Genetics Flashcards
1
Q
Where is DNA found?
A
•DNA is in every cell of every living thing
•it is found within the chromosomes of the cell
•chromosomes work to build proteins and assist in duplication or division of the cells
2
Q
James Watson and Francis Crick
A
•in 1953, they concluded that the DNA molecule appears as a three-dimensional double helix
3
Q
Rosalind Franklin and Maurice Wilkins
A
•they used X-ray crystallography to study DNA’s structure, which helped Watson and Crick with their discovery
4
Q
What is DNA
A
•the unique structure of DNA allows it to be the hereditary molecule and allows it to store instructions for directing cell activities
5
Q
Cell
A
•a cell is the smallest unit of an organism and cells are known as the building blocks of life
•most human cell types contain a nucleus
6
Q
Nucleus
A
•the nucleus control the cell, but it is also where genetic information is stored
•the nucleus contains structures called chromosomes
•chromosomes are made of DNA
7
Q
Chromosome
A
•each chromosome is made up of a single molecule of DNA
•the cross shape we associate with chromosomes arises when the DNA copies itself, coils and condenses for cell division (mitosis)
8
Q
DNA & Genes
A
•DNA (deoxyribose nucleic acid) carries the genetic information of a living being
•a section of DNA is known as a gene
•genes contain the code for the production of a particular protein within a cell
9
Q
Locating a gene
A
•the images show the levels of organization from the nucleus to a chromosome, DNA and finally a gene
10
Q
23 pairs
A
•each human body cell contains 46 chromosome (23 pair)
•the pairs carry the same type of genes
•people with specific conditions and syndromes may have an extra chromosome
11
Q
XX and XY
A
•the 23rd pair of chromosomes are known as the sex chromosomes
•in females, the chromosome pair are identical and known as XX
•in males, the chromosome pair are different and known as XY
12
Q
DNA makeup
A
•phosphate, base, and deoxyribose sugar
13
Q
Gene shape
A
double helix
14
Q
Nitrogen Bases
A
Adenine, Thymine, Cytosine, and Guanine (a & t, g & c)
15
Q
Nucleotide
A
•the backbone of DNA is formed by alternating sugar and phosphates held together by a strong bond
•the rings of the ladder are formed by the four nitrogen bases and are held together by weak hydrogen bonds
16
Q
What does DNA look like?
A
•the bases of DNA pair with each other in a predictable way
•a pairs with t
•c pairs with g
17
Q
How does DNA work?
A
•the 3 letters of DNA make up codons
•these chemicals are repeated in various orders over and over
•these codons make up genes
•these genes tell cells how to make a protein that controls everything in the cell
18
Q
Locus
A
•locus is a term that we use to tell us where on a chromosome a specific gene is
•so it’s really the physical location of a gene on a chromosome
•it’s a way of defining the gene’s neighborhood
•if you consider the entire chromosome as a country where the gene is found, and then a region of the chromosome would be the city
•the more specific area, or the locus, is this particular neighborhood where the gene is found
19
Q
DNA in forensic science
A
•DNA fingerprinting is an essential tool in forensic science
•it does not precisely determine the suspects identity but helps narrow it down
20
Q
DNA sequencing
A
•developed in 1970s (Sanger sequencing)
•determines the order of neucleotides in DNA
•originally slow and costly, sequencing has become faster and cheaper, leading to entire genome projects like the Human Genome Project
•revolutionized genetics by making it possible to study genetic variations, maps genes associated with diseases, and better understand evolutionary relationships
21
Q
Polymerase Chain Reaction (PCR)
A
•developed in 1983
•a technique used to amplify small amount of DNA, making it easier to analyze genetic material
•widely used in genetic testing, forensics, and medical diagnostics
•transformed genetics and biology by allowing precise detection of genetic material in areas such as disease diagnosis, forensic science, and environmental monitoring
22
Q
Genetically Modified Organisms (GMOs)
A
•developed 1970-1980
•organisms whose DNA had been altered using genetic engineering techniques to exhibit desired traits, such as pest resistance in crops
•have significantly impacted agriculture by increasing crop yields, reducing pesticide use, and enabling the development of nutrient-enriched foods like golden rice
23
Q
Recombinant DNA Technology
A
•developed in 1973
•involves combining DNA from different organisms to create hybrid molecules that can be replicated in host organisms
•this technology led to the production of human insulin, hepatitis vaccines, and various medical treatments marking the beginning of the biotechnology industry
24
Q
DNA Fingerprinting
A
•developed in 1984
•used variations in DNA sequences to identify individuals
•widely used in forensics, paternity testing, and genetic research
•has transformed criminal investigation and legal cases by providing a reliable method for identification based on genetic material, with wide implications in law and security
25
Gene Therapy (Social Benefits)
•could provide long-term cures for genetic diseases (cystic fibrosis), may lead to longevity of life within patients, reduce the burden on families and caregivers by addressing root causes of genetic diseases
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Gene Therapy (Ethical Concerns)
•risk of unintended side effects or mutations in other parts of genome, who can access treatments as they may be expensive and inaccessible to many, misuse for non-medical enhancements such as altering traits not related to health, raising concerns about “designer baby”
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Gene Therapy (Societal Impact)
