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Human Genetics
Midterm 1 CH 7 - 12
| Question | Answer |
|---|---|
| Monogenic Traits | Controlled by one gene (Mendelian). |
| Polygenic Traits | Controlled by more than one gene |
| Complex Traits | Controlled by more than one factor |
| Multifactorial Traits | Controlled by genes + environment. |
| Examples of Complex Traits | Lung Cancer, Height, Skin Color |
| Heritability (H) | Measures how much variation in a trait is due to genetics.Ranges from 0 to 1: H = 1.0 → Trait is 100% genetic (e.g., total fingerprint ridge count). H = 0.0 → Trait is 100% environmental. |
| Factors Affecting Heritability | Population-specific– Varies by group and environment. Time-dependent – Can change over generations. Influenced by Environment – High environmental variation lowers heritability. |
| Coefficient of Relatedness | Measures genetic similarity between relatives. Siblings/Parent-Child – 50% shared genes. Grandparent-Grandchild – 25% shared genes. First Cousins – 12.5% shared genes. |
| Monozygotic (MZ) Twins | Identical genes + shared environment.Higher concordance in MZ twins suggests genetic influence. |
| Dizygotic (DZ) Twins | 50% shared genes + shared environment. |
| Genome-Wide Association Studies (GWAS) | Compares genetic markers between groups with and without a trait.Single Nucleotide Polymorphisms (SNPs) – Single base changes. Copy Number Variants (CNVs) – Repeated DNA sequences. |
| Twins raised apart | Shared genotype but not environment |
| Adopted individuals | Shared environment but not genes |
| Leptin | Decreases appetite, produced by fat cells. |
| Ghrelin | Increases appetite, produced in the stomach. |
| BMI Heritability | 0.4 to 0.7, meaning both genetics and environment matter. |
| Skin Color & Genetics | Determined by melanin amount, type, and distribution. |
| Two types of melanin: | Eumelanin – Darker pigmentation. Pheomelanin – Lighter pigmentation. |
| Intelligence & Genetics | IQ is a complex trait with genetic & environmental influences. |
| Infertility | Inability to conceive after 1 year of unprotected intercourse. |
| Subfertility | Can conceive, but takes longer than usual. 1 in 6 couples struggle with fertility. |
| Male Infertility | Easier to detect, harder to treat. |
| Azoospermia | No sperm production. |
| Oligospermia | Low sperm count can be caused by Varicocele (enlarged scrotal veins). Hormonal imbalances. Heat exposure (tight underwear, hot tubs, laptops). Certain drugs (cancer drugs, pain relievers). |
| Female Infertility | More complex, due to structural and hormonal issues. Major Causes: Hormonal ovulation problems (40%). Oviduct blockage (30-50%). Uterine/cervical problems. Age-related infertility (older oocytes = more chromosomal errors) |
| Varicocele | Enlarged veins in the scrotum (similar to varicose veins). Common cause of male infertility (affects sperm production & quality). |
| Assisted Reproductive Technologies (ARTs) | Methods that assist fertilization, gamete replacement, or implantation |
| Intrauterine Insemination (IUI) | Donated sperm inserted into cervix/uterus. |
| In Vitro Fertilization (IVF) | Sperm fertilizes an oocyte in a lab, then implanted. |
| Intracytoplasmic Sperm Injection (ICSI) | A single sperm is injected into an oocyte. |
| Gamete Intrafallopian Transfer (GIFT) | Sperm and eggs placed in fallopian tubes. |
| Zygote Intrafallopian Transfer (ZIFT) | Fertilized zygote placed in fallopian tubes. |
| Louise Joy Brown. | First IVF baby (1978) |
| Preimplantation Genetic Diagnosis (PGD) | Screens embryos for genetic disorders before implantation. 29% success rate. |
| First PGD use (1989) | To select females to prevent X-linked conditions. |
| Polar Body Analysis | Predicts embryo genetics by analyzing a polar body. Still experimental, used with PGD. |
| Cloning | Producing genetically identical organisms. |
| Embryo Splitting | Natural (identical twins) or lab-induced. |
| Nuclear Transfer | DNA from somatic cell inserted into an egg. |
| Dolly the Sheep (1996) | First cloned mammal from adult cell. |
| Embryonic Stem Cells | inner cell mass of very early embryo; somatic cell nuclear transfer into egg cell |
| Induced Pluripotent Stem Cells (iPSCs) | Reprogrammed somatic cells. |
| Adult Stem Cells | Found in mature tissues, limited differentiation. |
