Genetics - Core A Flashcards
Define Genetics
The branch of biology that studies heredity and the variation of inherited characteristics. It’s about understanding how traits are passed down from one generation to the next.
What does a Geneticist do?
Investigates genes and their functions. They may study inheritance patterns, identify genetic disorders, or work on genetic engineering, like modifying DNA in crops to make them more resilient.
Basic Animal Cell Structure
Nucleus: Contains chromosomes and controls cell activities.
Cytoplasm: Jelly-like fluid where metabolic processes occur.
Cell membrane: Controls what enters and exits the cell.
Mitochondria: Produces energy.
Ribosomes: Makes proteins.
What do genes determine
A person’s characteristics (e.g., height, hair colour)
How many chromosomes does a human cell have?
46 chromosomes, arranged in 23 pairs. Half are inherited from each parent.
What’s pair 23 chromosome do?
biological sex: XX for females and XY for males.
Where are chromosomes and what are they made of?
Chromosomes are housed in the nucleus of cells and are made of DNA.
Describe the Watson and Crick Model of DNA
A double helix with two strands twisting around each other. Nucleotides: Each consists of a sugar, phosphate, and base (Adenine [A], Thymine [T], Cytosine [C], Guanine [G]). The sides of the double helix are formed by alternating sugar and phosphate groups.
What’s a nucleotide?
Building block of DNA and RNA
and has three parts:
- A sugar (deoxyribose in DNA, ribose in RNA)
- A phosphate group (helps link nucleotides together)
- A nitrogenous base (A, T, C, G in DNA; A, U, C, G in RNA)
What’s the orientation of DNA
one in the 5’ (prime) 3’ direction and the other in the 3’ to 5’ direction.
Leading vs. Lagging Strand
Leading strand (fast) → Runs 5’ to 3’, so DNA polymerase can easily add nucleotides in one smooth, continuous motion.
Lagging strand (slow) → Runs 3’ to 5’, but DNA polymerase can only build in the 5’ to 3’ direction. So, it has to work in small sections called Okazaki fragments, which later get stitched together.
Complimentary Bases
Adenine: Thymine
Guanine: Cytosine
Draw a labelled diagram of DNA
What kinds of cells does mitosis occur
all cells except gametes (somatic cells) diploid cells
What kinds of cells does meiosis create
gametes (egg and sperm) are haploid cells
define diploid and haploid
a cell that contains a single set of chromosomes is haploid, while a cell containing two copies of each chromosome is diploid
What’s a somatic cell
Any cell of a living organism other than the reproductive cells.
What’s the abbreviation for mitosis and meiosis?
I(PMAT)
I-Interphase
P-Prophase
M-Metaphase
A-Anaphase
T-Telophase
What happens in each stage of IPMAT
Interphase: DNA replicates.
Prophase: Chromosomes condense.
Metaphase: Chromosomes align at the centre.
Anaphase: Chromatids separate.
Telophase: Cells nuclei form, forming 2 identical cells.
What does mitosis produce
2 identical daughter cells to the parent cell
What does meiosis produce
4 haploid daughter cells that are different from each other and the parent
What’s binary fission
a type of asexual reproduction typically observed in prokaryotes and a few single-celled eukaryotes.
What’s cytokinesis?
after telophase - the cytoplasm is physically divided to form two daughter cells
What’s mitosis for?
Division for growth and tissue repair in asexual reproduction.
What’s meiosis for?
responsible for producing sperm and egg cells for reproduction
what’s the starting cell for meiosis?