•reduce healthcare costs associated with managing chronic genetic conditions, alter how society views disability and illness with a view of “curing” it, ethical and societal debates may arise regarding what constitutes acceptable genetic modifications
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Stem-Cell Research (Social Benefits)
•potential to regenerate damaged tissues and organs, which could treat conditions like diabetes and Parkinson’s disease, advances in personalized medicine where stem cells can be tailored to an individual’s needs, could improve treatment efficacy, reduce the need for organ transplants and risks
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Stem-Cell Research (Ethical Concerns)
•use of embryonic stem cells raises moral and ethical issues about the status of embryos, risks related to potential tumor formation from stem cell implants, concerns about “playing God” and altering human biology at a fundamental level
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Stem-Cell Research (Societal Impact)
•may lead to major changes in the treatment of chronic conditions and life-threatening diseases, could shift medical research and funding toward regenerative therapies, ethical debates may influence policies around research funding, afecto by scientific advancement
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Genetic Screening (Social Benefits)
•can provide early detection of genetic disorders, allowing for proactive management of lifestyle changes, helps parents understand the genetic risks of their children, potentially reducing incedences of genetic disorders, can guide personalized medicine approaches, improving treatment affectiveness
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Genetic Screening (Ethical Concerns)
•privacy concerns regarding who has access to genetic information and potential discrimination by insurers of employers, potential psychological impact of knowing one’s genetic predisposition to serious diseases, risk of stigmatization or social pressures based on genetic traits
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Genetic Screening (Societal Impact)
•could lead to more preventive healthcare, shifting focus from treatment to early intervention, raises questions about genetic privacy laws and the need for regulatory frameworks, may intensify social divides if access to genetic screening is uneven, particularly if costs remain high
34
Bioinformatics (Social Benefits)
•enables researchers to analyze large datasets, leading to faster discoveries in disease mechanisms, drug development, and personalized treatments, can enhance our understanding of complex diseases like cancer, potentially leading to better treatments, supports the integration of genomics into everyday healthcare, improving diagnosis and treatment options
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Bioinformatics (Ethical Concerns)
•privacy issues related to the storage and sharing of genetic data, with risks of data breaches, consent concerns, as people may not fully understand the implications of sharing their genetic information, risk of misuse of genetic data for surveillance or discrimination
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Bioinformatics (Societal Impact)
•could transform healthcare by making it more data-driven and individualized, raises important questions about data ownership, privacy, and the ethics of sharing genetic information, might lead to societal shifts in how we handle personal health data and approach medical privacy
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Intro To RNA
•RNA, or ribonucleic acid is a single-stranded molecule similar to DNA but with some key differences
•it has a ribose sugar, unlike DNA’s deoxyribose, and instead of thymine (T), RNA has the base uracil (U), which pairs with adenine (A)
•RNA plays several essential roles in cells, especially in translating the genetic code from DNA to create proteins
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Types of RNA and Their Function
•there are three main types of RNA, each with a unique role in protein synthesis:
•Messenger RNA, Transfer RNA, and Ribosomal RNA
•together these types of RNA convert genetic information into functional proteins, which performs various tasks in the cell
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Messenger RNA (mRNA)
•carries genetic information from DNA to the ribosome, where proteins are made
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Transfer RNA (tRNA)
•brings amino acids to the ribosome, helping to assemble them into proteins
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Ribosomal RNA (rRNA)
•is a component of ribosomes, providing structural support and helping catalyze protein assembly
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Overview of Protein Synthesis
•the process by which cells build proteins, following instructions encoded in DNA
•it consists of two main stages: transcription and translation
•during transcription, the DNA sequence of a gene is copied into messenger RNA (mRNA) in the nucleus
•in translation this mRNA travels to the ribosome, where it is used as a template to assemble amino acids into a protein
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Transcription
•in transcription, RNA polymerase binds to DNA and unwinds a section of the double helix
•it synthesizes a complementary strand of mRNA based on the DNA template
•the mRNA then exits the nucleus and moves to the ribosome in the cytoplasm
44
Translation
•in translation, the mRNA is read in sets of three bases called codons, each coding for a specific amino acid
•transfer RNA (tRNA) brings amino acids to the ribosome, matching them to the codons on the mRNA
•these amino acids are linked together to form a polypeptide chain, which folds into a functional protein
•start codon usually AUG, stop codon is UAA or UAG
45
What is DNA Replication?
