define: Genotype/phenotype
Genotype and Phenotype
These terms are used to describe an organism’s genetic makeup and the physical traits that result from it.
1. Genotype
- Definition: The genotype refers to the genetic makeup of an organism—the specific set of alleles it carries for a particular gene or trait. The genotype is determined by the combination of alleles inherited from both parents.
- Key Points:
- It is the internal genetic code of an organism.
- The genotype is typically represented by letters that indicate the alleles for a gene (e.g., AA, Aa, aa).
- The genotype includes both dominant and recessive alleles.
- Example: If a plant has the genotype Aa, it has one dominant allele (A) for a trait and one recessive allele (a). This means it carries the genetic information for that trait, but the dominant allele will influence the phenotype.
2. Phenotype
- Definition: The phenotype is the observable physical or behavioral traits of an organism that result from the interaction of its genotype with the environment. It is the expression of the genotype in the organism’s appearance or behavior.
- Key Points:
- The phenotype is the visible or measurable traits, such as flower color, height, or blood type.
- It is influenced not only by the genotype but also by environmental factors (e.g., diet, climate, exposure to sunlight).
- Example: If a plant with the genotype Aa (heterozygous) has purple flowers because the dominant allele (A) codes for purple, the phenotype would be “purple flowers”. Even though the plant has both A and a alleles, the dominant A allele determines the visible trait.
Genotype vs. Phenotype
Key Differences:
- Genotype: Refers to the actual genetic sequence (alleles) an organism has.
- Phenotype: Refers to the physical expression of those genetic traits, which is influenced by the genotype and the environment.
In summary, the genotype is what an organism inherits, and the phenotype is what it expresses or shows.
Term | Definition | Example |
|—————|——————————————————————-|——————————————–|
| Genotype | The genetic makeup (the combination of alleles) of an organism. | AA (homozygous dominant), Aa (heterozygous), aa (homozygous recessive) |
| Phenotype | The observable characteristics or traits of an organism. | Purple flowers (from genotype AA or Aa) or White flowers (from genotype aa) |