| Friedrich Miescher (1860s) | Discovered nuclein (now known as DNA). |
| Watson & Crick (1953) | Discovered double-helix structure of DNA. |
| Rosalind Franklin | Used X-ray diffraction to show DNA’s helix shape. |
| Adenine (A) pairs with Thymine (T) | 2 hydrogen bonds. |
| Guanine (G) pairs with Cytosine (C) | 3 hydrogen bonds (stronger, more heat-resistant). |
| Phosphodiester bonds | Link nucleotides into a strand. |
| Purines | Adenine (A) and Guanine (G) |
| Pyrimidines | Cytosine (C) and Thymine (T) |
| Antiparallel strands | One runs 5' → 3', the other 3' → 5'. |
| Chromatin | DNA wrapped around histones for compaction. |
| Nucleosome | "Bead-like" DNA-histone structure. |
| DNA Replication (Semiconservative Model) | Occurs during S-phase of cell cycle. |
| Helicase | Unwinds DNA at replication fork. |
| Binding Proteins | Stabilize separate strands |
| Primase | Adds RNA primer (shorter) to template strand. |
| DNA Polymerase | Adds new nucleotides, builds new strands. |
| Ligase | Seals gaps in sugar-phosphate backbone by joining okazaki fragments. |
| Leading strand | Synthesized continuously (5' → 3'). |
| Lagging strand | Synthesized in fragments (Okazaki fragments). |
| Polymerase Chain Reaction (PCR) | Uses DNA polymerase to copy specific sequences in a test tube.Technique to amplify DNA (make copies). |
| Applications of PCR | Forensics – Identify DNA from crime scenes. Disease detection – Identify viruses (e.g., COVID-19, HIV). Ancient DNA analysis – Study extinct species. |
| Traditional PCR | Amplifies DNA but does NOT quantify it. Uses gel electrophoresis to detect products. Cannot determine the exact amount of DNA in a sample. |
| qPCR | Measures DNA amplification in real-time (while it happens). Uses fluorescent dyes to track DNA levels. Provides relative quantification of DNA |
| Sanger Sequencing | Determines order of nucleotides in DNA. |
| Next-Generation Sequencing (NGS) | Rapid, high-throughput sequencing. |
| Nanopore Sequencing | Can read long DNA fragments (50-200 kb). |
| Digital PCR | Divides DNA into thousands of tiny reactions. Each reaction is analyzed separately. Provides absolute quantification of DNA (more precise than qPCR) |
| DNA | Double-stranded, deoxyribose, thymine (T), stores genetic info. |
| RNA | Single-stranded, ribose, uracil (U) replaces thymine, carries genetic info & helps make proteins. |
| mRNA (Messenger RNA) | Carries genetic info, contains codons. (LEAST ABUNDANT) |
| rRNA (Ribosomal RNA) | Forms ribosomes, catalyzes protein synthesis. (MOST ABUNDANT) |
| tRNA (Transfer RNA) | Carries amino acids, contains anticodons. |
| Initiation | Transcription factors & RNA polymerase bind to promoter. |
| Elongation | RNA polymerase reads DNA, builds mRNA. |
| Termination | Stops at terminator sequence, releasing RNA. |
| Transcription | Synthesizes an RNA molecule |
| Translation | Uses the information in the RNA to manufacture a protein by aligning and joining specified amino acids |
| 5' Cap | Added for ribosome recognition. |
| Poly-A Tail (3' End) | Protects mRNA from degradation. |
| Splicing | Removes introns, joins exons. |
| Alternative Splicing | Creates multiple proteins from one gene. |
| Primary Protein Structure 1st | Amino acid sequence in polypeptide chain |
| Secondary Protein Structure 2nd | Alpha helices & beta sheets (hydrogen bonds). |
| Tertiary Protein Structure 3rd | 3D folding due to R-group interactions. |
| Quaternary Protein Structure 4th | Multiple polypeptide chains forming a complex. |
| Chaperone Proteins | Help proteins fold correctly. Prevents protein from getting stuck in an intermediate form |
| Misfolded Proteins | Tagged with ubiquitin, degraded in proteasome. |
| Prions | Infectious misfolded proteins |
| Post-Translational Modifications (PTMs) | Chemical changes to proteins (e.g., phosphorylation, methylation) that affect function. |
| proteome | is the complete set of proteins produced by a cell, tissue, or organism at a given time. |
| Gene Expression Basics | Not all genes are active at the same time. |
| Housekeeping Genes | Always active in all cells. |
| Specialized Genes | Turn on/off based on cell type & conditions. |
| Transcriptome | The collection of mRNA in a cell at a given time. |
| Globin Chain Switching | Hemoglobin gene expression changes during development: |