Germ cell (diploid)
describe each stage of meiosis
- Prophase I: Homologous chromosomes pair up & crossing over occurs (46 chromosomes, 92 chromatids)
- Metaphase I: Homologous pairs align (46 chromosomes, 92 chromatids)
- Anaphase I: Homologous chromosomes separate (46 chromosomes, 92 chromatids)
- Telophase I & Cytokinesis: Two haploid cells form (23 chromosomes, 46 chromatids per cell)
- Meiosis II (Equational Division)
- Prophase II: Chromosomes condense (23 chromosomes, 46 chromatids per cell)
- Metaphase II: Chromosomes align (23 chromosomes, 46 chromatids per cell)
- Anaphase II: Sister chromatids separate (46 chromosomes, 46 chromatids per cell temporarily)
- Telophase II & Cytokinesis: Four haploid cells form (23 chromosomes, 23 chromatids per cell)
Diagram of chromosome
describe each stage of mitosis in detail
Start (Before Mitosis): 46 chromosomes, 92 chromatids (DNA replicated in interphase)
Prophase: Chromosomes condense, spindle fibers form (46 chromosomes, 92 chromatids)
Metaphase: Chromosomes align at the metaphase plate (46 chromosomes, 92 chromatids)
Anaphase: Sister chromatids separate and move to opposite poles (92 chromosomes, 92 chromatids temporarily)
Telophase & Cytokinesis: Two diploid (2n) cells form (46 chromosomes, 46 chromatids per cell)
How does mitosis ensure DNA is copied exactly in each division?
During interphase and equally distributing identical sister chromatids during cell division. Metaphase ensures proper alignment, Anaphase separates chromatids, and Telophase & Cytokinesis create two identical diploid cells - UNLESS THERE IS A GENETIC MUTATION
What’s a mutation?
changes or alterations in the DNA sequence of an organism. They can occur naturally during DNA replication or be triggered by external factors.
Types of mutations
- Base Substitution
- Insertion
- Deletion
What are the Causes of Mutations?
Natural Errors During Replication:
Even though cells have proofreading mechanisms, mistakes can occasionally slip through during DNA copying.
External Factors (Mutagens):
Radiation: UV rays from the sun or X-rays can damage DNA.
Chemicals: Substances like tobacco smoke or industrial pollutants can induce mutations.
Infectious Agents: Viruses can insert their DNA into the host genome, potentially causing disruptions.
What’s Base Substitution
Involves the replacement of one nucleotide base with another.
Example: Changing an Adenine (A) to a Guanine (G).
Effect: May alter a single amino acid in a protein, sometimes with significant consequences.
What’s Insertion
An extra nucleotide is added to the DNA sequence.
Effect: Causes a frameshift, altering the reading frame of the genetic code and potentially rendering a protein nonfunctional.
What’s Deletion?
A nucleotide is removed from the sequence.
Effect: Also results in a frameshift, disrupting the genetic code and protein production.
Effects of mutations
Neutral:
Most mutations have no noticeable effect, as they may occur in non-coding regions or not affect the protein’s function.
Harmful:
Mutations that disrupt critical proteins can lead to diseases, such as cancer or genetic disorders like cystic fibrosis.
Beneficial:
Rarely, mutations can provide an advantage, such as better resistance to diseases or environmental adaptation (e.g., antibiotic resistance in bacteria).
Examples of Mutation-Related Conditions caused by the incorrect number of chromosomes in the cells
Down Syndrome:
Caused by an extra copy of chromosome 21 (not a mutation in the DNA sequence, but a chromosomal error during meiosis).
Klinefelter Syndrome
Occurs due to error in meiosis, chromosomes don’t separate properly during the formation of gametes. Results in male having an extra X chromosome.
Sickle Cell Anemia:
Results from a single base substitution in the hemoglobin gene.
Define inheritance
the passing on of traits from parents to offspring.
Define Heterozygous
Two different alleles
Define Homozygous
Same alleles
Define Genotype
Genetic makeup of alleles
Define Phenotype
Observable traits.
Define Biotechnology
The use of biological systems, organisms, or processes to develop products or technologies for human benefit. This often involves manipulating living organisms or their genetic material to solve problems in fields like agriculture, medicine, and industry.