•DNA replication as the biological process of producing two identical replicas of DNA from one original DNA molecule
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Importance of DNA Replication
•DNA replication is fundamental to cell division, which is how our bodies grow and heal
•Each new cell needs an exact copy of DNA to function properly, so DNA replication ensures genetic information is passed down accurately
•without DNA replication, cells wouldn’t have the instructions needed to build proteins and maintain life
47
3 Main Stages of DNA Replication
1.Initiation- during initiation, the double helix structure is unwound and split into 2 pieces of RNA
2.Elongation- This is where the new strands of DNA are synthesized
3.Termination- replication ends and DNA Strands separate completely
48
Initiation
•replication begins with Initiation. An enzyme called helicase unwinds the DNA double helix, creating a Y-shaped area known as the replication fork
•helicase breaks the hydrogen bonds between the base pairs, allowing the two DNA strands to separate
•this creates the template strands that will be used to make new DNA copies.”
49
Role of Primase
•primase is an enzyme that lays down RNA primers on the DNA strands. These primers serve as starting points for DNA synthesis
•think of RNA primers like placeholders that signal where DNA polymerase, the main enzyme in DNA synthesis, should begin working
•this primer is especially important because DNA polymerase can only add new nucleotides to an existing strand
50
Elongation
•during Elongation, DNA polymerase binds to each strand and starts adding new nucleotides, complementary to each template strand
•on the leading strand, synthesis is continuous in the same direction as the replication fork (5’ to 3’). On the lagging strand (3’ to 5’), synthesis is fragmented, creating short sequences called Okazaki fragments
•this dual mode of synthesis allows both strands to be replicated simultaneously, even though DNA polymerase works in only one direction
51
Okazaki Fragments and Ligase
•Okazaki fragments form on the lagging strand due to its opposite direction from the replication fork
•once these fragments are created, another enzyme, DNA ligase, comes in and joins them together, making a complete strand
•Ligase essentially ‘seals the gaps’ between fragments, ensuring a continuous DNA strand
52
Termination
•replication ends with Termination. Once the entire DNA strand is replicated, the process concludes, and the two DNA molecules separate
•Telomeres, which are protective caps at the ends of DNA, play a role in stabilizing the chromosome ends after replication
•the presence of telomeres is especially important because a small portion of DNA is lost with each replication cycle
53
Proofreading and Error Correction
•DNA polymerase has a proofreading function, which allows it to correct errors by replacing incorrect nucleotides during replication
•this proofreading helps maintain the accuracy of DNA replication and ensures genetic stability
•if errors do slip through, they can lead to mutations, which can sometimes cause diseases, so this step is crucial for health
•the accuracy of DNA replication is critical to cell reproduction, and estimates of mutation rates for a variety of genes indicate that the frequency of errors during replication corresponds to only one incorrect base per 109 to 1010 nucleotides incorporated. (NCBI, 2020)
54
Review of Mitosis
Definition: Mitosis is a type of cell division that results in two genetically identical daughter cells from a single parent cell.
Purpose: Enables growth, tissue repair, and replacement of cells in multicellular organisms.
Location: Occurs in somatic (non-reproductive) cells.
55
Overview of Cell Cycle
•Cell Cycle Phases:
•Interphase: Preparation phase, consisting of: G1 Phase: Cell growth, S Phase: DNA replication, G2 Phase: Final preparations for mitosis
•M Phase (Mitosis): The actual division phase. Prophase, Metaphase, Anaphase, Telophase
•Result: Two identical cells with the same number of chromosomes as the parent cell.
56
Importance of Meiosis
•Genetic Diversity: Creates genetic variation through recombination and independent assortment
•Chromosome Reduction: Reduces chromosome number by half, so when gametes combine, the offspring have the correct chromosome count
•Foundation of Evolution: Genetic diversity resulting from meiosis drives evolution and adaptation in populations
57
Stages of Meiosis
•Meiosis I: Separation of homologous chromosomes.