| Embryo: ε (epsilon) + ζ (zeta) | Very high oxygen affinity. |
| Fetus: γ (gamma) + α (alpha) | High oxygen affinity |
| Adult: β (beta) + α (alpha) | Lower oxygen affinity. |
| Epigenetics | Heritable chemical modifications to DNA & histones without changing the DNA sequence. |
| Epigenome | Collection of all epigenetic modifications in a cell. |
| DNA Methylation | Adds methyl (-CH₃) groups to DNA, silencing gene expression. |
| Histone Modifications | Chemical changes to histones that control DNA accessibility. |
| MicroRNA (miRNA) | Small RNA molecules that block translation of mRNA. |
| Promoter | DNA region (100-1000 bp) where transcription starts; contains TATA box. |
| Enhancer | Can increase gene transcription even from far away (up to 1 million bp away). |
| Histone Modifications | Histones help package DNA and control gene expression. |
| Acetylation (HAT enzyme) | Loosens chromatin, allowing transcription. |
| Deacetylation (HDAC enzyme) | Tightens chromatin, silencing genes. |
| Methylation & Phosphorylation | Modify gene activity. |
| Closed Chromatin | Tightly packed DNA that prevents transcription. Genes in closed chromatin are inactive (silenced). Mediated by histone modifications like methylation. |
| Lysine (K) in Histones | Amino acid found in histone proteins. Target for acetylation & methylation (modifies gene expression). Acetylation of lysine opens chromatin → gene activation. |
| Super Enhancer | Cluster of enhancers that strongly activate transcription. Regulate genes involved in cell identity (e.g., stem cells). Super enhancers form liquid condensates with transcription factors. |
| Mutation | A rare genetic change that affects phenotype. |
| Polymorphism | A gene variant present in >1% of the population. |
| Loss-of-Function Mutation | Recessive (reduces/eliminates function). |
| Gain-of-Function Mutation | Dominant (adds new function). |
| Germline Mutation | Occurs before meiosis, inherited by offspring. |
| Somatic Mutation | Occurs before mitosis, affects only some cells (mosaicism). |
| Spontaneous Mutation | Random errors in DNA replication (tautomeric shifts). |
| Induced Mutation | Caused by mutagens (radiation, chemicals). |
| Sickle Cell Disease | β-globin gene mutation, changes glutamic acid → valine |
| Cystic Fibrosis | CFTR gene mutation, affects chloride channels. |
| Duchenne Muscular Dystrophy | Deletion in dystrophin gene, leads to muscle loss. |
| Huntington’s Disease | Triplet repeat expansion of CAG in HTT gene. |
| Point Mutation | Single nucleotide change. |
| Splice-Site Mutation | Alters mRNA splicing, leading to exon skipping. |
| Deletion | Removes genetic material (e.g., male infertility, Y chromosome deletion). |
| Insertion | Adds extra genetic material (e.g., Gaucher disease). |
| Tandem Duplication | Extra copies of a gene (e.g., Charcot-Marie-Tooth disease). |
| Transposons ("Jumping Genes") | Move within the genome, disrupting genes. Example: Hemophilia A (transposon moved into Factor VIII gene). |
| Expanding Repeat | A short DNA sequence is repeated, growing over generations. |
| Anticipation | The repeat number increases, making the disease worse in each generation |
| DNA Repair Mechanisms | Most DNA errors are fixed before causing mutations. |
| p53 Protein | Monitors DNA & triggers apoptosis if damage is severe. |
| Failure of DNA Repair & Cancer | If DNA repair genes mutate, mutations accumulate → Cancer risk increases. |
| Silent Mutation | Change in DNA, but amino acid stays the same. No effect on protein function. Example: GAA → GAG (both code for Glutamic Acid). |
| Missense Mutation | Changes one amino acid in the protein. May or may not affect function. Example: Sickle Cell Disease (Glu → Val). |
| Nonsense Mutation | Changes a codon to a STOP codon. Protein is too short and nonfunctional.Example: Duchenne Muscular Dystrophy. |
| Frameshift Mutation | Insertion or deletion shifts the reading frame. Changes many amino acids, making a broken protein.Example: Tay-Sachs Disease. |
| Pseudogenes | A DNA sequence similar to a gene but which is not translated. May be transcribed into mRNA |
| Apoptosis | Programmed cell death (cell suicide). Removes damaged or unneeded cells. |
Created by:
Aly99
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