Benefits of Biotechnology
- Enhanced crop yields and resistance to pests, diseases, and extreme weather conditions.
- Development of nutrient-enriched foods, such as Golden Rice
Issues of biotechnology
- Ethical concerns about tampering with natural organisms.
- Potential unintended consequences, such as allergen introduction or environmental impacts (e.g., loss of biodiversity).
Benefits and issues with the cloning of crops
Benefits:
- Ensures uniformity and consistency in crop quality and yield.
- Helps propagate disease-resistant or high-yield plants quickly.
Issues:
- Reduction in genetic diversity, which could make crops more vulnerable to new diseases.
- Ethical questions about whether cloning is “natural” or acceptable.
Benefits of using biotechnology in medicine
- Previously, insulin was extracted from pigs or cows, which could lead to allergic reactions. Biotechnology allows for the production of recombinant human insulin using genetically modified bacteria or yeast, offering a purer and safer product.
- It enables large-scale, cost-effective production to meet global demand.
- IVF Helps individuals and couples struggling with infertility to conceive.
- Advances in genetic screening during IVF can reduce the risk of hereditary diseases being passed to offspring.
Issues of using biotechnology in medicine
- The ownership and patenting of genetically engineered medical products, which make life-saving medicines inaccessible to disadvantaged populations.
- Some worry about the potential misuse of the technology, such as “designer babies” (choosing traits like intelligence or appearance).
- Accessibility concerns, as IVF can be expensive and is not available to everyone.
Outline Mendel’s experiments with pea plants
studied pea plants to understand how traits are passed from parents to offspring. He focused on specific traits like plant height (tall or short) and flower colour (purple or white). Here’s what he did:
- Crossed purebred plants with opposite traits (e.g., tall vs. short).
- In the first generation (F1), all plants showed only one trait (e.g., all tall).
- He let the F1 plants self-pollinate, and in the second generation (F2), the “hidden” trait reappeared in 1 out of 4 plants (a 3:1 ratio).
Conclusion from Mendel’s Experiments
- Traits are controlled by “factors” (now called genes).
- Each parent passes one factor (allele) to their offspring.
- Some traits are dominant (always show up) and others are recessive (only show up if both factors are recessive).
- showed that heredity follows clear, predictable patterns!
Define dominant allele
An allele that always expresses its trait when present, even if there’s only one copy. For example, if the allele for tall plants is dominant, a plant with one or two copies of that allele will always be tall.
Define recessive allele
An allele that only expresses its trait if there are two copies (one from each parent). If there’s a dominant allele present, the recessive trait will remain hidden.
What are alleles?
different forms of the same gene. For example, a gene that controls eye colour might have a dominant allele for brown eyes (B) and a recessive allele for blue eyes (b). Each individual inherits two alleles for each gene, one from each parent. The combination of alleles determines the individual’s traits.
How do organisms inherit their genes?
Organisms inherit their genes by random chance, as each parent contributes one allele for every gene. This randomness leads to genetic variation, meaning offspring can inherit different combinations of alleles, resulting in unique traits.
What’s a locus
The physical location of a specific gene on a chromosome.
4 Types of inheritance
- Simple inheritance (Mendelian Inheritance)
- Incomplete inheritance (heterozygous phenotype is a blend of both traits)
- co-dominant inheritance (Both alleles are fully expressed in the heterozygous form)
- sex-linked inheritance (Genes are located on the X or Y chromosome)
Each codon describes the type and sequence of what?
Amino Acids
What is the name for all the information encoded in our genes?
Genome
What is the most common form of mutation?
Simple-gene mutation
What is the name for the building blocks of proteins?
Amino Acids
What’s a codon
- DNA contains the instructions for making proteins, and these instructions are written in the form of codons (three-letter sequences of nucleotides).
- Each codon corresponds to a specific amino acid or a stop signal in protein synthesis.
- There are 20 standard amino acids, and they are encoded by 64 possible codons in the genetic code.