•Prophase I, Metaphase I, Anaphase I, Telophase I
•Meiosis II: Separation of sister chromatids (similar to mitosis).
•Prophase II, Metaphase II, Anaphase II, Telophase II
58
Prophase 1 (Key Phase)
•Description: Homologous chromosomes pair up and exchange genetic material
•Key Events: Synapsis: Homologous chromosomes pair up, forming tetrads, Crossing Over: Sections of DNA are exchanged between chromatids, introducing genetic diversity, Spindle Formation: Begins in preparation for chromosome alignment
59
Metaphase 1
•Description: Homologous chromosome pairs line up along the cell’s equator
•Key Events: Chromosomes align in pairs (not single file like in mitosis)
•Independent Assortment: Chromosome pairs align randomly, contributing to genetic variation
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Anaphase 1
•Description: Homologous chromosomes are pulled to opposite poles of the cell
•Key Events: Sister chromatids remain together, while homologous pairs are separated, Reduction Division: Each pole receives a random mix of maternal and paternal chromosomes.
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Telophase 1 and Cytokinesis
•Description: Formation of two haploid cells, each with half the original chromosome number
•Key Events: Nuclear membranes may reform briefly, Cytokinesis divides the cytoplasm, resulting in two cells ready for Meiosis II
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Overview of Meiosis 2
•Description: Similar to mitosis, Meiosis II separates sister chromatids in each of the two haploid cells produced in Meiosis I
•Result: Four genetically unique haploid cells
63
Prophase 2 and Telophase 2
Brief Summary of Each Stage:
•Prophase II: Chromosomes condense; spindles form
•Metaphase II: Chromosomes align single-file at the cell’s equator
•Anaphase II: Sister chromatids are pulled to opposite poles
•Telophase II and Cytokinesis: Nuclear membranes reform; cytoplasm divides, resulting in four haploid cells
64
Recap of Chromosomes (Diploid)
Diploid (2n) Cells
•Definition: Cells with two complete sets of chromosomes, one set from each parent
•Chromosome Count in Humans: 46 (23 pairs)
65
Genetic Variation in Meiosis
•Crossing Over: Occurs in Prophase I, leading to exchange of genetic material
•Independent Assortment: Random alignment of homologous pairs in Metaphase I
•Random Fertilization: Further increases genetic variation when gametes combine
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Recap of Chromosomes (Haploid)
Haploid (n or 1n) Cells
•Definition: Cells with one complete set of chromosomes, half the number of diploid cells
•Chromosome Count in Humans: 23 (no pairs)
67
Haploids Function in Cell Division
•Mitosis: Haploid cells do not typically undergo mitosis in humans, as mitosis is primarily for growth and repair in diploid cells
•Meiosis: Haploid cells are the end result of meiosis, specifically used for creating gametes (sperm and eggs) in sexual reproduction
68
Spermatogenesis vs. Oogenesis
•Definition: Both are forms of gametogenesis, the process by which gametes (sperm and eggs) are formed in sexually reproducing organisms
•Location: Spermatogenesis: Occurs in the testes. Oogenesis: Occurs in the ovaries.
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What is Asexual Reproduction?
•Definition: A type of reproduction involving only one parent, resulting in offspring that are genetically identical to the parent
Characteristics: No need for a mate, Offspring are clones of the parent (no genetic diversity), common in single-celled organisms and some plants and animals
Examples: Binary Fission in bacteria, budding in yeast and hydra, Vegetative Propagation in plants like strawberries and potatoes
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What is Sexual Reproduction?
•Definition: A type of reproduction involving two parents, where offspring inherit a mix of genes from both parents, leading to genetic diversity
•Characteristics: Involves the fusion of male and female gametes (sperm and egg), creates genetic variation in the population, common in animals, plants, and some fungi
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Differences between Sexual and Asexual Reproduction
Asexual Reproduction: one parent, no genetic variation, low energy required, fast reproductive speed (e.g. bacteria starfish plants
Sexual Reproduction: two parents, high genetic variation, high energy required, slower reproductive speed (e.g. humans, animals, flowering plants)
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Advantages and Disadvantages
•Asexual Reproduction: Advantages: Quick, requires less energy, useful for stable environments. Disadvantages: Lack of genetic diversity makes populations vulnerable to environmental changes.
•Sexual Reproduction: Advantages: Genetic diversity, which helps populations adapt to changing environments. Disadvantages: Slower process, requires more energy and finding a mate.
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What is Karyotyping?
•the process of organizing and visualizing chromosomes in a cell by shape, size, and number
•used to analyze chromosomal abnormalities and diagnose genetic conditions
•involves staining chromosomes, taking photos, and arranging them in a standard layout
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Structures of Chromosomes
•composed of DNA and proteins ; each person has 23 pairs (46 total) in most cells
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Centromere
•central region where chromatids connect
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Telomere
•end region of chromosome
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Autosomes vs. Sex Chromosomes
•22 pairs are autosomes, and the 23rd pair determines biological sex (XX or XY)
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Steps in Karyotyping
1.Cell Collection
2.Culturing
3.Arresting Chromosomes
4.Staining and Imaging
5.Arrangement
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Cell Collection (step 1)
•obtain cells, often from blood, amniotic fluid, or bone marrow
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Culturing (step 2)
•grow cells in a lab to prepare for analysis.
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Arresting Chromosomes (step 3)
•cells are treated to stop division at metaphase
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Staining and Imaging (step 4)
•use stains like Giemsa to highlight chromosomal bands
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Arrangement (step 5)
•chromosomes are arranged from largest to smallest
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Applications of Karyotyping
•Genetic Disorder Diagnosis, Cancer Research, Prenatal Testing, Species Comparison
85
Genetic Disorder Diagnosis
•identifies chromosomal abnormalities (e.g. Down syndrome, Turner syndrome)
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Cancer Research
•detects chromosomal changes associated with cancer types
87
Prenatal Testing
•assesses the genetic health of a fetus
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Species Comparison
•in evolutionary studies, it helps compare chromosomal structures across species
89
Abnormalities and Karyotyping
•Numerical Abnormalities and Structural Abnormalities
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Numerical Abnormalities
•changes in chromosome number, like trisomy 21 (Down syndrome)
91
Structural Abnormalities
•Deletions: Missing segments
•Duplications: Extra segments
•Inversions: Reversed segments
•Translocations: Segments exchanged between chromosomes
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Non-disjunction
•is the failure of chromosomes to separate properly during cell division
93
Non-disjunction in Meiosis
•homologous chromosomes fail to separate
94
Non-disjunction in Meiosis 2
•sisters chromatids fail to separate
•this occurs during anaphase
•Results in gametes with an abnormal number of chromosomes (aneuploidy)
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Consequences of Non-disjunction
•monosomy: missing one chromosome (e.g., Turner Syndrome, 45, X)
•trisomy: extra chromosome (e.g., Down Syndrome, Trisomy 21)
96
Examples of Disorders Caused by Non-disjunction
1.Down Syndrome: Trisomy 21
2.Klinefelter Syndrome: XXY
3.Turner Syndrome: XO
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Interpreting a Karyotype
•examine chromosome count, shape, and band patterns, highlight common anomalies like trisomies, monosomies, and structural variations
•Case Examples: Normal: 46 chromosomes, typical banding patterns, Abnormal: Extra or missing chromosomes (e.g., 47, XXY in Klinefelter syndrome)
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Limitations of Karyotyping
•only large-scale abnormalities are visible; smaller mutations may require other methods
•requires cell culturing, which can be time-consuming
•interpreting karyotypes accurately requires experience and knowledge
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Summary of Karyotyping
•it is essential for identifying chromosomal
•it is crucial for genetic testing, cancer diagnostics, and prenatal screening
•emerging technologies are enhancing the precision of chromosome analysis
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Protein Synthesis and Mutations
•our DNA encodes for different proteins
•first our DNA is transcribed into mRNA (messenger RNA), which leaves the nucleus and is “read” by a ribosome to create the protein
•every 3 nucleotides is called a “codon”, and this codon is translated to one of the 20 amino acids, or a STOP codon (to stop the chain of amino acids)
101
Gene: Point Mutations
•one nucleotide is substituted for another
•often repaired by spellchecker enzyme
•may lead to amino acid change
•it may not lead to amino acid change (silent mutation) (e.g., DNA “CCC” is mutated into “CCG” but same amino acid is created (glycine)
102
Gene: Frame Shift Mutation
•insertion/deletion of a nucleotide
•entire DNA/RNA after the mutation is shifted
•much more serious to structure/function of the protein (mRNA sequence may have an early or late “stop codon”
103
Chromosome Mutations
•translocation: chromosome segments combine with non-homologous chromosome
•many genes wind up on entirely different chromosomes
•gene cut apart
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Impact on Offspring
Somatic Cell Mutations and Germ Cell Mutations
105
Somatic Cell Mutations
•affect only the individual
•not passed on to future generations
•ex: Muscle cell mutations, most cancers
106
Germ Cell Mutations
•germ cells= the diploid cells that undergo meiosis to make sperm and egg
•may be passed to future generations
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Mutation Causes
•mutagen: agents in the environment that can change DNA
•speed up replication process
•break apart nucleotides
•ex: UV sunlight breaks hydrogen bonds between thymine (T) and adenine (A)
108
Source of Genetic Variation
•in a large population, many new mutations are introduced every generation
•harmful mutations result in dead-ends, but beneficial (even neutral) mutations will persist or often increase frequency in a population
•meiosis allows individuals to produce many different gametes, sexual reproduction between dissimilar parents produce many new and different combinations of genes in the next generation
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Mutation
•the original source of variation
•occur regularly
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Diversity and Genetic Variation
•all species exhibit variation -> mutations (changes in genetic info)
•mutations create new genetic info and add genetic diversity
111
3 Kinds of Mutations
1.Harmful Mutation
2.Neutral Mutation
3.Beneficial Mutation
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Harmful Mutation
•mutation decreases reproductive success
113
Neutral Mutation
•mutation provides no selective advantage or disadvantage
•may not have immediate effect in DNA
114
Beneficial Mutation
•increased reproductive success
•mutation is favoured overtime; accumulated overtime
115
The Science of Breeding
•breeding selected individuals with certain favoured traits will result in the favoured traits becoming more prevalent and more pronounced
•independent variable: breeding population (selected by the breeder)
•dependant variable: appearance of favoured trait in the population
116
Procedure of Science Breeding
•choose a species that can be bred in captivity, breed a large number of individuals, choose a trait that you wish to favour, such as large size, a particular colour, or sweetness, Identify individuals that exhibit the favoured trait most strongly, breed only these individuals to produce the next veneration of individuals, repeat
117
Artificial Selection
•after many generations, artificial selection can produce dramatic changes in the traits of a population (ex. Dog Breeding)
•limited by genetic variability within the breeding population
•practice can reduce overall genetic diversity of population and can therefore contribute to the loss of biodiversity
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What is Gregor Mendel known as?
The Father of Modern Genetics
119
Gregor Mendel
•published results of pea experiment 1865/1866
•developed the basic laws of inheritance
•introduced idea of “all or nothing” inheritance
•contradicted the popular idea of the time
•blend of traits
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Polysomy
•a condition found in many species in which an organism has at least one more chromosome than normal
121
Punnet Squares
•a method for showing how sex cells from 2 parents can combine in offspring
•shows possibilities (probabilities %)
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Crosses
Monohybrid and Dihybrid
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Monohybrid Cross
•a cross between two organisms with variations at one genetic locus of interest
•1 trait and each individual is heterozygous for that trait
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Dihybrid Cross
•a cross between two individuals with two observed traits that are controlled by two distinct genes
•2 traits, hybrid (heterozygous) for each trait
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Dominant and Recessive inheritance
•autosomal dominant traits pass from one parent onto their child
•autosomal recessive traits pass from both parents onto their child
126
Complete Dominance
•when one allele is fully dominant over the other
•only one allele in the genotype is seen in the phenotype
127
Incomplete Dominance
•when a dominant allele is not always completely dominant over a recessive allele
•each allele is partially expressed (a mix of the two)
128
Codominance
•when two versions of an allele of the same gene are expressed separately to yield different traits in an individual
•both alleles in the genotype are seen in the phenotype (blood)
129
Sex-Linkage
•characteristics that are influenced by genes carried on the sex chromosomes
•allele located on sex chromosomes (pedigree chart)
130
Pedigree Charts
•shows patterns of inheritance in a “family tree”
•you can often determine the genotypes of many or all of the organisms in the pedigree chart
•shows the occurrence of certain traits through different generations
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Genotypes
•the genetic makeup of an organism
•refers to alleles, or varient forms of a gene that are carried by an organism
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Phenotypes
•an observable trait
•anything from a common trait, such as height or hair colour, to presence or a sense of a disease
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Dominant Allele
•produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent
•only one copy of a dominant allele is needed to express the trait
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Recessive Allele
•an allele that when present on its own will not affect the individual
•one recessive allele will not produce a trait
•two recessive alleles are needed in order to express the trait
